Isolation and Purification of Antioxidant and ACE-Inhibitory Peptides from Yak (Bos grunniens ) Skin

Yak (Bos grunniens) is a kind of cattle which can survive on Tibetan plateau. In addition, yak skin is an unused resource during production of meat. In this research, the potential angiotensin I-converting enzyme (ACE)-inhibitory and antioxidant bioactivities of yak skin gelatin hydrolysates (YSGH) were investigated. Orthogonal test was applied to optimize the pretreatment process. Then the gelatin was treated with combinations of different kinds of enzymes and YSGH was separated by ultrafiltration membranes. Interestingly, all hydrolysates below 3 kDa by different enzyme combination treatments showed excellent antioxidant activities, and the fraction (<3 kDa) hydrolyzed by Proteinase K exhibited high ACE-inhibitory activity with an IC50 value of 1.119 mg mL−1. Furthermore, the hydrolysis condition for better activity of ACE-inhibitory fraction was optimized, and then a novel ACE-inhibitory peptide B4P was obtained through purification, which exhibited the highest ACE-inhibitory activity (IC50 = 35 µg mL−1). The molecular mass of B4P was 1496.7 Da. Practical Applications This study introduces the antioxidant and ACE-inhibitory activities of the peptides isolated from yak skin. During this process, the purification methods were also optimized. The peptides showed excellent bioactivities, which indicated that yak skin offers the potential for the production of functional foods or medicines with antihypertensive and antioxidant activities.