This work was designed to comparatively investigate 27 dietary flavonoids that act as α-glucosidase inhibitors and insulin sensitizers. On the basis of the results of an in vitro experiment of α-glucosidase inhibition, myricetin (IC50 = 11.63 ± 0.36 μM) possessed the strongest inhibitory effect, followed by apigenin-7-O-glucoside (IC50 = 22.80 ± 0.24 μM) and fisetin (IC50 = 46.39 ± 0.34 μM). A three-dimensional quantitative structure–activity relationship model of α-glucosidase inhibitors with good predictive capability [comparative molecular field analysis, q 2 = 0.529, optimum number of components (ONC) = 10, R 2 = 0.996, F = 250.843, standard error of estimation (SEE) = 0.064, and two descriptors; comparative similarity index analysis, q 2 = 0.515, ONC = 10, R 2 = 0.997, F = 348.301, SEE = 0.054, and four descriptors] was established and indicated that meta positions of ring B favored bulky and minor, electron-withdrawing, and hydrogen bond donor groups. The presence of electron-donating and hydrogen bond acceptor groups at position 4′ of ring B could improve α-glucosidase activity. Position 3 of ring C favored minor, electron-donating, and hydrogen bond donor groups, whereas position 7 of ring A favored bulky and hydrogen bond acceptor groups. Molecular docking screened five flavonoids (baicalein, isorhamnetin-3-O-rutinoside, apigenin-7-O-glucoside, kaempferol-7-O-β-glucoside, and cyanidin-3-O-glucoside) that can act as insulin sensitizers and form strong combinations with four key protein targets involved in the insulin signaling pathway. Apigenin-7-O-glucoside (60 μM) can effectively improve insulin resistance, and glucose uptake increased by approximately 73.06% relative to the model group of insulin-resistant HepG2 cells. Therefore, apigenin-7-O-glucoside might serve as the most effective α-glucosidase inhibitor and insulin sensitizer. This work may guide diabetes patients to improve their condition through dietary therapy.

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The present study investigated the phenolic profiles and antioxidant properties of different fractions from Prinsepia utilis Royle fruits using molecular docking analysis to delineate their inhibition toward digestive enzymes. A total of 20 phenolics was identified and quantified. Rutin, quercetin-3-O-glucoside, and isorhamnetin-3-O-rutinoside were the major phenolic compounds in the total phenolic fraction and flavonoid-rich fraction. The anthocyanin-rich fraction mainly contained cyanidin-3-O-glucoside and cyanidin-3-O-rutinoside. All of the fractions exhibited strong radical scavenging activities and good inhibition on cellular reactive oxygen species (ROS) generation in H2O2-induced HepG2 cells, as evaluated by DPPH and 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) assays. Moreover, the powerful inhibitory effects of those fractions against pancreatic lipase and α-glucosidase were observed. The major phenolic compounds that were found in the three fractions also showed good digestive enzyme inhibitory activities in a dose-dependent manner. Molecular docking analysis revealed the underlying inhibition mechanisms of those phenolic standards against digestive enzymes, and the theoretical analysis data were consistent with the experimental results.

The inhibitory effects of 30 dietary flavonoids on dipeptidyl peptidase-IV (DPP-IV) were investigated to illustrate their quantitative structure−activity relationship (QSAR) and further explore their inhibition at the cellular level. Results of in vitro experiment show that isorhamnetin-3-O-glucoside (IC 50 , 6.53 ± 0.280 μM) had the strongest inhibition followed by cyanidin-3-Oglucoside (IC 50 , 8.26 ± 0.143 μM) and isorhamnetin-3-O-rutinoside (IC 50 , 8.57 ± 0.422 μM). A 3D QSAR model [comparative molecular field analysis, q 2 = 0.502, optimum number of components (ONC) = 3, R 2 = 0.983, F = 404.378, standard error of estimation (SEE) = 0.070, and two descriptors; comparative similarity index analysis, q 2 = 0.580, ONC = 10, R 2 = 0.999, F = 1617.594, SEE = 0.022, and four descriptors] indicates that the DPP-IV inhibition of flavonoid was facilitated by crucial structural factors. Position 3 of ring C favored bulky, hydrogen bond acceptors and hydrophilic and electron-donating substituents. The presence of minor and electron-withdrawing groups at position 4′ of ring B and positions 5 and 7 of ring A could improve DPP-IV inhibition. Moreover, the three flavonoids mentioned above could effectively suppress DPP-IV activity and expression in Caco-2 cells. This work may supply new insights into dietary flavonoids as DPP-IV inhibitors for controlling blood glucose.

