Search

Abstract Endophytic bacteria are one of the symbiotic microbial groups closely related to host algae. However, less research on the endophytic bacteria of marine algae. In this study, the endophytic bacterial community of Sargassum thunbergii was investigated using the culture method and high-throughput sequencing. Thirty-nine endophytic bacterial strains, belonging to two phyla, five genera and sixteen species, were isolated, and Firmicutes, Bacillus and Metabacillus indicus were the dominant taxa at the phylum, genus and species level, respectively. High-throughput sequencing revealed 39 phyla and 574 genera of endophytic bacteria, and the dominant phylum was Proteobacteria, while the dominant genus was Ralstonia. The results also indicated that the endophytic bacteria of S. thunbergii included various groups with nitrogen fixation, salt tolerance, pollutant degradation, and antibacterial properties but also contained some pathogenic bacteria. Additionally, the endophytic bacterial community shared a large number of groups with the epiphytic bacteria and bacteria in the surrounding seawater, but the three groups of samples could be clustered separately. In conclusion, there are a variety of functional endophytic bacteria living in S. thunbergii, and the internal condition of algae is a selective factor for the formation of endophytic bacterial communities. This study enriched the database of endophytic bacteria in marine macroalgae, paving the way for further understanding of the interrelationships between endophytic bacteria, macroalgae, and the environment.

Endophytic bacteria are one of the symbiotic microbial groups closely related to host algae. However, less research on the endophytic bacteria of marine algae. In this study, the endophytic bacterial community of Sargassum thunbergii was investigated using the culture method and high-throughput sequencing. Thirty-nine endophytic bacterial strains, belonging to two phyla, five genera and sixteen species, were isolated, and Firmicutes, Bacillus and Metabacillus indicus were the dominant taxa at the phylum, genus and species level, respectively. High-throughput sequencing revealed 39 phyla and 574 genera of endophytic bacteria, and the dominant phylum was Proteobacteria, while the dominant genus was Ralstonia. The results also indicated that the endophytic bacteria of S. thunbergii included various groups with nitrogen fixation, salt tolerance, pollutant degradation, and antibacterial properties but also contained some pathogenic bacteria. Additionally, the endophytic bacterial community shared a large number of groups with the epiphytic bacteria and bacteria in the surrounding seawater, but the three groups of samples could be clustered separately. In conclusion, there are a variety of functional endophytic bacteria living in S. thunbergii, and the internal condition of algae is a selective factor for the formation of endophytic bacterial communities. This study enriched the database of endophytic bacteria in marine macroalgae, paving the way for further understanding of the interrelationships between endophytic bacteria, macroalgae, and the environment. [ABSTRACT FROM AUTHOR]

Endophytic bacteria have a complex coevolutionary relationship with their host macroalgae. Dioecious macroalgae are important producers in marine ecosystems, but there is still a lack of research on how sex influences their endophytic bacteria. In this study, the endophytic bacterial communities in male and female S. thunbergii and their reproductive tissues (receptacles) were compared using culture methods and high-throughput sequencing. The endophytic bacterial communities detected by the two methods were different. Among the 78 isolated strains, the dominant phylum, genus, and species were Bacillota, Alkalihalobacillus, and Alkalihalobacillus algicola, respectively, in the algal bodies, while in the receptacles, they were Bacillota, Vibrio, and Vibrio alginolyticus. However, 24 phyla and 349 genera of endophytic bacteria were identified by high-throughput sequencing, and the dominant phylum and genus were Pseudomonadota and Sva0996_ Marine_ Group, respectively, in both the algal body and the receptacles. The two methods showed similar compositions of endophytic bacterial communities between the samples of different sexes, but the relative abundances of dominant and specific taxa were different. The high-throughput sequencing results showed more clearly that the sex of the host alga had an effect on its endophyte community assembly and a greater effect on the endophytic bacterial community in the receptacles. Moreover, most specific bacteria and predicted functional genes that differed between the samples from the males and females were related to metabolism, suggesting that metabolic differences are the main causes of sex differences in the endophytic bacterial community. Our research is the first to show that host sex contributes to the composition of endophytic bacterial communities in dioecious marine macroalgae. The results enrich the database of endophytic bacteria of dioecious marine macroalgae and pave the way for better understanding the assembly mechanism of the endophytic bacterial community of algae. [ABSTRACT FROM AUTHOR]

It is well-known that high specific surface area and improved pore structure is significantly desired for the application of supercapacitor based on biomass-based activated carbon. Herein, Sargassum thunbergii was selected as carbon precursor. Then, a simple and environmentally friendly method was designed to synthesize heteroatom self-doped porous carbon materials via synchronous activation and graphitization by using K2FeO4. Our results demonstrated that activation temperature plays an important role in porous structure, morphology, and degree of graphitization, thus affecting the performance of supercapacitance. Sargassum thunbergii-based graphitized porous carbons STGPC-2 sample (calcination temperature at 700 °C) has a large specific surface area (1641.98 m2 g−1), pore volume (0.91 cm3 g−1), high microporosity (Vmicro = 0.62 cm3 g−1, more than 68%), and a certain degree of graphitization. In three-electrode system, The STGPC-2 electrode exhibited a high specific capacitance of 325.5 F g−1 at 0.5 A g−1 and displays high rate capability (248 F g−1 at 10 A g−1 in 6 M KOH electrolyte). The symmetric STGPC-2 supercapacitor exhibits energy density as high as 21.3 Wh kg−1 (at a power density of 450 W kg−1) and excellent long-term cycling stability (97% capacitance retention after 3000 cycles) in 1 M Na2SO4 electrolyte.

Sargassum thunbergii is distributed on reefs and rock marshes in mid- and low-tide zones, and some are periodically exposed to lengthy low tides. Dehydration is a key factor affecting the survival of S. thunbergii at low tides. In this study, using wild S. thunbergii as experimental material, the water loss rate, chlorophyll fluorescence parameters, and biochemical parameters under different stresses were determined by dehydrating the thalli in an incubator for 0, 1, 3, and 6 h. The results showed that: (1) algae of different sizes have significantly different water loss rates under different stresses. The shorter the stress time and the larger the algae, the lower the water loss rate, indicating that the water retention capacity of S. thunbergii with larger thalli is higher. Wild S. thunbergii grow in clusters on reefs. The leaves in the lower part of the branches and near the holdfast are wide. The middle and upper leaves are narrow and long, respectively. The lower broad leaves are easily blocked by the upper branches. Therefore, differences in the growth environment cause differences in the ecological structure and biochemical components of S. thunbergii. High temperature, strong light, and water loss at low tide are the main factors that cause severe environmental stress to sessile S. thunbergii in the intertidal zone. (2) Dehydration significantly reduced the chlorophyll fluorescence value of S. thunbergii, and different parts of the same individual of S. thunbergii had significantly different tolerance to dehydration, with the lowest tolerance at branch tips and the strongest tolerance at the base. The non-regulatory energy-dissipation mechanism plays a major role in the dehydration response of S. thunbergii. Under dry exposure, the light energy utilization efficiency of S. thunbergii was significantly reduced. This reduction in active light protection capacity indicates that dehydration reduces the adaptability of S. thunbergii to excessive light intensity. Dehydration can damage the tips of small individuals that cannot recover, while the base part of large individuals could return to a normal physiological state. (3) Antioxidant enzymes (ASAFR, SOD) and non-antioxidant substances (soluble sugar and proline) in the tip part responded to dehydration, and the base part mainly responded by upregulation of protein, soluble sugar, and proline content to resist stress. S. thunbergii, located in the high and middle tide zones, is more likely to be stressed by high temperatures, strong light, and dehydration, and the physiological and biochemical characteristics of different parts of the thallus are also variable due to differences in external morphology. Algae mainly reduce damage to the photosynthetic system caused by a lack of water through a non-regulatory energy dissipation mechanism. The water retention capacity of the base was better than branch tips during dry exposure, and the damage to algal cells was low. The main roles are as heat shock proteins, soluble sugars, proline, and other small molecules, which can pass stress response, osmotic regulation, and anti-oxidation resists damage to cells caused by stress. The water retention capacity of the top cells was weak, and the stress was relatively strong. Antioxidant enzymes such as ASAFR and SOD in algae and non-antioxidant enzymes such as soluble sugars and proline, work together to resist dry exposure stress, reduce cell damage and maintain cell viability. In summary, under the stress of dry exposure, the antioxidant enzymes, antioxidant substances, and non-regulatory energy dissipation mechanisms of S. thunbergii play a role in maintaining cell activity. This study provides important guidance for exploring the ecological adaptability of S. thunbergii in resisting environmental stress.

