The antioxidant activity and free radical-scavenging capacity of dietary phenolic extracts from horse gram (Macrotyloma uniflorum (Lam.) Verdc.) seeds

Total phenolics and the antioxidative properties of two varieties of horse gram (Macrotyloma uniflorum) were studied. The raw and dry-heated seed samples were extracted successively with methanol and 70% acetone separately. After removing the solvents, the extracts were freeze-dried. The black seeds contained relatively high levels of total phenolics and tannins than the brown seeds with respect to the treatments and solvents extraction. The extracts were subjected to assess their potential antioxidant activities using systems such as α,α-diphenyl-β-picrylhydrazyl (DPPH), ABTS+, FRAP, linoleic acid emulsion, O2- and OH. The superoxide anion radical-scavenging activity was found to be higher in 70% acetone extract of the both raw and dry heated seeds of the respective varieties at the concentration of 600 μg in the reaction mixture. The DPPH radical and ABTS cation radical-scavenging activities were well proved and related with the ferric-reducing/antioxidant capacity of the extracts. Interestingly, among the various extracts, 70% acetone extracts of dry-heated samples of brown variety, and raw and dry-heated samples of black variety showed significantly (P < 0.05) higher hydroxyl radical-scavenging activity. In general, all extracts exhibited good antioxidant activity (53.3–73.1%) against the linoleic acid emulsion system but were significantly (P < 0.05) lower than the synthetic antioxidant, BHA (93.3%).