Search

Olive leaves are rich in phenolic compounds. This study explored the chemical profiles and contents of free phenolics (FPs) and bound phenolics (BPs) in olive leaves, and further investigated and compared the antioxidant properties of FPs and BPs using chemical assays, cellular antioxidant evaluation systems, and in vivo mouse models. The results showed that FPs and BPs have different phenolic profiles; 24 free and 14 bound phenolics were identified in FPs and BPs, respectively. Higher levels of phenolic acid (i.e., sinapinic acid, 4-coumaric acid, ferulic acid, and caffeic acid) and hydroxytyrosol were detected in the BPs, while flavonoids, triterpenoid acids, and iridoids were more concentrated in the free form. FPs showed a significantly higher total flavonoid content (TFC), total phenolic content (TPC), and chemical antioxidant properties than those of BPs (p < 0.05). Within the range of doses (20–250 μg/mL), both FPs and BPs protected HepG2 cells from H2O2-induced oxidative stress injury, and there was no significant difference in cellular antioxidant activity between FPs and BPs. The in vivo experiments suggested that FP and BP treatment inhibited malondialdehyde (MDA) levels in a D-galactose-induced oxidation model in mice, and significantly increased antioxidant enzyme activity of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT), and the total antioxidant capacity (T-AOC). Mechanistically, FPs and BPs exert their antioxidant activity in distinct ways; FPs ameliorated D-galactose-induced oxidative stress injury partly via the activation of nuclear factor erythroid-2-related factor 2 (Nrf2) signaling pathway, while the BP mechanisms need further study. [ABSTRACT FROM AUTHOR]

Summary: In this work, the release pattern of bound phenolics in salt‐dried bamboo shoots (SDBS), steamed dried bamboo shoots (TDBS), fumigation dried bamboo shoots (UDBS) and fermentation dried bamboo shoots (FDBS) during simulated in vitro digestion was studied. The result exhibited that polyphenols in dried bamboo shoots (DBS) mainly existed in the form of bound phenolics, amongst them the content of FDBS was the highest, followed by SDBS and TDBS, and UDBS was the lowest. In addition, release amounts of bound phenolics in SDBS, TDBS, UDBS and FDBS after gastrointestinal digestion were significantly higher than that after gastric digestion, accounting for 19.61%, 19.40%, 45.64% and 19.66% of the total, respectively. Moreover, IC50 values for scavenging ability of DPPH and ABTS radicals by gastric and gastrointestinal digestion supernatant for DBS were in a descending order: FDBS, UDBS, SDBS and TDBS. Rutin, p‐coumaric and ferulic acid were discovered to be the predominant compounds in digestion supernatant. Trustworthy, fluorescence microscope pictures of DBS at different digestion stages further confirmed the release regularity of bound phenolics. Therefore, these findings could provide a theoretical support for the optimal processing of DBS. [ABSTRACT FROM AUTHOR]

Diet rich in phenolics would potentially associate with multiple health benefits. Response surface methodology (RSM) was introduced to optimize the process of ultrasound- and microwave-assisted extraction of bound phenolics from the bran of a newly developed black wheat breeding line Jizi439 and then compared with the traditional alkaline method. The optimum conditions were found to be 66 °C, 48 min, and power 240 W for ultrasound-assisted extraction (UAE), and 120 s, power 420 W for microwave-assisted extraction (MAE), respectively. Total bound phenolic contents (TBPCs), determined by Folin-Ciocalteu reagent, were 8466.7 ± 240.9 μg gallic acid equivalents per gram (μg GAE/g) bran for UAE and 8340.7 ± 146.7 μg GAE/g bran for MAE under optimized conditions, which were both significantly higher than that of the traditional method (5688.9 ± 179.6 μg GAE/g) (p < 0.05). Antioxidant activities (AAs) were determined by DPPH and ABTS methods. UAE extracts showed the highest DPPH scavenging activity (77.5 ± 0.9%), while MAE extracts showed the highest ABTS scavenging activity (72.1 ± 0.6%). Both were significantly higher than that of the traditional method (69.6 ± 1.1% for DPPH and 65.9 ± 0.5% for ABTS) (p < 0.05). Total bound phenolics (TBPs) profiles were further analyzed by HPLC, and results indicated that ferulic acid was dominant, followed by vanillic acid and p-coumaric acid. The contents of each identified individual phenolics were significantly increased by ultrasound and microwave. In conclusion, UAE and MAE were comparable with each other in TBP yields and AAs; however, when taking operation time and energy consumption into consideration, MAE was more efficient than UAE. Our study suggested efficiency extraction methods for further use of bound phenolics as a healthy food ingredient. [ABSTRACT FROM AUTHOR]

