[Constituents of Amanita phalloides. XXXIX. Isolation and characterization of an antitoxic cyclopeptide, antamanid from the lipophilic fraction]

The most widely recognized mushroom: chemistry of the genus Amanita

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.

Immunosuppressive activity of antamanide and some of its analogues

In connection with our discovery of a strong immunosuppressive activity of cyclolinopeptide A (CLA), we investigated immunosuppressive properties of antamanide and a number of its analogues, including symmetrical antamanide, and compared them with the activities of cyclosporin A and CLA. The peptides were investigated by using plaque forming cell (PFC), graft-versus-host (GvH), delayed type hypersensitivity (DTH), and autologous rosette formation cell (ARFC) tests. Antamanide and symmetrical antamanide exhibit an immunosuppressive activity lower than CLA. Linear antamanide fragments are also active. At higher concentrations of the latter peptides, toxic effects occur.

Characterization of a transporting system in rat hepatocytes. Studies with competitive and non-competitive inhibitors of phalloidin transport

Primary cultures of rat hepatocytes were used for assaying several drugs not previously known for inhibiting the transport of phalloidin. In order to have 50% inhibition (IC50) of the entrance of a tritiated phallotoxin derivative ([3H]demethylphalloin, 1 microM) from the medium into the cells the following concentrations (microM) of the various inhibitors were determined: cyclolinopeptide (0.5), Nocloprost (5.0), Nileprost (7.0), beta-estradiol (42), Verapamil (70). For comparison, the corresponding IC50 values of some known antagonists of phalloidin toxicity were determined by the same method. Moreover, we studied several natural and synthetic phallotoxins and alpha-amanitin for their ability to displace [3H]demethylphalloin from the transporting system. Lineweaver-Burk plots made it obvious that two groups of inhibitors exist. Competitive inhibitors are, for example, antamanide, beta-estradiol, silybin, Nileprost, taurocholate, and the cyclic somatostatin analog cyclo[Phe-Thr-Lys-Trp-Phe-D-Pro], whereas Verapamil and monensin inhibit phallotoxin uptake in a non-competitive way. Considering the very different chemical features of the competitive inhibitors, we tentatively conclude that the phallotoxin transport system selects compounds not on the basis of their chemical features, but rather their physical properties. The physical properties of a typical substrate are low molecular mass, lipophilic nature, and, possibly the presence of rigid ring structures. Negative charges accelerate the transport of a substrate, while positive charges have the opposite effect. The phalloidin-transporting system may represent part of a hepatic equipment which clears portal blood from, for example, bile acids, lipophilic hormones, or xenobiotics. By chance, the transporting system incorporates phallotoxins into the hepatocytes leading to the death of these cells.

The toxic peptides from Amanita mushrooms

The results of 50 years of effort in the chemistry of Amanita toxins are reviewed. The phallotoxins, fast acting components, but not responsible for fatal intoxications after ingestion, are bicyclic heptapeptides. They combine with F-actin, stabilizing this protein against several destabilizing influences. The virotoxins likewise fast acting are monocyclic heptapeptides. The amatoxins which are the real toxins lead to death within several days by inhibiting the enzymatic synthesis of m-RNA. They are bicyclic octapeptides. The structures of all of these compounds are described, as well as conformations, chemical reactions and modification, syntheses and correlations between structures and biological activities.

Amatoxins, phallotoxins, phallolysin, and antamanide: the biologically active components of poisonous Amanita mushrooms

This review gives a comprehensive account of the molecular toxicology of the bicyclic peptides obtained from the poisonous mushrooms of the genus Amanita. The discussion of the biochemical events will be preceded by a consideration of the chemistry of the toxic peptides. The structural features essential for biological activities of both the amatoxins and the phallotoxins will be discussed, also including the most important analytical data. Similar consideration will be given to antamanide, a cyclic peptide, which counteracts phalloidin. In addition, the phallolysins, three cytolytic proteins from Amanita phalloides will be discussed. The report on the biological activity of the amatoxins will deal with the sensitivity of the different RNA-polymerases towards the toxins and with their action on various cell types. Consideration will also be given to systems in which alpha-amanitin was used and can be used as a molecular tool; in the past, many investigators used the inhibitor in molecular biology, genetics, and even in physiological research. As for the phallotoxins, discussion of the affinity of these toxins for actin is provied. Further discussion attempts to understand the course of intoxication by filling in the gap between the first molecular event, formation of microfilaments, and the various lesions in hepatocytes during the intoxication.