Inhibitory mechanism of pterostilbene and pinostilbene on aldose reductase and α-glucosidase: a new insight from inhibition kinetics and molecular docking studies

Pterostilbene, a dietary polyphenol in blueberries, grapes and wine, possesses an anti-diabetic efficacy. However, the mechanism of anti-diabetic efficacy for pterostilbene is poorly understood. The purpose of the present study was to systematically investigate inhibitory effects and inhibition mechanisms of pterostilbene or its metabolite (pinostilbene) against aldose reductase and α-glucosidase. In the present study, inhibition kinetics and molecular docking were applied to investigate the effect of pterostilbene and pinostilbene on the activity of aldose reductase and α-glucosidase. The results showed that pinostilbene exhibited stronger inhibition on aldose reductase (IC₅₀ = 55.41 ± 4.31 μM) and α-glucosidase (IC₅₀ = 11.69 ± 0.888 μM) in noncompetitive-type manner. Whereas, pterostilbene displayed the weak effect on aldose reductase and α-glucosidase (IC₅₀ = 1569 ± 177.858 μM) inhibition. Moreover, pinostilbene interacted with amino acid residues outside of aldose reductase and α-glucosidase active site to inhibit its activities by van der Waals, π-anion or π-alkyl interactions. The current study has provided comprehensive reference not only for the anti-diabetic mechanism of pterostilbene, but also offered a basis to develop and design adjuvant antidiabetic drugs or novel functional foods.