Phyllobates

Very rapid-acting paralytic neurotoxin that binds to sodium channels of nerve and muscle cells depolarizing neurons by increasing the sodium channel permeability. It is obtained from South American poison-dart frogs (Phyllobates aurotaenia, Phyllobates terribilis). It is insoluble in water but soluble in hydrocarbons and other nonpolar solvents. The dried toxin can remain active for at least a year. However, it is relatively nonpersistent in the environment. 

The batrachotoxins were the first class of unique alkaloids to be characterized from skin extracts of frogs of the family Dendrobatidae (see ref. 23 for a review of amphibian alkaloids). Batrachotoxin was detected in only five species of dendrobatid frogs and these frogs were then classified as the monophyletic genus Phyllobates, based in part on the presence of batrachotoxins (24). However, levels of batrachotoxins differ considerably, with the Colombian Phyllobates terribilis containing nearly 1 mg of batrachotoxins per frog, while the somewhat smaller Phyllobates bicolor and Phyllobates aurotaenia, also from the rain forests of the Pacific versant in Colombia, contain 10-fold lower skin levels (8). The two... 

The active principle of dart frog poisons is alkaloids. The study of the den-drobatid poisons led to the discovery of over 200 new alkaloids, including batrachotoxins Pig. 10.5), pumiliotoxins, histrionicotoxins, gephyrotoxins, and decahydroquinolines (Daly et al., 1994). The most common compounds have the basic structure of piperidine and include histrionotoxin. In Phyllobates, the synthesis of other alkaloids is suppressed in favor of batrachotoxins. These are... 

The chloroform extracts are combined, dried over sodium sulfate, and concentrated under vacuum until dry. The residue will be crude, a mixture of about three different alkaloids. Yield will depend on the species of the frogs used. In one test, 5000 adult Phyllobates aurotaema yielded 157 mg of mixed alkaloids, while 750 adult Dendrobates tricolor yielded 80 nig. 

Dendrobatidae Phyllobates aurotaenia Cardiotoxin Neuro toxin Batrachotoxin Homobatrachotoxin... 

Batrachotoxin A (III), just one of many steroidal alkaloids, is one of the most lethal substances known (LD50 = 2/xg/kg subcutaneously in mice). It is found in the skin secretions of the brightly colored tropical frog Phyllobates aurotaenia and is used by Colombian Indians to prepare poison darts. 

The above three alkaloids are found in the skins of dendrobatid frogs of the genus Phyllobates terribilis, P. aurotaenia, and P. bicolor, all of Colombia, and to a very minor extent in P. vittatus of Costa Rica and P. lugubris of Panama (28). 

The apparent occurrence of decahydroquinolines as major alkaloids in dendrobatid frogs of the genera Dendrobates, Epipedobates, and Phyllobates, and in bufonid toads of the genus Melanophryniscus, strongly suggests the independent evolutionary development of biosynthetic pathways to decahydroquinolines in two separate amphibian lineages. 

The pseudophrynamines have not been detected elsewhere in Nature. In myobatrachid frogs of the genus Pseudophryne, they occur in varying amounts in all species examined (56). The pair of dimeric indole alkaloids, chimonanthine/calycanthine, have been detected in amphibians only in the dendrobatid frog Phyllobates terribilis and, tentatively, as a trace alkaloid in Phyllobates bicolor (14). 

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