C23 Steroids from the Venom of Bufo bufo gargarizans

Five new C23 steroids (1–5) together with five known bufadienolides (6–10) were isolated from the venom of Bufo bufo gargarizans (ChanSu in Chinese). The structures of the new steroids were elucidated by extensive spectroscopic methods in combination with X-ray diffraction analysis. Among these C23 steroids, only compound 3 showed cytotoxicities against HepG2 and A549 cancer cells, with respective IC50 values of 26.8 ± 8.3 and 45.6 ± 2.5 μM. In contrast, the bufadienolides (7–10) displayed potent inhibitory activities against these cancer cells, with respective IC50 values in the ranges 0.5–5.5 and 0.6–6.5 μM, but relatively less cytotoxicity on normal mouse spleen cells. In addition, the Na+/K+-ATPase inhibitory activities of 2, 5, and 7 revealed that the lactone moiety of a bufadienolide was important for the inhibitory activity.