Antioxidant activity and anti-exercise-fatigue effect of highly denatured soybean meal hydrolysate prepared using neutrase.

Highly denatured soybean meal is a by-product of soybean oil extraction obtained through high-temperature desolventization. High-temperature treatment can result in soybean protein denaturation. Compare with ordinary soybean meal, the protein structure of highly denatured soybean meal has changed. Highly denatured soybean meal was pretreated with thermal treatment or ultrasonication, and then hydrolyzed with neutrase. The ultrasonicated hydrolysate exhibited better antioxidant activity than the thermally treated hydrolysate. The ultrasonication increased 1,1-diphenyl-2-pycryl hydrazyl (DPPH) radical scavenging activity by 8.31 % and reduction capacity by 10.19 %. The highly denatured soybean meal hydrolysate ultrasonicated at 400 W exhibited the highest antioxidant activity. The DPPH radical scavenging activity was 56.22 % and reduction capacity was 0.717. The ultrasonicated hydrolysate at 400 W was fractionated using ultrafiltration into three fractions: I (>10 kDa), II (5 kDa to 10 kDa), and III (<5 kDa). The in vitro antioxidant activity and others in vivo anti-exercise-fatigue effect of the three fractions (I, II, and III) were determined. Fraction III exhibited the highest DPPH radical scavenging activity and reduction capacity, improved the hemoglobin and hepatic glycogen content and reduced blood urea nitrogen and blood lactic acid. Fraction III improved the activity of superoxide dismutase (SOD) and glutathione peroxidase (GSH-PX) and reduced the malonaldehyde (MDA) content in mouse livers. Therefore, the highly denatured soybean meal hydrolysate has an anti-oxidative effect and it significantly alleviates exercise-fatigue in mice. Amino acids of hydrolysate were determined. Results showed that the antioxidant activity and anti-exercise-fatigue effect were related to the amino acid compositions.