Abstract

The present study was aimed at determining the optimum dose of anthocyanins-rich extract (ARE) from Thai pigmented rice for its antioxidant effects. Three different methods of antioxidant analysis [Oxygen Radical Absorbance Capacity (ORAC) assay, Folin Cioculteau Phenol (FCP) assay and Vanillin assay] were used and the results obtained were excellently correlated (r > 0.98). Among red rice, black rice and black sticky rice, black sticky rice had the highest antioxidant level within the range 1368.34 ± 16.85 TE mM /kg dry mass, 922.03 ± 3.84 mM GE/kg dry mass and 218.97 ± 0.74 CE mM/kg dry mass, respectively. ARE with the highest antioxidant level was used in the following tests: Hemolysis test and Heinz body formation, which were used to assess the antioxidant activities of ARE on human erythrocytes, respectively. Comet assay was also used to assess the antioxidant activities of ARE on mononuclear leukocytes  and it was found that the optimum dose of ARE (600 mg/L) inhibited hemolysis induced by 2,2'-Azobis(2-amidinopropane) dihydrochloride and Heinz body formation induced by N-acetylphenylhydrazine. Moreover, 200 - 1000 mg/L of ARE was able to inhibit hydrogen peroxide-induced genotoxicity in mononuclear leukocytes in a dose-dependent manner. Nevertheless, high dose of ARE (≥ 800 mg/L) induced cytotoxicity and genotoxicity by itself. The results strongly suggested that optimum dose of ARE was beneficial for health promotion by reducing oxidative stress in cellular model.

Key words: Antioxidant, pigmented rice, comet assay, hemolysis, Heinz body.