Bufagin is a toxic steroid C24H34O5 obtained from toad's milk, the poisonous secretion of a skin gland on the back of the neck of a large toad (Rhinella marina, synonym Bufo marinus, the Cane Toad). The toad produces this secretion when it is injured, scared or provoked. Bufagin resembles chemical substances from digitalis in physiological activity and chemical structure.
Bufagin also refers to any of several similar substances found as components of the mixture bufotoxin in secretions of other toads, as well as plants and mushrooms.
Bufagin and bufagins are bufadienolide derivatives. This means they are steroids with a pyran- (delta-)lactone ring attached to ring D (the five-membered one). The difference to digitalis compounds is that the latter have a furan- (gamma-)lactone ring that has one carbon atom and one double bond less.
^Wang, G., G. Sun, et al. (1994). "The application of traditional Chinese medicine to the management of hepatic cancerous pain". J Tradit Chin Med14 (2): 132–138. PMID7967697.
^Jiun-Yih Yeh, William J. Huang, Shu-Fen Kan, Paulus S. Wang (2002). "Effects of bufalin and cinobufagin on the proliferation of androgen dependent and independent prostate cancer cells". The Prostate54 (2): 112–124. doi:10.1002/pros.10172. PMID12497584.
^Jing, Y., H. Ohizumi, et al. (1994). "Selective inhibitory effect of bufalin on growth of human tumor cells in vitro: association with the induction of apoptosis in leukemia HL-60 cells". Jpn J Cancer Res85 (6): 645–651. doi:10.1111/j.1349-7006.1994.tb02408.x. PMID8063619.
^Yin, P. H.; Liu, X; Qiu, Y. Y.; Cai, J. F.; Qin, J. M.; Zhu, H. R.; Li, Q (2012). "Anti-tumor activity and apoptosis-regulation mechanisms of bufalin in various cancers: New hope for cancer patients". Asian Pacific journal of cancer prevention : APJCP13 (11): 5339–43. doi:10.7314/apjcp.2012.13.11.5339. PMID23317181.edit
^Bick, RJ; Poindexter, BJ; Sweney, RR; Dasgupta, A (2002). "Effects of Chan Su, a traditional Chinese medicine, on the calcium transients of isolated cardiomyocytes: Cardiotoxicity due to more than Na, K-ATPase blocking". Life Sciences72 (6): 699–709. doi:10.1016/s0024-3205(02)02302-0. PMID12467910.