The Bracken Fern Pteridium aquilinum Toxic effects on

The Bracken Fern (Pteridium aquilinum) Toxic effects on surrounding organisms and environment By: Peter Andriakos

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

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

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

Non- Human Consumption Animal consumption q Domestic Herbivores ü Restricted feed availability ü Will consume readily q Major problem ü Toxic effects on animals ü Indirect effects on humans Cows consuming Pteridium aquilinum while grazing Toxic effects observed in all animal species known to consume Pteridium aquilinum

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

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

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

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

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

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

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

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

Toxic Compounds q Numerous molecules isolated Ø Carcinogenic, mutagenic Ø Quercetin mutagen Ø Ptaquiloside (PT) 10 carcinogenic principle Quercetin molecule Ptaquiloside molecule

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

PT Action Mechanism Proposed scheme of PT reaction pathway

Carcinogenic basis of PT q Carcinogenesis initial DNA damage ü DNA alkylation (adenine, guanine) Guanine Adenine DNA Structure

PT Cancer Model Multistage model for bracken-induced carcinogenesis

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

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

Soil Horizons q Focus was on topsoil layers q. Horizons O and A 1 Soil Horizon Diagram http: //www. dpi. vic. gov. au/CA 25677 D 007 DC 87 D/LUby. Desc/AG 1060 a/$File/AG 1060 a. gif

q Other measurements taken ü ü ü Soil p. H Organic Carbon Content Bracken Biomass Precipitation level Light exposure Turnover rate q. PT analysis üFronds, litter, O/A horizons üExtraction using de-ionized H 20 ü“cleaning" of sample with a resin üConversion to pterosin B üLiquid chromatograph utilized q Partial Least Square Regression Analysis (PLSR) üPerformed on all variables less PT content üCorrelate parameters with PT content in fronds, horizons

Results Ptaquiloside content q PT content in… ü Fronds 110 - 3800 [μg g-1 ], mean = 550 [μg g-1 ] ü O horizons 0. 09 - 6. 43 [μg g-1 ], mean = 0. 39 [μg g-1 ] ü A horizons 0. 011 – 0. 713 [μg g-1 ], mean = 0. 031 [μg g-1 ]

Results PLSR findings Fronds A horizons (+) (-) Frond height Soil p. H Precipitation Turnover Rate Stand Size Carbon Content Easting (+) (-) Light exposure O horizons (+) (-) Precipitation Amt. of Litter Turnover Rate Stand Size

Conclusions Ø Definitive evidence that PT is found in topsoils beneath Bracken stands ØPossibility that leaching does occur ØHigh precipitation areas most susceptible to watershed contamination

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