Indolizidine 239Q and quinolizidine 275I. Major alkaloids in two Argentinian bufonid toads (Melanophryniscus)

Abstract

Alkaloid profiles in skin of poison frogs/toads (Dendrobatidae, Mantellidae, Bufonidae,and Myobatrachidae) are highly dependent on diet and hence on the nature of habitat.Extracts of the two species of toads (Melanophryniscus klappenbachi and Melanophryniscuscupreuscapularis) from similar habitats in the Corrientes/Chaco Provinces of Argentinahave similar profiles of alkaloids, which differ considerably in profiles from otherMelanophryniscus species from Brazil, Uruguay and Argentina. Structures of two majoralkaloids 239Q (1) and 275I (2) were determined by mass, FTIR, and NMR spectralanalysis as 5Z,9Z-3-(1-hydroxybutyl)-5-propylindolizidine and 6Z,10E-4,6-di(pent-4-enyl)quinolizidine, respectively. A third alkaloid, 249F (3), is postulated to be a homopumiliotoxinwith an unprecedented conjugated exocyclic diene moiety.