Variation of Anthocyanin Content and Antioxidant Capacity among Local Thai Purple Glutinous Rice Genotypes

Abstract

Purple rice is rich in nutritional values and bioactive compounds such as anthocyanins found mostly in pericarp layer of the grain. They illustrate antioxidant properties by reacting against reactive oxygen species. For this reason, consuming purple rice has recently become popularly among health concerning people. The objective of this study was to determine variation of grain yield, anthocyanin content and antioxidant capacity among 19 local purple rice genotypes. The experiment was arranged in RCBD with 3 replications. Rice plants were grown in the same growing condition and harvested at maturity for yield evaluation. Anthocyanin content and antioxidant capacity were analyzed in brown rice caryopsis. The results show significant variation in grain yield, anthocyanin content and antioxidant capacity among the 19 purple rice genotypes. Grain yield varied significantly from 260 to 625 kg/rai, anthocyanin content ranged from 9.73 - 54.68 mg/100 g and antioxidant capacity ranged from 251.76 - 709.38 mg Trolox/100 g and 2304.6 - 6247.0 µmol Fe (II)/100 g determined by DPPH and FRAP assays, respectively. The genotype Kum 7677 had the highest amount of grain yield, anthocyanins and antioxidants determined by DPPH assay. These 2 assays was used to determine the antioxidant capacity in purple rice as they were significantly correlated (r = 0.71, p < 0.01). The correlation was not observed between anthocyanin content and antioxidant capacity determined by both assays. There should be some other compounds play the similar role as anthocyanin which is requiring further study. However, the information in this study encourages further study on physiological mechanisms of anthocyanin and antioxidant accumulation in rice grain among different rice genotypes and the selection of rice genotypes in breeding program for high anthocyanin and antioxidant capacity genotypes which will be benefit for rice consumers.