Anthocyanin content and antioxidant capacity in bran extracts of some Thai black rice varieties

This study investigated both the anthocyanin content and the antioxidant capacity of a set of genetically related glutinous and nonglutinous Thai black rice varieties. The ethanol/water extracts of the brans of these black rice varieties showed relatively potent antioxidant activities compared with those of tocopherol. These antioxidant activities were determined by thiocyanate, H2O2-scavenging chemiluminescence (XYZ), Cu++/bathocuproine colorimetry (PAO) and 1,1-diphenyl-2-picrylhydrazyl radical-scavenging assay. The structural identification and quantification of the black rice anthocyanins performed by high-performance liquid chromatography coupled with electrospray ionisation and tandem mass spectrometry found cyanidin-3-O-glucoside and peonidin-3-O-glucoside as the major anthocyanins in the ranges of 16.0134.40 and 2.437.36 mu g mL-1, respectively. The comparative study in terms of quantity of these phytochemicals and antioxidant capacity of the black rice bran extracts suggested the contribution of overall phenolic components rather than that of the particular anthocyanin pigments.