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New Class of Alkaloids Found in Amazonian Poison Frogs

Scientists have identified a new class of alkaloids in some Amazonian poison frogs (family Dendrobatidae). The class of alkaloids, N-methyldecahydroquinolines, has not been previously identified in the frogs or, it is believed, in nature. Senior author Dr. H. Martin Garraffo and colleagues noted that there are more than 500 alkaloids, potentially toxic substances, known to exist in the skin of poison frogs of the family Dendrobatidae. The frogs use the alkaloids as a chemical defense to discourage predators from biting and eating them. Western Colombian natives have used skin extracts from another group of frogs, unrelated to those in the new study, to coat blow-darts for hunting. The frogs obtain nearly all of the alkaloids from their diet--removing the chemicals from ants, mites, small beetles, millipedes, and possibly other small arthropods; concentrating them with incredible efficiency; and storing them in their skin. Although the researchers speculate that the frogs could get the new alkaloids from ants, they are, in fact, not certain about the origin of the chemicals, which could also be produced in the frogs' own bodies. Feeding experiments with alkaloids fed to captive frogs are planned, which might settle this point. This work was published online ahead-of-print in the American Chemical Society’s Journal of Natural Products and is scheduled for publication in the June 26 issue of the journal. [Journal of Natural Products article]