Sex pheromone candidates with a conjugated triene system: Synthesis and chemical characterization

Sex pheromone candidates with a conjugated triene system, 8,10,12-, 9,11,13- and 11,13,15-hexadecatrienyl acetates (double bond positional isomers of theGlyphodes pyloalis pheromone, 10,12,14-triene) were synthesized by introducing anE configuration stereospecifically to two of three double bonds and rather nonspecifically to another double bond, so as to obtain two geometrical isomers;E,E,E andE,E,Z orE,Z,E isomers. The two geometrical isomers of each triene acetate were separated on a reverse-phase HPLC column and characterized by¹H NMR analysis. The¹³C NMR signals in the olefinic region of each isomer were assigned by two-dimensional NMR techniques and also by an empirical rule based on the changes of the chemical shifts by converting the configuration. Based on the assignments, substituent parameters for calculating the chemical shifts of 1,6-dialkyl conjugated trienes were generated. Electron impact mass spectrometry showed characteristic fragment ions that enabled the double bond positional isomers to be distinguished from each other.     

Further studies on artificial geometrical isomers of α-linolenic acid in edible linolenic acid-containing oils

Fifteen samples of commercial edible soybean and rapeseed oils (and mixtures of these) from Belgium, Great Britain and Germany have been analyzed for theirtrans-polyunsaturated fatty acid content. Only one sample out of the 13 refined samples, and the two cold-pressed samples, contained trace amounts oftrans isomers. Others contained between 1 and 3.3% of their total fatty acids as geometrical isomers of linoleic and linolenic acids. The degree of isomerization (DI) of linolenic acid varied between 10.5 and 26.9%. Combining results obtained in this study together with corresponding data for French oils (totalling 21 samples) indicates that the relative percentages of individual linolenic acid geometrical isomers depend on linolenic acid DI. Relationships linking these parameters could be approximated by straight lines, at least for DIs lying between 9 and 30%. Extrapolation to DI=0 suggests that the relative probabilities of isomerization of double bonds in positions 9, 12, and 15 are 41.7, 6.1 and 52.1%, respectively, at the very beginning of the isomerization reaction. At that time, the probability of a simultaneous isomerization of double bonds in positions 9 and 15 is close to zero. Thet,c,t isomer is apparently formedvia thec,c,t and thet,c,c isomers, the former being somewhat more prone to a second geometrical isomerization than the latter. The relative proportion of thec,t,c isomer is practically independent from the DI, at least between 9 and 30%, which would suggest that this isomer is an “end-product” of thecis-trans isomerization reaction.     

Filbertworm sex pheromone

(E,E)- and (E,Z)-8,10-Dodecadien-1-ol acetates were identified in a 14.3 ratio in the extract of abdominal tips of female filbert-worm moths,Melissopus latiferreanus (Walsingham). The identifications were based on electroantennogram (EAG) analysis, gas chromatography, mass spectrometry, ozonolysis, and synthesis. TheE,Z isomer produced the stronger EAG response. In the field tests of various ratios ofE,EE,Z, the ratio found in the extract captured the most males. The pureE,E isomer initially was not attractive by itself (<0.1%E,Z) but became attractive after a few days, presumably because of isomerization. TheE, Z isomer (<0.1%E,E) was attractive initially, but this compound might have isomerized faster than theE,E isomer. A study of the isomerization showed that regardless of the initial mixture of 8,10-dodecadien-1-ol acetate isomers, almost complete equilibration existed after one month. The equilibrium mixture consisted of 9%Z8,E10, 65%E8,E10, 23%E8,Z10, and 3%Z8,Z10. Concentrations in rubber septa (14 ratio ofE,E toE,Z) of 0.03–3.0 mg/septum produced equivalent trap catches.This paper reports the results of research only. Mention of a commercial product in this paper does not constitute a recommendation by the U.S. Department of Agriculture.     

