Antioxidant activities of the synthesized thiol-contained peptides derived from computer-aided pepsin hydrolysis of yam tuber storage protein, dioscorin.

Our previous report showed that yam dioscorin and its peptic hydrolysates exhibit radical scavenging activities; however, the functions of these peptic hydrolases are still under investigation. In this study, the thiol-containing peptides derived from computer-aided simulation of pepsin hydrolysis of dioscorin, namely, KTCGNGME (diotide1), PPCSE (diotide2), CDDRVIRTPLT (diotide3), KTCGY (diotide4), and PPCTE (diotide5) were synthesized to compare their antioxidant activities with GSH and/or carnosine by examining hydroxyl radical scavenging activity by electron spin resonance spectrometry, anti-low-density lipoprotein peroxidation, anti-AAPH-induced hemolysis, and oxygen radical absorbance capacity activity. We found that while all the synthesized diotides showed antioxidant activity, diotide4 exhibited the highest levels. Moreover, all diotides (100 μM) showed protective effects against methylglyoxal-induced human umbilical vein endothelial cell death. These results suggest that thiol-containing diotides derived from dioscorin hydrolysis exhibit antioxidant activities and reveal the benefits of yam tuber as an antioxidant-rich food.