Anti‐Diabetic Effects of Different Phenolic‐Rich Fractions from <i>Rhus Chinensis</i> Mill. Fruits <i>in vitro</i>

Abstract

This study investigated the inhibitory effects of the Ethanol Extract (EE), Free Phenolic (TF), Esterified Phenolic (TE) and Insoluble‐bound Phenolic (TI) from Rhus chinensis Mill. fruits on α ‐glucosidase, Dipeptidyl Peptidase‐4 (DPP‐IV), and the formation of Advanced Glycation End (AGE) products. Results showed that the TF had the strongest inhibition against α ‐glucosidase and DPP‐IV with IC 50 of 0.56 ± 0.04 and 66.08 ± 1.36 μg/mL, respectively ( p &lt; 0.05). TI exhibited the strongest inhibitory effect on the formation of AGEs with IC 50 of 0.43 ± 0.03 mg/mL ( p &lt; 0.05). Two major compounds (myricetin‐3‐ O ‐rhamnoside and quercetin‐3‐ O ‐rhamnoside) showed additive or synergistic effects on α ‐glucosidase inhibition, while displayed antagonistic effect on DPP‐IV inhibition. Correlation analysis indicated that myricetin‐3‐ O ‐(6″‐galloyl) glycoside and myricetin O ‐gallate contributed significantly on α ‐glucosidase inhibition, while di‐ O ‐galloyl‐glucoside and its isomer may contribute remarkably toward DPP‐IV inhibition. Protocatechuic acid and myricetin‐3‐ O ‐rhamnoside showed a positive correlation with the suppression of AGEs formation. Those results may provide some scientific information for exploring R. chinensis fruits as nutraceuticals and/or functional foods to prevent or improve diabetes.