The Occurrence and Chemotaxonomic Significance of Cyclopeptides in Select Species of Amanita

Mahoney, Shirley

ABSTRACT: Because of the difficulty encountered in the identification of some specimens of Amanita by morphological characters, the occurrence of cyclopeptides in select species of the genus was studied and evaluated as a possibly valid character field. Particular emphasis was placed upon a comparison of cyclopeptides occurring in the white species, A. virosa, A. bisporigera and forms which were considered to be intermediate between the two. Two color forms of A. caesarea, considered to be an edible species, were also investigated. Analyses of extracts of single specimens involved the separation of alcohol-soluble compounds by column chromatography on Sephadex LH-20 followed by their identification using thin-layer chromatography and cochromatography with known reference compounds. Five known cyclopeptides were detected in the elution fractions of the extracted specimens of white amanitas. Alpha amanitin, amanin, phallodin, and phallacidin were detected in all three white taxa. Beta-amanitin was detected only in A. bisporigera and some intermediates. A total of seven unknown cyclopeptides giving amatixin-like reactions were also detected. Of particular chemotaxonomic significance in the white amanita complex were three unknown cyclopeptides detected in A. virosa, which were absent in A. bisporigera, and which occurred in various combinations in the intermediates. The close interrelationship of the white amanitas raised questions for the validity of the recognition of A. bisporigera and A. virosa as separate, distinct species. Extracts of the red and brown color forms of A. caesarea were found to contain the same cyclopeptide components, indicating a close biochemical as well as morphological relationship. Beta-AMA was detected, as well as four unknown compounds giving amanitin-like reactions corresponding in R_ values to unidentified compounds in A. virosa, A. bisporigera, and intermediates. Elution profiles of each taxon examined showed some variation from one specimen to another. Enough consistency was obtained to construct standard elution patterns for A. virosa and A. bisporigera. The reproducibility of the patterns, in addition to the consistency of toxin occurrence, make them valuable aids in the evaluation of specimens whose taxonomy is uncertain on morphological bases.