The formation of epiphytic bacterial communities on macroalgae is closely related to host identity, but the effects of tissue location and sex of the host alga on this process, especially the relative contributions of these two factors, have not been studied. Here, the epiphytic bacterial community on three different tissues (tip, receptacle and holdfast) of male and female Sargassum thunbergii in the intertidal zone of Qingdao was investigated using high-throughput sequencing, and the results revealed obvious tissue and sex specificity of the epiphytic bacteria and significant differences from seawater bacterial samples. The biodiversity indexes, specific bacteria, biomarkers, indicator taxa and predicted function of epiphytic bacteria differed significantly among tissues of S. thunbergii and between sexes for the same tissue, confirming that both algal tissue location and sex impacted epiphytic bacterial community assembly on S. thunbergii. Additionally, β-diversity analysis showed that tissue location contributed more than host sex to epiphytic bacterial community structure, and the contributions of these two factors varied among tissues. Sex contributed less to epiphytic bacteria on the holdfast than on the tip and receptacle. Furthermore, the tissue and sex specificity of epiphytic bacteria on S. thunbergii were likely related mainly to host metabolism but also to the interaction between bacteria and algae and adaptability to the environment. This study shed light on the drivers of macroalga-associated bacterial community structure and broaden our understanding of the relationship between macroalgae and their epiphytic bacteria.

Abstract The epiphytic bacteria are the most abundant microorganisms on marine macroalga. However, there are few studies on the distribution of these epiphytic bacteria on male and female Sargassum thunbergii. In this study, the composition and diversity of epiphytic bacterial communities on male and female S. thunbergii were investigated by using the traditional culture-based method and 16S rDNA high-throughput sequencing. The results showed that the dominant bacterial phyla and genera were the same on both male and female S. thunbergii. However, there were significant differences in the relative abundance of epiphytic bacteria at the genus level. Furthermore, male and female S. thunbergii had their own indicative species and specific bacteria. In addition, the predicted functions of the epiphytic bacteria mainly differed in transport and metabolism, environmental adaptation and spore development. This study enriches the baseline knowledge of epiphytic bacteria related to dioecious algae and paves the way for further studies of the relationships between epiphytic microbial communities and the sex of algae.

Abstract Background Chronic exposure to ultraviolet B (UVB) causes a series of adverse skin reactions, such as erythema, sunburn, photoaging, and cancer, by altering signaling pathways related to inflammation, oxidative stress, and DNA damage. Marine algae have abundant amounts and varieties of bioactive compounds that possess antioxidant and anti-inflammatory properties. Thus, the objective of this study was to investigate the photoprotective effects of an ethanol extract of Sargassum thunbergii. Methods Sargassum thunbergii phenolic-rich extract (STPE) was prepared, and its activity against UVB damage was evaluated using L929 fibroblast cells and zebrafish. STPE was extracted and purified by 40% ethanol and macroporous resin XDA-7. Reactive oxygen species (ROS) and antioxidant markers, such as superoxide dismutase (SOD), catalase (CAT) activities, and malondialdehyde (MDA) content were analyzed. The effect of STPE on UVB-induced inflammation was determined by inflammatory cytokine gene and protein expression. The expression of signaling molecules in the Nuclear Factor KappaB (NF-κB) pathway was determined by western blotting. DNA condensation was analyzed and visualized by Hoechst 33342 staining. In vivo evaluation was performed by tail fin area and ROS measurement using the zebrafish model. Results The total polyphenol content of STPE was 72%. STPE reduced ROS content in L929 cells, improved SOD and CAT activities, and significantly reduced MDA content, thereby effectively alleviating UVB radiation-induced oxidative damage. STPE inhibited the mRNA and protein expression of TNF-α, IL-6, and IL-1α. STPE reversed DNA condensation at concentrations of 20 and 40 μg/mL compared with the UVB control. Moreover, STPE inhibited NF-κB signaling pathway activation and alleviated DNA agglutination in L929 cells after UVB irradiation. Additionally, 1.67 μg/mL STPE significantly increased the tail fin area in zebrafish, and 0.8–1.6 μg/mL STPE effectively eliminated excessive ROS after UVB radiation. Conclusions STPE inhibited UVB-induced oxidative stress, inflammatory cytokine expression, and DNA condensation via the downregulation of the NF-κB signaling pathway, suggesting that it prevents UVB-induced photodamage, and has potential for clinical development for skin disease treatment.

As a common macroalga living in the intertidal zone, Sargassum thunbergii (Sargassaceae, Phaeophyta) is often exposed to drastic changes in solar photosynthetically active radiation during a diurnal cycle; thus, the potential photosynthetic adaptation processes deserve attention. In this work, we examined the photosynthetic performance and xanthophyll cycle activity of this alga in response to high light (1,200 μmol photons m–2 s–1, the average in-situ light intensity at noon) by using chlorophyll fluorescence and high-performance liquid chromatography (HPLC). On exposure to high light, a rapid decrease in the effective quantum yield of photosystem II (PSII) (Y(II)) occurred, indicating down-regulation of PSII activity; a corresponding increase in non-photochemical quenching (NPQ) indicated the existence of energy-dissipating cycles. After turning off the light, Y(II) gradually increased to 0.7, accompanied by a decrease in NPQ. However, no complete recovery of NPQ was observed, and its value remained at ≈4, even after an 80-min dark treatment. The size of the xanthophyll cycle pigments pool was quantified using HPLC and was found to be ≈16 mol mol−1 Chl a × 100. The activity of the xanthophyll cycle, characterized by a de-epoxidation state (DPS), could reach up to ≈0.5. Such a large pigments pool and rapid accumulation of zeaxanthin may allow S. thunbergii to induce high values of NPQ (≈10). These results were further complemented by inhibitor (dithiothreitol, DTT) and pre-illumination experiments showing that (1) both NPQ and the xanthophyll cycle could be inhibited by DTT, and there was always a strong positive correlation between NPQ and DPS; (2) the previously formed antheraxanthin exhibited a long retention time and a slow epoxidation; and (3) the long retention of antheraxanthin contributed to a rapid accumulation of zeaxanthin. In conclusion, our present study demonstrated that xanthophyll cycle-induced NPQ can significantly protect S. thunbergii from light fluctuations in the intertidal zone.

The enhancement of ultraviolet-B radiation (UV-B) radiation reaching the Earth's surface due to ozone layer depletion is an important topic. Macroalgal species growing in the intertidal zone are often directly exposed to UV-B radiation periodically as the tide changes. In order to better understand the response of macroalgae to UV-B stressed condition, we studied the dominant dioecious intertidal macroalgae Sargassum thunbergii. After consecutive UV-B radiation treatments, we used metabonomics models to analyze and compare the maximum photosynthetic electron transport rate (ETRmax), central carbon cycle metabolism (CCCM) gene expression level, CCCM enzymic activities [pyruvate dehydrogenase and citrate synthase (PDH and CS)], and carbon-based metabolite (including pyruvate, soluble sugar, total amino acid, and lipids) content in male and female S. thunbergii. The results showed that under low and high UV-B radiation, the ETRmax values and six targeted CCCM gene expression levels were significantly higher in males than in females. Under high UV-B radiation, only the CS activity was significantly higher in males than in females. There was no significant difference in PDH activity between males and females. The CCCM models constructed using the metabonomics analysis demonstrate that S. thunbergii males and females exhibit obvious gender differences in their responses to UV-B radiation, providing us with a new understanding of the macroalgal gender differences under UV-B radiation, as past investigations always underestimated their diecious characteristics. [ABSTRACT FROM AUTHOR]

ABSTRACT Intertidal macroalgae face periodic water loss and rehydration caused by daily tidal changes. However, the effect of water loss stress on algal epiphytic bacteria has not yet been reported. In this study, the effects of water loss stress on the epiphytic bacteria community of Sargassum thunbergii were analyzed, and the different responses of epiphytic bacteria to water loss stress were compared between male and female algae. The results showed that after water loss stress, the diversity of the epiphytic bacterial community of S. thunbergii first decreased and then increased. Among the dominant taxa, the abundance of Cyanobacteria decreased significantly, whereas the abundance of Portibacter and Aquimarina first increased and then decreased. Additionally, the indicator species and the abundance of predicted functional genes related to carbon, nitrogen, and sulfur metabolism both changed significantly. More importantly, when the epiphytic bacteria were analyzed separately according to the algal sex, the changes in algal epiphytic bacterial community structure and indicator species were more significant, and there were sexual differences. Therefore, it was concluded that water loss stress has a significant effect on the community structure and function of the epiphytic bacteria on S. thunbergii. Meanwhile, the epiphytic bacteria community of two sexes of S. thunbergii differed in the response to water loss stress. IMPORTANCE Periodic water loss caused by the tide is an important environmental factor that is faced by intertidal macroalgae, but the impact of periodic water loss on the epiphytic bacterial communities associated with macroalgae is still unknown. Through this study, we found that the diversity, the relative abundance of dominant taxa, the indicator species, and the abundance of the predicted functional genes in the epiphytic bacteria on S. thunbergii changed with the time of water loss. Moreover, male and female S. thunbergii exhibited different responses to water loss stress. This study not only paves the way for the delineation of the interactions between S. thunbergii and its epiphytic bacteria but also provides new insights for the mechanisms of the adaptation and evolution of macroalgae in the intertidal zone.

