Strobilurins are a group of natural products and their synthetic analogs. A number of strobilurins are used in

agriculture Agriculture or farming is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled peop ...

as fungicides. They are part of the larger group of QIs (Quinone outside Inhibitors), which act to inhibit the

respiratory chain An electron transport chain (ETC) is a series of protein complexes and other molecules that transfer electrons from electron donors to electron acceptors via redox reactions (both reduction and oxidation occurring simultaneously) and couples t ...

at the level of

Complex III Complex commonly refers to: * Complexity, the behaviour of a system whose components interact in multiple ways so possible interactions are difficult to describe ** Complex system, a system composed of many components which may interact with each ...

. The first parent natural products, strobilurins A and B, were extracted from the fungus ''

Strobilurus tenacellus ''Strobilurus tenacellus'', commonly known as the pinecone cap, is a species of agaric fungus in the family Physalacriaceae. It is found in Asia and Europe, where it grows on the fallen cones of pine and spruce trees. The fruit bodies (mushrooms) ...

''. 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 Azoxystrobin is the ISO common name for an organic compound that is used as a fungicide. It is a broad spectrum systemic active ingredient widely used in agriculture to protect crops from fungal diseases. It was first marketed in 1996 using the ...

, kresoxim-methyl, picoxystrobin, fluoxastrobin, oryzastrobin, dimoxystrobin,

pyraclostrobin Pyraclostrobin is a quinone outside inhibitor ( QI)-type fungicide used in agriculture. Among the QIs, it lies within the strobilurin chemical class. Use Pyraclostrobin is used to protect '' Fragaria'', '' Rubus idaeus'', '' Vaccinium corymbosu ...

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

nutrient A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi, and protists. Nutrients can be incorporated into cells for metabolic purposes or excr ...

s; they inhibit

electron transfer Electron transfer (ET) occurs when an electron relocates from an atom or molecule to another such chemical entity. ET is a mechanistic description of certain kinds of redox reactions involving transfer of electrons. Electrochemical processes ar ...

in mitochondria, disrupting

metabolism Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run c ...

and preventing growth of the target fungi.

Natural strobilurins

Strobilurin A

: Strobilurin A (also known as mucidin) is produced by '' Oudemansiella mucida'', ''

'', '' Bolinea lutea'', and others. When first isolated it was incorrectly assigned as the E E E

geometric isomer Geometry (; ) is, with arithmetic, one of the oldest branches of mathematics. It is concerned with properties of space such as the distance, shape, size, and relative position of figures. A mathematician who works in the field of geometry is c ...

but was later identified by

total synthesis Total synthesis is the complete chemical synthesis of a complex molecule, often a natural product, from simple, commercially-available precursors. It usually refers to a process not involving the aid of biological processes, which distinguishes i ...

as being the E Z E isomer, as shown.

9-Methoxystrobilurin A

9-Methoxystrobilurin A is produced by ''Favolaschia'' spp.

Strobilurin B

: Strobilurin B is produced by ''S. tenacellus''.

Strobilurin C

: Strobilurin C is produced by '' X. longipes'' and '' X. melanotricha''.

Strobilurin D and G

: Strobilurin D is produced by '' Cyphellopsis anomala''. Its structure was originally incorrectly assigned and is now considered to be identical to that of strobilurin G, produced by ''B. lutea''. A related material, hydroxystrobilurin D, with an additional

hydroxyl In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydrox ...

group attached to the methyl of the main chain is produced by '' Mycena sanguinolenta''.

Strobilurin E

: Strobilurin E is produced by ''

Crepidotus fulvotomentosus ''Crepidotus'' is a genus of fungi in the family Crepidotaceae. Species of ''Crepidotus'' all have small, convex to fan-shaped sessile caps and grow on wood or plant debris. The genus has been studied extensively, and monographs of the North Amer ...

'' and '' Favolaschia'' spp.

Strobilurin F2

: Strobilurin F2 is produced by ''B. lutea''.

Strobilurin H

: Strobilurin H is produced by ''B. lutea''. The natural product with a phenolic hydroxy group in place of the aromatic methoxy group of strobilurin H is called strobilurin F1 and is found in ''C. anomala'' and ''

Agaricus ''Agaricus'' is a genus of mushrooms containing both edible and poisonous species, with over 400 members worldwide and possibly again as many disputed or newly-discovered species. The genus includes the common ("button") mushroom ('' Agaricus b ...

spp.

Strobilurin X

: Strobilurin X is produced by ''O. mucida''.

Oudemansins

The oudemansins are closely related to the strobilurins and are also quinone outside inhibitors. : Oudemansins general

Oudemansin A Oudemansin A is a natural product first isolated from the basidiomycete fungus ''Oudemansiella mucida''. Its chemical structure was determined by X-ray crystallography in 1979 and absolute stereochemistry by total synthesis. Two closely related de ...

with R₁ = R₂ = H was first described in 1979, after being isolated from mycelial fermentations of the

basidiomycete Basidiomycota () is one of two large divisions that, together with the Ascomycota, constitute the subkingdom Dikarya (often referred to as the "higher fungi") within the kingdom Fungi. Members are known as basidiomycetes. More specifically, Basi ...

fungus ''Oudemansiella mucida''. Later it was found in cultures of the basidiomycete fungi ''

Mycena polygramma ''Mycena polygramma'', commonly known as the grooved bonnet, is a species of mushroom in the family Mycenaceae. The inedible fruit bodies are small, pale gray-brown mushrooms with broadly conical caps, pinkish gills. They are found in small tr ...

'' and ''Xerula melanotricha''. The latter fungus also produces oudemansin B, with R₁ = MeO and R₂ = Cl. Oudemansin X, with R₁ = H and R₂ = MeO was isolated from ''

Oudemansiella radicata ''Hymenopellis radicata'', commonly known as the deep root mushroom or the rooting shank, is a widespread agaric readily identified by its deeply rooted stalk ( stipe). Description The cap is medium to large, flat, grayish or yellowish brown ...

''.

Synthetic strobilurins

The discovery of the strobilurin class of fungicides led to the development of a group of commercial fungicides used in agriculture. Examples are shown below. Image:Azoxystrobin.svg, Image:Trifloxystrobin.svg, Image:Kresoxim-methyl-2D-skeletal.png, Image:Pyraclostrobin.png,

References

External links

* * {{citation , url=http://www.davidmoore.org.uk/21st_Century_Guidebook_to_Fungi_PLATINUM/Ch18_04.htm , title=Agricultural mycocides for the 21st century: strobilurins , archive-url=https://web.archive.org/web/20190908155044/http://www.davidmoore.org.uk/21st_Century_Guidebook_to_Fungi_PLATINUM/Ch18_04.htm , archive-date=2019-09-08 , access-date=2019-09-08 , url-status=live , from: David Moore, Geoffrey D. Robson, Anthony P. J. Trinci, ''21st Century Guidebook to Fungi'', 2nd edition. Fungicides Respiratory toxins Complex III inhibitors Strobilurins