New acylated triterpenoid saponins from Maesa lanceolata

Ten new acylated triterpenoid saponins were isolated from the leaves of Maesa lanceolata. For their structure elucidation extensive use was made of homo- and heteronuclear 2D NMR techniques such as COSY, NOESY, HSQC and HMBC. All saponins identified contained the same tetraglycosidic side chain, but the triterpenoid moiety showed a variable esterification pattern. Monoester, diester and triester derivatives were present. Maesasaponin I was a 21-monoester derivative, i.e. {3 beta-O-[alpha-L-rhamnopyranosyl-(1 --> 2)-beta-D-galactopyranosyl-(1 --> 3)]-[beta-D-galactopyranosyl-( -->)]-beta-D-glucuronopyranosyl}-21 beta-angeloyloxy-13 beta,28-oxidoolean-16a, 22a, 28 alpha-triol. Maesasaponins III, IV3, V-3 and VI2 had an additional acetyl, propanoyl, n-butanoyl and angeloyl substituent, respectively, in position 22. Maesasaponins II, IV2, V-2, VI3 and VII1 were characterised as the 16-acetyl derivatives of maesasaponins I, III, IV3, V-3 and VI2, respectively. Structures of saponins previously reported in M. lanceolata had to be revised. (C) 1999 Elsevier Science Ltd. All rights reserved.