Identification and Inhibitory Mechanisms of Anti-α-glucosidase Peptides from Xiaojiao Baijiu Distillers’ Grains

T2DM (Type 2 diabetes mellitus) is a chronic metabolic disease typically managed with medications that often cause undesirable side effects, highlighting the urgent need for safe and effective natural alternatives. In this study, Baijiu distillers’ grains (BDGs) from Xiaojiao Baijiu were used to screen and identify anti-α-glucosidase peptides. The fraction under 3 kDa of the hydrolyzate generated by alcalase demonstrated the most potent inhibitory activity. This fraction was subsequently separated by RP-HPLC, resulting in the most effective subfraction, F2–2, with an inhibitory rate of 77.33 ± 1.15%. Six potential antidiabetic peptides (AAPFYAL, LAYPQ, IRLPFNQI, INPALPW, ATPVFL, SSSSAVVG) were identified from F2–2, with AAPFYAL showing the highest inhibitory activity (IC50 = 363.77 μM). Molecular docking demonstrated that these peptides competitively bind to key residues of α-glucosidase (such as D327, D542) via hydrogen bonds, which was further confirmed by pharmacophore model analysis. Our findings demonstrate that Xiaojiao BDGs are promising hypoglycemic resources.