Heat-induced geometrical isomerization of α-linolenic acid: Effect of temperature and heating time on the appearance of individual isomers

The formation of linolenic acid geometrical isomers (LAGIs) was studied in linseed oil that was heated under vacuum in sealed ampoules at different temperatures (190–260°C) for several durations (2–16 h). A temperature of about 190°C seems to be necessary to induce the formation of LAGIs. At higher temperatures, disappearance of linolenic acid follows a first-order kinetic. The formation of LAGIs increases with both heating time and temperature, degrees of isomerization of linolenic acid higher than 50–60% could easily be obtained by simply heating the oil under vacuum. Side reactions remain at a low level. The mean probabilities of isomerization of individual ethylenic bonds are similar to those determined in linolenic acid-containing oils marketed in European countries, 41.9, 4.7 and 53.3% for double bonds in positions 9, 12 and 15, respectively. The di-trans t,c,t (trans,cis,trans) isomer is formedvia the mono-trans c,c,t andt,c,c isomers by a two-step reaction. The proportions of thec,c,t andt,c,c isomers (relative to total LAGIs) decrease linearly with the heating time. The proportion of thec,t,c isomer is only slightly affected by this parameter; however, it increases with temperature. The proportion of thet,c,t isomer increases linearly with heating time at each tested temperature, at the expense of thec,c,t andt,c,c isomers. However, there is no simple relationship linking the disappearance of each of the mono-trans isomers and the formation of the di-trans isomer.     

Autoxidation of methyl linolenate: Analysis of methyl hydroxylinolenate isomers by high performance liquid chromatography

The mixture of methyl hydroxylinolenates obtained by reduction of the hydroperoxide isomers formed by autoxidation of methyl linolenate was resolved by high performance liquid chromatography into eight major components. These are positional isomers with the hydroxyl group at positions 9, 12, 13, and 16. Two geometrical isomers of each positional isomer are present; these differ in the configuration of the conjugated double bonds (cis-trans andtrans-trans). Autoxidation of methyl linolenate is regioselective and favors the formation of positional isomers 9 and 16.     

Attraction of pea mothCydia nigricana F. (Lepidoptera: Tortricidae) to female sex pheromone (E,E)-8,10-dodecadien-1-YL acetate,is inhibited by geometric isomersE,Z, Z,E, andZ,Z

Field attraction ofCydia nigricana males to synthetic female sex pheromone (E,E)-8,10-dodecadien-1-yl acetate, formulated on red rubber septa, declined continuously during two weeks. This was due to isomerization of (E,E)-8,10-dodecadien-1-yl acetate: eight days after application of purifiedE,E isomer, the proportion ofE,Z;Z,E; andZ,Z isomers in rubber septa aged in the laboratory was 4%; a 5% addition of any one of these isomers to fresh lures of (E,E)-8,10-dodecadien-1-yl acetate significantly reduced male attraction. Stereospecific syntheses of (E,Z)-, (Z,E)-, and (Z,Z)-8,10-dodecadien-1-yl acetate are described. The pheromone gland ofCydia nigricana contains 0.8 ng/female of (E,E)-8,10-dodecadien-1-yl acetate, accompanied by three monounsaturated acetates, (E)-9-dodecen-1-yl acetate, (Z)-5-tetradecen-1-yl acetate, and (Z)-7-tetradecen-1-yl acetate (0.1 ng/female each). These compounds did not augment male trap catch when added to (E,E)-8,10-dodecadien-1-yl acetate.     

Effect of conjugated FA on feed intake,body composition,and liver FA in mice

CLA is a generic term describing different isomers of linoleic acid with two conjugated double bonds. Various metabolic effects have been demonstrated following administration of CLA, including a change in body composition in animals. However, the effects of pure CLA isomers are not fully understood. In addition, conjugated octadecatrienoic acids such as calendic acid have not been extensively investigated. In this study, male and female ICR mice were fed pure CLA isomers (cis9,trans11 or trans10,cis12) or calendic acid (trans8,trans10,cis12) as their ethyl esters for 6 wk. Body protein content was significantly increased after feeding CLA isomers, either as pure isomers or as a mixture. Calendic acid significantly decreased body fat content in males. CLA (pure isomers or a mixture) significantly decreased body fat in both males and females, with the trans10,cis12 isomer being the most effective. The effect of the cis9,trans11 isomer was more pronounced in females than in males. It was concluded that the trans10,cis12 CLA isomer was mainly responsible for the decrease in fat content in mice, without a significant modification of feed efficiency, and that it was more effective than calendic acid.     

