Anvisa opens public consultation on isopyrazam

Anvisa, the National Health Surveillance Agency, has opened a deadline for comments in a public consultation on the proposed regulatory instruction including the pesticide isopyrazam (isopyrazam, CAS 881685-58-1, FRAC 7) in its list of products (IN 103/2021). Access to the suggested draft and the form for consideration occurs through the agency's website.

This fungicide is the active ingredient in several Syngenta products around the world. Among them, Rikali and Reflect. The inclusion of the product on the list in IN 103/2021 is part of the product registration process in Brazil.

Isopyrazam belongs to the group of SDHIs (succinate dehydrogenase inhibitors), which target complex II (or succinate dehydrogenase) in the mitochondrial respiration chain, interrupting the flow of electrons and thus altering cellular respiration.

According to the scientific literature, "the genes that encode succinate dehydrogenase proteins are nuclear. The succinate dehydrogenase enzyme complex is composed of 4 subunits. Two hydrophilic parts form a peripheral domain and have succinate dehydrogenase activity, the flavoprotein sdhA (643 amino acids in Z . tritici) and the iron-sulfur protein shdB (297 amino acids in Z. tritici) which contains 3 iron-sulfur complexes, [2Fe–2S], [4Fe–4S] and [3Fe–4S]. The sdhC subunits (size: 187 amino acids in Z. tritici) and sdhD (size: 193 amino acids in Z. tritici) form a lipophilic domain that anchors the complex to the mitochondrial membrane. Finally, a heme b group is complexed between sdhC and sdhD. The enzyme complex is active in electron transport through the aerobic respiratory chain, as well as in the citric acid cycle, coupling the oxidation of succinate to fumarate with the reduction of ubiquinone to ubiquinol".

Isopyrazam binds to the quinone binding site of the protein complex, which is composed of sdhB, sdhC and sdhD residues, close to the [3Fe-4S] and heme b cluster.