Five oligochitosans with increasing degrees of polymerization (DPs), i.e., from chitotriose to chitoheptaose, were examined to clarify the structure−bioactivity relationship between the DPs of oligochitosans and their effects on the isoflavone metabolites, total phenolic and flavonoid contents (TPC and TFC, respectively), and antioxidant activity of soybean (Glycine max) seeds during germination. Oligochitosans of different DPs exhibited varying influences on the TPC, TFC, and antioxidant activities of soybean seeds. Chitohexaose exerted a strong effect and significantly increased the aforementioned parameters in soybean seeds 72 h after germination. Genistin, malonylgenistin, and genistein were the main isoflavones found, and the genistin and genistein contents were significantly enhanced by 67.32% and 131.38%, respectively, after chitohexaose treatment. Several critical genes involved in the isoflavone biosynthesis (i.e., PAL, CHS, CHI, IFS) of soybeans treated with and without chitohexaose were analyzed, and results suggested that chitohexaose application could dramatically stimulate the transcription of these genes.

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Acrylamide is a harmful substance that could be inhibited by natural products. Vine tea is an edible herb belonging to the Vitaceae family and has been approved by Chinese authorities as a new food ingredient in 2013. However, the effects of vine tea extract on acrylamide formation and bread quality are rarely investigated. In this study, the polyphenol composition of hot-water extract from vine tea was characterized by ultrahigh-performance liquid chromatography coupled with high-resolution mass spectrometry (UHPLC-ESI-HRMS/MS), and its effects on acrylamide formation, quality, and consumer acceptability of bread were investigated. Vine tea extract and its main polyphenol, dihydromyricetin, significantly inhibited the acrylamide formation in bread, especially the low dose of vine tea extract (1.25 g/kg), which decreased the acrylamide formation by 58.23%. The color and texture of bread were significantly affected by vine tea extract or dihydromyricetin, whereas the moisture content was not changed remarkably. Triangle and paired preference tests indicated that, although the aroma, appearance, and taste of the bread with vine tea extract significantly differ from those of the control bread, vine tea extract did not significantly affect the consumer acceptability. In conclusion, the addition of vine tea extract could be used to develop a new and healthy bread product with low acrylamide content.

The aim of this study was to compare the protective effects of three dietary flavonoids (apigenin-7-O-glucoside (A7G), isorhamnetin-3-O-rutinoside (I3R), and cyanidin-3-O-glucoside (C3G)) on advanced glycation end products (AGEs)-induced inflammation and vascular endothelial dysfunction. Furthermore, the potential mechanisms of varied effects of those three dietary flavonoids were analyzed by molecular docking analysis. Results showed that C3G (40 μM) achieved the best inhibition on inflammatory cytokines (TNF-α, IL-1β, and IL-6) in AGEs-induced RAW264.7 cells, followed by I3R, and A7G was the weakest. The molecular docking results also showed that C3G exhibited the closest binding with the receptor for AGE. However, I3R (40 μM) demonstrated the best effect in improving endothelial dysfunction in AGEs-induced EA.hy926 cells, followed by C3G, and A7G was the weakest, as evidenced by the molecular docking results of flavonoids with profilin-1. This work may provide knowledge and helpful suggestions regarding the benefits of dietary flavonoids in diabetic vascular complications.