Studies on the constituents of palmae plants. II. The constituents of Rhapis exelsa Henry and R. humilis BL.

Abstract

Further studies have been done on the constituents of the stems, underground parts and leaves of two Palmae plants, Rhapis exelsa HENRY and R. humilis BL. We isolated and identified dioscin, Pb, deltonin, methyl proto-dioscin, methyl proto-Pb and methyl proto-deltonin from the stems, dioscin, methyl proto-dioscin and methyl proto-Pb from the underground parts, and saponaretin (=isovitexin), methyl proto-dioscin, methyl proto-Pb and methyl proto-rhapissaponin from the leaves of R. exelsa. On the other hand, we isolated and identified prosapogenin A of dioscin, dioscin, deltonin, methyl proto-prosapogenin A of dioscin, methyl proto-dioscin and methyl protodeltonin from the stems, dioscin, methyl proto-prosapogenin A of dioscin, methyl proto-dioscin and methyl proto-Pb from the underground parts, and saponaretin, vitexin, isoorientin, methyl proto-prosapogenin A of dioscin, methyl proto-dioscin and methyl proto-Pb from the leaves of R. humilis. Methyl proto-rhapissaponin is a new furostanol saponin and its structure has been established to be 26-O-β-D-glucopyranosyl 22-O-methyl-25(R)-furost-5-en-3β, 22, 26-triol 3-O-[β-D-glucopyranosyl(1→4)-α-L-rhamnopyranosyl(1→4)]-[α-L-rhamnopyranosyl(1→2)]-β-D-glucopyranoside. This is the second report of the isolation of steroidal saponins from Palmae plants, and the results are interesting from the standpoint of chemotaxonomy.