Amines, amphibian skin

A question which is invariably raised is that of the possible biological significance of active amines and polypeptides in the amphibian skin.At this early stage,an answer to this question seems premature.Before having more information on the occurrence of caerulein or oaerulein-like polypeptides in the skin of the different groups of amphibians any hypothesis on the function of the polypeptide would be futile. 

Gartner M, Weihofen R, Helmchen G. Enantioselective syntheses of 2,5-disubstituted pyrrolidines based on iridium-catalyzed allylic aminations-total syntheses of alkaloids from amphibian skins. Chem. Eur. J. 2011 17(27) 7605-7622. 

Three of the classes of compounds found from the skin of amphibians have been identified from the skin of bufonids, including Bufo marinus. These are steroids (bufadienolides), biogenic amines (catecholamines, indolylalkylamines and alkaloids) and bioactive peptides and proteins. 

Roseghini, M., Ealconieri-Erspamer, G., Severini, C., Simmaco, M. Biogenic amines and active peptides in extracts of the skin of thirty-two European amphibian species. Comp. Biochem. Physiol. C 1989, 94, 455-460. 

Occurrence Since most A. are nerve poisons they cannot form in larger amounts in the animal world, except in skin glands where they are excreted for specific purposes as neurotoxins (e.g. the amphibian venoms samandarine and other salamander alkaloids, tetrod-otoxin, batrachotoxins, bufotenine and other toad poisons, glomerine, serotonine, histamine, tyra-mine and other biogenic amines). Most A. occur in plants as by-products of amino acid metabolism where they are mostly stored in peripheral parts of the plant (leaves, roots, barks, fruits) and much less frequently in the wood. A. occur only rarely as free bases in plants and are mostly found as salts with oxalic, acetic, lactic, and citric acids, etc. Some higher plant families are... 

Numerous species of amphibians contain substances in their skin that render them noxious or toxic to potential predators. The active substances in the skin include amines (norepinephrine and histamine), piperidines, steroidal alkaloids, bufodienolides, and tetrodotoxin (reviews in Daly et al. 1978 Daly 1982). 

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