Alkaloids from Amphibian Skin:  A Tabulation of Over Eight-Hundred Compounds

Abstract

A diverse array of biologically active, lipid-soluble alkaloids have been discovered in amphibian skin. Such alkaloids include the following: the steroidal samandarines from salamanders, the batrachotoxins, histrionicotoxins, gephyrotoxins, and epibatidine from neotropical poison frogs (Dendrobatidae), the pumiliotoxins, allopumiliotoxins, homopumiliotoxins, and decahydroquinolines from certain genera of anurans from four families (Dendrobatidae, Mantellidae, Bufonidae, and Myobatrachidae), a variety of izidines (pyrrolizidines, indolizidines, quinolizidines, lehmizidines), pyrrolidines, piperidines, various tricyclics (related in structures to the coccinellines), and spiropyrrolizidines from the first three of these four families, the pseudophrynamines from one genus of Australian frogs, and a variety of unclassified alkaloids as yet of undetermined structure. With the exception of the samandarines and the pseudophrynamines, all alkaloids appear to be derived from dietary sources. Although only a few of the over 800 amphibian skin alkaloids have been detected in arthropods, putative arthropod sources for the batrachotoxins and coccinelline-like tricyclics (beetles), the pumiliotoxins (ants, mites), the decahydroquinolines, izidines, pyrrolidines, and piperidines (ants), and the spiropyrrolizidines (millipedes) have been discovered. Ants are likely sources for histrionicotoxins, lehmizidines, and tricyclic gephyrotoxins. Epibatidines represent an important alkaloid class without a putative dietary source. The structures for many of these alkaloids have been rigorously established, while the structures of others represent tentative proposals, based only on mass spectral and FTIR spectral data, along with analogies to structures of well-defined alkaloids.

Oribatid mites as a major dietary source for alkaloids in poison frogs

“…Poison frogs include certain species from four anuran families worldwide, which include the dendrobatids from Central and South America, mantellids from Madagascar, bufonids from South America, and myobatrachids from Australia. Over the past 30 years, Ͼ800 lipophilic alkaloids from the skin of poison frogs have been characterized (6), a number that appears to directly reflect the diversity of alkaloids present in dietary arthropods.…”

Correlation between the Selectivity and the Structure of an Asymmetric Catalyst Built on a Chirally Amplified Supramolecular Helical Scaffold

“…[1] The development of methods to access partly or fully reduced enantiopure heterocycles has increased in scope and importance in recent years. The enantioselective reduction of heterocyclic compounds is becoming more important in the preparation of their partly or fully reduced analogues, as this strategy benefits from a great diversity of starting materials and minimizes the need for manipulation of functional groups during the preparation of target compounds.…”

Discovery of skin alkaloids in a miniaturized eleutherodactylid frog from Cuba

“…In addition, the great majority of alkaloid-containing amphibians are characterized by vivid colours of probable aposematic function, often covering the entire body although sometimes restricted to the ventral or dorsal side. Representatives of more than 80 other genera of frogs screened contained no alkaloids [3,7,8], confirming that these compounds are restricted to only a small number of lineages.…”