Monocerin is a dihydroisocoumarin and a

polyketide Polyketides are a class of natural products derived from a precursor molecule consisting of a chain of alternating ketone (or reduced forms of a ketone) and methylene groups: (-CO-CH2-). First studied in the early 20th century, discovery, biosynth ...

metabolite that originates from various

fungal A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from th ...

species. It has been shown to display antifungal, plant pathogenic, and

insecticidal Insecticides are substances used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. Insecticides are used in agriculture, medicine, industry and by consumers. Insecticides are claimed t ...

characteristics. Monocerin has been isolated from '' Dreschlera monoceras'', '' D. ravenelii'', '' Exserohilum turcicum'', and '' Fusarium larvarum''.

Biosynthesis

Polyketide synthase Polyketides are a class of natural products derived from a precursor molecule consisting of a chain of alternating ketone (or reduced forms of a ketone) and methylene groups: (-CO-CH2-). First studied in the early 20th century, discovery, biosynth ...

s (PKSs) of fungi are Type I PKSs. Monocerin has been confirmed by biosynthesis studies to have heptaketide origins. Monocerin PKS produces an intermediate with initially a high degree of reductive modification but ends with a classical β-polyketide moiety. Dihydroisocoumarin is the first PKS-free intermediate which would be formed from the reduced heptaketide whose assembly pathway is shown in figure 1. Ketosynthase, ketoreductase, dehydrates, enol reductases and cyclisases are shown as domains of the Monocerin PKS and methyl transferase is considered to be a tailoring enzyme. # Formation of an enolate ion on the carbon three carbons away from sulfur allows aldol addition onto the carbonyl six carbons distant along the chain. This produces the secondary alcohol. Dehydration proceeds to give the alkene. Enolization then occurs to reach the stability of the aromatic ring. #The modified chain is transferred to the TE domain. This will allow lactonization and release from the enzyme. # Hydroxylation occurs at ortho-position to two substituents. O-methylation occurs. # O-methylation # Cyclic-

ether In organic chemistry, ethers are a class of compounds that contain an ether group—an oxygen atom connected to two alkyl or aryl groups. They have the general formula , where R and R′ represent the alkyl or aryl groups. Ethers can again be ...

formation

Biological effects

Monocerin produced by ''Exserohilum turcicum'' causes Northern Corn Leaf blight disease in

maize Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American and Australian English), is a cereal grain first domesticated by indigenous peoples in southern Mexico about 10,000 years ago. The ...

. The maize will develop brown lesions on its leaves and will have decreased viability in its root cap cells. Monocerin has also been shown to be an effective insecticide against wooly aphids. Monocerin is also an effective herbicide against

Johnson grass Johnson grass or Johnsongrass, ''Sorghum halepense'', is a plant in the grass family, Poaceae, native to Asia and northern Africa. The plant has been introduced to all continents except Antarctica, and most larger islands and archipelagos. It re ...

by inhibiting seedling growth. It has a lesser effect against cucumber.

References

{{isocoumarin Dihydroisocoumarins Mycotoxins Polyketide antibiotics Methoxy compounds

Biosynthesis

Biological effects

See also

References