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.