Synthesis and cytotoxic effect of pseudodiosgenyl saponins with thio-ring F

Both the sugar moieties and aglycons of steroid saponins play important roles for their bioactivities. In order to test the biological contribution of the glycosyl residue and search new saponins with notable anticancer activity, mono- and di-saccharide pseudodiosgenyl saponins 22-28 together with two pseudodiosgenyl conjugates 29 and 30 were conveniently synthesized, all of which were based on the aglycon 7 bearing the thio-ring F. The cytotoxicity on human cancer cells (MCF-7, HepG-2, A549) for all of the synthesized compounds 7 and 22-30 was evaluated by MTT method. The thio-aglycon 7 when conjugated with sugars exhibited potent cytotoxicity, and the introduction of d-glucosamine into aglycon 7 led to the most potent compound 28. Furthermore, DAPI staining, AV/PI staining, AO-relocation, AO-uptake and LysoTracker Red-uptake assays demonstrated that the cell death caused by neosaponin 28 was at least partially through apoptosis involving lysosomal membrane permeabilization.