Cytotoxic isovaleryl sucrose esters from Ainsliaea yunnanensis: reduction of mitochondrial membrane potential and increase of reactive oxygen species levels in A549 cells

Eight isovaleryl sucrose esters, named ainslosides A–H (1–8), were isolated from Ainsliaea yunnanensis Franch. Their structures, including the absolute configurations of the sugar residues, were elucidated by extensive analysis of NMR spectra and acid hydrolysis. All compounds were tested in vitro for cytotoxicity against four human tumour cell lines, A549, HCT116, MDA-MB-231, and BEL7404. Among the compounds tested, ainsloside B (2) showed potent cytotoxicity against the A549 cell line with an IC50 value of 3.3 μM. Flow cytometry analysis showed that compound 2 can arrest the cell cycle at the G0/G1 phase and induce cell apoptosis in A549 cells. Further studies indicated that the apoptosis-inducing effect of compound 2 may be involved in the reduction of mitochondrial membrane potential (MMP) and increase of reactive oxygen species (ROS) level in A549 cells.