Subcritical water extraction of phenolic antioxidants with improved α-amylase and α-glucosidase inhibitory activities from exocarps of Castanea mollissima Blume

Herein, subcritical water extraction (SWE) technology was applied for the recovery of phenolics from chestnut exocarps. Results showed that extracts obtained by SWE had significantly higher extraction yield (Ye), total phenolic contents (TPC), as well as stronger antioxidant (AAs), alpha-amylase and alpha-glucosidase inhibitory activities than conventional techniques. The optimal temperature of SWE for reaching the highest Ye, TPC and AAs was 220 degrees C, while the strongest alpha-amylase and alpha-glucosidase inhibitory activities were observed at 120 degrees C. UPLC-MS/MS, heatmap and radar chart analysis revealed that the phenolic profiles of different extracts varied markedly with extraction methods, and SWE extract at 120 degrees C had potential application for glycemic control by non-competitively inhibiting alpha-amylase and/or alpha-glucosidase. The major components contributed to the inhibitory activities were putative chlorogenic acid and flavonoids, such as rutin and quercetin, etc. These observations suggest that SWE is a promising technology for obtaining bioactive phenolics from chestnut exocarps. (C) 2020 Elsevier B.V. All rights reserved.