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
 Rapid invasion of de-forested areas
 Cover increasing at a global level
 Major problems in the UK, Scotland, Wales,
South America
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
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
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 Pteridium aquilinum
while grazing
Toxic effects observed in all animal species known to
consume Pteridium aquilinum
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
Bracken carcinogens in the human diet
(Mahmood Shahin, 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
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
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
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
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
 Mice
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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
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)
Toxic Compounds
 Numerous molecules isolated
 Carcinogenic, mutagenic
 Quercetin  mutagen
 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
Carcinogenesis  initial DNA damage
 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)
 relevance  human uptake via watersheds
 Investigate occurrence of PT in fronds, topsoil materials
 Multivariate data analysis
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
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
 Other measurements taken
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Soil pH
Organic Carbon Content
Bracken Biomass
Precipitation level
Light exposure
Turnover rate
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
 Partial Least Square Regression Analysis (PLSR)
Performed on all variables less PT content
Correlate parameters with PT content in fronds, horizons
Results
Ptaquiloside 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 ]
Results
PLSR findings
Fronds
A horizons
(+)
(-)
Frond height
Soil pH
Precipitation
Turnover Rate
Stand Size
Carbon Content
Easting
(+)
(-)
Light exposure
O horizons
(+)
(-)
Precipitation
Amt. of Litter
Turnover Rate
Stand Size
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
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…