Alkaloids in Animals

Abstract

For a long time, the ability to produce alkaloids was thought to be restricted to the plant kingdom. It is now clear that at least some animals are able to biosynthesize these compounds, even if the remarkable variety of structures found in plants has no parallel in the animal kingdom. Generally, alkaloids are defined as being basic, nitrogen-containing natural compounds. However some compounds, such as colchicine, which contain a nonbasic nitrogen atom, are nevertheless considered as alkaloids. In this chapter, we will use the term alkaloid in a broad sense, but we will not consider nitrogen-containing derivatives such as amino acids, purine and pyrimidine bases, pigments, common poly-amines (e.g., spermine, putrescine), nitro compounds, or cyanogenic glycosides. Similarly, biogenic amines which are widespread in mammals (see Brossi, 1993; Collins, 1983) and alkaloids sequestered or derived from plants by insect herbivores and their natural enemies which are covered elsewhere (see Wink, Chapter 11, this volume) will not be included in this chapter. Even so, it will not be possible to present an exhaustive list of species producing alkaloids, nor an exhaustive list of the alkaloids identified in animals. All major taxa in which alkaloids were described will be considered, however, as well as all major classes of alkaloids in terrestrial animals. Because of the huge number of alkaloids from marine animals, this overview is restricted to a few examples illustrating the diversity of compounds isolated from this source. When possible, review papers in which more detailed information can be found will be quoted.