Saundersiosides C-H, rearranged cholestane glycosides from the bulbs of Ornithogalum saundersiae and their cytostatic activity on HL-60 cells.

Six novel rearranged cholestane glycosides with a six-membered hemiacetal ring system, designated as saundersiosides C-H, were isolated from the bulbs of Ornithogalum saundersiae. Their structures were determined on the basis of spectroscopic analysis and the result of hydrolysis. The conformation of the six-membered hemiacetal ring of the rearranged cholestanes was shown to be almost a boat-form by molecular mechanics and molecular dynamics calculation studies. Among the isolated compounds, saundersioside E, F, G and H with an aromatic acid ester group at the glycoside moiety were found to be highly cytostatic to human leukemia HL-60 cells, showing IC50 values of 0.021, 0.019, 0.063 and 0.052 microM, respectively, which are as potent as those of the clinically applied anticancer agents, etoposide and methotrexate.