[A novel dammarane-type saponin from Gynostemma pentaphyllum and its neuroprotective effect]

One new and two known dammarane-type saponins were isolated from the leaves of Gynostemma pentaphyllum using various chromatographic methods. Their structures were identified by HR-ESI-MS,~( 1)H-NMR, ~(13)C-NMR, 2 D-NMR spectra as 2α,3β,12β,20,24(S)-tetrahdroxydammar-25-en-3-O-[β-D-glucopyranosyl(1→2)-β-D-glucopyranosyl]-20-O-β-D-xylopyranosyl(1→6)-β-D-glucopyranoside(1, a new compound, namely gypenoside J5) and 2α,3β,12β,20,24(R)-tetrahdroxydammar-25-en-3-O-[β-D-glucopyranosyl(1→2)-β-D-glucopyranosyl]-20-O-β-D-xylopyranosyl(1→6)-β-D-glucopyranoside(2) and 2α,3β,12β,20-tetrahydroxy-25-hydroperoxy-dammar-23-en-3-O-[β-D-glucopyranosyl(1→2)][β-D-glucopyranosyl]-20-O-[β-D-xylopyranosyl(1→6)]-β-D-glucopy-ranoside(3), respectively. Compounds 1 and 2 were a pair of C-24 epimers. All compounds showed weak cytotoxicity agxinst H1299, HepG2, PC-3, SH-SY5 Y cancer cell lines. However, they exerted protective effect against SH-SY5 Y cellular damage induced by H_2O_2 dose-dependently, of which compound 1 displayed the strongest antioxidant effect. The present study suggested that G. pentaphyllum has antioxidative potential and the saponins from G. pentaphyllum are considered as the active compounds with neuroprotecitve effect.