Composition Differences of Procyanidins in Chestnut Shell and Pellicle before and after Digestion Based on in Vitro Digestion Model

In this study, the composition changes of procyanidins in chestnut shell and pellicle after simulated digestion were analyzed by extensive targeted metabolomics based on ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The results showed that a total of 33 procyanidin metabolites were identified in chestnut shell, pellicle and their metabolites. Differential metabolite analysis showed that 16 procyanidin compounds, including epicatechin, procyanidin C2 and procyanidin A1 were significantly (P<0.05) down-regulated in chestnut shell after digestion. Seventeen procyanidins, including gallocatechin-catechin-catechin, gallocatechin and gallocatechin gallate, were significantly (P<0.05) down-regulated in chestnut pellicle after digestion. Among them, the most significant (P<0.05) down-regulation was gallocatechin-catechin-catechin, which was reduced by 98.23% (chestnut shell) and 97.86% (chestnut pellicle) after gastrointestinal digestion in vitro. In conclusion, the stability of proanthocyanidins in chestnut shell and pellicle was poor during digestion. In future studies, targeted release carriers could be designed to encapsulate them, so as to improve their bioavailability.