Assay of ptaquiloside, the carcinogenic principle of bracken, Pteridium aquilinum, by mutagenicity testing in Salmonella typhimurium.

The mutagenicity of ptaquiloside, the carcinogenic principle of Pteridium aquilinum, was tested in Salmonella typhimurium TA100 and TA98. Under weakly basic conditions (pH 8.5), ptaquiloside decomposed into a conjugated dienone (considered to be the ultimate form), which was mutagenic in both strains. A novel bioassay, using the pre-incubation method at pH 8.5 with S. typhimurium tester strains was developed for the assay of ptaquiloside extracted from plants. By this bioassay the ptaquiloside content of ferns collected at different localities during various seasons, and in various parts of the plant was determined. The ubiquitous presence of ptaquiloside in fresh plant materials was confirmed. Bracken processed in alkali was found not to contain the carcinogen.