Inhibitory effects of phenolic compounds from blueberry leaf on <i>α</i>‐amylase and <i>α</i>‐glucosidase: kinetics, mode of action, and molecular interactions
Han Wu, Xiaoli Liu, Shudong Xie, Jianzhong Zhou, Maria G. Corradini, Yue Pan, Xiaozhen Cui
Abstract
Abstract Background The interactions between blueberry leaf polyphenols (BLPs) and digestive enzymes were analyzed using multiple techniques to gain insights into their inhibitory effects on enzyme kinetics and modes of action. Results 3‐ O ‐Caffeoylquinic acid (3‐CQA) was the most abundant compound identified. Quercetin (QR) exhibited the strongest inhibitory activity against α ‐amylase ( α ‐AMY) and α ‐glucosidase ( α ‐GLU). The BLP extracts acted as typical mixed‐type inhibitors for both digestive enzymes, showing stronger inhibition of α ‐GLU (IC50 = 7.36 ± 0.03 μg mL −1 ) than α ‐AMY (IC50 = 12.52 ± 0.65 μg mL −1 ). Stern–Volmer plots showed static quenching of enzyme fluorescence intensity. The quenching and binding constants of α ‐GLU were higher than those of α ‐AMY, showing greater affinity of the former for BLP. The conformational changes of 3‐CQA and QR in the BLP were studied at the molecular level. The stability of the complexes formed followed this order: α ‐GLU‐3‐CQA > α ‐AMY‐QR > α ‐GLU‐QR > α ‐AMY‐3‐CQA. This trend supported the observation that QR had a greater impact on α ‐AMY conformation, whereas 3‐CQA more effectively altered α ‐GLU. Conclusion These findings elucidated the inhibitory mechanisms of BLP on glucose‐regulating enzymes, providing novel insights relevant for the treatment of diabetes. © 2025 Society of Chemical Industry.