Sargassum thunbergii (Mertens ex Roth) Kuntze (ST) is a brown alga rich in indole-2-carboxaldehyde. This study aimed to investigate the anti-obesity effects of ethanol extract from ST in in vitro and in vivo models. In 3T3-L1 cells, ST extract significantly inhibited lipid accumulation in mature adipocytes while lowering adipogenic genes (C/epba and Pparg) and enhancing metabolic sensors (Ampk, Sirt1), thermogenic genes (Pgc-1a, Ucp1), and proteins (p-AMPK/AMPK and UCP1). During animal investigation, mice were administered a chow diet, a high-fat diet (HF), or an HF diet supplemented with ST extract (at dosages of 150 and 300 mg/kg bw per day) for 8 weeks (n = 10/group). ST extract administration decreased weight gain, white adipose tissue weight, LDL-cholesterol, and serum leptin levels while improving glucose intolerance. In addition, ST extract increased the expression of Ampk and Sirt1 in adipose tissue and in the liver, as well as p-AMPK/AMPK ratio in the liver, compared to HF-fed mice. The abundance of Bacteroides vulgatus and Faecalibacterium prausnitzii in the feces increased in response to ST extract administration, although levels of Romboutsia ilealis decreased compared with those in HF-fed mice. ST extract could prevent obesity in HF-fed mice via the modulation of AMPK activation and gut microbiota composition. [ABSTRACT FROM AUTHOR]

The community structures of epiphytic bacteria on the surface of macroalgae are closely related to their host algae, but there is a lack of research on the differences between the epiphytic bacterial communities of male and female algae and their reproductive tissues. In this study, high-throughput sequencing was used to compare epiphytic bacterial community structures on the intertidal macroalgae Sargassum thunbergii and their receptacles between male and female samples. The epiphytic bacteria on the male and female algal bodies and receptacles had similar community structures with a large number of shared bacteria, but the samples clearly clustered separately, and the abundances of dominant taxa, specific bacteria, and indicator species differed, indicating that epiphytic bacterial communities differed significantly between the male and female S. thunbergii and their receptacles. In addition, the abundance of many predicted functional genes was significantly different between epiphytic bacteria on male and female algal bodies and receptacles, especially metabolism-related genes, and the abundances of predicted functional genes of epiphytic bacteria were significantly higher on both types of male samples than on female samples. Our study confirmed that the sex of the host algae influenced the epiphytic bacterial community structures on algae and algal reproductive tissues, and this role was mainly related to the host metabolism. The results reveal the role of host plant sex in the formation of epiphytic bacterial communities. These findings are helpful for obtaining an in-depth understanding of the construction mechanism of algae-associated bacteria. [ABSTRACT FROM AUTHOR]

The epiphytic bacteria are the most abundant microorganisms on marine macroalga. However, there are few studies on the distribution of these epiphytic bacteria on male and female Sargassum thunbergii. In this study, the composition and diversity of epiphytic bacterial communities on male and female S. thunbergii were investigated by using the traditional culture-based method and 16S rDNA high-throughput sequencing. The results showed that the dominant bacterial phyla and genera were the same on both male and female S. thunbergii. However, there were significant differences in the relative abundance of epiphytic bacteria at the genus level. Furthermore, male and female S. thunbergii had their own indicative species and specific bacteria. In addition, the predicted functions of the epiphytic bacteria mainly differed in transport and metabolism, environmental adaptation and spore development. This study enriches the baseline knowledge of epiphytic bacteria related to dioecious algae and paves the way for further studies of the relationships between epiphytic microbial communities and the sex of algae. [ABSTRACT FROM AUTHOR]

Abstract Glaciation‐induced environmental changes during the last glacial maximum (LGM) have strongly influenced species' distributions and genetic diversity patterns in the northern high latitudes. However, these effects have seldom been assessed on sessile species in the Northwest Pacific. Herein, we chose the brown alga Sargassum thunbergii to test this hypothesis, by comparing present population genetic variability with inferred geographical range shifts from the LGM to the present, estimated with species distribution modelling (SDM). Projections for contrasting scenarios of future climate change were also developed to anticipate genetic diversity losses at regional scales. Results showed that S. thunbergii harbours strikingly rich genetic diversity and multiple divergent lineages in the centre‐northern range of its distribution, in contrast with a poorer genetically distinct lineage in the southern range. SDM hindcasted refugial persistence in the southern range during the LGM as well as post‐LGM expansion of 18 degrees of latitude northward. Approximate Bayesian computation (ABC) analysis further suggested that the multiple divergent lineages in the centre‐northern range limit stem from post‐LGM colonization from the southern survived lineage. This suggests divergence due to demographic bottlenecks during range expansion and massive genetic diversity loss during post‐LGM contraction in the south. The projected future range of S. thunbergii highlights the threat to unique gene pools that might be lost under global changes.

Background: Chronic exposure to ultraviolet B (UVB) causes a series of adverse skin reactions, such as erythema, sunburn, photoaging, and cancer, by altering signaling pathways related to inflammation, oxidative stress, and DNA damage. Marine algae have abundant amounts and varieties of bioactive compounds that possess antioxidant and anti-inflammatory properties. Thus, the objective of this study was to investigate the photoprotective effects of an ethanol extract of Sargassum thunbergii. Methods: Sargassum thunbergii phenolic-rich extract (STPE) was prepared, and its activity against UVB damage was evaluated using L929 fibroblast cells and zebrafish. STPE was extracted and purified by 40% ethanol and macroporous resin XDA-7. Reactive oxygen species (ROS) and antioxidant markers, such as superoxide dismutase (SOD), catalase (CAT) activities, and malondialdehyde (MDA) content were analyzed. The effect of STPE on UVB-induced inflammation was determined by inflammatory cytokine gene and protein expression. The expression of signaling molecules in the Nuclear Factor KappaB (NF-κB) pathway was determined by western blotting. DNA condensation was analyzed and visualized by Hoechst 33342 staining. In vivo evaluation was performed by tail fin area and ROS measurement using the zebrafish model. Results: The total polyphenol content of STPE was 72%. STPE reduced ROS content in L929 cells, improved SOD and CAT activities, and significantly reduced MDA content, thereby effectively alleviating UVB radiation-induced oxidative damage. STPE inhibited the mRNA and protein expression of TNF-α, IL-6, and IL-1α. STPE reversed DNA condensation at concentrations of 20 and 40 μg/mL compared with the UVB control. Moreover, STPE inhibited NF-κB signaling pathway activation and alleviated DNA agglutination in L929 cells after UVB irradiation. Additionally, 1.67 μg/mL STPE significantly increased the tail fin area in zebrafish, and 0.8–1.6 μg/mL STPE effectively eliminated excessive ROS after UVB radiation. Conclusions: STPE inhibited UVB-induced oxidative stress, inflammatory cytokine expression, and DNA condensation via the downregulation of the NF-κB signaling pathway, suggesting that it prevents UVB-induced photodamage, and has potential for clinical development for skin disease treatment. [ABSTRACT FROM AUTHOR]

Ultraviolet-B (UV-B) radiation is a major environmental stress that suppresses or activates defense responses in organisms. UV-B radiation affecting growth and development in intertidal species have been researched for a long time, but a series of unknown knowledge remain in the male and female macroalgae comparison. To compare the different responses of male and female Sargassum thunbergii macroalgae under UV-B radiation, PSII photochemical efficiency determination, metabolomic analysis, and main carbon-based metabolites (including soluble sugar, total amino acid, and lipid) content measuring have been performed in our experiments. Results showed that males have significantly superiority performance in the chlorophyll fluorescence parameters of Fv/Fm, Y(II), and Y(NO) either low or high UV-B radiation treatments. Metabolomics analysis revealed that carbon and nitrogen metabolism pathways in male and female S. thunbergii were significant components responding to enhanced UV-B radiation. Based on measuring, female S. thunbergii lipid content expressed higher than males without any stimulation. Additionally, under low UV-B radiation stimulation, females total amino acid content shown significantly higher than control group and their lipid content also significantly higher than males. Under high UV-B radiation, males soluble sugar, total amino acid, and lipid content significantly varied from females, which meant that enhancing UV-B stress might altered mainly carbonbased metabolites flowing directions. The present study elucidated the potential role of enhanced UV-B radiation in regulating macroalgae physiological responses, metabolites changing, and reflecting differences between male and female S. thunbergii, contributing to understanding of brown-macroalgae diecious adopting mechanisms in defending intertidal UV-B stresses. [ABSTRACT FROM AUTHOR]

