Genotoxic activity and inhibition of soil respiration by ptaquiloside, a bracken fern carcinogen

• Published in: Environmental toxicology and chemistry 2005-11, Vol.24 (11), p.2751-2756
• Main Authors: Schmidt, Bjørn, Rasmussen, Lars Holm, Svendsen, Gitte Winkel, Ingerslev, Flemming, Hansen, Hans Christian Bruun
• Format: Article
• Language: English
• Subjects: Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; Carbon; Carbon - metabolism; Carbon transformation test; Carcinogens - chemistry; Carcinogens - toxicity; Ecotoxicology, biological effects of pollution; Ferns; Fundamental and applied biological sciences. Psychology; General aspects; Genome, Bacterial - drug effects; Genome, Bacterial - genetics; Genotoxicity; Groundwater; Indans - chemistry; Indans - toxicity; Leaching; Microorganisms; Moisture content; Molecular Structure; Mutagenicity Tests; Ptaquiloside; Pteridium - chemistry; Pteridium aquilinum; Respiration; Sandy loam; Sandy soils; Sesquiterpenes - chemistry; Sesquiterpenes - toxicity; Soil adsorption; Soil Microbiology; Soil moisture; Soil testing; Temperature; Terrestrial environments; Time Factors; Toxicity; Toxins; Umu test
• ISSN: 0730-7268; 1552-8618
• DOI: 10.1897/04-469R.1

Ptaquiloside (PTA) is a natural toxin produced by bracken (Pteridium aquilinum [L.] Kuhn). Assessment of PTA toxicity is needed because PTA deposited from bracken to soil may leach to surface and groundwater. Inhibition of soil respiration and genotoxic activity of PTA was determined by a soil microbial carbon transformation test and an umu test, respectively. In the carbon transformation test, sandy loam soil was incubated at five different initial concentrations of PTA for a period of 28 d, after which glucose was added and respiration measured for 12 consecutive hours. The tests were performed at 20°C and soil moisture content of approximately 15%. For soil material sampled in the autumn, initial PTA concentrations ranging from 0.008 to 40.6 μg PTA/g dry soil were tested. From fitting of data by a sigmoidal function, a 10% effect dose (ED10) was estimated to 13 μg PTA/g dry soil, with an upper 95% confidence limit of 43 μg PTA/g dry soil and a 95% lower confidence limit of — ∞ μg PTA/g dry soil. For soil material sampled in late winter, initial PTA concentrations ranging from 1.56 to 212 μg PTA/g dry soil were tested, resulting in an ED10 value of 55 μg PTA/g dry soil, with an upper 95% confidence limit of 70 μg PTA/g dry soil and a 95% lower confidence limit of 40 μg PTA/g dry soil. The genotoxic activity of PTA was determined using the umu test without and with metabolic activation (addition of S9 rat liver homogenate). In tests with addition of S9, the induction ratio exceeded the critical ratio of 1.5 at a PTA concentration of 46 ± 16 μg/ml and, in tests without S9, the eritical ratio was exceeded at a PTA concentration of 279 ± 22 μg/ml. The genotoxicity of PTA is comparable to that of quercetin, another bracken constituent. The toxicity of PTA toward microorganisms prolongs the persistence of PTA in terrestrial environments, increasing the risk of PTA leaching to drainage and groundwater.