It is identified to be the main carcinogen of the ferns and to be responsible for their biological effects, such as haemorrhagic disease and bright blindness in livestock and oesophageal, gastric cancer in humans.

Except in the plants, ptaquiloside has been detected in the milk and meat of affected livestock, as well as in the underground water and dry soil around bracken fern vegetation.

[4][5][6] The prevalence of ptaquiloside in daily sources along with its carcinogenic effects make it an increasing biological hazard in modern days.

The presence of ptaquiloside has been detected in a variety of ferns, including the species in the genera Pteridium (bracken), Pteris, Microlepia, and Hypolepis.

Bracken fern is a very adaptable plant and is capable of forming dense, rapidly expanding populations in course of the first phases of the ecological succession in forest cleanings and other disturbed rural areas.

Its aggressive growth, characterized by an extensive rhizome system and rapidly growing fronds, sometimes enables it to be a dominant species in certain plant communities.

In 1996, Alonso-Amelot, Smith and co-workers found that ptaquiloside was excreted in milk at a concentration of 8.6 ± 1.2% of the amount ingested by a cow from bracken, and was linearly dose-dependent.

[12] Main routes that can lead to human exposure to the toxic effects of bracken fern include ingestion of the plant (particularly the croziers and young fronds), inhalation of the airborne spores, consumption of the milk and meat of affected animals, and drinking ptaquiloside contaminated water.

In acidic conditions, ptaquiloside gradually undergoes aromatization with the elimination of D-glucose to afford ptaquilosin, and finally pterosin B.

Under weakly alkaline conditions, ptaquiloside and its aglycone ptaquilosin are converted into an unstable conjugated dienone intermediate.

Due to the constitution of a cyclopropyl carbinol system, ptaquilodienone is a strong electrophile and acts as a powerful alkylating agent that reacts directly with biological nucleophiles including amino acids, nucleosides, and nucleotides under weakly acidic conditions at room temperature (as shown in the scheme below).

The alkylation of amino acids with the dienone mostly takes place at the thiol group in cysteine, glutathione and methionine.

The alkylation at the carboxylate group of each amino acid, forming the corresponding ester, is also observed to a small extent based on the previously reported literature.

[14] In 1998, Prakash, Smith and co-workers showed that the alkylation of adenine by ptaquiloside in codon 61 followed by depurination and error in the DNA synthesis resulted in the activation of H-ras proto-oncogene in the ileum of calves fed bracken.

[24] In 2003, Santos group reported significantly increased levels of chromosomal abnormalities, such as chromatid breaks in cultured peripheral lymphocytes.

The usual procedure that is performed before eating the plant is to pre-treat the fern with boiling water in the presence of different chemicals, such as sodium bicarbonate and wood ash, to degrade or inactivate ptaquiloside and other toxic agents.

[10][26] As shown by Kamon and Hirayama, the risk of oesophageal cancer was increased approximately by 2.1 in men and 3.7 in women who regularly consume bracken in Japan.