Intraspecific variation in morphology is widespread among seaweed species in different habitats. We examined the morphological variation in Sargassum thunbergii involving diverse environmental factors. We quantified 16 morphological characteristics on 15 rocky intertidal shores in Korea. A cluster analysis based on morphology identified three groups. Group M1 comprised populations on the northern part of the east coast, where the thalli was short and thick, with large leaf and air-vesicle. Group M3 consisted of populations on the west coast exclusively separated from other populations, with short, slender and sparsely branched thalli. Group M2 comprised populations on the southern part of the east coast and on the south coast (including Jeju Island), with longest thalli and lateral branches. Principal coordinate analyses showed that group M1 and M3 were mostly influenced by strong wave action and large tidal amplitudes, respectively. Group M2 were under the influence of warm temperatures and high irradiance. Biota-environment matching analysis showed that the morphology is affected by combinations of different local environmental factors and also that tidal condition is important as a single variable, suggesting that morphology of S. thunbergii reflects and adapts to local environmental conditions. [ABSTRACT FROM AUTHOR]

Two important brown algae, Sargassum horneri and Sargassum thunbergii are widely distributed along the coastal line of China. In this study, antioxidant, angiotensin-converting enzyme (ACE) inhibitory effects, and anticoagulant activities of the methanol extracts of S. horneri and S. thunbergii were investigated and compared. Total phenolic compounds and the fucoxanthin content were determined by the spectrophotometric and HPLC analyses, respectively, to relate phytochemical content to bioactivities of two Sargassum species. The phenolic compounds of S. horneri and S. thunbergii were also analyzed by LC-MS/MS. The results showed that S. horneri displayed higher antioxidant activities compared to S. thunbergii in all antioxidant bioassays evaluated, except the DPPH radical scavenging assay. Moreover, S. horneri showed a stronger ACE inhibitory effect (IC50 = 0.44 mg/mL) compared to S. thunbergii (IC50 = 1.81 mg/mL). Both S. horneri and S. thunbergii significantly prolonged the activated partial thromboplastin time (APTT) in blood plasma, and the APTT-prolonging effect of S. horneri was stronger than that of S. thunbergii. Salicylic acid was identified as the main phenolic compound in S. horneri, followed by m-coumaric acid, ferulic acid, and p-coumaric acid. Furthermore, S. thunbergii contained carnosic acid and salicylic acid. The total phenolic and fucoxanthin contents are positively correlated with antioxidant, ACE inhibitory and anticoagulant activities. These results indicated that S. horneri and S. thunbergii can be used as natural sources of functional foods because of their abundant bioactive compounds. [ABSTRACT FROM AUTHOR]

Glaciation‐induced environmental changes during the last glacial maximum (LGM) have strongly influenced species' distributions and genetic diversity patterns in the northern high latitudes. However, these effects have seldom been assessed on sessile species in the Northwest Pacific. Herein, we chose the brown alga Sargassum thunbergii to test this hypothesis, by comparing present population genetic variability with inferred geographical range shifts from the LGM to the present, estimated with species distribution modelling (SDM). Projections for contrasting scenarios of future climate change were also developed to anticipate genetic diversity losses at regional scales. Results showed that S. thunbergii harbours strikingly rich genetic diversity and multiple divergent lineages in the centre‐northern range of its distribution, in contrast with a poorer genetically distinct lineage in the southern range. SDM hindcasted refugial persistence in the southern range during the LGM as well as post‐LGM expansion of 18 degrees of latitude northward. Approximate Bayesian computation (ABC) analysis further suggested that the multiple divergent lineages in the centre‐northern range limit stem from post‐LGM colonization from the southern survived lineage. This suggests divergence due to demographic bottlenecks during range expansion and massive genetic diversity loss during post‐LGM contraction in the south. The projected future range of S. thunbergii highlights the threat to unique gene pools that might be lost under global changes. [ABSTRACT FROM AUTHOR]

Sargassum thunbergii (Mertens ex Roth) Kuntze (ST) is a brown alga rich in indole-2-carboxaldehyde. This study aimed to investigate the anti-obesity effects of ethanol extract from ST in in vitro and in vivo models. In 3T3-L1 cells, ST extract significantly inhibited lipid accumulation in mature adipocytes while lowering adipogenic genes (C/epba and Pparg) and enhancing metabolic sensors (Ampk, Sirt1), thermogenic genes (Pgc-1a, Ucp1), and proteins (p-AMPK/AMPK and UCP1). During animal investigation, mice were administered a chow diet, a high-fat diet (HF), or an HF diet supplemented with ST extract (at dosages of 150 and 300 mg/kg bw per day) for 8 weeks (n = 10/group). ST extract administration decreased weight gain, white adipose tissue weight, LDL-cholesterol, and serum leptin levels while improving glucose intolerance. In addition, ST extract increased the expression of Ampk and Sirt1 in adipose tissue and in the liver, as well as p-AMPK/AMPK ratio in the liver, compared to HF-fed mice. The abundance of Bacteroides vulgatus and Faecalibacterium prausnitzii in the feces increased in response to ST extract administration, although levels of Romboutsia ilealis decreased compared with those in HF-fed mice. ST extract could prevent obesity in HF-fed mice via the modulation of AMPK activation and gut microbiota composition.

Intraspecific variation in morphology is widespread among seaweed species in different habitats. We examined the morphological variation in Sargassum thunbergii involving diverse environmental factors. We quantified 16 morphological characteristics on 15 rocky intertidal shores in Korea. A cluster analysis based on morphology identified three groups. Group M1 comprised populations on the northern part of the east coast, where the thalli was short and thick, with large leaf and air-vesicle. Group M3 consisted of populations on the west coast exclusively separated from other populations, with short, slender and sparsely branched thalli. Group M2 comprised populations on the southern part of the east coast and on the south coast (including Jeju Island), with longest thalli and lateral branches. Principal coordinate analyses showed that group M1 and M3 were mostly influenced by strong wave action and large tidal amplitudes, respectively. Group M2 were under the influence of warm temperatures and high irradiance. Biota-environment matching analysis showed that the morphology is affected by combinations of different local environmental factors and also that tidal condition is important as a single variable, suggesting that morphology of S. thunbergii reflects and adapts to local environmental conditions.

Endophytic bacteria have a complex coevolutionary relationship with their host macroalgae. Dioecious macroalgae are important producers in marine ecosystems, but there is still a lack of research on how sex influences their endophytic bacteria. In this study, the endophytic bacterial communities in male and female S. thunbergii and their reproductive tissues (receptacles) were compared using culture methods and high-throughput sequencing. The endophytic bacterial communities detected by the two methods were different. Among the 78 isolated strains, the dominant phylum, genus, and species were Bacillota , Alkalihalobacillus , and Alkalihalobacillus algicola , respectively, in the algal bodies, while in the receptacles, they were Bacillota , Vibrio , and Vibrio alginolyticus . However, 24 phyla and 349 genera of endophytic bacteria were identified by high-throughput sequencing, and the dominant phylum and genus were Pseudomonadota and Sva0996_ Marine_ Group , respectively, in both the algal body and the receptacles. The two methods showed similar compositions of endophytic bacterial communities between the samples of different sexes, but the relative abundances of dominant and specific taxa were different. The high-throughput sequencing results showed more clearly that the sex of the host alga had an effect on its endophyte community assembly and a greater effect on the endophytic bacterial community in the receptacles. Moreover, most specific bacteria and predicted functional genes that differed between the samples from the males and females were related to metabolism, suggesting that metabolic differences are the main causes of sex differences in the endophytic bacterial community. Our research is the first to show that host sex contributes to the composition of endophytic bacterial communities in dioecious marine macroalgae. The results enrich the database of endophytic bacteria of dioecious marine macroalgae and pave the way for better understanding the assembly mechanism of the endophytic bacterial community of algae., Competing Interests: TS was employed by Qingdao Branch CCCC Water Transportation Consultants Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Zhao, Sun, Li, Yang, Chen, Wang, Yu, Tang and Xiao.)

