A study of the action mechanism of 2-aryloxy-2-thio-1,3,2-oxazaphosphorinane series pesticides

The interaction of 2-aryloxy-2-thio-1,3,2-oxazaphosphorinan exhibiting nema tocide, insecticide/acaricide, and synergetic activities with monoamine oxi dases and the interaction of the corresponding oxones, 2-aryloxy2-oxo-1,3,2 -oxazaphosphorinanes, with various cholinesterases, carboxyl esterases, and monoamine oxidases were studied. We showed that the thioderivatives inhibi ted monoamine oxidases, whereas oxones, which are, as a rule, weak cholines terase inhibitors, strongly inhibited carboxyl esterases of the American co ckroach and were transformed with monoamine oxidases into the strong cholin esterase inhibitors, acyclic phosphamidates. This allowed us to explain the low toxicity of the thioderivatives, the high toxicity of the oxoderivativ es, and the great difference in toxicities of thio- and oxocompounds in the 1,3,2-oxazaphosphorinane series. The capacity of thioderivatives to inhibi t monoamine oxidases and of oxoderivatives and their further activation pro ducts to inhibit carboxyl esterases, i.e., both enzymes responsible for pyr ethroid detoxication in insects, explains the synergetic activity of the 1, 3,2-oxazaphosphorinane series.