Cis-trans isomerization of octadecatrienoic acids during heating. Study of pinolenic (cis-5,cis-9,cis-12 18∶3) acid geometrical isomers in heated pine seed oil

To understand the heat-inducedcis-trans isomerization of ethylenic bonds in octadecatrienoic acids, pine seed oil, which contains the unusual nonmethylene-interrupted pinolenic (cis-5,cis-9,cis-12 18∶3) acid as a major component, was heated under vacuum at 240°C for 6 h together with linseed and borage oils. As a results, a small percentage of pinolenic acid undergoescis-trans isomerization. The main isomer that accumulates is thetrans-5,cis-9,trans-12 18∶3 acid. Minor amounts of the three mono-trans isomers are also present. Identification of isomers was realized by combining gas-liquid chromatography on a CP Sil 88 capillary column, argentation thin-layer chromatography and comparing the equivalent chainlengths of artifacts to those of isomers present in NO₂-isomerized pine seed oil. Hydrazine reduction was used to demonstrate that there was no positional shift of double bonds. Heat-induced geometrical isomerization of pinolenic acid differs from that of α- and γ-linolenic acids in at least two aspects. The reaction rate is slower (about one-fourth), and mono-trans isomers are formed in low amounts.     

Cis-trans isomerization of oleic,linoleic and linolenic acids

The equilibrium composition ofcis andtrans isomers obtained by isomerizing oleic, linoleic, and linolenic acids with selenium or nitrous acid has been studied using gas chromatography and infrared spectroscopy. The oleic/elaidic equilibrium mixture was found to contain 75–80% elaidic acid instead of the generally accepted 66% value. It is felt that the greater accuracy of gas chromatography and infrared analyses over older methods allows this equilibrium to be defined with greater precision. Similar studies on thecis-trans isomerization of linoleic and linolenic acids indicated that their equilibrium mixtures also contained 75–80%trans double bonds. With linoleic acid, thesetrans bonds were shown to be randomly distributed among the double bonds present. Cis-trans isomerization of linoleic or linolenic acids with selenium produced by-products having elution times equivalent to 18∶2, 18∶1, and 18∶0 on a gas chromatograph. No such by-products were observed when oleic acid was isomerized. Apparently some type of hydrogen-transfer reaction accompanies thecis-trans isomerization of polyunsaturated acids with selenium. Presented at the AOCS meeting in Toronto, Canada, 1962.     

Synthesis and Characterization of 2,13- and 3,13-Octadecadienals for the Identification of the Sex Pheromone Secreted by a Clearwing Moth

In addition to 2,13- and 3,13-octadecadien-1-ols and their acetates, aldehyde analogs have been identified from lepidopteran species in the family Sesiidae. To establish a reliable analytical method for determining the positions and configurations of the two double bonds in natural pheromone components, all geometric isomers of the 2,13- and 3,13-octadecadienals were synthesized by Dess-Martin oxidation of the corresponding alcohols with limited isomerization of the double bond at the 2- or 3-position. GC-MS analysis of these aldehydes showed isomerization of (Z)-2-, (Z)-3-, and (E)-3-double bonds to an (E)-2-double bond, even with a cool on-column injection. In contrast, HPLC analysis with an ODS column was accomplished without isomerization. The geometric isomers of each dienal eluted in the order ZZ → EZ → ZE → EE. The conjugated 2,13-dienals were detectable in nanogram amounts with a UV detector at 235 nm. Whereas the detection of 3,13-dienals was difficult because of the lack of a chromophore, a highly sensitive analysis was achieved after derivatization with 2,4-dinitrophenylhydrazine. LC-MS with atmospheric pressure chemical ionization showed a strong [M-1]^- at m/z 443 for the derivatives. Based on these analytical data, a pheromone extract of a sesiid moth, Macroscelesia japona, was examined by HPLC and LC-MS, and it was confirmed that the octadecadienal tentatively identified by a previous GC-MS analysis did indeed have the 2E,13Z configuration. Furthermore, field evaluation of four synthetic geometric isomers of the 2,13-dienal revealed specific attraction to a lure with the (2E,13Z)-isomer as a main component.     

