Extraction and Identification of Black Rice Polyphenolic Compounds by Reversed Phase High Performance Liquid Chromatography-Electrospray Ionization Mass Spectrometry

Abstract

Seven kinds of phenolic compounds in black rice were isolated and identified by reversed phase high performance liquid chromatography–electrospray ionization mass spectrometry. Proanthocyanidins glucoside which has the strongest ability of antioxidant and free radical scavenging was tentatively identified in black rice for the first time. By mass spectrometry in negative ion mode, three types of phenolic acids compounds which were caffeic acid hexose, procyanidinB2-3-O-gallate hexose, epiafzelchineepicatechin-O-dimethylgallate were first confirmed. In this experiment, liquid–mass spectrometry model was established to detect traces of polyphenolic compounds in black rice. This model can increase the efficiency of electron capture and the sensitivity of mass spectrometry detection. The sensitivity, mass accuracy legitimated the identification of phenolic compounds present in black rice extract. So the method of reversed phase high performance liquid chromatography (HPLC)–electrospray ionization mass spectrometry can rapidly detect traces of unknown phenolic compounds in grain. Practical Applications The plant phenols possess the ability to scavenge both active oxygen species and electrophiles. They are the most important group of natural antioxidants because of their diversity and extensive distribution. The interest in the exploitation of novel antioxidants from black rice is increasing accordingly due to abundant contents of polyphenols. Black rice which is a kind of typical whole grain is considered a good source of fiber, minerals, and phytochemicals as well as basic nutrients.