Free-radical-scavenging and anti-inflammatory effect of yak milk casein before and after enzymatic hydrolysis

The free-radical-scavenging activities of yak casein and its enzymatic hydrolysate toward DPPH., superoxide and hydrogen peroxide were determined. Their effects on macrophage cell viability, nitric oxide (NO) production, and pro-inflammatory cytokine secretion in LPS-stimulated murine peritoneal macrophages were also examined. Results showed that casein hydrolysate, prepared with alcalase and trypsin, had significantly higher DPPH.-scavenging capacity than had its pepsin counterpart. Flavozyme and papain hydrolysates (P < 0.05), and the 7 h-hydrolysate obtained with alcalase, exhibited the highest DPPH scavenging activity. Compared with intact yak casein, its hydrolysate prepared with alcalase had a more significant effect on attenuating free radicals of DPPH, superoxide and hydrogen peroxide, and on down-regulating the production of NO, as well as the pro-inflammatory cytokines, interleukin-6 (IL-6), tumour necrosis factor-alpha (TNF-alpha), and IL-1 beta secretion in a concentration-dependent manner. These results suggest that yak casein hydrolysate possesses free-radical-scavenging and anti-inflammatory activities, and thus it can possibly be used in the prevention of oxidative stress and inflammation-related disorders. (C) 2010 Elsevier Ltd. All rights reserved.