The most widely recognized mushroom: Chemistry of the genus Amanita

Abstract

Many review papers have been published on mushrooms of the genus Amanita, as these are well known to both scientific and lay audiences, probably due to the toxic and/or hallucinogenic properties of some species. This article aims to supplement the content of previous reviews by categorizing all of the natural products isolated from any species in the genus Amanita. These compounds are subdivided into six major structural types, and references are provided for all species that have been examined chemically.

Introduction

Some of the morphological characteristics of the genus Amanita include white spore prints, gills free from the stem, and the presence of a universal veil (Lincoff, 1981). Species of this genus are found commonly throughout the world, and this includes mushrooms known to possess either toxic and/or hallucinogenic properties. Historical evidence suggests that at least three Roman emperors and a Pope may have been among the victims of mushroom poisoning (Block et al., 1955). Even in modern times, it has been estimated that nearly 90% of reported cases of lethal poisonings caused by the consumption of mushrooms, especially in Central Europe and North America, are due to two of the most poisonous species of this genus, the notorious death cap (A. phalloides) and destroying angel (A. virosa) (Wieland, 1968). Another important species of this genus, A. muscaria, also known commonly as ‘fly agaric,’ is one of the more beautiful and widely recognized mushrooms, due to its blood-red color and pyramidal, white patches (Lincoff, 1981). Consumption of A. muscaria for ceremonial and/or recreational purposes probably predates recorded history, due to its hallucinogenic effects, and there are many interesting descriptions of its use among Siberian tribesmen (Schultes, 1969). Idealized representations of this species permeate popular culture. Besides the well-known example of Lewis Carroll's Alice in Wonderland (Carroll, 2000), A. muscaria can be found in the background of many children's cartoons and as a major ‘obstacle' in video games (e.g., the Smurfs and Super Mario Bros., respectively) besides numerous other depictions on album covers, greeting cards, t-shirts, etc. In short, mushrooms from this genus are heavily investigated scientifically and extremely well known conceptually; in many ways, they have become an integral part of human society.

The number of species of Amanita has been approximated at 900–1000, and new species are being discovered continuously, including recent examples in the last 2 years (Sanmee et al., 2003, Yang, 2003, Yang et al., 2004). However, a search of the literature suggests that only 17 identified species of Amanita have been screened chemically, which resulted in the description of more than 70 compounds, representing six major structural classes. The broad familiarity of this genus, coupled with the diverse chemical components isolated from it, especially the deadly toxins, have drawn the attention of chemists and mycologists. Quite a few reviews have been written on various aspects of Amanita, such as the chemotaxonomy (Beutler and Der Marderosian, 1981), the history and use of the hallucinogenic properties (Schultes, 1969), and a recent review specifically on A. muscaria (Michelot and Melendez-Howell, 2003). However, to the best of our knowledge, a review on the chemistry of compounds isolated from mushrooms of the genus Amanita has not been prepared.

Chemical investigation of Amanita toxins can be traced to 1899 (Schlesinger and Ford, 1907), and qualitative and quantitative analyses of Amanita toxins using chromatographic methods were reported about a half of a century later (Block et al., 1955, Dubash and Teare, 1946). Yet, as evidenced by the references cited in the following sections, detailed structural analyses of compounds isolated from Amanita species, especially the peptides, only became achievable several decades later, probably due to recent advances in modern spectroscopic and spectrometric techniques. Broadly, the structures of the compounds reported from Amanita to date can be subdivided into the following six categories: peptides, amavadin, isoxazoles, simple amino acids and related derivatives, sterols, and ceramides.