The extraction of ferulic acid (FA) and other phenolic compounds from wheat bran can represent an interesting valorization step of this lignocellulosic biomass. In this work, pressurized hot water (PHW) and pressurized aqueous ethanol are used as solvents, and the amount of extracted FA in its free form and the total phenolic content of the extract have been evaluated. Total ferulic acid in the initial wheat bran was 2570.9 ± 1.8 µg/g of dry bran, being more than 98.5% esterified to arabinoxylans and other cell wall structures (insoluble-bound FA). Different concentrations of ethanol in water (0–20–50–80%), temperatures (130–145–160 °C) and extraction times (20–40–60 min) were tested. It was observed that low ethanol concentrations in the solvent, high temperatures and long extraction times favored the extraction, being the hydrolysis and not the solvolysis the reaction mechanism involved in the release of bound FA. Maximum FA extraction yield was found for pure water (PHW), 160 °C and 74 min of extraction that corresponds to a thermal severity factor of log (R0) ≈ 3.7. The so obtained FA extraction yields are higher than those obtained with an enzymatic hydrolysis treatment performed for comparison. [ABSTRACT FROM AUTHOR]

Bound phenolics are the main phytochemicals and important contributors to the health benefits of whole grains. The commonly used chemical methods for bound phenolic release are not appropriate for processing of food materials. The effects of cellulase and feruloyl esterase on releasing bound phenolics from rice bran dietary fibre (RBDF) and the auxiliary effects of autoclaving pretreatment were investigated in the present study to find a method to effectively increase bioaccessible phenolics in RBDF. The results showed that cellulase (CT) and feruloyl esterase (FT) alone and combined application (CFT) released limited bound phenolics. Autoclaving pretreatment could enhance the release of bound phenolics by enzymatic treatments significantly with 1.74, 5.56 and 1.76 folds increases when compared with the above mentioned enzymolysis, respectively. Moreover, the total quantity of phenolic compounds released from RBDF via combined enzymolysis of cellulase and feruloyl esterase with autoclaving pretreatment (A-CFT) were comparable with that via alkaline hydrolysis previously reported. The predominant phenolic compounds released by A-CFT from RBDF were vanillin and ferulic acid, while ferulic and p -couramic acids accounted for 99.30% of the sum of phenolics released by alkaline hydrolysis. The DPPH scavenging, FRAP and ORAC antioxidant activities of the enzymatic hydrolysates were positive correlated with their total phenolic contents. The phenolics released by A-CFT showed lower antioxidant activity than those by alkaline hydrolysis, which may ascribe to the difference in phenolic profiles between methods. This study provides a new approach for processing whole grain and the by-products for functional foods materials with higher phenolic bioaccessibility. [Display omitted] • Enzymolysis releasesa small part of bound phenolics from rice bran fiber (RBDF). • Autoclaving greatly increases the released bound phenolics via enzymolysis from RBDF. • Phenolics released by enzymolysis are different in composition from alkaline hydrolysis. [ABSTRACT FROM AUTHOR]

The phenolic-profiling of seven different wheat (Triticum aestivum) genotypes was investigated for the first time during different stages of grain development (milky, softy, physiological maturity and mature). Free and bound phenolic compounds were extracted separately and analyzed by UPLC-QTOF-MSE. Total phenolic content significantly decreased, up to 50% depending on the genotype, towards the maturation of grain. The highest content (free and bound) was observed in the most immature grains, while the lowest level was found in mature grains (408.0 and 165.0 GAE mg/100 g, respectively). Globally, 237 phenolic compounds were identified, divided into 5 classes: flavonoids (85), phenolic acids (77), other polyphenols (51), lignans (16) and stilbenes (8). UPLC-MS results showed a progressively decrease of the number of phenolic identification (ID) all along grain development, milky (213), softy (192), physiological maturity (169) and mature (144). The proportion bound to free phenolic progressively increased, reaching the maximum at physiological maturity, indicating a possible enzymatic reactions and complexation during grain growth. Ferulic acid, diphyllin, 4-hydroxybenzoic acid, ferulic acid isomer, apigenin 7-O-apiosyl-glucoside isomer and myricetin isomer were the most abundant compounds. Chemometric tools showed a clear separation between immature and mature grain for all genotypes. Phenolic profile varied significantly among genotypes, this result can help the selection of varieties towards a higher retention of bioactive compounds. Noteworthy, immature wheat grains can be considered a rich source of phenolic compounds and as an attractive ingredient to incorporate to functional foods. Unlabelled Image • Phenolic profile of 7 genotypes of immature and mature wheat was studied by UPLC-MS. • 237 phenolics including isomers were tentatively identified as free and bound forms. • Immature grains presented the highest abundance of phenolics than mature grains. • Phenolic profiles are different among genotypes and during the grain development. • Brazilian wheat showed a rich composition and abundance of phenolic compounds. [ABSTRACT FROM AUTHOR]

