Abstract:

Black soybean peptides (BSPs) with potent antioxidant activity, purified with ultrafiltration and macroporous
adsorption resin (MAR) from black soybean protein hydrolysates, were analyzed for relative molecular mass and amino acid
composition. A total of 125 mice were randomly divided into control group which were given normal saline, positive group
which were given reduced glutathione, and low, medium and high dose groups which were given BSPs for 30 days, then the
weight loaded-swimming time and blood lactic acid (BLA), serum urea nitrogen (SUN) and hepatic glycogen (HG) contents
were observed for evaluating the fatigue-relieving function of BSPs. The results showed that the peptide fraction with relative
molecular mass 亙 3000 eluted by 75% ethanol displayed the highest DPPH radical-scavenging activity. Compared with the
control group, the middle and high dose groups showed significantly (P 亙 0.01) prolonged loaded-swimming time, lowered
BLA, and improved HG storage status. This indicates that oral administration of BSPs can relieve physical fatigue in mice.
The effect of the low dose group (250 mg/(kg.d)) on BLA and HG and the effect of the middle dose group (500 mg/(kg.d)) on
loaded-swimming time were similar to that of the positive group (50 mg/(kg.d)). BSPs with relative molecular mass between 450
and 920 were obtained from further separation by Sephadex G-25 gel chromatography, which possessed high contents of Phe, Val,
Pro, Met, Thr, Cys and His, displaye better antioxidant activity, and also could relieve physical fatigue triggered by free radicals.

Key words: black soybean peptides, antioxidant capacity, mice, physical fatigu- relieving function, amino acid composition