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Seaweed contains various bioactive compounds rich in pharmacological potentials, such as antioxidants and anti-arthritic. This study aims to determine the antioxidant and anti-arthritic activities of the methanolic extract of Halimeda tuna. Halimeda tuna samples were extracted using the maceration method and methanol. The methanol extract was tested for antioxidant (2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP)) and anti-arthritic activity using denatured bovine serum albumin (BSA). The methanol extract was also subjected to phytochemical and Gas Chromatography-Mass Spectrometry (GC-MS) analysis. Research results revealed that the extract yield was 0.50 ± 0.06%. Phytochemical analysis showed that H. tuna methanolic extract contained flavonoids, steroids, and alkaloids. GC-MS analysis showed that H. tuna methanolic extract contained steroids, fatty alcohols, and fatty acids. The antioxidant activity tests revealed an IC50 value of 299.98 ± 121.15 ppm and a FRAP value of 200.02 ± 8.50 M/g, categorized as a weak antioxidant. Anti-arthritic activity of H. tuna methanolic extract showed an IC50 value of 877.29 ± 209.84 ppm. The anti-arthritic activity of H. tuna methanolic extract was lower than sodium diclofenac as a standard drug. The extract of H. tuna has antioxidant and anti-arthritic activities; hence, further exploration is needed as an alternative potential in the pharmacological field.

Halimeda tuna (J. Ellis & Solander) J.V. Lamouroux is the only Halimeda species found in the Mediterranean Sea, and it is an important habitat former. In the northern Adriatic, H. tuna is among the ten most abundant seaweeds in the upper-infralittoral belt in spring and autumn. The modular thalli consist of serially arranged calcified segments. Calcification is closely related to photosynthesis, which causes alkalinization of the inter-utricular space and triggers aragonite formation. Understanding of the complex patterns of segment shape plasticity in relation to CaCO3 content at different depth levels is still incomplete. Geometric morphometrics was used to investigate H. tuna segment shape variation on the depth transect at Cape Madona Nature Monument in the northern Adriatic Sea. The position on the thallus and the CaCO3 content of each studied segment were recorded, allowing slight changes in mineral content to be detected at the microscale of the segments. Our results showed that shape, size, or asymmetry of H. tuna segments were not significantly affected by depth. On the other hand, plants that grew deeper were generally more calcified. The apical and subapical segments contributed to the increase in CaCO3 content at the deeper sites, whereas the basal segments did not. This indicates that reniform or oval segments positioned apically or subapically play a key role in calcification of H. tuna in Mediterranean ecosystems. [ABSTRACT FROM AUTHOR]

Halimeda tuna (J. Ellis & Solander) J.V. Lamouroux is the only Halimeda species found in the Mediterranean Sea, and it is an important habitat former. In the northern Adriatic, H. tuna is among the ten most abundant seaweeds in the upper-infralittoral belt in spring and autumn. The modular thalli consist of serially arranged calcified segments. Calcification is closely related to photosynthesis, which causes alkalinization of the inter-utricular space and triggers aragonite formation. Understanding of the complex patterns of segment shape plasticity in relation to CaCO3content at different depth levels is still incomplete. Geometric morphometrics was used to investigate H. tuna segment shape variation on the depth transect at Cape Madona Nature Monument in the northern Adriatic Sea. The position on the thallus and the CaCO3 content of each studied segment were recorded, allowing slight changes in mineral content to be detected at the microscale of the segments. Our results showed that shape, size, or asymmetry of H. tuna segments were not significantly affected by depth. On the other hand, plants that grew deeper were generally more calcified. The apical and subapical segments contributed to the increase in CaCO3 content at the deeper sites, whereas the basal segments did not. This indicates that reniform or oval segments positioned apically or subapically play a key role in calcification of H. tuna in Mediterranean ecosystems.

