Metabolism strobilurins

Table 13.2.2 Factors affecting strobilurin properties Intrinsic activity, physicochemical data, metabolic degradation features, biokinetic properties and biological use patterns. 

In the patent literature, many claims and some data can be found about insecticidal and acaricidal activities of strobilurins. Attempts to optimize insecticidal performance did not lead to a commercial product. It seems that, with strobilurins, sufficient insecticidal activity can only be obtained if the compound has very high lipophilicity and very high metabolic stability. This combination of properties gave numerous compounds with excellent insecticidal activity but also with unacceptably high acute mammalian toxicity, so that candidates were abandoned rather early in the research phase. It seems impossible to separate the tight connection between insecticidal and mammalian toxicity in this particular case. Similar problems have been reported for respiration inhibitors of Complex I [82a]. 

For this validation six commercial fungicides were selected three strobilurins and three azoles. The fungicides were selected because their metabolism in whole plants is documented, and although they cover only 2 classes of fimgicides they do vary in their physical/chemical properties, the rates of metabolism and the metabolites which are formed. The compounds tested are listed below. 

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