Cytotoxic constituents from the mangrove endophytic Pestalotiopsis sp. induce G0/G1 cell cycle arrest and apoptosis in human cancer cells

Chemical examination of Chinese mangrove Rhizophora mucronata endophytic Pestalotiopsis sp., yielded  11 known metabolites with various structure types, including demethylincisterol A3 (1), dankasterone B (2), (22E, 24R)-ergosta-7,9(11), 22-triene-3β, 5α, 6α-triol (3), ergosta-5,7,22-trien-3-ol (4), 5, 8-epidioxy-5, 8-ergosta-6, 22E-dien-3-ol (5), stigmastan-3-one (6), stigmast-4-en-3-one (7), stigmast-4-en-6 -ol-3-one (8), flufuran (9), (2-cis, 4-trans)-abscisic acid (10), similanpyrone B (11). Their structures were unambiguously elucidated on the basis of extensive NMR spectroscopic and mass spectrometric analyses. Compounds 1, 4, 6–9 showed significant in vitro cytotoxicity against the human cancer cell lines Hela, A549 and HepG, of which compound 1 was the most potential with IC50 values reaching nM degree ranging from 0.17 to 14.16 nM. Flow cytometric investigation demonstrated that compound 1 mainly inhibited cell cycle at G0/G1 phase in a dose-dependent manner with a significant induction of apoptosis on the three tested cell lines. The involvement of the mitochondria in compound 1 induced apoptosis was investigated using MMP. We suggested that R. mucronata endophytic Pestalotiopsis sp. contained a potential anticancer compound demethylincisterol A3.