Amavadine, a Vanadium Compound in Amanita Fungi

This chapter is concerned with amavadine (also spelled as amavadin), a natural vanadium complex without the V=O bond, present in the fungus Amanita muscaria (L.:Fr.) Hook, which concentrates high levels of that metal (a capacity that is also known for a few other close Amanita fungi). The isolation, chemical synthesis and characterization of amavadine are reviewed, but its biological function remains unknown. However, the high stability constant of the complex, its redox behavior and ability to mediate the oxidation of some biological substrates support the possibility of a particular role (eventually concerning an enzyme) in the fungi, usually performed by other biomolecules, and biological functions of amavadine are suggested. The application of amavadine as a catalyst in chemical synthesis has been tested for some substrates, although under no biological conditions, and carboxylic acids, alcohols, ketones and halogenated compounds are obtained from oxidations of hydrocarbons catalyzed by very close models or a racemic mixture containing amavadine.