INFLUENCE OF pH AND EXTRACTION CONDITIONS ON ANTIOXIDANT PROPERTIES FROM PURPLE STICKY RICE (ORYZA SATIVA.L.GLUTINOSA)

Abstract

This study aimed to determine the effect of different extraction conditions on antioxidant activity of purple sticky rice (Oryza sativa L. Glutinosa). The extractions conditions were ultrasonic 30, 40 and 50 minutes and microwave extraction at 300, 400 and 500 W with various pH 3, 4 and 5. The antioxidant activities were determined in terms of phenolic compound, total monomeric anthocyanins, flavonoid, ABTS and DPPH assays. The results showed that microwave extraction at pH 3 and the power 500 W had the highest extraction yield 69.85% (DW), total phenolic compound 1318.92 mg GAE/100 g, flavonoid 627.74 mg QE/g. DPPH scavenging ability was 85.97% and ABTS 413.36 mg/g. Cyanidin-3-glucoside was the main anthocyanin that found in purple sticky rice in the range of 72.18% to 90.21%. The highest percentage of cyanindin-3-glucoside was microwave extraction at 500 W. These results suggested that microwave extraction at pH 3 and 500 W was the best condition of extraction.