Strobilurins are a group of natural products and their synthetic analogs. A number of strobilurins are used in agriculture as fungicides. They are part of the larger group of QIs (Quinone outside Inhibitors), which act to inhibit the respiratory chain at the level of Complex III.
The first parent natural products, strobilurins A and B, were extracted from the fungus Strobilurus tenacellus.
Commercial strobilurin fungicides were developed through optimization of photostability and activity.
Strobilurins represented a major development in fungus-based fungicides. First released in 1996, there are now ten major strobilurin fungicides on the market, which account for 23-25 % of the global fungicide sales.
Examples of commercialized strobilurin derivatives are azoxystrobin, kresoxim-methyl, picoxystrobin, fluoxastrobin, oryzastrobin, dimoxystrobin, pyraclostrobin and trifloxystrobin.
Strobilurins are mostly contact fungicides with a long half time as they are absorbed into the cuticle and not transported any further. They have a suppressive effect on other fungi, reducing competition for nutrients; they inhibit electron transfer in mitochondria, disrupting metabolism and preventing growth of the target fungi.
Natural strobilurins
Strobilurin A
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Strobilurin A (also known as mucidin) is produced by Oudemansiella mucida, Strobilurus tenacellus, Bolinea lutea, and others. When first isolated it was incorrectly assigned as the E E E geometric isomer but was later identified by total synthesis as being the E Z E isomer, as shown.
9-Methoxystrobilurin A
9-Methoxystrobilurin A is produced by Favolaschia spp.
Later it was found in cultures of the basidiomycete fungi Mycena polygramma and Xerula melanotricha. The latter fungus also produces oudemansin B, with R<sub>1</sub> = MeO and R<sub>2</sub> = Cl. Oudemansin X, with R<sub>1</sub> = H and R<sub>2</sub> = MeO was isolated from Oudemansiella radicata.