Quality evaluation of different black rice varieties of northeastern region of India.

Abstract

Black rice (Oryza sativa L.), which is rich in polyphenols and flavonoids, is indigenous to Northeast India, specifically Manipur, and traditionally consumed for its protective effects on human health. Due to its economic value, it is crucial to evaluate the quality of different black rice varieties to authenticate their therapeutic and nutritional properties. We aimed to evaluate the quality of pre- and post-marketed black rice samples by a validated high-performance thin layer chromatography method and determine variations of total phenolics and total flavonoids with antioxidant potential. The ferulic acid, gallic acid, quercetin, and caffeic acid contents of three black rice varieties-Poireiton, Amubi, and Sempak-along with two marketed samples of Amubi from Manipur, India, were quantified based on standards. Antioxidant potential was measured by the 2,2-diphenyl-1-picryl-hydrazyl hydrate free radical scavenging assay. The highest and lowest relative biomarker contents were found in hydroalcoholic extracts of Amubi [caffeic acid (1.43% w/w), ferulic acid (1.15% w/w), quercetin (0.6% w/w), and gallic acid (0.39% w/w)] and the marketed sample Var. Amubi from Kakching District, respectively. Pearson's correlation coefficient of antioxidant potential with phenolic and flavonoid content showed a moderate to strong correlation for all samples. This validated, rapid, accurate standardization method for black rice varieties will be beneficial for the quality evaluation of black rice and its derived products. It will also be helpful to authenticate the nutritional benefits for the consumers.