Glucose Tolerance and Antioxidant Activity of Spent Brewer's Yeast Hydrolysate with a High Content of Cyclo-His-Pro (CHP)

To elevate the Cyclo-His-Pro (CHP) content in yeast, the yeast hydrolysate that was obtained from enzymatic hydrolysis was subjected to various treatments. Flavourzyme-treated hydrolysate showed the highest CHP content (674.0 μg/g) among the various proteases treatments. Ultrafiltration was selected as the best method for concentrating CHP in yeast hydrolysate, based on the yields and CHP contents. In addition, we evaluated the radical scavenge and glucose tolerance of yeast hydrolysate with a high content of CHP. Yeast hydrolysate showed intense scavenging abilities of both 1, 1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radicals. The IC₅₀ values of yeast hydrolysate on DPPH and ABTS radicals were 1.9 and 0.9 mg/mL, respectively. There were significant differences in glucose level between the diabetes-control and yeast hydrolysate group at 30, 60, 90, and 120 min after injection in a type 1 diabetes model (P< 0.01). Also, there were significant differences in blood glucose levels between the 2 groups at 30, 60, and 100 min after injection in the type 2 diabetes group (P< 0.05). Therefore, it is possible to use the yeast hydrolysate with high levels of CHP as an antioxidative and/or antidiabetic material for the preparation of functional foods.