Ellagitannin Digestion in Moth Larvae and a New Dimeric Ellagitannin from the Leaves of Platycarya strobilacea.

Yosuke Matsuo,Yoshinori Saito,Takashi Tanaka,Dian-Peng Li,Yong-Lin Huang,Juri Takayoshi

doi:10.3390/molecules26144134

Yosuke Matsuo, Yoshinori Saito + Show 4 more

Open Access

https://doi.org/10.3390/molecules26144134

Copy DOI

Abstract

Ellagitannins (ETs) are plant polyphenols with various health benefits. Recent studies have indicated that the biological activities of ETs are attributable to their degradation products, including ellagic acid and its gut microflora metabolites, such as urolithins. Insect tea produced in the Guangxi region, China, is made from the frass of moth larvae that feed on the ET-rich leaves of Platycarya strobilacea. Chromatographic separation of the Guangxi insect tea showed that the major phenolic constituents are ellagic acid, brevifolin carboxylic acid, gallic acid, brevifolin, and polymeric polyphenols. Chemical investigation of the feed of the larvae, the fresh leaves of P. strobilacea, showed that the major polyphenols are ETs including pedunculagin, casuarictin, strictinin, and a new ET named platycaryanin E. The new ET was confirmed as a dimer of strictinin having a tergalloyl group. The insect tea and the leaves of P. strobilacea contained polymeric polyphenols, both of which were shown to be composed of ETs and proanthocyanidins by acid hydrolysis and thiol degradation. This study clarified that Guangxi insect tea contains ET metabolites produced in the digestive tract of moth larvae, and the metabolites probably have higher bioavailabilities than the original large-molecular ETs of the leaves of P. strobilacea.

Highlights

Tannins are a class of plant polyphenols that precipitate proteins [1] and are attracting increasing attention as food constituents with potential health benefits [2]
To identify the remaining major compound observed at 20.8 min and other minor constituents, the aqueous acetone extract was separated on a large scale, and a comparison of nuclear magnetic resonance (NMR) data showed that the major compound detected at 20.8 min was brevifolin carboxylic acid (3) [21,22]
Polymeric polyphenols detected at the origin on thin-layer chromatography (TLC) and observed as a broad hump on the high-performance liquid chromatography (HPLC) baseline were obtained by size-exclusion column chromatography using Sephadex LH-20 with 7 M urea in acetone as the elution solvent [26]

Summary

Introduction

Tannins are a class of plant polyphenols that precipitate proteins [1] and are attracting increasing attention as food constituents with potential health benefits [2]. Compared to the condensed tannins and gallotannins, ETs exhibit a large structural diversity associated with structures and location of the acyl groups as well as their molecular sizes. The tannin–protein interaction causes inhibition of digestive enzymes of herbivores, reducing the nutritional value of plants consumed as food [7]; ETs are thought to be plant defense substances, and the ecological significance of ETs and condensed tannins has long been discussed [8,9,10]. The purpose of this study was to reveal the ET-derived molecules in the insect tea and to clarify the metabolism of ETs in the insect digestive tract by comparing the constituents of the insect tea with the polyphenols in the larvae feed

Objectives

Methods

Results

Conclusion