Sterol-recognition ability and membrane-disrupting activity of Ornithogalum saponin OSW-1 and usual 3- O -glycosyl saponins

摘要

Abstract OSW-1 is a structurally unique steroidal saponin isolated from the bulbs of Ornithogalum saundersiae , and has exhibited highly potent and selective cytotoxicity in tumor cell lines. This study aimed to investigate the molecular mechanism for the membrane-permeabilizing activity of OSW-1 in comparison with those of other saponins by using various spectroscopic approaches. The membrane effects and hemolytic activity of OSW-1 were markedly enhanced in the presence of membrane cholesterol. Binding affinity measurements using fluorescent cholestatrienol and solid-state NMR spectroscopy of a 3- d -cholesterol probe suggested that OSW-1 interacts with membrane cholesterol without forming large aggregates while 3- O -glycosyl saponin, digitonin, forms cholesterol-containing aggregates. The results suggest that OSW-1/cholesterol interaction is likely to cause membrane permeabilization and pore formation without destroying the whole membrane integrity, which could partly be responsible for its highly potent cell toxicity. Graphical abstract Display Omitted Highlights ? OSW-1 has strong hemolytic and liposomal membrane activity owing to interactions with cholesterol in the membrane. ? Cholesterol recognition by OSW-1 is essential for the subsequent membrane permeabilization. ? OSW-1 induces membrane permeabilization via pore formation.