S2%20L9-10%20Pro-inflammatory%20plants

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S2 L9-10 Pro-inflammatory plants

• Anna Drew

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Plants producing dermatitis.

• environmental toxicology
• not pollen allergy
• Can result from contact with living, damaged or
  processed plant material
• Hazardous in
• Industry timber, cosmetic/perfume, paint/varnish
• Environment walks, gardening
• Veterinary grazing or domestic
• mouth areas inflammed, balding
• scouring severe diarrhoea food not utilised
  properly
• Main clinical problem
• identify cause and remove
• Treatment
• topical corticosteroids
• Dermatitis

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Plants producing contact dermatitis can be
classified into 5 groups

• Mechanical irritants
• Stinging nettles
• Phototoxic compounds
• Allergenic substances
• Direct or primary irritants

Ref Evans FJ, Schmidt RJ. Plants and plant
products that induce contact dermatitis. Planta
Medica 1980 38(4)
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Mechanical irritants

• Caused by
• Easily detachable rough hairs or bristles on
  surface of the plant
• break off into skin when touched
• move around the in the skin causing irritation
• or acicular calcium oxalate crystals produced
  onto plant surface
• Found in
• Boroginaceae - Borago, Echium, Pentaglottis,
  Pulmonaria, Symphytum
• Covered with coarse stiff trichomes
• highly lignified or produce silica around the
  hair
• Cornaceae - Cornus sanguinea
• T shaped trichomes
• Malpighiaceae Malpighia urens
• Barley (awns) and other cereal grasses

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Stinging nettles

• Caused by
• a defensive trichome which they have evolved
• combination of a spring release mechanism
  hypodermic syringe
• silica (glass) or calcium oxalate tip on surface
• when touched tip breaks triggering basal pump
  mechanism which releases small amount of toxin
  into the skin
• (equiv to muscles or contractile tissue!)

wound hollow tube
tip
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• Causes mild -gt very irritant dermatitis, even
  death
• Australia/India
• further evolved with enormous hairs to kill
  animals
• UK
• only one species Urtica dioica
• some plants mimic it but do not sting
• varies in form according to nutrient value of soil

Tragia involucrata
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• Composition of poison
• protein peptide material
• large molecule unusual
• when dried it denatures
• got poison out by dipping leaf in liquid nitrogen
  and brushing off trichomes onto paper
• has properties in common with acetylcholine,
  histamine, 5-HT
• Found in (over 50 species)
• Urticaceae - Urtica, Giardinia, Gyrotaenia,
  Laportea, Obetia
• Euphorbiaceae - Acidoton, Cnesmone, Tragia
• (Tragia involucrata Indian species)
• Loasaceae - Loasa, Evertesia, Eucnide
• Hydrophyllaceae - Wigandia
• lethal ones

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Phytotoxic substances

• Caused by
• Furanocoumarins (coumarin family)
• harmless animals and humans can eat plants
• veterinary problem
• photoactivated on skin -gt sunburn effect
• red inflammation peels to leave brown pigmented
  areas
• around muzzle, hair falls out, look in poor
  condition
• Photoactivated form binds to epidermal DNA and
  ribosomal RNA
• -gt pigment

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1/3 as active
¼ as active
6x as active

• Found in
• Umbellifereae Heracleum mantegazzanium,
  Pastinacea sativa
• Rutaceae Dictamnus albus, Phebalium argentium
• Leguminosae Psoralea sp.
• Moraceae Ficus carica
• Rosaceae

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Contact allergens

• Most common form of plant dermatitis
• allergenic eczematous contact dermatitis
• dry scaly erythema -gt severe papular/vescicular
  inflammation with oedema
• 1st exposure -gt sensitisation (eg 6-25 days)
• 2nd exposure -gt dermatitis (eg 24 hours)
• degree depends on exposure dose
• hard to diagnose (patch testing)
• population variability genetically determined
  (race, gender)
• cross sensitization between plants
• compounds of same basic chemical structure can
  cause reaction
• elictors may not be allergenic themselves

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Sri Lanka

• Kandy - plant dermatitis accounted for one third
  of cases
• Clinic incidence affected by
• industrial development of the area
• pattern of employment
• interest the dermatologist takes in contact
  dermatitis

Ref Perera WDH. Special problems and
perspectives from Sri Lanka. In See Ket Ng, Chee
Leok Goh (Eds). The Principles and Practice of
Contact and Occupational Dermatology in the
Asia-Pacific Region. World Scientific, 2001
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Groups of compounds

• URUSHIOLS Poison ivy toxins
• typical allergenic compounds
• simple molecules (low MWt, haptens)
• homologous long chain phenolics
• R1 and R3 can be -H, -OH or -COOH
• R2 can be C9 -gt C19 saturated or unsaturated
• lipid soluble and will penetrate skin and
  phenolic groups burn
• mechanism of action unknown (direct irritation,
  allergenic or inflammation)
• hard to separate compounds (need GLC) but all
  work
• cross sensitization takes place

