Bufospirostenin A (1) and bufogargarizin C (2), twonovel steroids with rearranged A/B rings, were isolated from the toad Bufobufogargarizans. Compound 1 represents the first spirostanol found in animals. Compound 2 is an unusual bufadienolide with a cycloheptatriene B ring. Their structures were elucidated by spectroscopic analysis, single crystal X-ray diffraction analysis, and computational calculations
Molecular docking studies have shown that Delta(8,14)-anhydrobufalin (1) exhibited more potent binding affinity on androgen receptor (AR) than.Delta(14,15)-anhydrobufalin (2) and bufalin (3). To validate the docking results, compounds 1 and 2 were synthesized. The AR competitive binding assay indicated that the IC50 values of 1-3 were 1.9, >50 and >50 mu M (relative binding affinity), respectively, which confirmed that our theoretical binding mode was reliable and predictable. Furthermore, compound 1 was found to show more potent inhibitory activity against the androgen dependent LNCaP cancer cells than the androgen independent PO cancer cells, but exhibited less inhibition on the Na+/K+ ATPase as compared with the parent compound 3. To the best of our knowledge, compound 1 represented the first AR antagonist derived from bufadienolide discovered through a series of combined approaches of molecular docking and actual experimental validation. (C) 2013 Elsevier Ireland Ltd. All rights reserved.
Kotake; Kuwada, Scientific Papers of the Institute of Physical and Chemical Research (Japan), 1939, vol. 36, p. 106,108