Tracking the cryptic pumiliotoxins
- Department of Chemistry, Virginia Military Institute, Lexington, VA 24450
Although the concept of chemical prospecting, cataloging the chemical expression of an ecosystem, is gaining credence, exceptional biological activity observed in particular groups of plants, animals, or microorganisms has always attracted the attention of biologists and chemists. A fascinating example is the account of the alkaloids found in the skins of the “poison dart” frogs. First documented in the early 19th century, the chemistry and biological activity of the toxic skin secretions of these tropical frogs have been the primary interest of John W. Daly for nearly 40 years (1–3). This work has uncovered >20 classes of alkaloids, the biological properties of which vary from highly toxic, cardiotonic, or anesthetic to nearly inactive. For the most part, the presence of these compounds depends on where the frogs are collected, and a dietary hypothesis has been put forth for their sequestration (1). The source of one of the most active of these classes, the pumiliotoxins, has remained a mystery. The work of Saporito et al. (4) in this issue of PNAS demonstrates the presence of the pumiliotoxins in two genera of formicine ants, noteworthy because of their ubiquity in poison dart frogs and their physiological activity.
Amphibian alkaloids with the largest diversity are found in the order Anura (frogs and toads), and the skin extracts from frogs of the Dendrobatidae family are an especially fruitful source of alkaloids. The frogs are notoriously toxic, and the natives of Western Columbia …