Fucoidan has been reported to have various biological activities, such as antioxidant, antitumor and anticoagulant, with various health benefits. However, few studies have been conducted to extract fucoidan from Sargassum thunbergii in terms of its immuno-enhancing activities. This aim of this study was to investigate the immuno-enhancing effect of fucoidan (S3) isolated from Sargassum thunbergii through water extraction and ethanol precipitation in RAW 264.7 macrophages and zebrafish. The results showed that S3 contained a relatively high content of fucose and sulfated polysaccharide. Fourier-transform infrared spectroscopy (FTIR) results show that the characteristic peaks at 845 cm−1 and 1220-1270 cm−1 indicate that S3 contains sulfate groups. In vitro , S3 effectively enhanced nitric oxide (NO) production and phagocytic activity. In addition, the results of the study demonstrated that the secretion of tumor necrosis factor-α, interleukin (IL)-6, IL-1β, and IL-10 was upregulated by nuclear factor kappa B (NF-κB) signaling pathway in a dose-dependent manner. In vivo , S3 activates zebrafish immune responses by promoting secretion of NO and activating the NF-κB pathway. Overall, these results suggest that S3 could be used as a functional ingredient added to nutritional supplements and functional foods. • Fucoidan was obtained by water extraction and ethanol precipitation (S3). • S3 activates the NF-ĸB signaling pathway both in vitro and in vivo. • S3 increases macrophage phagocytosis and the levels of immunomodulatory mediators. [ABSTRACT FROM AUTHOR]

The protective effect of sulfated polysaccharides (PS-4) isolated from Sargassum thunbergii against oxidative stress in cells and zebrafish was investigated. To begin, a variety of enzymatic extraction methods were used, including five carbohydrases and four proteases. Among the enzymatic extracts, the S. thunbergii Celluclast-assisted extract (STC) demonstrated the strongest scavenging activities against hydrogen peroxide (H 2 O 2). Five polysaccharide fraction (PS-1 to 5) were isolated from STC and purified using ion exchange column chromatography. The antioxidant activity of these fractions was then assessed. PS-4 demonstrated the most promising free radical scavenging and antioxidant activity. PS-4 had a higher content of sulfated polysaccharide than STC. Thus, increasing the proportion of sulfated polysaccharides may be attributed to protection against H 2 O 2 -mediated cell damage and oxidative stress in cell lines and in zebrafish. These results suggest that PS-4 could be a potent antioxidant agent in functional foods and cosmetics. • This study was designed to assess in vitro and in vivo antioxidant effect of PS-4. • PS-4 exhibited antioxidant effect activities in H 2 O 2 -induced zebrafish model. • PS-4 has a protective effect against H 2 O 2 -induced oxidative stress. [ABSTRACT FROM AUTHOR]

Seo, J.O.; Park, H.S., and Kim, N.G., 2023. Effects of temperature, photo irradiance and photoperiods on the early growth of Sargassum thunbergii. In: Lee, J.L.; Lee, H.; Min, B.I.; Chang, J.-I.; Cho, G.T.; Yoon, J.-S., and Lee, J. (eds.), Multidisciplinary Approaches to Coastal and Marine Management. Journal of Coastal Research, Special Issue No. 116, pp. 563-567. Charlotte (North Carolina), ISSN 0749-0208. This study investigated the effects of temperature and light on the germination rate and growth of embryos obtained from mature Sargassum thunbergii, and early embryo development. The Sargassum thunbergii used in the experiment was collected in June 2022 from the Tongyeong coast, Gyeongnam, Korea. The released embryos were cultured at 10-25°C, a light intensity of 40 and 80 µmol m-2s-1, and a 14L:10D photoperiod (light: dark). The rhizome development and elongation of the germinated Sargassum thunbergii thallus occurred at weeks 1 to 3 of culture. Serrated secondary leaves formed in week 4 of culture, and fourth leaves formed in 5 weeks. At 6–10 weeks, many scale-like leaves developed. The germination rate of Sargassum thunbergii embryos was maximal at 25°C and 80 µmol m-2s-1 and lowest at 10°C and 40 µmol m-2s-1. The growth characteristics of the germinated thallus of this species differed more depending on the temperature, which makes Sargassum thunbergii a photophilic eurythermal seaweed that grows well under large temperature variation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Both algal tissue location and sex impact epiphytic bacterial community construction. • Tissue location contributes more than sex to epiphytic bacterial community assembly. • Contribution of sex to epiphytic bacterial community assembly varies in each tissue. The formation of epiphytic bacterial communities on macroalgae is closely related to host identity, but the effects of tissue location and sex of the host alga on this process, especially the relative contributions of these two factors, have not been studied. Here, the epiphytic bacterial community on three different tissues (tip, receptacle and holdfast) of male and female Sargassum thunbergii in the intertidal zone of Qingdao was investigated using high-throughput sequencing, and the results revealed obvious tissue and sex specificity of the epiphytic bacteria and significant differences from seawater bacterial samples. The biodiversity indexes, specific bacteria, biomarkers, indicator taxa and predicted function of epiphytic bacteria differed significantly among tissues of S. thunbergii and between sexes for the same tissue, confirming that both algal tissue location and sex impacted epiphytic bacterial community assembly on S. thunbergii. Additionally, β-diversity analysis showed that tissue location contributed more than host sex to epiphytic bacterial community structure, and the contributions of these two factors varied among tissues. Sex contributed less to epiphytic bacteria on the holdfast than on the tip and receptacle. Furthermore, the tissue and sex specificity of epiphytic bacteria on S. thunbergii were likely related mainly to host metabolism but also to the interaction between bacteria and algae and adaptability to the environment. This study shed light on the drivers of macroalga-associated bacterial community structure and broaden our understanding of the relationship between macroalgae and their epiphytic bacteria. [ABSTRACT FROM AUTHOR]

The impact of human activities on global climate change has led to the intensification of multiple environmental stresses on intertidal zone macroalgae, which are crucial primary producers in marine ecosystems. Despite their economic and ecological importance, research on the differential response mechanism of male and female macroalgae has been limited to gender differentiation. This study investigated gender differences in carbon and nitrogen metabolism of male and female Sargassum thunbergii based on metabolomic and physiological experiments. Carbon and nitrogen metabolism, as the most essential processes of macroalgae, coupled with basic metabolites transporting and energy supplying for macroalgal growth and development. The results revealed that female macroalgae exhibited higher activity in the carbon metabolic pathway, with fixed carbon being more inclined towards allocation to lipid synthesis and the TCA cycle. The overrepresentation of the TCA cycle and lipid synthesis metabolism made the female S. thunbergii store a large amount of energy, which consequently assured them to complete the reproductive stages. Conversely, the male macroalgae were more active in nitrogen metabolic pathways, such as nitrogen fixation and glutamate metabolism, which contribute to the growth and development of the macroalgae and increase resistance to the external environment. These dichotomous strategies likely exemplify distinct reproductive adaptations, where females focus on reproductive investment and males prioritize personal vigor and adaptation to external pressures. These findings provide new insights into gender differences in physiological characteristics and carbon and nitrogen metabolism processes of macroalgae, and contribute to the study of differential response mechanisms of male and female macroalgae in adaptation to intertidal environments, energy and material allocation mechanisms. • Material allocation differed in diecious S. thunbergii. • Female macroalgae stored lipid during reproduction versus to the male prioritized resilience. • Male macroalgae prioritize growth, development, and resilience. [ABSTRACT FROM AUTHOR]

Halosmysin A, a new 14-membered macrodiolide with an unprecedented skeleton, was isolated from the fungus Halosphaeriaceae sp. OUPS-135D-4, which, in turn, was obtained from the marine algae Sargassum thunbergii. The chemical structure of the macrodiolide was elucidated using 1D and 2D NMR, as well as high resolution fast atom bombardment mass (HRFABMS) spectral analysis. The absolute stereochemistry was determined via chemical derivatization and comparison with a known compound, (6R,11R,12R,14R)-colletodiol. Additionally, halosmysin A was shown to be very potent against murine P388 leukemia, human HL-60 leukemia, and murine L1210 leukemia cell lines, with IC50 values ranging from 2.2 ± 3.1 to 11.7 ± 2.8 μM.

