4-nitrophenyl Phosphorothioate Research Articles

Two organophosphorus pesticides: methyl parathion and dicapthon.

Structural studies performed in this laboratory of organophosphorus pesticides continue with these related compounds. The -NO2 groups of methyl parathion (systematic name: dimethyl 4-nitrophenyl phosphorothioate, C8H10NO5PS) and dicapthon (systematic name: 2-chloro-4-nitrophenyl dimethyl phosphorothioate, C8H9ClNO5PS) make dihedral angles of 10.67 (8) and 5.8 (1)°, respectively, with the planes of their attached rings, which accompanies angular distortion at the ring C atoms to which the -NO2 groups are attached. Similar distortions are observed at the C atom to which the thiophosphate groups are attached. Significant differences in distances and angles around the phenolic O, versus the -OMe groups, explain why it is the site of hydrolysis for these compounds. A comparison of a torsion angle involving the thiophosphate group and phenolic O atom with similar pesticide structures is given and indicates steric influences on that angle.

Activation and degradation of the phosphorothionate insecticides parathion and EPN by rat brain

Cytochrome P-450-dependent monooxygenases are known to activate phosphorothionate insecticides to their oxon (phosphate) analogs by oxidative desulfuration. These activations produced potent anticholinesterases, decreasing the I 50 values to rat brain acetylcholinesterase almost 1000-fold (from the 10 −5 M range to the 10 −8 M range). Since the usual cause of death in mammals from organophosphorus insecticide poisoning is respiratory failure resulting, in part, from a failure of the respiratory control center of the brain, we investigated the ability of rat brain to activate and subsequently degrade two phosphorothionate insecticides, parathion (diethyl 4-nitrophenyl phosphorothioate) and EPN (ethyl 4-nitrophenyl phenylphosphonothioate). Microsomes from specific regions (cerebral cortex, corpus striatum, cerebellum, and medulla/pons) of the brains of male and female rats and from liver were incubated with the phosphorothionate and an NADPH-generating system. Oxon production was quantified indirectly by the amount of inhibition resulting in an exogenous source of acetylcholinesterase added to the incubation mixture as an oxon trap. The microsomal activation specific activity was low for brain when compared to liver [0.23 to 0.44 and 5.1 to 12.0 nmol · min −1 · (g tissue) −1 respectively]. The mitochondrial fraction of the brain possessed an activation activity for parathion similar to that of microsomes [about 0.35 nmol · min −1 · (g tissue) −1 for each fraction], but mitochondrial activity was slightly greater than microsomal activity for EPN activation [0.53 to 0.58 and 0.23 to 0.47 nmole · min −1 · (g tissue) −1]. Whole homogenates were tested for their ability to degrade paraoxon and EPN-oxon (ethyl 4-nitrophenyl phenylphosphonate), quantitated by 4-nitrophenol production. Specific activity for oxon degradation in liver was greater than that in brain [31 to 74 and 1.1 to 10.7 nmole · min −1 · (g tissue) −1 respectively]. Overall, the brain and liver had about 1.5- to 12-fold higher specific activities for degradation than activation depending on the compound used. These findings demonstrate that the brain possesses both phosphorothionate activation and oxon degradation abilities, both of which may be significant during exposures to organophosphorus insecticides.

REMOTE CONTROL OF DIASTEREOSELECTIVITY OF DN-ASE II AND ENDONUCLEASE ECO RI TOWARDS PHOSPHOROTHIOATE ANALOGUES OF OLIGONUCLEOTIDES

Abstract (Rp)-Thymidyl 3′-(4-nitrophenyl phosphorothioate) (TP(S)NP) is converted in the presence of DN-ase II into (Sp,Rp)-thymidyl (3′–5′)-thymidyl phosphorothioate 3′-(4-nitrophenyl phosphorothioate) (TP(S)TP(S)NP), while (Sp)-TP(S)NP under analogous conditions gives (Rp,Sp)-TP(S)TP(S)NP, but as a minor product only. The preponderant product was recognized as (Sp,Rp)-thymidyl (3′–5′) thymidyl phosphorothioate 5′–(4-nitrophenyl phosphorothioate) (NPP(S)TP(S)T). All phosphorothioyl transfer reactions occur with retention of configuration at phosphorus atoms, which speaks for a double-displacement process and involvement of phosphorothioylated enzymes as reactive intermediates. Nucleolytic activity of DN-ase II, characteristic for this enzyme with respect to natural oligonucleotides, is not observed if TP(S)NP are used as the substrates. However, the transferase activity is even extended for the (4-nitrophenyl phosphorothioate)-shift from 3′ to 5′-position of dinucleotide, but for diastereoisomer (Rp,Sp)-...

Activity of acid deoxyribonuclease towards diastereoisomers of thymidyl 3'-(4-nitrophenyl phosphorothioate). Stereochemistry of transnucleotidylation reaction.

The (Rp)- and (Sp)-diastereoisomers of thymidyl 3'-(4-nitrophenyl phosphorothioate) (1) were found to act as unusual substrates for acid deoxyribonuclease (DNase II). Instead of the expected thymidine 3'-phosphorothioate, the product resulting from the reaction of (Rp)-1 catalyzed by DNase II was identified as (Sp, Rp)-thymidyl (3'-5')thymidyl phosphorothioate 3'-(4-nitrophenyl phosphorothioate), while that from (Sp)-1 has been recognized as a 10:1 mixture of (Sp, Rp)-thymidyl (3'-5')thymidyl phosphorothioate 5'-(4-nitrophenyl phosphorothioate) and (Rp, Sp)-thymidyl (3'-5')-thymidyl phosphorothioate 3'-(4-nitrophenyl phosphorothioate), respectively. Both types of transnucleotidylations were found to occur with retention of configuration at phosphorus. Stereochemical results may be interpreted in terms of two step mechanisms involving the formation of the intermediate, covalent substrate enzyme complexes.

