Oxidative Transformation of Dihydroflavonols and Flavan-3-ols by Anthocyanidin Synthase from Vitis vinifera.

Jia-Rong Zhang,Katell Bathany,Jean Chaudière,Serge Delrot,Claudine Trossat-Magnin,Luc Negroni

doi:10.3390/molecules27031047

Abstract

Twelve polyphenols from three distinct families (dihydroflavonols, flavan-3-ols, and flavanones) were studied as potential substrates of anthocyanidin synthase from Vitis vinifera (VvANS). Only flavan-3-ols of (2R,3S) configuration having either a catechol or gallol group on ring B are accepted as substrates. Only dihydroflavonols of (2R,3R) configuration are accepted as substrates, but a catechol or gallol group is not mandatory. Flavanones are not substrates of VvANS. HPLC and MS/MS analyses of the enzymatic products showed that the VvANS-catalyzed oxidative transformation of (+)-dihydroflavonols, such as dihydroquercetin, dihydrokaempferol and dihydromyricetin, leads only to the corresponding flavonols. Among the flavan-3-ols recognized as substrates, (+)-gallocatechin was only transformed into delphinidin by VvANS, whereas (+)-catechin was transformed into three products, including two major products that were an ascorbate–cyanidin adduct and a dimer of oxidized catechin, and a minor product that was cyanidin. Data from real-time MS monitoring of the enzymatic transformation of (+)-catechin suggest that its products are all derived from the initial C3-hydroxylation intermediate, i.e., a 3,3-gem-diol, and their most likely formation mechanism is discussed.

Highlights

Anthocyanins, an important subfamily of flavonoids, are among the most widely distributed water-soluble pigments in plants, and are largely responsible for the colors of flowers, fruits, and vegetables that range from orange or red to purple or blue
We showed that anthocyanidin synthase from Vitis vinifera (VvANS) could not produce cyanidin in vitro with the natural stereoisomer of leucocyanidin as the substrate [32], and it seems that this observation applies to ANS from Arabidopsis thaliana, Perilla frutescens, and Ginkgo biloba [31,33,34,35,36,37], with which cyanidin was always observed as a minor product of the natural isomer of leucocyanidin in vitro
VvANS possesses a wide range of substrates, as expected from what had been observed with ANS from Arabidopsis thaliana and Gerbera hybrida [35,40,41,43], some differences were observed with VvANS, such as the absence of transformation of naringenin, and the transformation of (+)-catechin into an ascorbate–cyanidin adduct

Summary

Introduction

Anthocyanins, an important subfamily of flavonoids, are among the most widely distributed water-soluble pigments in plants, and are largely responsible for the colors of flowers, fruits, and vegetables that range from orange or red to purple or blue They have long been reported to fulfill multiple ecological and physiological functions within plants by contributing to their growth and subsistence in many ways. Numerous investigations of cell lines in vitro and animal models in vivo have been carried out during the past two decades, as well as epidemiological studies and clinical trials with human volunteers Such studies have demonstrated that several of these natural dietary phytochemicals exhibit pharmacological properties that could be useful in anticancer [15,16], anti-inflammatory [17], or anti-obesity [18,19,20,21] strategies, as well as for cardioprotection [22] or to alleviate diabetes [23,24]

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