Heavy metal pollution in aquatic system is becoming a serious problem worldwide. In this study, responses of Sargassum thunbergii to different concentrations (0, 0.1, 0.5, 1.0 and 5.0 mg/L) of zinc (Zn) and cadmium (Cd) exposure separately were studied for 15 days in laboratory-controlled conditions. The results show that the specific growth rates increased slightly under the lower Zn concentration treatment (0.1 mg/L) at the first 5 d and then decreased gradually, which were significantly reduced with the exposure time in higher Zn concentrations and all Cd treatments compared to respective control, especially for 1.0 and 5.0 mg/L Cd. Chlorophyll a contents showed significant increase in 0.1 mg/L Zn treatment, whereas the gradually reduction were observed in the other three Zn treatments and all Cd treatments. The oxygen evolution rate and respiration rate presented distinct behavior in the Zn-treated samples, but both declined steadily with the exposure time in Cd treatments. The P/R value analyses showed similar variation patterns as chlorophyll a contents. Real-time PCR showed that lower Zn concentration (0.1 mg/L) increased mRNA expression of rbcL gene, whereas higher Zn concentrations and Cd reduced the rbcL expression. Taken together, these findings strongly indicate that Zn and Cd had different effects on S. thunbergii both at the physiological and gene transcription levels, the transcript level of photosynthesis-related gene rbcL can be used as an useful molecular marker of algal growth and environment impacts. [ABSTRACT FROM AUTHOR]

Polysaccharide (ST) was prepared from Sargassum thunbergii using hot water. Two fractions (ST-1 and ST-2) were prepared using anion exchange chromatography. One desulfated polysaccharide (ST-1-DS) was also prepared. Electrospray ionization mass spectrometry (ESI–MS) performed on ST-1-DS showed that the desulfated polysaccharides contained methyl glycosides of mono-sulfated and di-sulfated galacto-fucooligosaccharides. This result suggested that ST-1 might contain sulfated galactofucan, which consists of a backbone of alternating (Gal) n and (Fuc) n and sulfated randomly on Gal and mainly on C-2 in Fuc. In addition, ST-1 was degraded in 1 M sulfuric acid. The solution was centrifuged, and the supernatant was concentrated and precipitated in ethanol to obtain the precipitate (ST-1-P). ST-1-P was then separated using gel chromatography and anion exchange chromatography to obtain the oligomers. ESI–MS spectra of oligomers indicated that ST-1 mostly contained sulfated glucuronomannan and fucoglucuronan. ESI–MS with collision-induced dissociation tandem mass spectrometry (ESI-CID-MS/MS) suggested that glucuronomannan contained alternating 2-linked Man and 4-linked GlcA, while fucoglucuronan contained 4-linked glucuronan with branched Fuc at C-3. Finally, the neuroprotective activities of ST, ST-1, ST-2 and MIX (a mixture of ST-1 and ST-2) were determined. ST showed the most neuroprotective activity, which indicated that ST might be a good candidate for curing neurodegenerative diseases. [ABSTRACT FROM AUTHOR]

Background: Long-term survival in isolated marginal seas of the China coast during the late Pleistocene ice ages is widely believed to be an important historical factor contributing to population genetic structure in coastal marine species. Whether or not contemporary factors (e.g. long-distance dispersal via coastal currents) continue to shape diversity gradients in marine organisms with high dispersal capability remains poorly understood. Our aim was to explore how historical and contemporary factors influenced the genetic diversity and distribution of the brown alga Sargassum thunbergii, which can drift on surface water, leading to longdistance dispersal. Results: We used 11 microsatellites and the plastid RuBisCo spacer to evaluate the genetic diversity of 22 Sargassum thunbergii populations sampled along the China coast. Population structure and differentiation was inferred based on genotype clustering and pairwise FST and allele-frequency analyses. Integrated genetic analyses revealed two genetic clusters in S. thunbergii that dominated in the Yellow-Bohai Sea (YBS) and East China Sea (ECS) respectively. Higher levels of genetic diversity and variation were detected among populations in the YBS than in the ECS. Bayesian coalescent theory was used to estimate contemporary and historical gene flow. High levels of contemporary gene flow were detected from the YBS (north) to the ECS (south), whereas low levels of historical gene flow occurred between the two regions. Conclusions: Our results suggest that the deep genetic divergence in S. thunbergii along the China coast may result from long-term geographic isolation during glacial periods. The dispersal of S. thunbergii driven by coastal currents may facilitate the admixture between southern and northern regimes. Our findings exemplify how both historical and contemporary forces are needed to understand phylogeographical patterns in coastal marine species with long-distance dispersal. [ABSTRACT FROM AUTHOR]

Monthly variations of polysaccharides from Sargassum thunbergii and their anti-complement and anti-tumour activities were investigated. It was observed that an increase in fucose and total sugar contents occurred during the growth period (from early April to mid-June), accompanied by a decrease in molar ratios of other monosaccharides to fucose. The highest yields were obtained from early July to early September, which was in accordance with the significant increase in molar ratio of glucose to fucose and decrease in molar ratio of other monosaccharides to fucose. And the above results suggested that S. Thunbergii synthesized large amount of laminaran, the storage substance of brown algae, during the senescence period. However, sulfate contents were relatively stable in the life cycle of S. thunbergii . These results suggested that S. thunbergii synthesized complex sulfated heteropolysacchairdes during inactive period, while during other periods, it synthesized more sulfated galactofucan. All polysaccharides showed anti-complement activity, suggesting that the harvesting time did not influence the anti-complement activities. In the anti-tumour assay in vitro , the polysaccharides taken during the senescence period had much lower anti-tumour activity, suggesting that fucoidan, but not laminaran, determined the anti-tumour activities. Therefore, polysaccharides from S. thunbergii might have great potential in anti-complement and anti-tumour application. [ABSTRACT FROM AUTHOR]

Polysaccharides derived from Sargassum thunbergii were prepared to investigate the structure-activity relationship between polysaccharides and anti-tumor activity in vitro . Many factors were examined. Overall, STW (polysaccharide extracted by hot water) had the best activity, followed by STJ (polysaccharide extracted by dilute alkali), and then STA (polysaccharide extracted by dilute acid). Location of algae had no effect at 500 μg/mL and 1000 μg/mL, while STW-QD (algae collected from Qingdao, China) had the best activity, followed by STW-WZ (algae collected from Wenzhou, China) and STW-LJ (algae collected from Lianjiang, China) and then STW-DL (algae collected from Dalian, China) and STW-RC (algae collected from Rongcheng, China) at 250 μg/mL. Moreover, molecular weight had no effect at 1000 μg/mL, while higher molecular weights were associated with better activities at 250 μg/mL and 500 μg/mL. Sulfate content had no effect at 1000 μg/mL, while anti-tumor activities decreased accompanying with the changes of sulfate content. Uronic acid content was an important factor influencing activity. The fractions of STW showed little anti-tumor activity; however, the mixture of the fractions of STW showed approximately 60% inhibition. Overall, these findings suggested that the anti-tumor activity of polysaccharides required multilateral cooperation and that some of the effective components were lost. [ABSTRACT FROM AUTHOR]

This study aimed to determine the chemical composition and physical characteristics of the step gradient ethanol precipitates of celluclast-assisted hydrolysate from Sargassum thunbergii (STCFs). Crude polysaccharides were obtained via step gradient ethanol precipitation using celluclast-assisted hydrolysate from Sargassum thunbergii (STC). The yields of STCFs were STCF1 3.78 ± 0.01 %, STCF2 1.13 ± 0.06 %, and STCF3 0.17 ± 0.05 %. Polysaccharide and sulfate contents significantly increased in STCF1 and STCF2 but decreased in STCF3. Their physical characteristics were determined via Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), multi angle light scattering (MALS), and mass spectrometry (MS). FTIR showed that STCF1 and STCF2 have specific S O, C-O-S bonds in sulfate, while STCF3 has a specific C O bond in glucan. Purified STCF1 and STCF3 have similar MS patterns and structural characteristics (fucose containing galactan and gluco-oligosaccharide, respectively). MALS and SEM showed that STCF1 has a significantly larger average molecular weight and surface particles but those of STCF3 were significantly decreased. Overall, step gradient ethanol precipitation significantly altered several molecular characteristics and may contribute to S. thunbergii polysaccharide bioactivities. • Fractional ethanol precipitates (STCF1, STCF2 STCF3) in STC possessed free radical scavenging activity. • Physical characters were changed during step gradient alcohol precipitation, Especially, the averaged molecular weight was decreased in STCF3 • STCF1 and STCF2 contained high levels of sulfate, fucose and galactose contents and Mass results indicate that STCF1 and STCF2 showed similar characters of galactan. • STCF3 contained high glucose content and Mass results indicate that STCF3 showed gluco-oligosaccharide [ABSTRACT FROM AUTHOR]

Glucose degradation is aberrantly increased in hyperglycemia, which causes various harmful effects on the liver. Glyoxalase-1 (Glo-1) is a ubiquitous cellular enzyme that participates in the detoxification of methylglyoxal (MGO), a cytotoxic byproduct of glycolysis that induces protein modification (advanced glycation end-products, AGEs) and inflammation. Here, we investigated the anti-inflammatory effect of indole-4-carboxaldehyde (ST-I4C), which was isolated from the edible seaweed Sargassum thunbergii, on MGO-induced inflammation in HepG2 cells, a human hepatocyte cell line. ST-I4C attenuated the MGO-induced expression of inflammatory-related genes, such as tumor necrosis factor (TNF)-α and IFN-γ by activating nuclear factor-kappa B (NF-κB) without toxicity in HepG2 cells. In addition, ST-I4C reduced the MGO-induced AGE formation and the expression of the receptor for AGE (RAGE). Interestingly, both the mRNA and protein expression levels of Glo-1 increased following ST-I4C treatment, and the decrease in Glo-1 mRNA expression caused by MGO exposure was rescued by ST-I4C pretreatment. These results suggest that ST-I4C shows anti-inflammatory activity against MGO-induced inflammation in human hepatocytes by preventing an increase in the pro-inflammatory gene expression and AGE formation. Therefore, it represents a potential therapeutic agent for the prevention of hepatic steatosis.