Competitive hydrogenation rates of isomeric methyl octadecadienoates

Determination of the relative reaction rates of isomeric methyl octadecadienoates is possible by competitive reduction of a mixture containing an inactive diene and a radioactively labeled isomer. The hydrogenation rate of methylcis-9,cis-12-octadecadienoate with platinum and nickel catalysts is compared to the hydrogenation rate of each of several isomers of methyl octadecadienoate, and the relative rate of the competitive hydrogenations is calculated by a digital computer. Methylcis-9,cis-12 linoleate is reduced the most rapidly of all the dienes studied. The relative rates of the positional isomers tend to decrease with the increasing number of methylene groups between the double bonds, except when one of the double bonds is in the more reactive 15 position. Comparison of the geometric isomers shows thattrans,trans diene is hydrogenated at a slower rate thancis,cis linoleate.

     

trans-Polyunsaturated fatty acids in French edible rapeseed and soybean oils

The fatty acid compositions of rapeseed and soybean oils marketed in France have been determined by gas liquid chromatography on a fused-silica capillary column coated with a 100% cyanopropyl polysiloxane stationary phase. Under the operating conditions employed, methyl esters of linolenic acid geometrical isomers could be separated and quantitated easily without any other complementary technique. With only one exception, all samples under study (eight salad oils and five food samples) contain geometrical isomers of linolenic acid in measurable, although variable, amounts. Totaltrans-18:3 acids may account for up to 3% of total fatty acids. This value corresponds to a degree of isomerization (percentage oftrans isomers relative to total octadecatrienoic acids) of 30%. Examination of our data indicates that the distribution pattern of linolenic acid geometrical isomers does not depend on the degree of isomerization. The two main isomers always have thec,c,t and thet,c,c configurations. These isomers occur in the almost invariable relative proportions of 47.8±1.7% and 41.1±1.0%, respectively. The third mono-trans isomer is present in lower amounts−6.5±0.7%. The only di-trans isomer that can be quantitated with sufficient accuracy is thet,c,t isomer (4.9±1.5%). Mono-trans isomers of linoleic acid are also present in these oils. However, their maximum percentages are lower than those determined for linolenic acid geometrical isomers. In the oils showing the highest degrees of isomerization,trans isomers of linoleic acid account for 0.5% (rapeseed oils) and 1% (soybean oils) of total fatty acids. Taking into account all data, it would appear that the probability of isomerization of linolenic acid is about 13–14 times that of linoleic acid.     

Field Trials with the Synthetic Sex Pheromone of the Oak Processionary Moth Thaumetopoea processionea

The biological activity of synthetic (Z,Z)-11,13-hexadecadienyl ace- tate, the major pheromone component found in female gland extracts of the oak processionary moth Thaumetopoea processionea, was evaluated in field trials. Traps baited with 10 mg of the chemical efficiently attracted a large number of males provided they were placed in the upper crown region of the oaks. Devices positioned 10–15 m high in the trees attracted significantly more males than those traps installed at 2 or 6–8 m above the ground. Pherocon traps were slightly more efficient than Delta traps, and lower or higher amounts of the attractant in the baits did not significantly influence the number of moths caught. The importance of the stereomeric purity of the lure and the easy isomerization of the (Z,Z)-acetate to other isomers, particularly to the E,E isomer, should be considered for the development of efficient formulations in the field.     

