Study on appropriate methods for extraction of antioxidant compounds from black glutinous rice

Abstract

Introduction: Black glutinous rice has high chemical constituents and antioxidant compounds. This research aimed to determine appropriate extraction method of black glutinous rice for highest antioxidant compounds of the crude extract. The method was considered on low cost, safety and efficiency condition.

Method: Black glutinous rice was extracted with 12 solvents. Total phenolic compound, total monomeric anthocyanin, cyanidin 3-glucoside and antioxidant activities determined by DPPH radical scavenging assay of the crude extracts were measured.

Result: The extraction with 1%hydrochloric acid (1%HCl) in 95%ethanol and 10%HCl in 95%ethanol were significantly highest chemical constituents and antioxidant activities. This solvent (1%HCI in 95%ethanol) was selected to study for black glutinous rice and solvent ratio. The result found that black glutinous rice and its solvent ratio was 1:5 or more solvent gave the high chemical constituents and antioxidant activity. The extraction time was also studied with 1%HCl in 95%ethanol as a solvent and ratio as 1:5. The appropriate time was 24 hours or more for extraction of this condition.

Discussion and Conclusion: The appropriate extraction method of black glutinous rice was 1%HCl in 95% ethanol as a solvent and ratio as 1:5 for 24 hours. This data was an alternative condition for black glutinous rice Thailand local genotypes extraction for using as ingredients in nutraceuticals in manufacture industry.

Key words: Black glutinous rice, Phenolic compound, Antioxidant