Antibacterial 5α-Spirostane Saponins from the Fruit of Cordyline manners-suttoniae

Antibacterial-activity-guided fractionation of a dichloromethane extract from the fruit of Cordyline manners-suttoniae and subsequent structure–activity investigations resulted in the identification of 10 new (1–10) and one known (11) 5α-spirostane saponin. The structures of the new compounds were established by 1D and 2D NMR analyses. The absolute configurations of the isolated compounds were determined by X-ray diffraction analysis or chemical derivatizations. The most active compound, suttonigenin F (6), inhibited the Gram-positive bacteria Staphylococcus aureus with MIC75 values that were comparable to those of the antibiotic chloramphenicol. Structure–activity relationships were also obtained from the assessment of antibacterial and cytotoxic activities of the isolated saponins.