Triterpene saponins in the defensive secretion of a chrysomelid beetle, Platyphora ligata

The secretion of the defensive glands of adults of the chrysomelid beetle P latyphora ligata from Panama has been shown to contain, besides chlorogenic acid (1) and a mixture of phosphatidylcholines, two new oleanane triterpen e saponins, named ligatosides A and B. Their structures were established as 3-O-beta-D-glucuronopyranosyl-16 alpha,23-dihydroxyoleanolic acid-28-O-2-( 3,4-dimethoxybenzoyl)-beta-D-glucopyranoside (2) and 3-O-beta-D-glucopyrano syl-(1-->2)-beta-D-glucuronopyranosyl-16 alpha,23-dihydroxyoleanic acid-28- O-2-(3,4-dimethoxybenzoyl)-beta-D-glucopyranoside (3), respectively, by a c ombination of extensive 1D and 2D NMR methods (COSY, HMQC, HMBC, and TOCSY) and FABMS. This is the first report of triterpene saponins in the defensiv e secretion of an insect.