Sulfated galactofucan (ST-2) was obtained from Sargassum thunbergii. It was then desulfated to obtain ST-2-DS, and autohydrolyzed and precipitated by ethanol to obtain the supernatant (ST-2-S) and precipitate (ST-2-C). ST-2-C was further fractionated by gel chromatography into two fractions, ST-2-H (high molecular weight) and ST-2-L (low molecular weight). Mass spectrometry (MS) of ST-2-DS was performed to elucidate the backbone of ST-2. It was shown that ST-2-DS contained a backbone of alternating galactopyranose residues (Gal)n (n ≤ 3) and fucopyranose residues (Fuc)n. In addition, ST-2-S was also determined by MS to elucidate the branches of ST-2. It was suggested that sulfated fuco-oligomers might be the branches of ST-2. Compared to the NMR spectra of ST-2-H, the spectra of ST-2-L was more recognizable. It was shown that ST-2-L contain a backbone of (Gal)n and (Fuc)n, sulfated mainly at C4 of Fuc, and interspersed with galactose (the linkages were likely to be 1→2 and 1→6). Therefore, ST-2 might contain a backbone of (Gal)n (n ≤ 3) and (Fuc)n. The sulfation pattern was mainly at C4 of fucopyranose and partially at C4 of galactopyranose, and the branches were mainly sulfated fuco-oligomers. Finally, the anti-tumor and anti-angiogenic activities of ST-2 and its derivates were determined. It was shown that the low molecular-weight sulfated galactofucan, with higher fucose content, had better anti-angiogenic and anti-tumor activities.

We report herein the facile fabrication of reduced graphene oxide (RGO) loaded with Fe 3 O 4 nanocomposites (consisting of gauze-like RGO nanosheets and Fe 3 O 4 nanoparticles) through a simple, low-cost and environmental-friendly procedure that employs a brown alga ( Sargassum thunbergii ) as the solely reducing agent. The RGO/Fe 3 O 4 nanocomposites could work as novel catalytic materials with magnetic and photo-Fenton catalytic properties. In the presence of Sargassum thunbergii , the spherical-shaped Fe 3 O 4 nanoparticles with an average diameter of 7 nm have uniformly anchored on the RGO nanosheets. The material has displayed excellent performance in terms of dye degradation (methylene blue, MB), showing a 96% degradation rate of MB after 120 min irradiation under almost neutral pH environment, and room temperature conditions. After the reaction, the RGO/Fe 3 O 4 nanocomposite could be easily separated and recycled due to its excellent ferromagnetism and superior stability. Our study provides a strong validation of RGO/Fe 3 O 4 remarkable capacity toward visible-light-driven degradation of organic contaminates. [ABSTRACT FROM AUTHOR]

The present study evaluates the seasonal photosynthetic performances of Sargassum thunbergii via chlorophyll fluorescence technique. During summer and early winter, no significant change was observed in maximum photochemical efficiency ( F v/ F m), and performance index (PIabs). During late winter and early spring, F v/ F m, and PIabs decreased significantly, implying that S. thunbergii photosystem II (PSII) suffered apparent photoinhibition. Subsequently, PSII gradually recovered during late spring and summer, as evidenced by an increase of both parameters. Throughout the year, the maximum decrease in the slope of MR/MR0 maintained low values indicated that photosystem I (PSI) was incative, the initial rate of P700 + re-reduction maintained low value indicated that cyclic electron transport (CET) were inactive; nevertheless, a seasonal down-regulation of both PSI and CET during late winter and early spring could be detected. The weak performance of PSI and CET can potentially limit the flexibility in response to winter stress and result in a delayed recovery of PSII. In conclusion, the seasonal variability of S. thunbergii photosynthetic activity was characterized by three periods: active state, down-regulation and restoration. The rapid growth during early spring was accompanied by weak photosynthetic performance, indicating that the carbohydrates consumed during this period were derived from previously stored starch. [ABSTRACT FROM AUTHOR]

In the present work, optimization of microwave-assisted extraction of polysaccharides from Sargassum thunbergii was investigated. The physicochemical properties, structural characteristics, and in vitro antioxidant and hypoglycemic activities were determined. The optimal extraction conditions with a yield of 2.84 ± 0.09% for extraction of polysaccharides (STP-1) were extraction time 23 min, microwave power 547 W, extraction temperature 80 °C, and the ratio of raw material to water 1:27 g/mL. STP-1 contained 32.7% of total carbohydrate, 1.86% of protein, and 15.2% of sulfates. STP-1 had a major molecular weight of 190.4 kDa, and comprised of arabinose, galactose, glucose, xylose, mannose, galacturonic acid, and glucuronic acid with molar percentages of 1.94, 30.7, 4.54, 23.2, 17.6, 8.11, and 13.9%, respectively. In addition, STP-1 showed strong antioxidant and α-glucosidase inhibitory activities, and could improve the glucose uptake in insulin-resistant HepG2 cells, suggesting that STP-1 can be exploited as a promising natural antioxidant and hypoglycemic agent. [ABSTRACT FROM AUTHOR]

Seaweed, a popular and abundant food ingredient mainly consumed in Asian countries, is a good source of bioactive compounds with anti-obesity effects. However, the anti-obesity effects of Sargassum thunbergii have not yet been established. In this study, we isolated six indole derivatives (STCs)—indole-2-carboxaldehyde (STC-1), indole-3-carboxaldehyde (STC-2), indole-4-carboxaldehyde (STC-3), indole-5-carboxaldehyde (STC-4), indole-6-carboxaldehyde (STC-5), and indole-7-carboxaldehyde (STC-6)—from S. thunbergii and evaluated their inhibitory effects on adipocyte differentiation in 3T3-L1 cells. We found that STC-1 and STC-5 resulted in non-toxic inhibition of the differentiation of 3T3-L1 adipocytes and thus selected these compounds for further study. STC-1 and STC-5 significantly inhibited lipid accumulation and downregulated the expression of peroxisome proliferator-activated receptor-γ (PPARγ), CCAAT/enhancer-binding protein (C/EBPα), and sterol regulatory element-binding protein 1c (SREBP-1c) in a dose-dependent manner. The specific mechanism mediating the effects of STC-1 and STC-5 was shown to be AMP-activated protein kinase (AMPK) activation. Our results demonstrated the inhibitory effect of STC-1 and STC-5 on adipogenesis through the activation of the AMPK signal pathway. Together, these findings suggested that STC-1 and STC-5 may be effective candidates for the prevention of obesity or obesity-related diseases. [ABSTRACT FROM AUTHOR]

The objective of this study was to isolate fucoxanthin from Sargassum thunbergii and develop microcapsules with palm stearin as the solid lipid core for stability and efficient oral delivery of fucoxanthin. The microcapsules had smooth surfaces with the volume weighted mean diameter ( d ) of 19.19 μm. Encapsulation efficiency and loading capacity of microcapsules with fucoxanthin were 98.3% and 0.04%, respectively. Moreover, the fucoxanthin in microcapsules presented higher stability than free fucoxanthin against light, humidity and temperature. Especially, the retention rates of fucoxanthin encapsulated in microcapsules reached 97.20% at 4°C, 92.60% at 25°C, 92.32% with the relative humidity of 33% and 92.60% in the dark. The cumulative amount of fucoxanthin released from microcapsules was 22.92% in simulated gastric fluid (SGF) and 56.55% in simulated intestinal fluid (SIF). [ABSTRACT FROM AUTHOR]

