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S2 L9-10 Pro-inflammatory plants. Anna Drew. 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

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plants producing dermatitis
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
      • itching -> scratching -> pain
        • oedema with blisters that weep. If break can get 2y infection
        • OR hyperplasia (thickening) of skin. Dries and breaks
plants producing contact dermatitis can be classified into 5 groups
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)

mechanical irritants
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
    • Cactaceae - Opunta ficus-indica, Opunta cochinillifera (prickly pears)
    • Narcissus (daffodil), Hyacinthus (hyacinth family)
          • secrete CaOx onto bulb surface
          • -> daffodil itch, lily rash which wears off in 12-12 hours
stinging nettles
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

slide6
Causes: mild -> 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

slide7
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
    • Leguminosae - Mucuna pruriens and other Mucuna sp.
        • trichomes on seed pods
        • mucunain, a proteinase, on surface responsible for pruritus and mechanical effect for dermatitis
phytotoxic substances
Phytotoxic substances
  • Caused by:
    • Furanocoumarins (coumarin family)
      • harmless – animals and humans can eat plants
      • veterinary problem
        • photoactivated on skin -> 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
      • -> pigment
slide9

1/3 as active

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

¼ as active

6x as active

contact allergens
Contact allergens
  • Most common form of plant dermatitis

= allergenic eczematous contact dermatitis

      • dry scaly erythema -> severe papular/vescicular inflammation with oedema
    • 1st exposure -> sensitisation (eg 6-25 days)
    • 2nd exposure -> 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
sri lanka
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

groups of compounds
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 -> 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
slide13
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
        • -> 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)
        • -> 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)
        • -> allergic contact dermatitis
        • from handling fruit, nut and also from cashew nut oil
    • Ginkgoaceae - Ginkgo biloba (fruit pulp)
    • Protaceae - Persiana
slide14
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)
      • γ-lactone and α-methylene group -> effect

guaiane

pseudoguaiane

eudesmane

germacrane

slide15

* widely distributed

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

Parthenolide

slide16
OTHER
    • Occupational hazards mainly in timber industry (sawing -> dusts)

(1) Quinones

      • in heartwood are responsible
      • Found in:
        • Primulaceae – Primula obconica

Primin

Mansenone

Larchol

slide17
(2)
  • Not present in the plant under normal circumstances
  • Formed when plant injured by hydrolysis of tuliposide A -> tulipalin A (enzyme β-glucosidase)
  • = allergenic material (phytoalexin)
  • Found in:
    • Liliaceae and related families
      • Tulipa, Erythronium, Alstroemeria

(3) Volatile oils

  • low allergenic sensitizing potential

(4) Many miscellaneous compounds

primary irritants
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

-> 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
slide19
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 -> erythema, no blistering
    • Gingerols, shagaols
      • Zingiberaceae – Zingiber officinalis
      • also capsaicin-like compounds -> 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
slide20

Capsaicin

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

Shogaol

The gingerols

slide21
Volatile oils
    • Thought to be phenols present if they burnt
    • Now realise terpinoids present
    • Affect certain types of smooth muscle -> spasm (contraction)
    • Mechanism unknown – may block Ca2+ channel
    • Uses: antibacterial, indigestion preparations
    • Two groups: aromatics, terpinoids
    • Beware: cajaput, clove, eucalyptus, nutmeg, pumilopine, rosemary, thyme, terpentine

Eugenol

Safrole

Limonene

α-pinene

slide22
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 -> digestion -> very painful dermatitis
      • Use: meat industry
slide23
Sulphur glycosides
    • Irritant to mucous membranes
      • Eg Allium sp.
        • peeling an onion – eye watering (volatile substances)
        • when damaged enzymes convert sulphur glycosides ->
  • Mustards
        • when damaged glucosinolate glycoside -> isothiocyanates (enzyme myrosinase)

propenyl sulphuric acid

eg isothiocyanate

slide24
Resins
    • Found in:
      • Berberidaceae
        • Podophyllum peltatum
        • Podophyllum hexandrum
    • Uses: to burn off worts, (antitumour properties)

Podophyllotoxin

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