Effects of Different Dietary Flavonoids on Dipeptidyl Peptidase-IV Activity and Expression: Insights into Structure-Activity Relationship.

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 (IC50, 6.53 ± 0.280 µM) had the strongest inhibition followed by cyanidin-3-O-glucoside (IC50, 8.26 ± 0.143 µM) and isorhamnetin-3-O-rutinoside (IC50, 8.57 ± 0.422 µM). A 3D QSAR model [comparative molecular field analysis, q2 = 0.502, optimum number of components (ONC) = 3, R2 = 0.983, F = 404.378, standard error of estimation (SEE) = 0.070, and two descriptors; comparative similarity index analysis, q2 = 0.580, ONC = 10, R2 = 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.

Antitumor effect and molecular mechanism of antioxidant polysaccharides from Salvia miltiorrhiza Bunge in human colorectal carcinoma LoVo cells.

Salvia miltiorrhiza Bunge polysaccharides (SMP) was comprehensively investigated in this study. The polysaccharides were extracted by the method of water boiling and ethanol precipitation with high purity. The monosaccharide composition of SMP was characterized using the established HPLC-UV protocol with PMP precolumn derivatization, and the results indicate that the polysaccharides are mainly composed of d-galactose (Gal), d-glucose (Glc) and d-galacturonic acid (GalUA), and their mole percentages are 64.5%, 31.1% and 4.4%, respectively. In addition, the antioxidant potential of SMP was evaluated in terms of reducing power, scavenging ability against DPPH, superoxide and hydroxyl free radicals. The results indicate that polysaccharides from S. miltiorrhiza Bunge possess versatile antioxidant activities in a dose-dependent manner. Furthermore, SMP is observed with high inhibition ratio against LoVo cells (typical tumor cells) in both dose- and time-dependent manners. FCM analysis demonstrates that SMP is able to induce apoptosis of LoVo cells, arrest the cell cycle at S phase, as well as elevate the intracellular reactive oxygen pressure. These findings for the first time reveal the potential anti-tumor mechanism of SMP, suggesting that SMP may serve a natural anticancer agent with lower cost and cytotoxicity, as well as a bioactive factor for functional food development.

Stachyose increases absorption and hepatoprotective effect of tea polyphenols in high fructose-fed mice.

SCOPE: The consumption of tea polyphenols (TP) and stachyose contributes to preventive effects on hepatic injury. This study examined the effects of stachyose on absorption and hepatoprotective effects of TP in mice. METHODS AND RESULTS: GC-MS measurement showed that stachyose significantly increased serum total phenolic, ECG and EGCG contents in mice. The mice fed with high fructose (HF)-diet for 56 days exhibited oxidative stress observed by an increase in hepatic MDA levels and decreases in GSH-Px and SOD activities. Serum TC, TG, LDL-C and CRP levels, and ALT and AST activities were increased, while HDL-C concentrations were decreased following HF diet. Co-supplementation of stachyose and TP more effectively improved all parameters mentioned above when compared to administration of stachyose or TP alone. Histological observations of hepatic tissues also confirmed the beneficial effects of co-administration of stachyose and TP. CONCLUSION: Our results suggest that stachyose enhances absorption and hepatoprotective effects of TP, and combined ingestion of stachyose and TP is a novel strategy for alleviating HF diet-induced hepatic injury.