Fungi , Hallucinogenic mushrooms
A number of basidiomycetes contain hallucinogenic principles, the most well-known examples being the Amanita muscaria and the Psilocybe types. The fly agaric Am. muscaria is the Euro pean archetypical ‘mother of all mushrooms’ in legends and fairy tales, with a red hood and white spots. It is indigenous to the northern hemisphere, but is also found in some parts of South Africa, South America, Australia and New Zealand. The most important toxin in Am. muscaria is not muscarine (which does occur in trace amounts), but ibotenic acid and its decarboxylation product muscimol . Poisoning with Am (Fig. 1) . muscaria usually results from deliberate ingestion to obtain a psychoactive response and symptoms occur within 20–180 minutes. Muscimol is a gamma-aminobutyric acid (GABA)-receptor agonist. It causes CNS depression that results in drowsiness and dizziness, followed by elation, increased motor activity, tremor, agitation and hallucinations. There are no specific antidotes and recovery is complete upon awakening.
A modification of the ion-interaction HPLC method of Gennaro et al. (1997) for ibotenic acid and muscimol was applied to urine and serum from two dogs who were found to have ingested Am. muscaria (Rossmeisl et al. 2005). Tsujikawa and colleagues determined ibotenic acid and muscimol in Amanita mushrooms by GC-MS (Tsujikawa et al. 2006) and by LC-MS/MS (Tsujikawa et al. 2007). Toxins from Am. phalloides and related Agaricales are among the most lethal natural substances. In countries where the consumption of wild mushrooms is popular, as in Middle and Eastern Europe and some Mediterranean countries, hundreds of fatalities are reported every summer and autumn. The toxic principles are cyclic polypeptides: the phallotoxins are bicyclic heptapeptides, the virotoxins are mono cyclic heptapeptides and the amatoxins are bicyclic octapeptides (Fig. 2). The most import ant biochemical effect of the amatoxins is an irreversible inhibition of ribonucleic acid (RNA) polymerase-II; the phallotoxins stimulate the polymerisation of G-actin and stabilise the F-actin filaments (De Wolff and Pennings 1995; Vetter 1998). Symptoms of Am. phalloides poisoning can roughly be divided in three phases, the first appearing over 6 h after mushroom consumption and characterised by violent emesis and cholera-like diarrhoea. This phase is ascribed to the action of the phalloidins, and can usually be treated successfully with fluid and electrolyte replacement. The second phase occurs after 2 to 3 days as a transient remission, which is, however, fallacious, since the most dangerous third phase may then begin to take place. This is characterised by hepatorenal symptoms from the effect of amatoxins on RNA polymerase. Liver injury is evident by immensely elevated serum aminotransferase activities. Numerous antidotes against amatoxins have been proposed, but none has been proved to be successful, as hepatorenal symptoms appear only after irreversible binding of the toxins to their target enzyme. Liver trans plantation seems to be an option for effective symptomatic treatment (De Wolff and Pennings 1995).
Figure 1 Muscimol.
Figure 2 α-Amanitin.
Identification and measurement of the toxins in blood for diagnostic purposes have proved a considerable challenge because of their complicated chemical structures and the low plasma concentrations. Immunoassay procedures are available (Abuknesha and Maragkou, 2004; Butera et al. 2004). A number of HPLC methods have been described. Electrochemical detection can achieve a sensitivity of 2 lg/L. An ESI-LC-MS procedure for a- and b-amanitin described by Maurer (1998) has a detection limit of 10 lg/L. a-Amanitin in serum has been analysed by LC-MS/MS/MS (Filigenzi et al. 2007). Consumption of one of the many species of the cosmopolitan genera Psilocybe, Panaeolus, Copelandia, Gymnophilus or Stropharia gives rise to the so-called ‘psilocybe syndrome’. These mushrooms contain the indole-alkylamine hallucinogen psilocybin (Fig. 3) and its dephosphorylated congener psilocin, which is about 1.5 times as potent as psilocybin. These hallucinogens are about 100 times less potent than lysergide (LSD). Intoxication with psilocybin-containing mushrooms is almost always intentional. Some of the somatic reactions to psilocybin resemble anticholinergic effects, for example mydriasis and urinary retention, which may be reversed successfully with physostigmine.
Figure 3 Psilocybin.
Measurement of psilocybin and related indole alkaloids in mushroom samples or patient material may assist the diagnosis and treatment of patients with suspected poisoning. A TLC method has been described (Stienstra et al. 1981). Quantitative procedures have been described using HPLC or ion-mobility spectrometry and GC-MS. In clinical and forensic practice, the HPLC method with electrochemical detection, as described by Hasler et al. (1997), seems to be most useful. An LC-MS method has also been developed for analysis of psilocin and psilocybin in mushroom samples (Kamata et al. 2005). Saito et al. (2004) quantified psilocybin in mushroom samples by HPLC with fluorescence detection after derivatization and in mushrooms and rat serum by LC-ESI/MS.
