Antioxidant activities of the fractionated protein hydrolysates from heat stable defatted rice bran

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Summary

The hydrolysates from heat stable rice bran (HSDRB) treated by Alcalase 2.4L and Protease 500G were desalted and fractionated by hydrophobicity using a nonpolar, styrene divinylbenzene resin and macroporous adsorption resin DA201-C. The antioxidant activities of HSDRB hydrolysates (HSDRBH) eluted by 25%, 50%, 75% and 100% ethanol were investigated using 2, 2-di (4-tertoctylphenyl)-1-picrylhydrazyl free radical-scavenging activity assay, reducing power assay, ferrous ion-chelating activity assay and lipid peroxidation inhibition assay. The HSDRBH-75 had the highest reducing power assay and inhibition ratio of linoleic acid autoxidation, which might be associated with reduced molecular weight, amino acid composition and hydrophobicity. The highest metal-chelating activity of four different fractions (at the concentration of 4 mg mL−1) had a positive correlation (= 0.768, P = 0.116) with the total content of basic amino acid (Lys, Arg, and His) and a negative correlation (= −0.886, P = 0.057) with the range of molecular weight (Mw < 1000 Da). The HSDRBH-75 had the highest antioxidant activities in many assays, which suggests that it may become a good natural antioxidant as a food additive.

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