Structural Changes and Digestibility of Onion Quercetin and Grape Resveratrol during <em>In Vitro</em>&nbsp;Human Digestion

Abstract

This study was conducted to investigate the effects of in vitro human digestion on digestibility and structural changes of onion quercetin and grape resveratrol that simulates the composition of saliva, gastric, duodenal, and bile juice. We observed that the change the content of resveratrol and quercetin in grapes and onion were 52.45 ± 0.32, 46.48 ± 0.32% in small intestine of in vitro human digestion system. In LC-MS analysis, we found that the structure of grape resveratrol was influenced in vitro human digestion, whereas onion quercetin was less influenced. Before and after in vitro human digestion, the DPPH radical scavenging activities of homogenized, water and ethanolic extracts from grapes were higher than those of onion extracts, with 72.96 ± 0.32, 66.60 ± 0.16 and 67.36 ± 0.12 at mg/ml, respectively. The DPPH radical scavenging activities was decreased by in vitro human digestion in both of grape and onion extracts. These results will improve the understanding how in vitro human digestion influenced the structural changes and free radical scavenging activity of onion quercetin and grape resveratrol during digestion.