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 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

Toxic effects observed in all animal species known to consume Pteridium aquilinum

Cows consuming Pteridium aquilinum while grazing

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 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 RisksIndirect 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

Ptaquiloside moleculeQuercetin 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)

Adenine

Guanine

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

http://www.dpi.vic.gov.au/CA25677D007DC87D/LUbyDesc/AG1060a/$File/AG1060a.gif

Soil Horizon Diagram

Focus was on topsoil layers

Horizons O and A1

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

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

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

(+) (-)Light exposure Frond height

Turnover Rate

Carbon Content

Fronds

(+) (-)

Precipitation Amt. of Litter

Turnover Rate

Stand Size

O horizons

(+) (-)

Soil pH Precipitation

Stand Size

Easting

A horizons

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…