Estimation of the fern toxin, ptaquiloside, in certain Indian ferns other than bracken

Ptaquiloside (Pta) concentration was determined in 40 non-bracken fern samples collected mostly from the northern mountaineous State of Uttaranchal (Ut), India. Of these, only Onychium contiguum contained high levels; 499 and 595 mg/kg of Pta on dry matter basis in the two samples collected. A few samples of Diplazium esculentum, Polystichum squarrosum and Dryopteris juxtaposita showed moderate levels (19 to 31 mg/kg), but most samples had no detectable Pta present. Other ferns species such as Cheilanthes farinosa and Christella dentata contained nil to a very low level of Pta (0.4 mg/kg), while Adiantum incisum and Pteris stanophylla had no detectable Pta present. Samples of O. contiguum were collected from high-altitude areas of the Himalayas (District Chamoli and Uttarkashi), where enzootic bovine haematuria is not uncommon. This fern was reported in trials with guinea pigs to induce ileac, urinary bladder and mammary tumours on prolonged feeding, although in experimental rats it failed to induce any mortality and malignancy. The present study indicates that a few non-bracken fern species can contain high levels of the fern toxin, Pta, which may induce hazardous effects for animals and men, either alone or in combination with bracken fern.