Inhibitory effect of epigallocatechin-3-O-gallate on α-glucosidase and its hypoglycemic effect via targeting PI3K/AKT signaling pathway in L6 skeletal muscle cells.

Epigallocatechin-3-O-gallate (EGCG), a tea polyphenol is renowned for its anti-diabetic properties, however limited studies elucidate its hypoglycemic mechanism from multi-perspectives. In the present study, the interaction between EGCG and α-glucosidase was investigated through kinetics analysis, fluorescence spectra, Fourier transform infrared (FT-IR) spectra and molecular docking studies. Additionally, the effect of EGCG on glucose uptake and its related signaling pathway in L6 muscle cells were also investigated. The results showed that the α-glucosidase inhibitory activity of EGCG (IC = 19.5 ± 0.3 μM) was higher than that acarbose (IC = 278.7 ± 1.1 μM). EGCG inhibited α-glucosidase in a reversible and non-competitive manner. EGCG quenched the fluorescence of α-glucosidase due to the complex formation between EGCG and α-glucosidase, where the hydrogen bonds played a critical role. Microenvironment and the secondary structure of α-glucosidase were highly influenced by EGCG. Molecular docking results indicated that the binding sites on α-glucosidase for EGCG were close to the active site pocket of the enzyme. EGCG was also found to enhance the glucose uptake and promote GLUT4 translocation to plasma membrane via PI3K/AKT signaling pathway in L6 skeletal muscle cells. Overall, these results revealed the possible hypoglycemic mechanism of EGCG.