Testing for presence of some amatoxins and some tryptamines
Some mushrooms contain deadly toxins known broadly as ‘amatoxins’ [see Amanita]; the presence of the amanitin-type amatoxins can be test- ed for with the ‘Meixner test’, devised by A. Meixner. Juice from a piece of fresh mushroom is dripped onto a piece of lignin-containing paper [not newsprint as it is too thin and usually bears ink, both of which can affect the results]; once dry, a drop of concentrated hydrochloric acid [HCl] is applied to the same spot. Under these conditions, amanitins [when present at 0.2mg/ml or higher] react with lignins in the paper to form a blue or light greenish-blue coloured stain within several minutes. This test may also be done with dried mushrooms, either by soaking and crushing a small piece of the mushroom in a small amount of absolute methanol, and applying this liquid to the paper, followed by HCl treatment; or by di- rectly extracting the contents of the mushroom in a mixture of methanol and concentrated HCl, and applying this solution to the paper. This test should be done away from strong light, which can produce some ‘false’ re- actions. Judgement should be made on any results within 15min., as the colour reaction usually fades and changes hue after this time.
The Meixner test can also be applied to testing for the presence of some tryptamines; though it works best for 5-substituted tryptamines [such as bufotenine, 5-methoxy-DMT, 5-hydroxytryptophan, 5-methoxytryptamine and serotonin], it does not distinguish between them. After application of HCl, presence of such compounds is indicated by the development of a reddish-brown stain, turning ‘greyish-purplish-red’, then ‘moderate red- dish-purple’, ending with a bluish colour like that shown with amanitins. Tryptamines with 4-substitution [such as psilocybin and psilocin] were not tested directly via this method but Psilocybe cyanescens was, giving at first a grey stain, within 1 minute turning greyish-blue to pale blue; low concentrations gave a light greenish-blue stain. Although similar to the colour reaction of the amanitins, it could be distinguished by the quick- ly fading colour and the initial grey hue. However, untrained people may find it difficult to distinguish between such similar colour reactions, espe- cially without known reference standards for comparison, and as such the Meixner test can not be relied upon to identify compounds definitively.
It is advisable to use a ‘control sheet’ of non-lignin paper [such as filter paper] to check for false reactions, which may be seen when the same col- our reaction occurs on both types of paper, indicating the presence of oth- er compounds not undergoing a ‘Meixner reaction’. Of course, such a test should not be seen as definitive proof that a mushroom contains no tox- ins (Beuhler et al. 2004; Beutler & Vergeer 1980), yet in the case of the 5- substituted tryptamines, it could serve as a useful field indicator for plants worthy of further chemical analysis.