EFFECTS OF SOLVENT TYPES AND CITRIC ACID CONCENTRATIONS ON THE EXTRACTION OF ANTIOXIDANTS FROM THE BLACK RICE BRAN OF ORYZA SATIVA L. CV. HOM NIN

Thai colored rice has been reported as a potential source of antioxidants. This research aimed to study the effects of different solvents on the antioxidant extraction of Hom Nin rice bran. The solvents (water, methanol and ethanol) combined with citric acid at concentrations of 0, 0.05 and 0.1 mol/dm(3) were used for the extraction. The antioxidant activities and the contents of phenolics, flavonoids and anthocyanins were determined. The results showed that the methanolic extract with 0.1 mol/dm(3) of citric acid gave the highest yield whereas phenolics, flavonoids and anthocyanin were 43.72%, 86.63 mg of GAE/g DM, 14,667.48 mu g CE/g DM and 6.18 mg/g DM, respectively. Moreover, the antioxidant activities as ABTS, DPPH and FRAP were 25.76, 29.02 and 140.57 tmol TE/g DM, respectively. In addition, the total phenolic contents of the extract indicated a highly positive correlation with antioxidant activity.