Triterpenoids from Gynostemma pentaphyllum and their inhibition activity to α-glycosidase and protein tyrosine phosphatase 1B / 中草药

ABSTRACT

Objective: To determine the total saponins from Gynostemma pentaphyllum, the dammarane-type triterpenoids of its hydrolysate, and its hypoglycemic activity. Methods: Compounds from the acid hydrolyzate extracts and total saponins were isolated by silica gel, recrystal and preparative liquid chromatography, and their structures were identified by the NMR spectral analysis. The sensitive screening modles of α-glucosidase and PTP1B inhibitors were established in vitro. The inhibitory kinetics of compounds were also investigated. Using the method of computer aided drug design of active site, PTP1B interact with the strongest active compound for docking simulation. Results: Seven compounds were isolated from the acid hydrolyzate of total saponins, which identified as gpsapogenin A (1), 20(S)-panaxadiol (2), gypensapogenin F (3), 20(R)-protopanaxadiol (4), (23S)-3β- hydroxydama-20,24-diene-21-carboxylic acid 21,23-lactone (5), gypsapogenin A (6), and (20S,24S)-3β,20,21β,23β,25- pentahydroxy-21,24-epoxydammarane (7). Five compounds were isolated from total saponins, including (20R,23R)- 3β,20-dihydroxydammar-24-en-21-oic acid 21,23-lactone 3-O-[α-L-rhamnopyranosyl(1→2)][β-D-xylopyranosyl(1→3)]-6-O- acetyl-β-D-glucopyranoside (8), (20S,23S)-3β,20-dihydroxydammar-24-en-21-oic acid 21,23-lactone 3-O-[α-L-rhamnopyranosyl(1→2)][β-D-xylopyranosyl(1→3)]-6-O-acetyl-β-D-glucopyranoside (9), (20R,23R)-19-oxo-3β,20-dihydroxydammar-24-en-21-oci acid 21,23-lactone3-O-[α-L-rhamnopyranosyl-(1→2)][β-D-xylopyranosyl(1→3)]-α-L-arabinopyranoside (10), (20S)-3β,20,21- trihydroxydammar-23,25-diene 3-O-{[α-L-rhamnopyranosyl(1→2)][β-D-xylopyranosyl(1→3)]-β-D-glucopyranosyl}-21-O-β- D-glucopyranoside (11), and (20S,23S)-3β,20-dihydroxydammar-24-en-21-oic acid and 21,23-lactone 3-O-[α-L-rhamnopyranosyl(1→2)][β-D-xylopyranosyl-(1→3)]-β-D-glucopyranoside (12). Conclusion: Beside compound 4, the other compounds showed inhibitory activity against α-glucosidase and PTP1B. For the α-glucosidase and PTP1B inhibitions assay, compound 9 indicated the strongest inhibitory effect with IC50 2.10 and 1.07 μmol/L, respectively.