Triterpene Saponins in the Defensive Secretion of a Chrysomelid Beetle, Platyphora ligata

The secretion of the defensive glands of adults of the chrysomelid beetle Platyphora ligata from Panama has been shown to contain, besides chlorogenic acid (1) and a mixture of phosphatidylcholines, two new oleanane triterpene saponins, named ligatosides A and B. Their structures were established as 3-O-β-d-glucuronopyranosyl-16α,23-dihydroxyoleanolic acid-28-O-2-(3,4-dimethoxybenzoyl)-β-d-glucopyranoside (2) and 3-O-β-d-glucopyranosyl-(1→2)-β-d-glucuronopyranosyl-16α,23-dihydroxyoleanolic acid-28-O-2-(3,4-dimethoxybenzoyl)-β-d-glucopyranoside (3), respectively, by a combination of extensive 1D and 2D NMR methods (COSY, HMQC, HMBC, and TOCSY) and FABMS. This is the first report of triterpene saponins in the defensive secretion of an insect.