Abstract

Mulberry fruits were shown to possess good antioxidant properties. Flavonoids were extracted from three mulberry species (Morus alba L., Morus rubra L., and Morus nigra L.) and characterized using mass spectrometry. The methanol extract was subjected to 1D and 2D NMR analysis in DMSO-d6 using TMS as an internal standard. Mass spectrometry in combination with NMR spectra of crude mixture (methanol extract) was shown as a reliable tool for the characterization of flavonoids with already published NMR spectra in DMSO-d6. However, in case of compounds not very well established, it does not show relevance, so separation of the crude mixture into individual components and their 1D and 2D NMR characterization is necessary. However, the results of this article would be useful in mulberry drink quality control and mulberry functional food research.

INTRODUCTION

Mulberry (Morus, Moraceae) is known as food, and mulberry leaves have been used as feed for silkworms. In general, there are 10-16 species of mulberry, generally accepted by the majority of botanical authorities (1). Morus nigra L. is a rustic plant growing wildly, cultivated in gardens or commonly used in sericulture. It is hard to commercialize products made from mulberry because of fragile structure and low stability on storage. Morus alba and Morus nigra have their origins in western Asia, and the red mulberry is a native of North America (2). It was shown that dried mulberry fruits possess anti-oxidant, anti-microbial, and anti-inflammatory properties (3, 4). Mulberry plants contain various bioactive components, such as alkaloids, and flavonoids (1, 2, 5, 6). Qualitative analysis of the nonanthocyanin phenolics from 2 mulberry cultivars was performed using HPLC-DAD-ESI-MS/MS method. As a result of the analysis, six nonanthocyanin phenolics were identified (procatechuic acid, chlorogenic acid, 4-caffeoylquinic acid, taxifolin, rutin, quercetin) and three others (3,5-diCQA, taxifolin-hexoside, kaempfero ...