Monocerin is a polyketide
Polyketides are secondary metabolites from bacteria, fungi, plants, and animals. Polyketides are usually biosynthesized through the decarboxylative condensation of malonyl-CoA derived extender units in a similar process to fatty acid synthesis...

Metabolites are the intermediates and products of metabolism. The term metabolite is usually restricted to small molecules. A primary metabolite is directly involved in normal growth, development, and reproduction. Alcohol is an example of a primary metabolite produced in large-scale by industrial...

 that originates from various fungal species. It has been shown to display antifungal, plant pathogenic, and insecticidal
An insecticide is a pesticide used against insects. They include ovicides and larvicides used against the eggs and larvae of insects respectively. Insecticides are used in agriculture, medicine, industry and the household. The use of insecticides is believed to be one of the major factors behind...

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


PKSs of fungi are Type I PKSs. Monocerin has been confirmed by biosynthesis
Biosynthesis is an enzyme-catalyzed process in cells of living organisms by which substrates are converted to more complex products. The biosynthesis process often consists of several enzymatic steps in which the product of one step is used as substrate in the following step...

 studies to have heptaketide origins. Monocerin PKS is particularly interesting because it produces an intermediate with initially a high degree of reductive modification but ends with a classical β-polyketide moiety. Dihydro isocoumarin 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.
  1. 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.
  2. The modified chain is transferred to the TE domain. This will allow lactonization and release from the enzyme.
  3. Hydroxylation occurs at ortho-position to two substituents. O-methylation occurs.
  4. O-methylation
  5. Cylclic-ether
    Ethers are a class of organic compounds that contain an ether group — an oxygen atom connected to two alkyl or aryl groups — of general formula R–O–R'. A typical example is the solvent and anesthetic diethyl ether, commonly referred to simply as "ether"...


Biological effects

Monocerin produced by Exserohilum turcicum causes Northern Corn Leaf blight disease in maize
Maize known in many English-speaking countries as corn or mielie/mealie, is a grain domesticated by indigenous peoples in Mesoamerica in prehistoric times. The leafy stalk produces ears which contain seeds called kernels. Though technically a grain, maize kernels are used in cooking as a vegetable...

. 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
Sorghum halepense, commonly called Johnsongrass, is a plant in the grass family, Poaceae, native to the Mediterranean region, but growing throughout Europe and the Middle East. The plant has been introduced to all continents except Antarctica and most larger islands and archipelagos...

 by inhibiting seedling growth. It has a lesser effect against cucumber
The cucumber is a widely cultivated plant in the gourd family Cucurbitaceae, which includes squash, and in the same genus as the muskmelon. The plant is a creeping vine which bears cylindrical edible fruit when ripe. There are three main varieties of cucumber: "slicing", "pickling", and...


See also

  • Polyketide synthase
    Polyketide synthase
    Polyketide synthases are a family of multi-domain enzymes or enzyme complexes that produce polyketides, a large class of secondary metabolites, in bacteria, fungi, plants, and a few animal lineages...

  • Fungicide use in the United States
    Fungicide use in the United States
    - Alternaria leaf spot :Symptoms of Alternaria leaf spot appear as lesions with tan spots on the leaves. The centers of these lesions become black with fungal sporulation. This infection can lead to tree death within 3–4 years of the first serious outbreak. Orchards in high humidity areas result in...

  • Setosphaeria turcica
    Setosphaeria turcica
    Setosphaeria turcica is the causal agent of Northern Leaf Blight in corn. It is a serious fungal disease prevalent in cooler climates and tropical highlands wherever corn is grown...

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