Presence of the carcinogen ptaquiloside in fern-based food products and traditional medicine: Four cases of human exposure

Ptaquiloside (PTA) is a natural carcinogen present in many ferns. Brackens (Pteridium sp.) contain PTA and are classified by WHO/IARC as ‘ … possibly carcinogenic to humans’, however, these ferns are used in food, traditional medicine and as food supplements around the world. This study aimed to outline the presence of PTA in different human exposure routes by using and validating an LC-MS based protocol to test the contents of PTA in commercial products, the degradation product Pterosin B (PtB) and wild specimens from Europe, Asia and North America. The Limit of Detection of the protocol was 0.024 μg g(−1) for PTA and 0.028 μg g(−1) for PtB. PTA and PtB were present in most wild specimens (PTA: BD – 6300 ± 520 μg g(−1); PtB: BD - 449 ± 1 μg g(−1)) while commercial products made from fronds, as well as fronds prepared as traditional Chinese medicine, were in the range 44 ± 3 to 666 ± 33 μg g(−1) for PTA and BD to 1653 ± 184 μg g(−1) for PtB. This study did not find PTA/PtB in rhizomes and products made thereof nor in homoeopathic products based on bracken. Boiling or drying bracken showed to reduce PTA some degree but cannot remove it completely. Interestingly, crosiers with no PTA/PtB were found in the USA, indicating a potential for commercial production of PTA-free fronds.