batra

Batrachotoxin (BTX) is an extremely potent cardiotoxic and neurotoxic steroidal alkaloid found in certain species of beetles, birds, and frogs. The name is from the Greek word . Structurally-related chemical compounds are often referred to collectively as batrachotoxins. In certain frogs, this alkaloid is present mostly on the skin. Such frogs are among those used for poisoning darts. Batrachotoxin binds to and irreversibly opens the sodium channels of nerve cells and prevents them from closing, resulting in paralysis and death. No antidote is known.

==History== Batrachotoxin was discovered by Fritz Märki and Bernhard Witkop, at the National Institute of Arthritis and Metabolic Diseases, National Institutes of Health, Bethesda, Maryland, U.S.A. Märki and Witkop separated the potent toxic alkaloids fraction from Phyllobates bicolor and determined its chemical properties in 1963. They isolated four major toxic steroidal alkaloids including batrachotoxin, homobatrachotoxin (isobatrachotoxin), pseudobatrachotoxin, and batrachotoxinin A. Due to the difficulty of handling such a potent toxin and the minuscule amount that could be collected, a comprehensive structure determination involved several difficulties. However, Takashi Tokuyama, who joined the investigation later, converted one of the congener compounds, batrachotoxinin A, to a crystalline derivative and its unique steroidal structure was solved with x-ray diffraction techniques (1968). When the mass spectrum and NMR spectrum of batrachotoxin and the batrachotoxinin A derivatives were compared, it was realized that the two shared the same steroidal structure and that batrachotoxin was batrachotoxinin A with a single extra pyrrole moiety attached. In fact, batrachotoxin was able to be partially hydrolyzed using sodium hydroxide into a material with identical TLC and color reactions as batrachotoxinin A. The structure of batrachotoxin was established in 1969 through chemical recombination of both fragments. Batrachotoxinin A was synthesized by Michio Kurosu, Lawrence R. Marcin, Timothy J. Grinsteiner, and Yoshito Kishi in 1998.