Seaweed belongs to marine biota and contains nutrients and secondary metabolites beneficial for health. This study aimed to determine the antidiabetic activity of extracts and fractions of green seaweed Halimeda tuna. The H. tuna sample was extracted with the maceration method using methanol and then partitioned using ethyl acetate and water to obtain ethyl acetate and water fractions. The methanol extract, ethyl acetate fraction, and water fraction of H. tuna were tested for their inhibitory activity against α-amilase and α-glucosidase. The methanol extract and the fractions with the highest inhibitory activity were phytochemically tested and analyzed using gas chromatography–mass spectrometry (GC-MS). The results showed that the ethyl acetate fraction (IC50 = 0.88 ± 0.20 mg/mL) inhibited α-amylase relatively similar to acarbose (IC50 = 0.76 ± 0.04 mg/mL). The methanol extract (IC50 = 0.05 ± 0.01 mg/mL) and the ethyl acetate fraction (IC50 = 0.01 ± 0.00 mg/mL) demonstrated stronger inhibitory activity against α-glucosidase than acarbose (IC50 = 0.27 ± 0.13 mg/mL). Phytochemical testing showed that the methanol extract and the ethyl acetate fraction contained secondary metabolites: alkaloids, flavonoids, steroids, and phenol hydroquinone. The compounds in methanol extract predicted to have inhibitory activity against α-amylase and α-glucosidase were Docosanol, Neophytadiene, Stigmasta-7,22-dien-3-ol,acetate,(3.beta.,5.alpha.,22E), Octadecanoic acid,2-oxo-,methyl ester, and phytol, while those in the ethyl acetate fraction were n-Nonadecane, Phytol, Butyl ester, 14-.Beta.-H-pregna, Octadecenoic acid, and Oleic acid. [ABSTRACT FROM AUTHOR]

Calcifying green algae of the genus Halimeda J.V. Lamouroux are typical for the modular thalli composed of serial segments. Their CaCO3 content gradually increases with age due to calcification, the intensity of which is largely linked to photosynthesis. The dynamics of segment phenotypic plasticity at different scales and its relation to CaCO3 content is not well known. We investigated the populations of Halimeda tuna in the upper sublittoral of four regions on the Adriatic Sea coast. Using geometric morphometrics, we explored the patterns of segment shape plasticity, their relationships with the spatial factors and CaCO3 content. The results showed that segment position on thalli was the main determinant of their shape features. This effect was considerably more prominent than the differences among plants, populations, or regions. Likewise, the segment shape proved to be a significant predictor of their CaCO3 content. Segments with inversely conical shapes, typical for the lower parts of branches, contained significantly less CaCO3 than the reniform and oval segments that probably contribute most to the overall carbonate budget of the Mediterranean Halimeda draperies. [ABSTRACT FROM AUTHOR]

Seaweed belongs to marine biota and contains nutrients and secondary metabolites beneficial for health. This study aimed to determine the antidiabetic activity of extracts and fractions of green seaweed Halimeda tuna. The H. tuna sample was extracted with the maceration method using methanol and then partitioned using ethyl acetate and water to obtain ethyl acetate and water fractions. The methanol extract, ethyl acetate fraction, and water fraction of H. tuna were tested for their inhibitory activity against α-amilase and α-glucosidase. The methanol extract and the fractions with the highest inhibitory activity were phytochemically tested and analyzed using gas chromatography–mass spectrometry (GC-MS). The results showed that the ethyl acetate fraction (IC50 = 0.88 ± 0.20 mg/mL) inhibited α-amylase relatively similar to acarbose (IC50 = 0.76 ± 0.04 mg/mL). The methanol extract (IC50 = 0.05 ± 0.01 mg/mL) and the ethyl acetate fraction (IC50 = 0.01 ± 0.00 mg/mL) demonstrated stronger inhibitory activity against α-glucosidase than acarbose (IC50 = 0.27 ± 0.13 mg/mL). Phytochemical testing showed that the methanol extract and the ethyl acetate fraction contained secondary metabolites: alkaloids, flavonoids, steroids, and phenol hydroquinone. The compounds in methanol extract predicted to have inhibitory activity against α-amylase and α-glucosidase were Docosanol, Neophytadiene, Stigmasta-7,22-dien-3-ol,acetate,(3.beta.,5.alpha.,22E), Octadecanoic acid,2-oxo-,methyl ester, and phytol, while those in the ethyl acetate fraction were n-Nonadecane, Phytol, Butyl ester, 14-.Beta.-H-pregna, Octadecenoic acid, and Oleic acid.