Identification of Anthocyanin Composition and Functional Analysis of an Anthocyanin Activator in Solanum nigrum Fruits.

Shaoli Wang,Xiaoqi Fan,Mingxing Ren,Changbao Zhao,Yingzi Wang,Xinhua Ding,Ru Jia,Dan Fei,Zhaohui Chu,Hao Su,Xiaotian Zhang,Yang Li

doi:10.3390/molecules22060876

Abstract

Solanum nigrum fruits have been conventionally used in beverages due to their nutritional substances such as minerals, vitamins, amino acids, proteins, sugars, polyphenols, and anthocyanins. The characterization of components and regulatory mechanism of anthocyanins in S. nigrum fruits have rarely been reported. In this study, we determined that the peel and flesh of S. nigrum fruits shared similar HPLC profiles but different contents and total antioxidant activities for anthocyanins. After an efficient purification method, mainly including extraction with pH 1.0 distilled water and then desorption with pH 1.0 95% ethanol after a DM-130 resin adsorption step to obtain more pure anthocyanin extracts, the purity of anthocyanins extracted from S. nigrum fruits reached 56.1%. Moreover, eight anthocyanins from S. nigrum fruit were identified with HPLC-MS/MS for the first time. A typical R2R3-MYB transcription factor gene, SnMYB, was also cloned for the first time by rapid amplification of cDNA ends (RACE)-PCR from S. nigrum. Moreover, the contents of anthocyanins were shown to correlate well (r = 0.93) with the expression levels of SnMYB gene during the fruit’s developmental stages. Most significantly, SnMYB gene successfully produced high anthocyanin content (1.03 mg/g) when SnMYB gene was transiently expressed in tobacco leaves. Taken together, S. nigrum fruits are a promising resource for anthocyanin extraction, and SnMYB gene is an activator that positively regulates anthocyanin biosynthesis in S. nigrum.

Highlights

As a group of natural pigments, anthocyanins are water-soluble and provide many flowers and fruits with their purple, blue, and red colors, which promotes pollination and seed distribution [1].Natural anthocyanins have the ability to protect plants from biotic and abiotic stress [2]
It has been reported that the peels of apples have greater antioxidant activity than does the flesh due to the presence of more anthocyanins and quercetin glycosides [23]
These results indicate that anthocyanins are the major contributor to the total antioxidant capacity of S. nigrum fruit, which is consistent with previous reports [25,26]

Summary

Introduction

As a group of natural pigments, anthocyanins are water-soluble and provide many flowers and fruits with their purple, blue, and red colors, which promotes pollination and seed distribution [1]. Natural anthocyanins have the ability to protect plants from biotic and abiotic stress [2]. Anthocyanins can provide plants with increased resistance to some fungal diseases and insect. Anthocyanins are capable of protecting plants from cold damage and UV irradiation [5]. In addition to the physiological effects in plants, a healthy diet rich in anthocyanins has a variety of notable health-promoting effects. Anthocyanins offer protection against certain chronic illnesses including hyperglycemia [6] and inhibit the growth of tumor cells in humans [7,8]

Methods

Results

Discussion

Conclusion