C₂₁ steroids from the roots of Marsdenia tenacissima

A phytochemical investigation of the dichloromethane soluble fraction of the ethanolic extract obtained from the roots of Marsdenia tenacissima led to the discovery of the sixteen undescribed pregnane C₂₁ steroids (1-16) and isolation of eleven known C₂₁ steroidal analogues (17-27). Their chemical structures were elucidated by one- and two-dimensional nuclear magnetic resonance spectroscopy and, high resolution-electrospray ionization mass spectrometry and their absolute configurations were determined using electronic circular dichroism or single-crystal X-ray diffraction. The in vitro anti-proliferative effects of 1-16 were evaluated against HepG2 (human hepatocellular cancer), A549 (lung cancer), and MCF-7 (human breast cancer) cell lines. Even though some of them showed moderate cytotoxic activities, marsectohexol derivative 12 exhibited significant cytotoxicity against A549 cells with an IC₅₀ value of 5.2 μM.