Purification and identification of antioxidant and angiotensin converting enzyme-inhibitory peptides from Guangdong glutinous rice wine

Guangdong glutinous rice wine, a type of Chinese yellow rice wine, is rich in a variety of bioactive peptides. In this study, polypeptides with antioxidant and angiotensin converting enzyme (ACE)-inhibitory activities were isolated from Guangdong glutinous rice wine, and their activities and molecular mechanisms were studied. The peptide fraction (F2-2), which exhibited the strongest antioxidant and ACE inhibitory activities, was separated by ultrafiltration and RP-HPLC. A total of 76 peptides were identified by LC-MS/MS, and four peptides with potential antioxidant activities were obtained: VLSGA (445.2536 Da), VISGA (445.2536 Da), MGKAA (476.2417 Da) and GHVAA (453.2336 Da). These four peptides showed significant antioxidant activity with EC50 values of 0.118 mg/mL, 0.056 mg/mL, 0.054 mg/mL and 0.027 mg/mL respectively, and effectively protected cells against oxidative damage. Molecular docking showed that all these four peptides could interact with key active sites on the receptor proteins CD38 and Keap1. Furthermore, these peptides showed good safety and stability according to in silico prediction.