Antioxidant and Anti-Inflammatory Effects of Defatted Rice Bran (Oryza SativaL.) Protein Hydrolysates on Raw 264.7 Macrophage Cells

Abstract

Defatted rice bran (DRB) is a by-product of oil extraction from rice bran (Oryza sativa L.), and has health benefits. This in vitro study investigated the antioxidant and anti-inflammatory effects of four crude DRB protein hydrolysate fractions prepared by pepsin-pancreatin digestion and fractionated by ultrafiltration on a transformed macrophage cell line, RAW264.7. Protein hydrolysates with MW <3 kDa (F4 fraction) had the lowest IC50 for NO-, DPPH˙ and ABTS radical scavenging activities (0.38 ± 0.01, 1.24 ± 0.03 and 0.17 ± 0.01 µg/mL, respectively). The pooled fraction formed after Reverse phase-High-performance liquid chromatography (HPLC) (F4-5) had the highest percentage inhibition of radical scavenging for DPPH˙, and NO- (25.04 ± 0.88, and 6.50 ± 0.39%, respectively). LC-MS of F4-5 revealed peptides exhibiting antioxidant activity were composed of His (H), Trp (W) and Tyr (Y) that known to enhance the scavenging activities of peptides. The F4 fraction suppressed lipopolysaccharide and rmIFN-γ mediated increase in iNOS, IL-6 and TNF-α mRNA levels in RAW264.7 cells, suggesting the interference was mediated at the transcriptional level. Practical Application Defatted rice bran (DRB) is a good source of nutritional proteins. In this study, DRB protein was hydrolyzed using proteases and further fractionated by ultrafiltration. The results demonstrated that DRB hydrolysates and their fractions exhibited antioxidant and anti-inflammatory activities indicating these as a potential source of functional food and medicines.