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• 150 derivatives have been found in
• Anacardiaceae
• Toxicodendron (poison ivy)
• Pentaspadon
• Semecarpus (5 species in SL)
• medium-sized forest trees found in the wet zone
• -gt itchy vesicular dermatitis in sensitized
  individuals
• streaks of vesicles correspond to points of
  contact (face, exposed areas) with the plant
• reactions often severe requiring treatment with
  systemic steroids
• Mangifera indica (mango tree)
• -gt allergic contact dermatitis
• from contact with stem, leaves, skin of unripe
  fruit
• seen on lips and around mouth
• climbing a tree can produce dermatitis all over
  body
• Anacardium occidentale (cashew nut tree)

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• SESQUITERPENE LACTONES
• Mainly found in Compositae
• Allergenic ones also found in Jubilaceae,
  Lauraceae
• Concentrated in pollen and trichomes
• distributed by wind over large areas in spring
• distinct from hayfever caused by protein
  constituents in pollen exine
• 250 characterised - 4 main types structurally
• All essentially have C15 hydrocarbon nuclei
• Not all tested on humans (50)
• ?-lactone and a-methylene group -gt effect

guaiane
pseudoguaiane
eudesmane
germacrane
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widely distributed

• Found in
• Compositae
• Ambrosia
• Artemisia
• Chrysanthemum
• Eupatorium
• Helenium
• Iva
• Parthenium eg Tanacetum parthenium (feverfew)
• Jubilaceae
• Fruillania
• Lauraceae
• Laurus

Parthenolide
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• OTHER
• Occupational hazards mainly in timber industry
  (sawing -gt dusts)
• (1) Quinones
• in heartwood are responsible
• Found in
• Primulaceae Primula obconica

Primin
Mansenone
Larchol
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• (2)
• Not present in the plant under normal
  circumstances
• Formed when plant injured by hydrolysis of
  tuliposide A -gt tulipalin A (enzyme
  ß-glucosidase)
• allergenic material (phytoalexin)
• Found in
• Liliaceae and related families
• Tulipa, Erythronium, Alstroemeria
• (3) Volatile oils
• low allergenic sensitizing potential
• (4) Many miscellaneous compounds

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Primary irritants

• Largest group of all
• Cause most damage
• End up in all kinds of cosmetics, perfumes,
  soaps, eye makeup dermatitis common
• Burn directly (1st and every exposure)
• can be widespread
• -gt severe erythema, itching, flaking etc
• Have diverse structures
• Not all mechanisms understood
• phorbol esters from croton (Euphorbiaceae) best
  understood
• activate protein kinase C inflammation pathway
• some simply acids or phenols which burn
• Time for reaction depends on lipid solubility
• volatile oils worse
• may induce irritation and malignancy at a later
  stage

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• Capsaicins ginger group
• Capsaicin irritant principle found in red
  pepper family
• Solanaceae - Capsicum minimum, C.fructescens
• burning effect on membranes throughout GI tract
  (curry ingredients)
• externally -gt erythema, no blistering
• Gingerols, shagaols
• Zingiberaceae Zingiber officinalis
• also capsaicin-like compounds -gt rubefacient
• Uses
• Go into deep heat products paraffin-based
  creams for massage, counterirritants to increase
  blood flow to damaged muscle
• Itching powders (mechanical trichome) or chemical
  irritants
• Some foods

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Capsaicin
Shogaol
The gingerols

• Electron dense centre with lipid side chain
• lipophilic, will penetrate cells easily

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• Volatile oils
• Thought to be phenols present if they burnt
• Now realise terpinoids present
• Affect certain types of smooth muscle -gt spasm
  (contraction)
• Mechanism unknown may block Ca2 channel
• Uses antibacterial, indigestion preparations
• Two groups aromatics, terpinoids

Eugenol
Safrole
Limonene
a-pinene
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• Proteolytic enzymes
• Found in the sap of some plants
• Papain Carica sp.
• Ficia Ficus sp.
• Bromelain Ananus sp.
• Nepenthin - Nepenthus sp.
• Eg pitcher plant insectivorous
• insects attracted into modified leaf structure
• contains sugary solution with proteolytic enzyme
• Insects are a source of nitrogen
• On skin -gt digestion -gt very painful dermatitis
• Use meat industry

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• Sulphur glycosides
• Irritant to mucous membranes
• Eg Allium sp.
• peeling an onion eye watering (volatile
  substances)
• when damaged enzymes convert sulphur glycosides
  -gt
• Mustards
• when damaged glucosinolate glycoside -gt
  isothiocyanates (enzyme myrosinase)

propenyl sulphuric acid
eg isothiocyanate
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• Resins
• Found in
• Berberidaceae
• Podophyllum peltatum
• Podophyllum hexandrum
• Uses to burn off worts, (antitumour properties)

Podophyllotoxin