Antioxidant and free radical scavenging capacity of the underutilized legume, Vigna vexillata (L.) A. Rich

The raw and processed seeds of the underutilized legume, Vigna vexillata (L.) A. Rich were extracted with 70% acetone and used for the evaluation of its antioxidant potential. The different heat treatments included dry heating, soaking followed by autoclaving with 0.1% sodium bicarbonate, soaking followed by autoclaving and autoclaving without soaking. The raw seed extract contained higher levels of total phenolics (11.7 g/100 g) and tannins (5.9 g/100 g) than the processed seed extracts. The extracts were further evaluated for their antioxidant activities using FRAP, Fe2+ chelation, phosphomolybdenum reduction, DPPH and ABTS+ radical scavenging, antihemolytic and β-carotene/linoleic acid emulsion systems. In general, the raw seed extracts were the most potent antioxidant suppliers and free radical scavengers. Interestingly, among the various processing methods, acetone extract of dry heated seed sample registered higher antihemolytic activity (86.2%) at the concentration of 500 μg/ml, whereas, in β-carotene/linoleic acid emulsion system, the extracts of raw seeds and the presoaked seeds followed by autoclaving with 0.1% sodium bicarbonate exhibited higher and comparable activity than other processed seed extracts.