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Sources & Chemistry of Pesticides


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Sources of all pesticides
Chemistry of all pesticides are described.
Dr. Yousuf Ali Sarker
DVM(BAU), MS in Pharmacology

Published in: Science
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Sources & Chemistry of Pesticides

  1. 1. SOURCES & CHEMISTRY OF PESTICIDES Course No. : VPHA 613 Course Title: Toxicology of Pesticides & Other Toxic Agents Dr. MD YOUSUF ALI SARKER Department of Pharmacology Faculty of Veterinary Science, BAU
  3. 3. BACKGROUND  Pesticides use in agriculture is dated back to the beginning of agriculture  In Bangladesh pesticides are used vigorously to increase the agricultural production  About 70 % of pesticides are used in rice field in Bangladesh  Worldwide use of pesticides causes toxicity  However toxicity depends on the sources & chemical nature of pesticides Chowdhury et al., 2012
  4. 4. FATE OF PESTICIDES PESTICIDES Atmosphere Water Soil Living individual Fate of Pesticides
  5. 5. PEST & PESTICIDES Pest  Any substance or mixture of substances intended for preventing, destroying, or controlling any pest  Insecticides, rodenticides, herbicides etc.  An organism, usually an insect, regarded as injurious or unwanted.  Causes damage to agriculture through feeding on crops or parasitizing livestock Pesticides
  6. 6. GENERAL SOURCE OF POISONING  Accidental exposure  Intentional exposure and  Occupational exposure Source of poisoning
  7. 7. Accidental exposure  Ingestion of pesticide sprayed crops, fodder, straw and drinking water  Aerial spraying of pesticides  Ingestion of contaminated concentrates  Feeding/watering in pesticide contaminated containers  Spraying of interior walls of animal house  Improper storage  Improper and indiscriminate use of pesticides  Ingestion of bait
  8. 8. Intentional exposure  Residues of pesticides in agricultural products (in grain, pulse, vegetable)  Residues of pesticides in animal products (in meat, milk, egg)  Use as feed additives
  9. 9. Occupational exposure  Faulty spray of pesticides by unskilled workers or inefficient equipments Satish K. Garg, 2000
  10. 10.  Chemodynamic processes depends on inherent physico-chemical properties  Chemodynamic processes are  Oxidation  Reduction  Hydrolysis  Photodegredation and  Biodegredation of pesticides CHEMICAL PROPERTIES OF PESTICIDES Zacharia et al.
  11. 11.  Water insoluble but soluble in oil & organic solvent  Can enter the neural membrane  Reducing the potassium transport through pores  Inhibiting Na+-K+ and Ca+-Mg+ ATPases  Antagonize GABA Organochlorines Insecticides Satish K. Garg, 2000 Chemical properties
  12. 12. Organochlorines Insecticides (Cntd) DDT Lindane Dicofol Aldrin
  13. 13. Organophosphorous Insecticides  General chemical structure; (RO)2P(A)X  R= methyl/ ethyl  A= sulfur/ oxygen  X= different variables  Stable in water and alkali  Highly lipid soluble  Less volatile  Irreversible inhibition of AChE by alkyl phosphorylation Chemical properties
  14. 14. Organophosphorous Insecticides (Cntd) Parathion Malathion
  15. 15.  The basic structure of carbamate  R1 = Phenol, naphthalene or other cyclic hydrocarbons  R2 & R3 = -H, -CH3, -C2H5 or other short chain alkyl groups  Decarbamylation & hydroxylation is key features Carbamate Insecticides Chemical properties Carbaryl
  16. 16. Synthetic Pyrethroids  Polarizing ability of both type I & II  Type II: Inactivated Na gate  Hydrolytic degradation  Inhibiting Na+-K+ and Ca+-Mg+ ATPases  Inhibit GABA receptors Chemical properties
  17. 17.  Compound/S that has the potential of either killing or damaging unwanted plants or weeds The biochemical differences  Plants biochemical difference is used to kill weeds Herbicides Table: Classification based on chemical structure Type Example Dinitro compounds DNOC, DNP Phenoxyacetic acids 2,4-D, 2,4,5-T Bipyridinium compounds Diaquat, paraquat Triazenes Atrazine, propazine
  18. 18. Herbicides (Cntd) Chemical properties  Little soluble in water  Stable in sterile water  PH labile  Non-volatile  Stable upto 300°C
  19. 19. Herbicides (Cntd) DNOC 2,4-D AtrazineParaquat
  20. 20.  Chemical used to kill pest rodents, moles, rabbits and hare, etc  Commonly used rodenticides are alphanapthyl thiourea (ANTU), warfarins, zinc phosphate, flouroacetate, red squill etc. Rodenticide
  21. 21. Colorless, crystalline powder (ANTU, warfarin, Zn3P2) Slightly soluble in water Antocoagulant properties (interfere Vit. K) (Warfarin) Inactivated by CYP450 (Warfarin) Slowing TCA cycle by inhibiting aconitase enzyme (Fluoroacetate) Rodenticide (Cntd) Chemical properties
  22. 22. Rodenticide (Cntd) Chemical properties Red Squill  Obtained from plant Urginea maritima (sea onion)  Contains many types of steroidal cardioactive glycosides Most common cardiac glycosides are Scilliroside, Scillaren, Proscillaridin, Glucoscillaridin Garcia Casado, 2000
  23. 23. Rodenticide (Cntd) ANTU Zn3P2 Warfarin
  24. 24. REFERENCES Bhattacharjee, S., Fakhruddin, a. N. M., Chowdhury, M. a Z., Rahman, M. a., & Alam, M. K. (2012). Monitoring of selected pesticides residue levels in water samples of paddy fields and removal of cypermethrin and chlorpyrifos residues from water using rice bran. Bulletin of Environmental Contamination and Toxicology, 89(2), 348–353. 0686-8 Balbaa SI, Khafagy SM, Khayyal SE, Girgis AN. TLC- spectophotometric assay of the main glycosides of red squill, a specific rodenticide. J Nat Prod. 1979;42:522-524 FAO. (2004). International Code of Conduct on the Distribution and Use of Pesticides, Rome Italy.
  25. 25. Chowdhury, M. A. Z., Banik, S., Uddin, B., Moniruzzaman, M., Karim, N., & Gan, S. H. (2012). Organophosphorus and carbamate pesticide residues detected in water samples collected from paddy and vegetable fields of the Savar and Dhamrai Upazilas in Bangladesh. International Journal of Environmental Research and Public Health, 9(9), 3318–3329. Garcia Casado P , Renedo MJ , Fernandez M , Vega FA . Proscillaridin A yield from squill bulbs. Pharm Acta Helv. 2000;52: 218-221. Jinde, C. D. (1994). Physic0 -Chemical Properties and Environmental Fate of Pesticides. REFERENCES (CNTD)
  26. 26. Thank You All