Cytotoxic Saponins from the Seeds of Pittosporum angustifolium

Three new acylated R₁-barrigenol triterpene glycosides, 1 - 3, were isolated from the seeds of Pittosporum angustifolium Lodd. together with four known glycosides, 4 - 7, containing R₁- and A₁-barrigenol backbones. On the basis of spectroscopic, spectrometric, and chemical analyses the novel compounds were named pittangretosides N- P and established as 21s-acetoxy- 22α-angeloyloxy- (1), 21s-acetoxy-22α-(2-acetoxy-2-methylbutyroyloxy)- (2), and 21s-(2-methylbutyroyloxy)- 22α-acetoxy-3s-[b-D-glucopyranosyl- (1→2)]-[α-L-arabinopyranosyl-(1→3)]-[α- L-arabinofuranosyl-(1!4)]-s-D-glucuronopyranosyloxyolean-12-ene-15α,16α,28-triol (3). Evaluation of the in vitro cytotoxicity against three tumour cell lines and one non-tumourigenic cell line revealed antiproliferative effects with IC₅₀ values in a range of 1:74 - 34:1 μM