New seco-limonoids from Cipadessa baccifera: Isolation, structure determination, synthesis and their antiproliferative activities

Abstract

A comprehensive reinvestigation of chemical constituents from CHCl₃-soluble extract of Cipadessa baccifera led to the isolation of two new limonoids 1, 2 together with six known compounds 3-8. Their structures were established on the basis of extensive analysis of spectroscopic (IR, MS, 2D NMR) data. Further, a series of cipaferen G (3) derivatives were efficiently synthesized utilizing Yamaguchi esterification (2, 4, 6-trichlorobenzoyl chloride, Et₃N, THF, DMAP, toluene) at the C-3 position of the limonoids core, which is being reported for the first time. The anti-proliferative activity of the isolates and the synthetic analogues were studied against HeLa, PANC 1, HepG2, SKNSH, MDA-MB-231 and IMR32 cancer cells using the sulphorodamine B assay. Among the tested compounds, 13d and 13h manifested potent activity against IMR32, HepG2 cell lines with GI₅₀ 0.013 and 0.01μM, respectively.

Keywords: Cipadessa baccifera; Ester derivatives and anti-proliferative activity; Limonoids; Yamaguchi esterification.