Triterpenoid saponins and sapogenin lactones from Albizia gummifera

Abstract

The structures of two new monodesmosidic and bisdesmosidic triterpenoid saponins (1 and 2) and the known compound Δ5-stigmasterol-3-O-β-D-glucopyranoside (3) as well as two new oleanane type triterpene lactone glycosides 4, 5 and a new sapogenin lactone 6 isolated from the stem bark of Albizia gummifera C.A. Smith (Mimosaceae) have been elucidated as 3-O-{β-D-glucopyranosyl(1→2)-[α-L-arabinopyranosyl(1→6)]-β-D-glucopyranosyl}-oleanolic acid (1), β-D-glucopyranosyl(1→2)-β-D-glucopyranosyl 3-O-{β-D-glucopyra-nosyl(1→2)-[α-L-arabinopyranosyl(1→6)]-β-D-glucopyranosyl}-oleanolate (2), 3β-{O-D-glucopyranosyl-(1→2)-[O-α-L-arabinopyranosyl(1→6)]β-D-glucopyranosyloxy}-machaerinic acid γ-lactone (4), 3β-O-β-D-glucopyranosiduronic acid (1→2)-β-D-glucopyranosyloxy]-machaerinic acid γ-lactone (5), and A-homo-3a-oxa-5β-olean-12-en-3-one-28-oic acid (6), respectively. The complete assignment of the and resonances of 1, 2, 4 and 6 and of the peracetate of 5 were achieved by means of 2D-NMR studies.