Antioxidant efficacy of phytochemical extracts from defatted rice bran in in-vitro model emulsions

Abstract

Defatted rice bran (DRB) is the byproduct of rice bran oil extraction. On HPLC analysis, methanolic extracts prepared from DRB was found to contain oryzanols (OYL), tocols and ferulic acid (FA). Solvent fractionation was employed to prepare extracts enriched with beneficial phytochemicals from crude methanolic extract (CME). The antioxidant potential of DRB extracts and their phytochemical constituents in emulsified media were evaluated by linoleic acid emulsion system and beta-carotene bleaching test. In linoleic acid model, the activity indexed as percent inhibition values followed the order TBHQ (83.9) > BHT (60.1) > AE-PP = AE-LP = OYL = tricin (51.7) > Tmix (48.0) > FA (44.1) > AE (36.0) > CME (29.9) > sterol (22.8) with inhibition percentages at 200 ppm levels given in parentheses. The order for the beta-carotene model was TBHQ (75.2) > BHT (54.1) > OYL = tricin = AE-LP = AE-PP (47.2) > Tmix (43.9) > FA (41.0) > AE (29.9) > CME (25.1) > sterol (20.1), with inhibition percentages at 200 ppm levels given in parentheses. The results demonstrated that DRB extracts could be used as antioxidant substitutes in heterogeneous food matrix and could also be used in protecting both linoleic acid and beta-carotene against oxidation. The increase in activity with purification might be due to enhanced levels of antioxidants in purified extracts as compared to CME.