Saponins of Allium elburzense

A phytochemical investigation of the bulbs of Allium elburzense has been undertaken, leading to the isolation of 13 furostanol and spirostanol saponins, eight of which are new, namely, elburzensosides A1/A2 (1a/1b), B1/B2 (2a/2b), C1/C2 (3a/3b), and D1/D2 (4a/4b). On the basis of spectroscopic analysis, mainly 2D NMR and mass spectrometry, and chemical methods, the structures of the new compounds were determined as furost-2alpha,3beta,5alpha,6beta,22alpha-pentol 3-O-beta-D-glucopyranosyl 26-O-beta-D-glucopyranoside (1a), furost-2alpha,3beta,5alpha,6beta,22alpha-pentol 3-O-beta-D-glucopyranosyl-(1-->4)-O-beta-D-glucopyranosyl] 26-O-beta-D-glucopyranoside (2a), furost-2alpha,3beta,5alpha,22alpha-tetrol 3-O-beta-D-glucopyranosyl 26-O-beta-D-glucopyranoside (3a), and furost-2alpha,3beta,5alpha,22alpha-tetrol 3-O-[beta-D-xylopyranosyl-(1-->3)-O-beta-D-glueopyranosyl-(1-->4)-O-beta-D-galactopyranosyl 26-O-beta-D-glucopyranoside (4a), and the corresponding epimers at position 22 (1b-4b). Along with these compounds we have isolated the corresponding 22-O-methyl derivatives that we consider extraction artifacts. All the new elburzensosides A1/A2-D1/D2 possess as a common structural feature an OH-5alpha that is rare among furostanol saponins. The reported compounds have been isolated in large amounts, and this makes A. elburzense a prolific producer of saponins of the furostanol and spirostanol types.