Study on the Antioxidant Activity of Different Forms of Phenolic Compounds in Rice Bran
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Abstract:
In this study, the contents of different forms of polyphenol, viz. free, soluble ester, soluble glycoside, insoluble ester, and insoluble glycoside forms, in rice bran were investigated. The in vitro antioxidant activities, including the Fe3+ reducing capacity and 2,2-diphenyl-1-picrylhydrazyl (DPPH), O2-, and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical scavenging activities, were evaluated. The results showed that the polyphenol content in free, soluble ester, soluble glycoside, insoluble ester, and insoluble glycoside form in rice bran were 44.70, 80.81, 63.84, 128.63, and 95.46 mg GAE/100 g, respectively. Polyphenols existing in the different forms in rice bran had different antioxidant effects on different systems. Compared to other polyphenols, the polyphenols in the soluble ester form had the strongest Fe3+ reducing capacity (IC50: 37.62 μg/mL). The polyphenols in the insoluble ester form exhibited the best DPPH radical scavenging ability; the DPPH scavenging rate was 93.56% at an insoluble ester concentration of 16.33 μg/mL. The polyphenols in the soluble ester form showed the strongest O2- scavenging capability; the O2- scavenging rate was 91.12% at a soluble ester concentration of 9.66 μg/mL. The polyphenols in the insoluble ester form showed good ABTS scavenging capability, and the ABTS scavenging rate was 91.19% at an insoluble ester concentration of 64.05 μg/mL. These results indicated that rice bran was rich in polyphenols, which had relatively good antioxidant abilities.