Substrate specificity and stereospecificity of calf spleen phosphodiesterase towards deoxyribonucleosidyl 3'-(4-nitrophenyl phosphates) and phosphorothioates.

Phosphodiesterase from calf spleen exhibits nucleotidyltransferase activity when incubated with either the (PR) or the (PS) diastereomer of thymidyl 3'-(4-nitrophenyl phosphorothioate). Thymidylyl(3'-5')thymidyl phosphorothioate 3'-(4-nitrophenyl phosphorothioate) was identified as the main product of the enzyme-catalyzed reaction and the absolute configuration at the internucleotide phosphorus atom of the product was determined. The nucleotidyltransferase reaction is shown to proceed with retention of configuration at phosphorus, implying involvement of a double displacement mechanism with the formation of a nucleotidylated enzyme intermediate. To study the substrate specificity of spleen phosphodiesterase a series of deoxyribonucleosidyl 3'-(4-nitrophenyl phosphates) and phosphorothioates were synthesized, and Km and V parameters for each substrate were measured. The results obtained show virtually no specificity for substrates with different nucleosidyl moieties, while about a 20 - 30-fold drop in V and a slight increase in Km values is observed for phosphorothioate analogues as compared with corresponding phosphates. The enzyme showed no significant stereoselectivity towards phosphorothioates of opposite configurations at phosphorus.

Concentration of Methyl Parathion from Penncap-M in Pollens of Various Lipid and Oil Contents 1

Samples of hand-collected pollens ( Franseria confertiflora , Cupressus arizonica , and Helianthus annuus ), a bee-collected pollen ( Taraxacum officinale ), and the extracted lipids (chloroform-methanol, 2:1) from H. annuus and T. officinale were exposed to fumes of methyl parathion [ O , O -dimethyl O - ( p -nitrophenyl) phosphorothioate] from Penncap-M capsules. Amounts of methyl parathion absorbed were quantitatively determined by gas-liquid chromatography. The pollens generally absorbed methyl parathion in amounts related to their lipids and ether-extractables content. The extracted lipids absorbed two to three times as much methyl parathion as did the intact pollens. Slender ragweed pollen, Franseria confertiflora , did not accumulate as much methyl parathion as the other pollens. In Penncap-M-treated fields, pollens of certain plants may become toxic to pollen-eating and pollen-collecting insects, due to pesticide absorption by lipids, but some pollens may be less hazardous than others, due to differential absorption.

ChemInform Abstract: SYNTHESIS OF 4‐NITROPHENYL ESTERS OF THYMIDINE 3′‐PHOSPHATE AND 3′‐PHOSPHOROTHIOATE USING A NEW PHOSPHORYLATING AGENT

AbstractDie durch Substitution des entsprechenden Dichlorids mit Anilin zugängliche Verbindung (II) reagiert mit dem Thymidin (I) zu den Diastereomeren (III), die durch Säulenchromatographie getrennt werden können.

Comparative Metabolism of O,O-Dimethyl O-p-Nitrophenyl Phosphorothioate (Methyl Parathion) and O,O-Dimethyl O-(3-Methyl-4- Nitrophenyl) Phosphorothioate (Sumithion)12

The metabolism of methyl parathion and of Sumithion®, O,O-dimethyl O-(3-methyl-4-nitrophenyl) phosphorothioate, by mouse liver and fat body from the American cockroach, Periplaneta Americana (L.), was compared, in an effort to find the reason for the comparatively low mammalian toxicity of Sumithion. Fat body activated both compounds while mouse liver slices activated methyl parathion but not Sumithion. Isolated liver microsomes were able to activate either of the 2 substances, an observation indicating that the absence of activation in the case of Sumithion incubated with liver slices was not due to any difference in the specificity of the activating system as such. A comparative study of the degrading ability of liver revealed a distinetly more efficient breakdown of Sumithion. The enzyme system(s) responsible for this differential rate of detoxification was localized in the supernatant fraction of a mouse liver homogenate. The hypothesis is proposed that the ability of liver tissue to degrade Sumithion faster than methyl parathion is, at least partly, the reason for the extremely low mammalian toxicity exhibited by the former substance.

Laboratory studies of insecticides against the coffee leaf-miner Leucoptera Meyricki Ghesq. (Lepidoptera, Lyonetiidae)

The coffee leaf-miners Leucoptera meyricki Ghesq. and L. caffeina Wshbn. are serious pests of arabica coffee in Kenya. At the present time sprays containing parathion, methyl-parathion or diazinon are used extensively for their control.To facilitate preliminary investigations into various aspects of insecticidal control of the larval stages of these pests, a laboratory bioassay technique was developed. Larvae were reared on detached coffee leaves placed on moist filter paper in plastic boxes. When the larvae were in their third instar, the leaves were sprayed in a Potter tower and then kept in a moist air stream for three days before the mines were dissected to enable mortality counts to be made.Of 22 new insecticides screened, only Sumithion (O, O–dimethy1 O–(3–methy1–4–nitrophenyl) phosphorothioate) and fenthion gave mortalities higher than those achieved with diazinon. Parathion gave somewhat higher mortalities than methyl-parathion, and emulsifiable formulations of these insecticides were more effective than wettable powders. The inclusion of additional wetting agents increased the efficiency of commercial formulations of these two insecticides. These results are subject to confirmation in field trials.The mode of action of parathion was investigated. Dosage/mortality lines were constructed for parathion, methyl-parathion and diazinon so that resistance to these insecticides by L. meyricki could be detected should it develop at some future date. L. caffeina was found to be apparently more susceptible to these insecticides than L. meyricki and this was believed to be due to its greater rate of feeding.