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The Bracken Fern ( Pteridium aquilinum )

The Bracken Fern ( Pteridium aquilinum ). Toxic effects on surrounding organisms and environment. By: Peter Andriakos. General Information. Wide distribution Globally extensive Widest distribution of any fern genus Among most common plants on the planet. Locally intensive

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The Bracken Fern ( Pteridium aquilinum )

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  1. The Bracken Fern (Pteridiumaquilinum) Toxic effects on surrounding organisms and environment By: Peter Andriakos

  2. General Information • Wide distribution • Globally extensive • Widest distribution of any fern genus • Among most common plants on the planet • Locally intensive • Rapid invasion of de-forested areas • Cover increasing at a global level • Major problems in the UK, Scotland, Wales, South America

  3. General Info. (cont.) • Persistence • spreads via rhizome • widespread underground rootstock • forms expansive stands, dense thickets • Resilience • limited only by extreme cold, altitude • observed growing in wide range of soil pH • highly successful dispersal abilities

  4. Human Bracken Fern Consumption • Bracken fiddleheads harvested • Many cultures throughout history • Maori (NZ) • herbal remedy, food • Eastern Asia (Japan, China, Korea) • staple vegetable • Still utilized today as a foodstuff • Toxic effects are now known • continues to be utilized

  5. Non- Human Consumption Animal consumption • Domestic Herbivores • Restricted feed availability • Will consume readily • Major problem • Toxic effects on animals • Indirect effects on humans Cows consuming Pteridiumaquilinumwhile grazing • Toxic effects observed in all animal species known to consume Pteridiumaquilinum

  6. Toxic and Carcinogenic Effects of Bracken Fern • Wide variety of toxic effects observed • vary by species • among other factors • Several known toxins isolated from Bracken • several carcinogenic • others mutagenic • Experimental determination of toxicity • studies conducted with laboratory animals • myriad of syndromes observed • again, vary by species

  7. Bracken carcinogens in the human diet(MahmoodShahin, Barry L. Smith, Arungundrum S. Prakash) An all encompassing article… • Bracken Fern issues seen in animals • Human health risks • Primary carcinogenic principal • Mode of carcinogenic action • Cancer model

  8. Toxic syndromes in animals • Numerous acute, toxic syndromes observed • induced thiamine deficiency • acute hemorrhagic syndrome • Severity dependant on… • species and age of animal • quantity/quality of plant consumed • consumption rate

  9. Acute hemorrhagic syndrome • seen in ruminants • degenerative change in more rapidly dividing cells • epithelial necrosis - larnyx, pharynx, small intestine • bone marrow aplasia -Platelet production ceases -“Hemorrhagic crisis” occurs -Leucopenia, thrombocytopenia, granulocytopenia Death occurs in a matter of weeks

  10. Chronic Toxic Syndromes Chronic toxicity in animals also observed… • Bright blindness • seen in sheep (ruminant) (Watson et al., 1965) • retinal stenosis, atrophy (Watson et al.,1972) • Enzootic hematuria • Tumors in the bladder mucosa • hemorrhaging in bladder wall • Pamukcu et al., 1967 • Carcinomas • upper digestive tract

  11. Laboratory Animal Experimentation • Rats • first report of carcinogenic potential (Evans, Mason. 1965) • Diets containing Bracken powder, fronds, rhizomes • Higher incidence of tumor formation vs. control • Fronds vs. rhizomes (Hirono et al.,1973) • Duration of exposure  critical factor • Subjects fed 33% dried bracken (Hirono et al., 1970) • 4 months vs. 8 months

  12. Mice • feeding trials, dried bracken (Yasuda et al.,1974) • rib anomalies, sternebrae fusion • Tumor formation • Carcinogenic effects of cow milk (Pamukcu et al., 1978) • Other experimental animals… • Guinea Pigs • Japanese Quail • Egyptian Toads

  13. Human Health Risks • Indirect effects of animal consumption • milk obtained from bracken fed cattle • leaching in to water supply • aerial dispersion of spores • Esophageal carcinomas observed • Japan (Kamon et al., 1975) • Gastric cancer frequency • Wales (Galpin et al., 1990) • Costa Rica (Villalobos-Salazar et al., 1989) • Brazil (Marliere et al., 1995)

  14. Toxic Compounds • Numerous molecules isolated • Carcinogenic, mutagenic • Quercetin mutagen • Ptaquiloside (PT)  10 carcinogenic principle Ptaquiloside molecule Quercetinmolecule

  15. Ptaquiloside (PT) • Principal carcinogen in Bracken • Norsesquiterpene glucoside • Difficult to isolate • Carcinogenicity confirmed by Hirono et al. in 1984 • Various other experimental confirmations

  16. PT Action Mechanism Proposed scheme of PT reaction pathway

  17. Carcinogenic basis of PT • Carcinogenesis  initial DNA damage • DNA alkylation (adenine, guanine) Guanine Adenine DNA Structure

  18. PT Cancer Model Multistage model for bracken-induced carcinogenesis

  19. Occurrence of the carcinogenic Bracken constituent ptaquiloside in fronds, topsoils, and organic soil layers in Denmark (Rasmussen, Kroghsbo, Frisvad, Hansen) • relevance  human uptake via watersheds • Investigate occurrence of PT in fronds, topsoil materials • Multivariate data analysis

  20. Materials/Methods • 20 populations chosen in Denmark • 3 sub-sites at each location • Sample at end of growing season • Soil + plant material • Dried  milled  stored @ 40 C • Frond height and density measured Map of Denmark, study sites indicated

  21. Soil Horizons • Focus was on topsoil layers • Horizons O and A1 Soil Horizon Diagram http://www.dpi.vic.gov.au/CA25677D007DC87D/LUbyDesc/AG1060a/$File/AG1060a.gif

  22. PT analysis • Fronds, litter, O/A horizons • Extraction using de-ionized H20 • “cleaning" of sample with a resin • Conversion to pterosin B • Liquid chromatograph utilized • Other measurements taken • Soil pH • Organic Carbon Content • Bracken Biomass • Precipitation level • Light exposure • Turnover rate • Partial Least Square Regression Analysis (PLSR) • Performed on all variables less PT content • Correlate parameters with PT content in fronds, horizons

  23. ResultsPtaquiloside content • PT content in… • Fronds  110 - 3800 [μg g-1 ], mean = 550 [μg g-1 ] • O horizons  0.09 - 6.43 [μg g-1 ], mean = 0.39 [μg g-1 ] • A horizons  0.011 – 0.713 [μg g-1 ], mean = 0.031 [μg g-1 ]

  24. Results PLSR findings Fronds A horizons O horizons

  25. Conclusions • Definitive evidence that PT is found in topsoils beneath Bracken stands • Possibility that leaching does occur • High precipitation areas most susceptible to watershed contamination

  26. Questions Raised • How concerned should a local human population be? • Should Bracken management be implemented? • Has been in some areas… • Do these strategies need to be re-evaluated for their efficacy? • Bracken cover is increasing rapidly… • Need to think about Bracken management in agriculture from an environmental point of view…

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