Systox toxicity

Rider JA, Moeller HC, Puletti EJ, et al. 1969. Toxicity of parathion, systox, octamethyl pyrophosphoramide, and methyl parathion in man. Toxicol Appl Pharmacol 14 603-611. 

Among other insecticides may be mentioned systox, first synthesized by Schrader.1 Ripper calls for caution in its use on food crops until more is known about the toxic metabolites. 

There is, however, one means of achieving the conflicting properties required for apoplastic transport without resort to compromise. This is by using precursors which have characteristics favouring uptake and are then converted within the plant to active toxicants which are more readily translocated. The principle is best illustrated by the long-established organophosphorus insecticides of the systox type such as demeton, disulfoton and phorate which are relatively lipophilic... 

Uses Demeton-s-methyl is a pale yellow oil that has a sulfur-like odor. It is a systemic and contact insecticide and acaricide. It kills insects that feed on plants by sucking juices. It is used to control aphids, sawflies, and spider mites in fruits, vegetables, potatoes, cereals, ornamentals, and forestry. Demeton-s-methyl replaces methyl demeton, a mixture of demeton-s-methyl and demeton-o-methyl sold as systox meta. Demeton-s-methyl is more toxic to insects than demeton-o-methyl. It is available as an emulsifiable concentrate.28,40... 

Another group of organophosphoms insecticides consists of preparations with the so-called systemic (inside the plant) effect. They are absorbed by plant tissue, making the plant poisonous for insects feeding on it. These insecticides are mercaptophos (systox) and M-74 (pisyston), derivatives of mono- and dithiophosphoric acid. However, both substances are very toxic for people and cattle and are even more dangerous than thiophos that is why they are not used in Russia. Other systemic preparations, such as methylmercaptophos (metasystox) synthesised by G.Schrader, and M-81 (intrathion) obtained in the laboratory of Academician M.I.Kabachnik, are less toxic than methaphos but more toxic than trichlorfon. 

Fig. 6. Summarization of results correlating inhibition efficacy (piso) and toxicity (log LD50) for some OP and nerve agents. Equation y = 9.87 — 1.26x p < 0.01 rxy = —0.9489. The lines indicate experimentally determined piso (human brain AChE) values (axe y) or extrapolated values (axe x) of LD50 for systox and VX. Each point represents the value of piso corresponding to LD50 value for rabbit, rat, guinea pig, mouse, and dog. The compounds under code are designated by the abbreviation of the oxyalkyl group on the phosphorus head, and by the alkyl on the nitrogen atom - e.g. VX is designated as Et-iPr (modified from B11, B14 and P3).

Among the commercial insecticides listed in Table 12.32, Dimeton (Systox) is a mixture of thi-ono and thiolo isomers (Chapter 9). It can be made by reaction (12.100). The thiolo isomer has 10 times the toxicity and 100 times the solubility of the thiono isomer. 

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