ANTIOXIDANT ACTIVITIES AND CYTOTOXICITY OF THAI PIGMENTED RICE

Objective: This research quantified the phytochemical profile, antioxidant activities and cytotoxicity of Thai pigmented rice.Methods: Acidified ethanol extracts from seeds of twelve Thai pigmented rice cultivars (six black and six red rice) were investigated for their content of bioactive compounds (phenolics, anthocyanins, and procyanidins), antioxidant activities (ferric reducing antioxidant power; FRAP, DPPH radical scavenging activity; DPPH, and inhibition of lipid peroxidation; TBARS), and cytotoxicity on human promyelocytic leukemia (HL-60) cells.Results: Black rice cultivars (0.05–0.54 mg GAE/ml extract) and red rice cultivars showed total phenolic content (0.21–0.99 mg GAE/ml extract). The predominant phenolic pigments were anthocyanins (1.51±1.70 mg C3G/l extract) for black rice and procyanidins (0.35±0.23 mg EPE/ml) for red rice. Antioxidant activity ranged within 0.06–1.36 mg AAE/ml for FRAP, IC500.10–1.12 mg/ml for DPPH and 7.57–40.48 % for TBARS. Red rice tended to exhibit higher antioxidant activities than black rice in the FRAP assay, but there were no significant differences between the rich colors in the DPPH and TBARS assays. Pigmented rice extracts containing the highest total phenolic content were selected to assess their cytotoxicity on human promyelocytic leukemia (HL-60) cells. Black rice showed higher cytotoxicity, corresponding with the lower IC50 compared to red rice.Conclusion: The results revealed that Thai pigmented rice is a natural antioxidant source with potential for use as an active ingredient in cosmetics, functional food and pharmaceuticals. Â