Two major saponins from seeds of Barringtonia asiatica: Putative antifeedants toward Epilachna sp. larvae

Two major saponins have been isolated from a methanol extract of the seeds of Barringtonia asiatica, and their structures elucidated (mainly by two-dimensional NMR spectroscopy) as 3-O-{[β-D-galacto-pyranosyl(1→3)-β-D-glucopyranosyl (1→2)]-β-D-glueuronopyranosyloxy}-22-O-(2-methylbutyroyloxy) -15,16,28-trihydroxy-(3β,15α,16α,22α) -olean-12-ene (3) and 3-O-{[β-D-galactopyranosyl(1→3)-β-D-gluco-pyranosyl (1→2)]-β-D-glueuronopyranosyloxy}-22-O-[2(E) -methyl-2-butenyloyloxy]-15,16,28-trihydroxy- (3β,15α,16α,22α)-olean-12-ene (4). The antifeedant properties of 3 and 4 toward Epilachna larvae are discussed.