α-Glucosidase inhibitors from leaves of Forsythia suspense in Henan province

OBJECTIVE: The alpha-glucosidase inhibitory compounds were searched from Forsythia suspense. METHOD: The active compounds were isolated by the method of bioassay-guided in vitro and column chromatographic techniques. The structures of compounds were identified by MS and NMR spectroscopy. The inhibitory kinetics of the isolated compounds were investigated. RESULT: The ethyl acetate extract showed the strongest inhibitory activity, and five active compounds were isolated from this extract. The IC50 value of compound 1-5 were all lower than that of acarbose as positive control. Compound 1, the mixture of 1, 2 and 4 all showed noncompetitive type model on alpha-glucosidase. CONCLUSION: Compound 1-3 as the inhibitors of alpha-glucosidase were reported for the first time. Compound 3 was isolated from the genus for the first time.