Il Buono, il Brutto, il Cattivo. The flowering plants. Pesticide Application, transport and effects. Wild and cultivated plants.

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1 Il Buono, il Brutto, il Cattivo Pesticide Application, transport and effects Jens C. Streibig Lars Schrübbers Jens C. Streibig Plants The flowering plants Good Bad Ugly Wild and cultivated plants Weeds Noxious weeds

2 Outline How compounds enter an organism How is the compound are distributed in the organism What happens with the compound within the organism How (if) does the compounds leaves the organism A Absorption D Distribution M Metabolism E Elimination + toxicity

3 Uptake Plant cuticle Animal skin Animal cuticle (insects) Inhalation Digestive tract No Cuticle hydrophilicity hydrophobicity Devine et al 1993

name Log P o/w permeability coefficient (μm/h) Terrestrial animals glyphosate -1.7 0.04 caffeine 0.16 4.5 benzoic acid 1.

4 Uptake? Cuticle and skin important: vehicle (donor liquid), molecular size, skin properties (injury etc.)... e.g.: very polar compound in water, or an organic solvent as carrier. name Log P o/w permeability coefficient (μm/h) Terrestrial animals glyphosate caffeine benzoic acid malathion Ngo 2009 Skin Lungs (inhale) Specialized to selective molecular Gastrointestinal tract (swallow) Specialized to selective molecular important: vehicle (donor liquid), molecular size, skin properties (injury etc.)...

5 Eventually herbicides must enter living cells to cause the desired effect e.g.: Photosynthesis Chloroplast Respiratory Mitochondria ALS Chloroplast... Distribution Phloem: 2,4-D Glyphosate Imazapyr Haloxyfop distribution Xylem: Atrazine Benomyl Thiophanate methyl Dimethoate Uptake and Translocation distribution Chemical properties and mobility distribution Devine et al. 1993

6 Penetrating membrane: - Non-polar - MW lower than 1000 g/mol - Actively transported Ion trapping Gastric juice, ph = 1.4 Plasma, ph = 7.4 Opposite for weak bases! distribution Toxicity Seven routes to death toxicity 1. Enzyme inhibitors 2. Disturbance of signal systems 3. ROS (Reactive Oxygen Species) 4. Degrading ph gradients (proton pumps) 5. Dissolving membranes 6. Disturbing osmotic balance or ph 7. Strong electrophilic compounds J. Stenersen 2004 toxicity toxicity WHO Hazard asses The Globally Harmonized System of assification and Labeling of Chemicals (GHS) ass Property Oral (LD50) Dermal (LD50) Solid Liquid Solid Liquid Ia Extremely hazardous _5 <20 <10 <40 Ib Highly hazardous II Moderately hazardous III Slightly hazardous >500 >2000 >1000 >4000 Active ingredients unlikely to present acute hazard assified using animal LD50s (oral: rat, dermal: rat or rabbit) The relative toxicity of compounds in human poisoning is complicated by the ease of treatment for example, class I organophosphorus pesticides can be treated with atropine and oximes with some effect, whereas selfpoisoning with class II organochlorines is practically untreatable in many locations

Examples toxicity toxicity Aluminium phosphide is used as a rodenticide, insecticide, and

The acid in the digestive system of the rodent reacts with the phosphide to generate the toxic

In 2002, Sir Derek Bibby, (Bibby Line shipping company) aged 80 and terminally ill with

caused his body to emit dangerous fumes forcing the evacuation of the hospital department where

7 Examples toxicity toxicity Aluminium phosphide is used as a rodenticide, insecticide, and fumigant for stored cereal grains. It is used to kill small verminous mammals. The acid in the digestive system of the rodent reacts with the phosphide to generate the toxic phosphine gas. In 2002, Sir Derek Bibby, (Bibby Line shipping company) aged 80 and terminally ill with leukaemia, committed suicide by the use of aluminium phosphide - the poison, hours later, caused his body to emit dangerous fumes forcing the evacuation of the hospital department where his body was being held AlP + 3 H 2 O Al() 3 + PH 3 AlP + 3 H + Al 3+ + PH 3 At the site of action I 50 -Levels for an ALS inhibitor Metabolism Four routes to recovery Conversion Conjugation Deposition Excretion

Comparative Not to confuse with secondary metabolite Even though same enzymes might be used mammals plants mobility mobile immobile carbon source heterotroph autotroph circulatory system well

8 Comparative Not to confuse with secondary metabolite Even though same enzymes might be used mammals plants mobility mobile immobile carbon source heterotroph autotroph circulatory system well developed poorly developed special organc for toxification liver - excreation of water solulable metabolites yes limited CYP glutathion conjugates + + Amino acid conjugates + + sulphate conjugates + - glucuronic acid conjugates + - glucose conjugates - + phase III not important important Comparative animal/plant Glutathione: Gamma-Glutamyl-cysteinyl-glycine, GSH, tripeptide

9 Metabolism Devine et al 1993 Deactivation Deactivation Diflubenzuron

10 Conjugation reaction (phase II )...mercapturic acid/malonic acid pathway Example for phase II : Mammal or plant?? methoxychlor methoxychlor phenol CO O O H C O CH 3 mammals CH 2 O O P O glucose-1-phosphate +UTP + 2 NAD P 2 O 7-2 NADH + UDP-glucuronic acid CO O O H C + Glucuronosyl transferase O CH 3 Glucuronide plants (and insects) DDT ether glucuronide + UDP Glucoside

11 Activation excretion Excretion pesticides plants Activation Activation o o o Limited excreation via roots and via volatilization Deposition: Glycosides mainly in the vacuole Amino acid conjugates mainly in the cell wall Possibility for deciduous species to remove xenobiotics

Toxicant Disposition and Metabolism. Jan Chambers Center for Environmental Health Sciences College of Veterinary Medicine

Toxicant Disposition and Metabolism Jan Chambers Center for Environmental Health Sciences College of Veterinary Medicine chambers@cvm.msstate.edu Definitions Disposition Absorption passage across membrane.