Unraveling the Glucosylation of Astringency Compounds of Horse Chestnut via Integrative Sensory Evaluation, Flavonoid Metabolism, Differential Transcriptome, and Phylogenetic Analysis.

Qinggang Yin,Wei Sun,Han Gao,Xiaoyan Han,Jingwang Chen,Yiding Wei

doi:10.3389/fpls.2021.830343

Abstract

The seeds of Chinese horse chestnut are used as a source of starch and escin, whereas the potential use of whole plant has been ignored. The astringency and bitterness of tea produced from the leaves and flowers were found to be significantly better than those of green tea, suggesting that the enriched flavonoids maybe sensory determinates. During 47 flavonoids identified in leaves and flowers, seven flavonol glycosides in the top 10 including astragalin and isoquercitrin were significantly higher content in flowers than in leaves. The crude proteins of flowers could catalyze flavonol glucosides' formation, in which three glycosyltransferases contributed to the flavonol glucosylation were screened out by multi-dimensional integration of transcriptome, evolutionary analyses, recombinant enzymatic analysis and molecular docking. The deep exploration for flavonol profile and glycosylation provides theoretical and experimental basis for utilization of flowers and leaves of Aesculus chinensis as additives and dietary supplements.

Highlights

The Chinese horse chestnut (Aesculus chinensis) is a deciduous tree native to Qinling Mountains of China
Screening of 170 AcUGTs identified three that participate in the formation of isoquercitrin and astragalin, which are abundant in the flowers of A. chinensis. These results demonstrated that these AcUGT genes, which are responsible for the accumulation of flavonol glycosides in A. chinensis, are important to the flavor of herbal tea, and should prove helpful for the development of healthy foods derived from A. chinensis
The flavonoid profiles of herbal tea made from A. chinensis leaves and flowers were investigated to identify flavonoids that determine the degree of astringency

Summary

Introduction

The Chinese horse chestnut (Aesculus chinensis) is a deciduous tree native to Qinling Mountains of China. The seeds of A. chinensis are used as a source of starch via alkali treatment or hightemperature detoxification, as well as a source of escin, which is a pentacyclic triterpenoid saponin (Zlatanov et al, 2013; Cheng et al, 2018; Zhang et al, 2020a). Some Aesculus spp. contain components that are beneficial to human health, especially flavonoids (Wei et al, 2004; Kapusta et al, 2007; Zlatanov et al, 2013; Oszmianski et al, 2014; Zhang et al, 2020b; Jarzebski et al, 2021). As compared with the widespread use of the seeds of A. chinensis, the flowers and leaves have been mostly ignored due to the lack of detailed analysis of key compounds that are potentially beneficial to human health

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Conclusion