Identification and quantification of anthocyanins from the grains of black rice (Oryza sativa L.) varieties

The purpose of this research was conducted to determine anthocyanin content from the grains of 10 Korean black rice varieties. Moreover, the primary constituents including protein and oil were evaluated. Anthocyanins, cyanidin-3-O-glucoside (1) and peonidin-3-O-glucoside (2), were isolated and elucidated using reversephase C₁₈ chromatography, nuclear magnetic resonance (NMR) spectroscopy, and high performance liquid chromatography (HPLC) with diode array detection and electrospray ionization/mass spectrometry (DAD-ESI/MS). Anthocyanin showed significant differences and cyanidin-3-O-glucoside (1) (52.1±6.3-1,601.0±8.5 μg/g) exhibited a markedly higher content than peonidin-3-O-glucoside (2) (ND-82.6±1.2 μg/g). Among varieties, ‘Heugjinjubyeo’ showed the highest anthocyanin (1: 1,601.0±8.5, 2: 82.6±1.2 μg/g), whereas ‘Heughyang’ was the lowest (1: 52.1±6.3 μg/g, 2: ND). Protein and oil exhibited the minor differences and their contents ranged from 10.7±0.0 to 14.1±0.1% and from 2.1±0.0 to 2.9±0.0%. Overall results suggest that anthocyanin can be a key factor in functional property of black rice and ‘Heugjinjubyeo’ may be very important source concerning nutritional value.