In this study, we aimed to use different strategies to further uncover the anti-angiogenic molecular mechanism of a fucoidan-like polysaccharide STPC2, isolated from brown alga Sargassum thunbergii. A desulfated derivative, STPC2-DeS, was successfully prepared and identified. The native polysaccharide and desulfated product were subjected to evaluate their anti-angiogenic effects. In the tube formation assay, STPC2 showed dose-dependent inhibition. In addition, STPC2 could distinctly inhibit the permeation of HUVEC cells into the lower chamber. Moreover, a significant reduction of microvessel density was observed in chick chorioallantoic membrane assay treated with STPC2. Meanwhile, STPC2 was found to repress the VEGF-induced neovessel formation in the matrigel plug assay in vivo. However, STPC2-DeS failed to suppress the anti-angiogenic activity via these in vitro and in vivo strategies. In addition, we demonstrated that STPC2 could significantly downregulate the phosphorylation of VEGFR2 and its related downstream Src family kinase, focal adhesion kinase, and AKT kinase. Furthermore, surface plasmon resonance assay revealed that STPC2 bound strongly to VEGF to interfere with VEGF-VEGFR2 interaction. Taken together, these results evidently demonstrated that STPC2 exhibited a potent anti-angiogenic activity through binding to VEGF via sulfated groups to impede VEGF-VEGFR2 interaction, thus affected the downstream signaling molecules. [ABSTRACT FROM AUTHOR]

Aim Oceanic currents are among the most pervasive hydrodynamic features in shaping community dynamics, population connectivity and phylogeographical structure of intertidal species. Here, we test whether population structure and biogeographical gradients of genetic diversity in the brown alga Sargassum thunbergii are correlated with oceanic currents in the north-west Pacific ( NWP). Location North-west Pacific (25.07°N-43.36°N). Methods Nuclear internal transcribed spacer-2 and mitochondrial cox3 sequences were obtained from 835 and 810 individuals of S. thunbergii respectively. Parsimony networks and phylogenetic trees (maximum parsimony and Bayesian inference) were constructed to evaluate phylogeographical structure. Pairwise FST estimates and analyses of molecular variance ( AMOVA) at various hierarchical levels (latitude, longitude, marine provinces, biogeographical basins and zoogeographical zones) were conducted to elucidate population genetic differentiation. migrate software was used to estimate the number of migrants between adjacent populations. Results Several lines of evidence indicate that S. thunbergii is characterized by shallow population structure. Geographical distances do not correlate with population pairwise genetic differentiations. The corridor/stepping-stone model-based coalescent analyses reveal high levels of asymmetric gene flow among S. thunbergii populations, with the numbers of migrants largely corresponding to the directions of oceanic current systems in the NWP. Genetic signatures also indicate that Jeju Island, Korea might act as a transition zone for dispersal of S. thunbergii in the NWP driven by the Kuroshio Current, thus facilitating subsequent transportation northward into the Sea of Japan and the Yellow-Bohai Sea. Main conclusions Population genetic homogeneity in S. thunbergii was mainly structured by oceanic currents rather than palaeoclimatic events. Our study illustrates an important phylogeographical case of how coastal hydrodynamic factors contributed to population connectivity and geographical shifts of genetic diversity for marine organisms without a pelagic stage. [ABSTRACT FROM AUTHOR]

A water-soluble polysaccharide (STPC2) was isolated from the boiling-water extract of Sargassum thunbergii , purified by CaCl 2 precipitation and chromatography on DEAE-cellulose and Sephacryl S-300 column. It was found that STPC2, with a molecular weight of 57 kD, was composed of fucose, xylose, galactose and glucuronic acid, in a ratio of 8.1: 3.8: 2.1: 1.0. Additionally, we found that STPC2 significantly inhibited endothelial cell migration and tube formation without toxicity. Moreover, STPC2 significantly inhibited lung cancer cell A549 migration and proliferation. It was found that STPC2 treatment suppressed MMP-2 gene expression at transcriptional level and enzymatic activity. Furthermore, STPC2 reduced the mRNA and protein expression of vascular endothelial growth factor-A (VEGF-A) and hypoxia-inducible factor (HIF)-1 alpha in the endothelial cells. Taken together, our findings indicated that STPC2 was a potent bioactive polysaccharide with distinct anti-angiogenesis activity against tumor migration via down-regulation of MMP-2 activity and VEGF/HIF-1α signaling pathway. [ABSTRACT FROM AUTHOR]

Although macroalgae are regarded as the emerging fourth category of "blue carbon", few studies are available on the dynamics of dissolved organic carbon (DOC) release. Sargassum thunbergii is a typical intertidal macroalgae; and tidal action usually triggers instantaneous changes in temperature, light and salinity. Therefore, we investigated the mechanism of short-term changes in temperature, light and salinity on DOC release by S. thunbergii. As well as these factors coupled with desiccation, the combined effect of DOC release was revealed. The results showed the DOC release rate of S. thunbergii was from 0.028 to 0.037 mg C g −1(FW) h−1 under different photosynthetically active radiation (PAR, 0–1500 μmol photons m−2 s−1). The DOC release rate of S. thunbergii was from 0.008 to 0.208 mg C g −1(FW) h−1 under different salinity (5–40). The DOC release rate of S. thunbergii was from 0.031 to 0.034 mg C g −1(FW) h−1 under different temperature (10–30 °C). Either the increase in intracellular organic matter concentration due to increased photosynthesis (change in PAR and temperature, active), cell dehydration due to dry-out process (passive) or the decrease in extracellular salt concentration (passive) would lead to an increase in the difference in osmotic pressure and promote DOC release. • A flow-through algal carbon fixation capacity measurement system was designed. • The measuring system has four advantages for carbon flux studies. • Short-term changes in light intensity and salinity can affect DOC release. • The difference in osmotic pressure may be the driving force for DOC release. • This work can provide a reference for the study of carbon sinks in macroalgae. [ABSTRACT FROM AUTHOR]

This study investigated the potential lipid inhibitory and anti-obesity effects of compounds derived from Sargassum thunbergii in vitro and in vivo. We prepared a Celluclast-assisted hydrolysate from Sargassum thunbergii (STC) and three fractional ethanol precipitates (STCF1, STCF2, STCF3). We investigated their proximate composition, and anti-obesity effects in vitro and in vivo. STC and STCFs all significantly reduced intracellular lipid accumulation in PA-treated 3T3-L1 and HepG2 cells. STC, STCF1, and STCF3 had profound anti-obesity effects on high fat diet (HFD)-fed obesity model mice. Oral administration of STC, STCF1, and STCF3 significantly reduced body weight and white adipose tissue (WAT) mass. Furthermore, serum lipid levels were significantly decreased. Additionally, adipose specific hormone levels (adiponectin and fibroblast growth factor-21 (FGF-21)) were significantly decreased, and serum insulin levels were also decreased by STC, STCF1, and STCF3 treatment. A mechanistic study revealed that the adipogenesis and lipolysis associated proteins in epididymal adipose tissue, and free fatty acid oxidation in liver tissues were effectively regulated by STC, STCF1, and STCF3. Overall, our findings show the potent anti-obesity effects of STC, STCF1, and STCF3, achieved by regulation of adipogenesis, lipolysis, and the fatty acid oxidation pathway in HFD-treated obesity model mice. [ABSTRACT FROM AUTHOR]

Two new compounds, asperversin A (1) and 9ξ-O-2(2,3-dimethylbut-3-enyl)brevianamide Q (2), and nine known compounds, brevianamide K (3), brevianamide M (4), aversin (5), 6,8-di-O-methylnidurufin (6), 6,8-di-O-methylaverufin (7), 6-O-methylaverufin (8), 5α,8α-epidioxyergosta-6,22-dien-3β-ol (9), ergosta-7,22-diene-3β,5α,6β-triol (10), and 6β-methoxyergosta-7,22-diene-3β,5α-diol (11), were obtained from the culture of Aspergillus versicolor, an endophytic fungus isolated from the marine brown alga Sargassum thunbergii. The structures of these compounds were established by spectroscopic techniques. Compounds 4, 7 and 8 exhibited antibacterial activities against Escherichia coli and Staphyloccocus aureus, and 7 also showed lethality against brine shrimp (Artemia salina) with an LC50 value of 0.5 μg/mL.

This study aimed to investigate the In vitro lipid inhibitory effects of sulfated polysaccharide fractions derived from fractional ethanol precipitate 1 of Celluclast assisted hydrolysate from Sargassum thunbergii (STCF1-PSs). Three polysaccharide fractions were obtained, and physical characteristics were determined by SEM, FTIR, and MALS analysis. Monosaccharide analysis indicated that STCF1-PS3 contained high fucose and galactose contents. The intracellular lipid inhibitory effects of STCF1-PS3 were evaluated on PA-treated 3T3-L1 and HepG2 cells and was found to be significant. Furthermore, it suppressed intracellular triglyceride and free fatty acid levels in these cells. Western blot analysis showed that the lipid inhibitory activity was achieved through the regulation of the adipogenesis and lipolysis pathway in PA-treated 3T3-L1 cells and the free fatty acid oxidation pathway in PA-treated HepG2 cells. Overall, sulfated polysaccharide from Sargassum thunbergii has a beneficial effect on intracellular lipid metabolism and it could be used as a functional ingredient in functional food industry. [ABSTRACT FROM AUTHOR]