Dissipation of pterosin B in acid soils - Tracking the fate of the bracken fern carcinogen ptaquiloside.
Bracken ferns (Pteridium spp.) are well-known for their carcinogenic properties, which are ascribed to the content of ptaquiloside and ptaquiloside-like substances. Ptaquiloside leach from the ferns and may cause contamination of drinking water. Pterosin B is formed by hydrolysis of ptaquiloside. In soil, Pterosin B is adsorbed more strongly and it is expected to have a slower turnover than ptaquiloside. We thus hypothesized that pterosin B may serve as an indicator for any past presence of ptaquiloside. Pterosin B degradation was studied in acid forest soils from bracken-covered and bracken-free areas. Soil samples were incubated with pterosin B at 3 and 8 μg g-1for 10 days, whereas sterile (autoclaved) samples were incubated for 23 days. Pterosin B showed unexpected fast degradation in soils with full degradation in topsoils in 2-5 days. Pterosin B dissipation followed the sum of two-first order reactions. The initial fast reaction with half-lives of 0.7-3.5 h contributed 11-59% of the total pterosin B degradation, while the slow reaction was 20-100 times slower than the fast reaction. Total dissipation half-lives were shorter for loamy sand (4 h) than for sandy loam soils (28 h). No degradation of pterosin B took place under sterile conditions assuming observed dissipation during the first 3 h could be attributed to irreversible sorption. Our results demonstrate that pterosin B is microbially degraded and that pterosin B is as unstable as ptaquiloside and hence cannot be used as an indicator for former presence of ptaquiloside in soil.
Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C., Denmark.
Eirini
E
Skourti-Stathaki
Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C., Denmark. Electronic address: pfck@plen.ku.dk.
Frederik
F
Clauson-Kaas
Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C., Denmark.
Kristian Koefoed
KK
Brandt
Department of Technology, Metropolitan University College, Sigurdsgade 26, DK-2200 Copenhagen N, Denmark.
Lars Holm
LH
Rasmussen
Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C., Denmark.
Hans Christian Bruun
HCB
Hansen
D002273:Carcinogens / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007189:Indans / Q000737:chemistry*; D032498:Pteridium / Q000737:chemistry*; D012717:Sesquiterpenes / Q000737:chemistry*; D012989:Soil Pollutants / Q000737:chemistry*
D002273:Carcinogens; D007189:Indans; D012717:Sesquiterpenes; D012989:Soil Pollutants; C586064:pterosin B; C043680:ptaquiloside
Degradation kinetics; Microbial degradation; Natural toxins; Soil; Sorption