Three New Steroids from the Roots of <i>Marsdenia tenacissima</i>

Three undescribed pregnane steroids, 12β-O-4-hydroxybenzoyl tenacigenin D (1), 12β-O-4-hydroxybenzoyl tenacigenin A (2), and 11α-nicotinoyl-17β-marsdenin (3), along with two known analogues (4 and 5), were isolated from the roots of Marsdenia tenacissima. Their structures were elucidated using one- and two-dimensional NMR, high-resolution electron ionization-mass spectrometry, single-crystal X-ray diffraction data, and experimental and density-functional-theory-calculated electronic circular dichroism measurements. All isolated compounds were evaluated for their cytotoxic activities against human lung cancer cells (A549), ovarian carcinoma cells (SKOV-3), gastric cancer cells (MGC 803) and breast cancer cells (MCF-7). Notably, 3 exhibited significant cytotoxic activity against both A549 (median inhibitory concentration (IC₅₀)=16.79 μM) and SKOV-3 (IC₅₀=12.30 μM) cells while exhibiting moderate cytotoxicity on MGC803 and MCF-7 cells.