Strobilurins target activity

A decisive factor is the activity of the respective active substance for its molecular target in the fungus and potentially also in non-target organisms. With strobilurins, intrinsic activity is primarily determined by the binding affinity of the active substance to the Qo site of the bci complex of the respiratory chain (see Chapter 13.1 of this volume). 

Table 13.2.2 lists, for comparison, data for the commercialized strobilurin fungicides. The F values for mitochondrial target activity according to Eq. (1) were... 

Besides target activity, dosage transfer of a strobilurin from the point of application to the receiving bci complex of the fungal target organism and its availability at this receptor determines its activity in vivo. 

From the BASF group, a first review concentrated on the discovery of BAS 490 F (kresoxim-methyl), on pharmacophore variations and on structure-activity relationships at the mitochondrial target level [7]. Another paper was focused more on biokinetic features, and their affect on final biological properties [8j. In 1999 a general review summarized the historical evolution from natural products to commercial strobilurins up to trifloxystrobin, and the international R D competition, including some dramatic patent races [9j. Additionally, strobilurins have been reviewed in Russian, Chinese and Indian journals [10-13]. 

Fig. 13.2.5. Strobilurins with the kresoxim-methyl side chain and variations on the pharmacophore. Their relative activities at the target level are given below the formulas F is inversely proportional to the activity (see text).

Fig. 13.2.7. Target-level activity of a series of strobilurin oximino esters as a function of the lipophilicity of the substituents X. p/50 is the negative logarithm of the /50 value from the yeast mitochondria test. Each point represents a variant of the general structure shown.

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