Xiaoshi He, Xia Li, Danyang Zhang, Hui Jiang, Yuesheng Dong
Background: Combining natural products with conventional antidiabetic agents to inhibit α-glucosidase activity is an effective strategy for preventing postprandial hyperglycemia. Baicalein, a natural flavonoid with well-documented low toxicity, showed potential synergistic effect with acarbose in diabetic models; however, the synergistic performance and mechanisms of the two agents targeting human maltase-glucoamylase (MGAM) remain unclear. Methods: Recombinant human MGAM-C and MGAM-N were expressed in Pichia pastoris for in vitro inhibition assays. Maltose-loaded mice were used to assess the in vivo hypoglycemic activity and intestinal maltase inhibition. Inhibitor-enzyme interactions were investigated by fluorescence spectroscopy, circular dichroism (CD), multiple molecular docking, and molecular dynamics (MD) simulations. Results: Baicalein potently inhibited MGAM-C and MGAM-N with IC50 values of 20.41 ± 4.80 μM and 14.04 ± 0.94 μM, respectively, and demonstrated a synergistic effect when combined with acarbose. In vivo, co-administration significantly reduced blood glucose levels and suppressed small intestinal maltase activity in maltose-loaded mice. Mechanistic studies revealed that baicalein functions as a non-competitive inhibitor by binding to the allosteric site of MGAM-C via stable hydrogen bonds with residues Ile1716 and Trp1749. This interaction induces conformational changes in the enzyme's secondary structure and optimizes the hydrophobic microenvironment of the active site, thereby enhancing the binding affinity and hydrogen bond stability of acarbose. These molecular events collectively contribute to the synergistic inhibition of MGAM-C hydrolytic activity. Conclusions: This research revealed the synergistic inhibitory effect of baicalein and acarbose on MGAM and the underlying mechanisms, thereby providing a theoretical basis for developing pharmaceutical formulations to enhance acarbose efficacy.