The Bracken Fern - PowerPoint Presentation

Slide1

The Bracken Fern (Pteridium aquilinum)

Toxic effects on surrounding organisms and environment

By: Peter

AndriakosSlide2

General InformationWide distributionGlobally extensiveWidest distribution of any fern genusAmong 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

Slide3

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 Slide4

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 utilizedSlide5

Non- Human Consumption Animal consumption Domestic HerbivoresRestricted feed availabilityWill consume readily Major problem

Toxic effects on animalsIndirect effects on humans

Toxic effects observed in all animal species known to consume

Pteridium

aquilinum

Cows consuming

Pteridium

aquilinum

while grazingSlide6

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 Slide7

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 modelSlide8

Toxic syndromes in animals Numerous acute, toxic syndromes observedinduced thiamine deficiency acute hemorrhagic syndrome Severity dependant on… species and age of animal quantity/quality of plant consumed

consumption rateSlide9

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 weeksSlide10

Chronic Toxic SyndromesChronic 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 wallPamukcu et al., 1967

Carcinomas

upper digestive tractSlide11

Laboratory Animal Experimentation Rats first report of carcinogenic potential (Evans, Mason. 1965) Diets containing Bracken powder, fronds, rhizomesHigher 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 monthsSlide12

Mice feeding trials, dried bracken (Yasuda et al.,1974) rib anomalies, sternebrae fusionTumor formation Carcinogenic effects of cow milk (Pamukcu et al., 1978)Other experimental animals…Guinea Pigs

Japanese QuailEgyptian ToadsSlide13

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) Slide14

Toxic Compounds Numerous molecules isolatedCarcinogenic, mutagenicQuercetin  mutagenPtaquiloside (PT)  10 carcinogenic principle

Ptaquiloside

molecule

Quercetin

moleculeSlide15

Ptaquiloside (PT)Principal carcinogen in BrackenNorsesquiterpene glucosideDifficult to isolate Carcinogenicity confirmed by Hirono et al. in 1984Various other experimental confirmationsSlide16

PT Action MechanismProposed scheme of PT reaction pathwaySlide17

Carcinogenic basis of PTCarcinogenesis  initial DNA damage DNA alkylation (adenine, guanine)

Adenine

Guanine

DNA StructureSlide18

PT Cancer ModelMultistage model for bracken-induced carcinogenesisSlide19

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 analysisSlide20

Materials/Methods20 populations chosen in Denmark3 sub-sites at each locationSample at end of growing seasonSoil + plant materialDried  milled  stored @ 4

0 C

Frond height and density measured

Map of Denmark, study sites indicatedSlide21

Soil Horizonshttp://www.dpi.vic.gov.au/CA25677D007DC87D/LUbyDesc/AG1060a/$File/AG1060a.gifSoil Horizon Diagram

Focus was on topsoil layersHorizons O and A

1

Slide22

Other measurements takenSoil pHOrganic Carbon ContentBracken BiomassPrecipitation levelLight exposureTurnover 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 H

2

0

“cleaning" of sample with a resin

Conversion to pterosin B

Liquid chromatograph utilizedSlide23

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 [μ

g

g

-1

]

A horizons  0.011 – 0.713 [

μ

g

g

-1

], mean = 0.031 [

μ

g

g

-1

]

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Results PLSR findings(+)(-)Light exposure

Frond heightTurnover Rate

Carbon Content

Fronds

(+)

(-)

Precipitation

Amt.

of Litter

Turnover

Rate

Stand Size

O horizons

(+)

(-)

Soil

pH

Precipitation

Stand

Size

Easting

A horizonsSlide25

Conclusions Definitive evidence that PT is found in topsoils beneath Bracken standsPossibility that leaching does occurHigh precipitation areas most susceptible to watershed contaminationSlide26

Questions RaisedHow 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…