Antiradical efficacy of phytochemical extracts from defatted rice bran.

The phytochemical compounds oryzanols, tocopherols, tocotrienols and ferulic acid were identified in the crude methanolic extracts (CME) of defatted rice bran (DRB) by HPLC. Enrichment of antioxidants in CME was achieved by sequential extraction and fractionation resulting in three enriched fractions viz. acetone extract (AE), acetone extract-lipophilic fraction (AE-LP) and acetone extract-polar fraction (AE-PP). The scavenging effects of DRB extracts and their phytochemical constituents against DPPH and superoxide radicals were investigated. The EC(50) (g antioxidant/kg DPPH) values of CME, AE, AE-LP, AE-PP, oryzanols, ferulic acid, tocols (Tmix), tricin, beta-sitosterol, BHT and TBHQ were 1,977, 1,945, 7,985, 1,072, 972, 174, 164, 3,947, 21,416, 1,120 and 61, respectively. Tricin and beta-sitosterol isolated from CME were identified with the help of spectral data. The DRB extracts and their phytochemical constituents when assayed by cytochrome c and NBT methods showed positive superoxide radical scavenging effects. The order of efficacies of the extracts was AE-PP>AE>CME>AE-LP in both assays, but the activities were higher for the former method. The DPPH as well as superoxide scavenging activities of AE, AE-LP and AE-PP could largely be attributed to the levels of total phenols (TPC) and ferulic acid in it.