New acylated triterpenoid saponins from Maesa lanceolata

Ten new acylated triterpenoid saponins were isolated from the leaves of Mae sa lanceolata. For their structure elucidation extensive use was made of ho mo- 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. Monoeste r, diester and triester derivatives were present. Maesasaponin I was a 21-m onoester derivative, i.e. {3 beta-O-[alpha-L-rhamnopyranosyl-(1 --> 2)-beta -D-galactopyranosyl-(1 --> 3)]-[beta-D-galactopyranosyl-( -->)]-beta-D-gluc uronopyranosyl}-21 beta-angeloyloxy-13 beta,28-oxidoolean-16a, 22a, 28 alph a-triol. Maesasaponins III, IV3, V-3 and VI2 had an additional acetyl, prop anoyl, n-butanoyl and angeloyl substituent, respectively, in position 22. M aesasaponins II, IV2, V-2, VI3 and VII1 were characterised as the 16-acetyl derivatives of maesasaponins I, III, IV3, V-3 and VI2, respectively. Struc tures of saponins previously reported in M. lanceolata had to be revised. ( C) 1999 Elsevier Science Ltd. All rights reserved.