Two Glycosides of a Novel Dammarane Alcohol from Gynostemma pentaphyllum

抄録

From the aerial parts of Gynostemma pentaphyllum MAKINO (Cucurbitaceae), two glycosides were isolated, namely gynosaponin TN-1 (III), C₃₆H₆₂O₉·3/2H₂O, mp 168-173°, [α]D+34.5°and gynosaponin TN-2 (IV), C₄₂H₇₂O₁₃·1/2H₂O, mp 236-240°, [α]D+11.6°. On acid hydrolysis, gynosaponin TN-1 (III) yielded glucose as its sugar moiety and 2α-hydroxypanaxadiol (II), C₃₀H₅₂O₄ as an artificial genin, while gynosaponin TN-2 (IV) afforded rutinose and II. The structure of II was elucidated to be 20, 25-epoxydammarane-2α, 3β, 12β-triol on the basis of its mass spectrum, molecular optical rotation and nuclear magnetic resonance (NMR) spectra (¹H, ¹³C) in comparison with those of panaxadiol (I). Carbon 13 NMR spectra of III and IV indicated that their aglycone moiety has a (20S)-dammar-24-en-20-ol partial structure. Their chemical structures were established as (20S)-dammar-24-ene-2α, 3β, 12β, 20-tetraol 20-O-β-D-glucopyranoside (III) and (20S)-dammar-24-ene-2α, 3β, 12β, 20-tetraol 20-O-α-L-rhamnopyranosyl-(1→6)-β-D-glucopyranoside (IV).