Non-extractable polyphenols and in vitro bile acid-binding capacity of dried persimmon (Diospyros kaki) fruit

Abstract

Dried persimmon is thought to be a rich source of non-extractable polyphenols (NEPPs). Here, we analyzed the NEPP content of dried persimmon and its bile acid-binding activity in vitro. To determine total NEPP content and epicatechin equivalent (ECE) of intact NEPPs, acid hydrolysis and non-destructive methods with 70% (v/v) acetone-insoluble solids (AIS), respectively, were conducted using Folin-Ciocalteu reagent. The ECE of intact NEPPs exceeded 1000 mg/100 g in the non-destructive method, but total NEPP content was approximately 3900 mg/100 g with the acid hydrolysis method. Thiolysis showed that the non-extractable proanthocyanidins in dried persimmon mainly comprised epigallocatechin-gallate, epigallocatechin, epicatechin, and epicatechin-gallate. AIS from dried persimmon showed stronger bile acid-binding activity than AIS from apple, quince, and fresh astringent persimmon. These results suggest that the high content of NEPPs in dried persimmon may contribute to a strong bile acid-binding activity.