[Display omitted] • Co-pigmentation pretreatment protected blackberry anthocyanins during drying. • Ethanol pretreatment with phenolic acids only enhanced water effective diffusivity. • Non-anthocyaninic soluble phenolics were better preserved under contact sonication. • Bound phenolics were less affected by pretreatments and ultrasound-assisted drying. In this work, the spraying of ethanol solution containing phenolic acid (ferulic acid or caffeic acid) was performed before subjecting to contact ultrasound-assisted air drying of blackberry. The mass transfer modeling results revealed that sonication intensified both internal water diffusion and external water exchange during drying, and ethanol pretreatment enhanced the effective diffusivity of water. Compared with air drying alone, the drying time for sequential ferulic acid pretreatment and drying with sonication was shortened by 89.2%. Owing to the co-pigmentation between phenolic acid and anthocyanins, the retention of anthocyanins was significantly enhanced after dehydration. At the end of drying, the total anthocyanin contents in the ultrasound-dried samples pretreated with ferulic acid and caffeic acid were 25.3% and 10.5% higher than the sonicated samples without pretreatments, respectively. Furthermore, drying simultaneously with sonication promoted the preservation of non-anthocyaninic soluble phenolics including catechin, phloretic acid, rutin in blackberry compared to air drying alone. Besides, bound phenolics in blackberry were less influences by the applied dehydration treatments. This study demonstrates that the combination of phenolic acid co-pigmentation pretreatment and ultrasound drying could be a promising method to protect anthocyanin pigments during dehydration of berry fruits. [ABSTRACT FROM AUTHOR]

[Display omitted] • 4 new and 18 known compounds were isolated from brown rice bound phenolic extracts. • Three known phenolic compounds were reported from brown rice for the first time. • The contents of 22 compounds in brown rice, bran and polished rice were determined. • The ORAC, PSC, and CAA antioxidant activity of isolated compounds were measured. Chemical profiles, distribution, and antioxidant activity of bound phenolics from brown rice were investigated. Four new dehydrodiferulic acid dimers (DFA) along with eighteen known phenolics were isolated from brown rice bound phenolic extracts and their structures were determined by multiple spectroscopic methods. Among them, ferulic acid and 8–5′ DFA were the most abundant monomeric and dimeric bound phenolics in brown rice, rice bran and polished rice. In whole brown rice, polished rice contributed more than 50% of three phenolic monomers and six phenolic dimers, while rice bran contributed more than half of the other thirteen phenolics including eight monomers, four dimers, and one trimer. All the isolated compounds exhibited oxygen radical absorbance capacity. Thomasidioic acid, caffeic acid, methyl caffeate, and 8–5′ DC DFA displayed potent peroxyl radical scavenging capacity, and the last three compounds also showed moderate cellular antioxidant activity. [ABSTRACT FROM AUTHOR]

• The majority phenolics in walnut kernel were free phenolics. • Acetone was better to extract soluble phenolics, and methanol for insoluble bound phenolics. • Jeuglone, kaempferol, quercetin-7-o-β- D -glucoside and dihydroquercetin were only found in free phenolics. • There was positive linear correlation between antioxidant activities and total phenolic contents. The free, esterified and bound forms of 37 phenolic compounds (including hydroxybenzoic acid, hydroxycinnamic acids, flavanols, flavonols and flavones) from walnut kernel (Juglans regia L.) were investigated in this study. Results showed that the majority of walnut phenolics were presented in the free form (51.1%–68.1%), followed by bound (21.0%–38.0%) and esterified forms (9.7%–18.7%). Ellagic acid, gallic acid, ferulic acid, sinapic acid and caffeic acid were widely distributed in three forms. Differently, jeuglone, kaempferol, quercetin-7-o-β- d -glucoside and dihydroquercetin were only found in free phenolics. Among the three forms, free phenolics had the highest radical scavenging activity (IC 50 : DPPH, 15.5 µg/ml; ABTS, 13.6 µg/ml). The correlation coefficients between the antioxidant activities of phenolics and their corresponding contents were 0.82–0.92. More soluble phenolics (free and esterified forms) could be extracted by acetone, while methanol was better at extracting insoluble bound phenolics. [ABSTRACT FROM AUTHOR]

Pitahaya peel is a good source of bioactive polyphenols. However, the bound phenolics and their antioxidant activity remain unclear. The bound phenolics of pitahaya peel from two red-skinned species with red pulp (RP) and white pulp (WP) were released with different methods (acid, base, and composite enzymes hydrolysis). The results revealed that base hydrolysis was the most efficient method for releasing the bound phenolics from RP (11.6 mg GAE/g DW) and WP (10.5 mg GAE/g DW), which was 13.04-fold and 8.18-fold for RP and 75.07-fold and 10.94-fold for WP compared with acid hydrolysis and enzymatic hydrolysis, respectively. A total of 37 phenolic compounds were identified by UPLC-TOF/MS with most chlorogenic acid, caffeic acid, ferulic acid and p-coumaric acid in RP, whereas chlorogenic acid, caffeic acid, ferulic acid, rutin and isoquercitrin were the main compounds in WP. Regardless of the hydrolysis method, the extracts having the highest phenolic content showed the strongest antioxidant activities. The work shows that hydrolysis methods have a significant effect on the release of phenolics, and the contents of major characteristic bound phenolic compounds are related to the ecological type of pitahaya. [ABSTRACT FROM AUTHOR]