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.
Highlights
Rice (Oryza sativa L. indica) is a major rice cereal crop in the developing world and important in Asian countries, especially Thailand, the world’s largest rice exporter
Comet assay was used to assess the antioxidant activities of anthocyanins-rich extract (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 Nacetylphenylhydrazine
azobis(2-amidinopropane) dihydrochloride (AAPH) was a source of free radical formation capable of inducing oxidation of lipid and protein structurally located on erythrocyte membrane (Chaudhuri et al, 2007), while APHZ was a source of free radical formation inside cytosol of red blood cells (RBCs) leading to induction of proteins mostly hemoglobin and lipid bilayer membrane oxidation (Sangkitikomol et al, 2001)
Summary
Rice (Oryza sativa L. indica) is a major rice cereal crop in the developing world and important in Asian countries, especially Thailand, the world’s largest rice exporter. An enriched source of flavonoids, is widely used for therapeutic purposes in traditional and folk medicine and gradually becoming popular in Thailand. The major flavonoids of pigmented rice are anthocyanins. Cyanidin 3-glycoside and peonidin 3-glycoside, have been identified as the major polyphenolic compounds extracted from black rice (Zhang et al, 2006). Experimental and clinical studies have reported a positive correlation between cardiovascular health status and consumption of black rice and/ or black rice pigments. This particular rice possesses protective effects through many mechanisms, including antioxidant, anti-inflammatory, anti-proliferation, lipid lowering effects.
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