Steroidal glycosides from the underground parts of Helleborus caucasicus

Four polyhydroxylated and polyunsaturated furostanol glycosides, named caucasicosides A–D, have been isolated from the MeOH extract of the underground parts of Helleborus caucasicus. Elucidation of their structures was carried out by 2D NMR spectroscopy in combination with ESI-MS and HR-ESI-MS analyses. Four polyhydroxylated and polyunsaturated furostanol glycosides ( 1– 4), named caucasicosides A ( 1), B ( 2), C ( 3) and D ( 4), were isolated from the MeOH extract of the underground parts of Helleborus caucasicus, along with four spirostanol derivatives, a furostanol glycoside, a furospirostanol glycoside, 20-hydroxyecdysone and the bufadienolides hellebrigenin and deglucohellebrin. The structures of 1– 4 were elucidated as furosta-5,20(22),25(27)-triene-1β,3β,11α,26-tetrol 26- O-β- d-glucopyranoside ( 1), 26- O-β- d-glucopyranosylfurosta-5,20(22),25(27)-triene-1β,3β,11α,26-tetrol 3- O-α- l-rhamnopyranosyl-(1→2)-β- d-glucopyranoside ( 2), 26- O-β- d-glucopyranosyl-22α-methoxyfurosta-5,25(27)-diene-1β,3β,11α,26-tetrol 3- O-α- l-rhamnopyranosyl-(1→2)-β- d-glucopyranoside ( 3), 26- O-β- d-glucopyranosylfurosta-5,20(22),25(27)-triene-1β,3β,26-triol 3- O-β- d-xylopyranosyl-(1 → 3)-α- l-rhamnopyranosyl-(1→2)-4- O-sulfo-α- l-arabinopyranoside ( 4). Structure elucidation was accomplished through the extensive use of 1D- and 2D NMR experiments including 1H– 1H (COSY, 1D-TOCSY) and 1H– 13C (HSQC, HMBC) spectroscopy along with ESI-MS and HR-ESI-MS. The aglycones of 1– 4 have never been reported before.