Environmental exposure to bracken-derived carcinogenic compounds: A multidisciplinary assessment in northern Spain

Bracken (Pteridium aquilinum) is a globally distributed fern that produces carcinogenic illudane glycosides (IGs), raising concerns about environmental exposure in livestock-dominated ecosystems. However, the occurrence, mobility, and biological effects of these compounds in natural water systems remain insufficiently characterized. Here, we present a multidisciplinary assessment of IG distribution and genotoxic activity in northern Spain, integrating chemical analyses of plant tissues and environmental waters with in vivo and in vitro bioassays. Croziers and water samples from bracken-infested areas were analyzed for ptaquiloside (PTA), ptesculentoside (PTE), and thepterosins A and B. IGs and/or their derivatives were detected in all plant samples and widely in water sources, demonstrating environmental dissemination and persistence. Notably, elevated PTA levels were observed in croziers from sites associated with cattle mortality. Genotoxicity was assessed using the SMART assay in Drosophila melanogaster (in vivo) and comet assays in human cell lines (in vitro), revealing induction of somatic mutations and DNA damage by plant extracts and, to a lesser extent, by concentrated water samples. While genotoxicity in plants correlated with pterosin levels, weaker associations were observed in water samples. These findings identify a relevant pathway of environmental exposure linking bracken, water contamination, and biological effects. The widespread occurrence and bioactivity of IGs highlight potential risks for ecosystems and livestock, underscoring the need for environmental monitoring in bracken-dominated landscapes.