Methyl-paraoxon

Blasiak J, Kowalik J. 1999. Effect of paraoxon-methyl and parathion-methyl on DNA in human lymphocytes and protective action of vitamin C. Pestic Sci 55 1182-1186. 

Paraoxon, methyl parathion, fenitrothion, ethyl parathion... 

A multiresidue method for analyzing 28 common organophosphorus pesticides and three of their main metabolites (paraoxon-ethyl, paraoxon-methyl, and malaoxon) in a variety of crop samples has been developed (59). The use of LC-DAD techniques allowed identification of both organophosphorus pesticides and metabolites by means of standard and spectral comparisons, respectively. A typical chromatogram for fortified apple extract is shown in Figure 4. 

Fig. 4 Chromatograms of a blank apple sample (top) and the same apple sample spiked with 27 of the 31 organophosphorus at the following concentration levels (bottom). 1 = paraoxon methyl 500 2 = malaoxon 6400 3 = paraoxon ethyl 800 4 = metidathion 500 5 = azinphos-methyl 200 6 = phosmet 200 7 = parathion methyl 800 8 = malathion 2000 9 = triazophos 200 10 = fenitrothion 800 11= azinphos ethyl 200 12 = chlorfenvinphos 200 13 = quinalphos 200 14 = parathion-ethyl 400 16 = ethrimphos 1000 17 = diazinon 800 18 = coumaphos 800 19 = fonophos 200 21 = phoxim 400 23 = chlorpyriphos-methyl 500 24 = disulfoton 2000 26 = isofenphos 500 27 = fenchlorphos 500 28 = temephos 400 29 = chlorpyriphos ethyl 200 30 = pyrimiphos-ethyl 200 31 = carbophenothion-ethyl 400. The chromatography was carried out with the Altima column using CH3CN/H20 as mobile phase in gradient elution CHjCN from 28 to 39% in 20 min, and then from 39 to 88% in 40 min. (From Ref. 59.)...

The reactions show some typical oxidations of insecticides catalyzed by CYP enzymes. Carbofuran is hydroxylated to another active compound carbaryl is demethylated or hydroxylated and aldrin is epoxidated to diel-drin, which also has insecticidal properties. Phosphorothionates must be oxidized to the phosphates by CYP enzymes in order to become inhibitors of acetyl cholinesterase. Parathion-methyl is transformed to the oxon analogue, paraoxon-methyl, which is the toxic compound. It also can be demethylated to the inactive desmethyl-parathion-methyl. 

The cotton bollworm, Helicoverpa armigera, in Australia is of great economic importance and is cross-resistant to parathion-methyl and profenofos, but not to chlorpyrifos. It has an acetylcholinesterase with low sensitivity to paraoxon-methyl and profenofos, but the sensitivity to chlorpyrifos is unaltered. As Table 9.3 shows, the enzyme of the resistant insects is a little less efficient by having a slightly higher Km. (Km is the substrate concentration at which an enzyme-catalyzed reaction proceeds at one-half its maximum velocity.) This indicates a somewhat less efficient enzyme, but the difference is so slight that it does not cause any reduced fitness for the insects. The amount of and activity of acetylcholinesterase are almost always much higher than strictly necessary. 

Dimethoate, fenitrothion, fenthion, diazinon, dichlorvos, malathion, parathion-methyl, parathion, methidathion, EPN, disulfoton, ethion, chlorpyriphos-methyl, chlorpyriphos, propaphos, pyrida-phenthion, edifenphos, dimethyl-vinphos, isoxathion, phenthoate Methamidophos, acephate, omethoate, monocrotophos, oxydemeton-methyl, vamidothion Mevinphos, dichlorvos, azinphos-methyl, azinphos-ethyl, parathion-methyl, parathion-ethyl, malathion, fenitrothion, chlorvinphos, fenthion, diazinon Paraoxon, methyl-parathion, ethyl-parathion, fenitrothion... 

Parathion-methyl, fenitrothion, parathion-ethyl, paraoxonmethyl, fenitrooxon, paraoxon methyl... 

Paraoxon, methyl parathion Amperometry Arthrobacter sp. Entrapment Up to 5 pM 10 nM paraoxon 162... 

An acid phosphatase (AP) hybrid biosensor was developed using a thin layer of potato tissue coupled to an amperometric GOD-based biosensor based on internal sensing of H202. The reversible inhibition of AP was utilized for the determination of malathion, paraoxon methyl, paraoxon, and aldicarb with limits of detection of 0.5 ppb for paraoxon methyl, and 40 ppb for aldicarb. The tissue-based biosensor exhibited a longer shelf life and abetter reliability on the amperometric results than a bi-enzymatic sensor with purified AP and GOD. A similar biosensor was also developed using a potato layer with a Clark-type dissolved oxygen electrode. ... 

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