Aldehydic pheromone components

Table V. Release rates of 14-carbon acetate, alcohol, and aldehyde pheromone components from a PVC matrix.

Fig.i General biosynthetic pathways for the production of alcohol, aldehyde, and acetate ester pheromone components in female moths. Top production of saturated fatty acids. Middle production of monounsaturated fatty acids and limited chain shortening produces intermediate compounds that can be reduced to an alcohol. Aldehyde and acetate ester pheromones are produced by an oxidase and acetyl-transferase, respectively. Bottom biosynthetic pathway for the production of the acetate ester pheromone components in the cabbage looper moth, Trichoplusia ni. The CoA derivatives are reduced and acetylated to form the acetate esters. Additional pheromone components include 12 OAc and ll-12 OAc... 

Production of acetate ester pheromone components utilizes an enzyme called acetyl-CoA fatty alcohol acetyltransferase that converts a fatty alcohol to an acetate ester. Therefore, alcohols could be utilized as substrates for both aldehyde and acetate ester formation. In some tortricids an in vitro enzyme assay was utilized to demonstrate specificity of the acetyltransferase for the Z isomer of ll-14 OH [66]. This specificity contributes to the final ratio of... 

An example of a larval parasitoid that responds to the host sex pheromone is seen with Cotesiaplutellae (Braconidae), also a parasitoid of the diamondback moth. These insects were attracted equally to the pheromone blend (31,32,33, see above), the acetate 32, or aldehyde 31 components [80]. This larval parasitoid, however, was also strongly attracted to host frass volatiles, in particular, dipropyl disulfide 34, dimethyl disulfide 35, allyl isothiocyanate 36, and dimethyl trisulfide 37. In contrast, the egg parasitoid Trichogramma chilonis was only weakly attracted to 36. In both, T. chilonis and C. plutellae, plant volatiles, in particular (3Z)-hex-3-en-l-yl acetate 38, significantly enhanced attraction by the pheromone [80]. 

The sex pheromones of moths generally are mixtures of two or more chemical components, typically aldehydes, acetates, alcohols, or hydrocarbons, produced in specialized glands by biosynthesis and modification of fatty acids (34). Often, a species-specific blend of components is the message, and males of many moth species, including M. sexta, give their characteristic, qualitatively and quantitatively optimal behavioral responses only when stimulated by the correct blend of sex-pheromone components and not by individual components or partial blends lacking key components (43, 44). 

Third, some of the pheromone components are simple and cheap compounds such as straight-chain esters and aldehydes, that are readily available in bulk. Others fall into a middle ground, whereby multigram-scale synthesis to produce sufficient material for use as trap lures should be possible. However, the pheromone structures of a number of species appear to be of sufficient complexity that it is unlikely that they could be made in sufficient quantity and at affordable cost for widespread use in pheromone-based control programs. 

In some species, ( )-2-nonenol 72 represents a second pheromone component along with the lactone 69 [ 141,144], while in Anomala schonfeldti 72 is the only attractive component [155]. The alcohol 72, the corresponding aldehyde, lactone 69 and methyl benzoate make up the pheromone of Anomala albopilosa albopilosa [144]. 

Simultaneous GC-EAD analyses of the extracts of the sex pheromone gland of the female bronzed cutworm, Nephelodes minians, indicated two compounds which eficited strong EAD responses from conspecific male antennae, (2 )-ll-hexadecenal and (2 )-ll-hexadecenyl acetate. Double bond positions were confirmed by the dimethyl disulfide derivatives of the pheromone component. In a field test, a 5 1 blend of aldehyde and ester attracted male N. minians. ... 

Analyses of methanolic extracts of the male webbing clothes moth (WCM), Tineola hisselliella (Hum.) (Lepidoptera Tineidae) showed three candidate pheromone components namely, hexadecanoic acid methyl ester, (.Z)-9-hexadecenoic acid methyl ester, and octadec-anoic acid methyl ester. In bioassay experiments, the 16 carbon esters were attractive to both males and virgin females but the 18 carbon ester was inactive. The extracts of female WCM showed two compounds as candidate sex pheromone components, namely (T, )-2,13-octadecadienal and E,Z) 2,13-octadecadienol. The synthetic samples of the aldehyde and alcohol were attracting WCM males in bioassay experiments successfully ... 

Comparative GC, GC-EAD and GC-MS analyses of extracted Setora nitens (nettle caterpillars) compounds and authentic standards showed that the candidate pheromone components were ( )-9-dodecenal and (-Z)-9,11 dodecadienal. The other two EAD-active compounds were the corresponding alcohols of these aldehydes. ... 

The next example is used to demonstrate how different pathways could produce the same pheromone component. Helicoverpa zea and Helicoverpa assulta are closely related species that use aldehydes as the major pheromone. Helicoverpa zea uses a blend of components with Z11-16 Aid as the major component, and minor components include 16 Ald, Z9-16 Aid, and Z7-16 Aid (Klun et al., 1980). H. assulta uses Z9-16 Ald as the major component and Z11-16 Aid as a minor component (Cork et al., 1992 Sugie et al., 1991). The biosynthesis of Zll-16 Aid occurs by Al 1 desaturation of 16 CoA to produce Z1 l-16 CoA, which is reduced to the aldehyde. This probably occurs in both species, but Z9-16 Ald could be produced by the action of a A9 desaturase using 16 CoA as a substrate or by the Al 1 desaturation of 18 CoA to produce Zll-18 CoA that is then chain shortened to Z9-16 CoA. To determine between these two pathways, deuterium-labeled precursors were applied topically to the glands in dimethyl sulfoxide and females injected with PBAN 1 h later the glands were extracted and analyzed for incorporation using GC/MS (Choi et al., 2002). Figure 3.4 shows the data and biosynthetic pathways. 

Figure 3.4 Biosynthetic pathways for producing the sex pheromone components of Helicoverpa zea and Helicoverpa assulta. The CoA derivatives indicated with an arrow are reduced to aldehydes. The unlabeled and labeled aldehyde amounts for each pheromone component are shown in the graphs on the right. The y-axis indicates ng/gland for each aldehyde indicated in the biosynthetic pathway. The graphs indicate unlabeled and labeled aldehyde amounts after application of D3-16 acid (left bars) and D3-18 acid (right bars). No label was found in Z7-16 Ald when D3-16 acid was applied to glands of H. zea. No label was found in either Z9-16 Ald or Z11-16 Ald when D3-18 acid was applied to glands of H. assulta.

A considerable amount of knowledge has accumulated about how pheromone components are produced in female moths since the first pathway was identified some 20 years ago. It appears that most female moths produce their pheromone through modifications of fatty acid biosynthesis pathways. For moths that utilize aldehydes, alcohols, or esters biosynthesis occurs in the pheromone gland. The exceptions are those that utilize linoleic or linolenic acids, which must be obtained from the diet. However, modifications of these fatty acids occur in the gland. For moths that utilize hydrocarbons or epoxides of hydrocarbons, the hydrocarbon is produced in oenocyte cells and then transported to the pheromone gland where the epoxidation step takes place. 

Reed J. R., Vanderwel D., Choi S., Pomonis J. G., Reitz R. C. and Blomquist, G. J. (1994) Unusual mechanism of hydrocarbon formation in the housefly cytochrome P450 converts aldehyde to the sex pheromone component (Z)-9-tricosene and C02. Proc. Natl. Acad. Sci. USA 91, 10000-10004. 

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