Chemical‐Free Approach for Z‐Isomerization of Lycopene in Tomato Powder: Hot Air and Superheated Steam Heating above the Melting Point of Lycopene

Z‐isomers of lycopene exhibit higher bioavailability and antioxidant capacity than those of the all‐E‐isomer. Therefore, it is important to develop an efficient and environmentally friendly procedure for Z‐isomerization. The current methods for Z‐isomerization of (all‐E)‐lycopene use toxic chemicals such as organic solvents and catalysts. This study is aimed to develop a chemical‐free method for Z‐isomerization of (all‐E)‐lycopene in tomato powder by hot air and superheated steam heating. The Z‐isomerization reaction is promoted by heating above the melting point of lycopene. When heated with superheated steam, the thermal decomposition of lycopene is suppressed compared to that when heated with hot air. When tomato powder is heated at 240 °C for 5 min by superheated steam, the total Z‐isomer content and remaining lycopene are 69.0% and 90.7%, respectively, while with hot air heating, the total Z‐isomer content and remaining lycopene are 69.9% and 68.0%, respectively. These results indicate that the thermal Z‐isomerization of lycopene occurs in the molten state and heating in a low oxygen atmosphere suppresses the thermal decomposition of lycopene. Practical Applications: Tomato powder rich in lycopene Z‐isomers is an important ingredient for the food and animal feed industries. Since Z‐isomers of lycopene are more soluble in solvents including ethanol which is a low‐toxicity and environmentally friendly solvent, the efficiency of lycopene extraction with ethanol can be improved by using the Z‐isomer‐rich tomato powder as a raw material. The obtained Z‐isomer‐rich extract has a high added value because the Z‐isomers have higher bioavailability and antioxidant capacity than those of the all‐E‐isomer. In addition, since lycopene Z‐isomers exhibit higher accumulation efficiency and better color improvement in hen egg yolks than those of the all‐E‐isomer, Z‐isomer‐rich tomato powder is an effective animal feed.     

Characterization of monomers produced from thermal high-pressure conversion of meadowfoam and oleic acids into estolides

The monomers produced from thermal high-pressure conversion of meadowfoam or oleic acids into estolides were characterized as a complex mixture of fatty acids. Mild reaction conditions produced little change in the starting acids. However, vigorous reaction conditions,e.g. ≥3 h at 250°C with stirring, significantly altered the starting fatty acids.Cis/trans isomerization occurred readily, with the proportion oftrans isomers reaching 57%. In addition, the double bonds migrated throughout all positions of the hydrocarbon chain with concentrations diminishing outward from the starting double bond position. Branching was also observed to a small extent under these conditions and was even more pronounced in the absence of water. Lactones were also identified in the reaction mixture, with contents near 16% in the meadowfoam series. All products can be explainedvia carbocation rearrangement mechanisms that result from protonation of the starting olefins.     

Participation of thecis-12 ethylenic bond tocis-trans isomerization of thecis-9 andcis-15 ethylenic bonds in heated α-linolenic acid

To understand thecis-trans isomerization reaction of ethylenic bonds in heated octadecatrienoic acids (occurring during industrial deodorization of oils), we have prepared a mixture ofcis-9,cis-12,cis-15, andcis-9,cis-15 18:2 acids by partial hydrazine reduction ofcis-9,cis-12,cis-15 18:3 acid present in linseed oil. This mixture (as fatty acid methyl esters) was heated under vacuum at 270°C for 2.25 h. The two methylene-interrupted acids isomerize at a similar rate under such conditions, but the nonmethylene-interruptedcis-9,cis-15 18:2 acid remains unchanged. This means that the mechanism of isomerization does not involve a direct interaction between the two external ethylenic bonds as previously hypothesized. The centralcis-12 ethylenic bond is apparently necessary for the isomerization of the two externalcis-9 andcis-15 ethylenic bonds. However, this bond is itself rather protected against isomerization in the originalcis-9,cis-12,cis-15 18:3 acid which is mainly isomerized totrans-9,cis-12,trans-15,cis-9,cis-12,trans-15, andtrans-9,cis-12,cis-15 18:3 acids. Thecis-9,trans-12,cis-15 18:3 isomer is less than 10% of totaltrans isomers of α-linolenic acid. As a general rule, only one of the two double bonds in a methylene-interrupted diethylenic system can undergocis-trans isomerization when submitted to heat treatment, at least for temperatures equal to or less than 270°C.     

Derivative UV spectra of lipid conjugated dienes

Zeroth and second order derivative UV spectra of some lipids and model substances having a conjugated system of double bonds were recorded. The second derivative spectra showed fine spectral structures with at least three negative peaks. The wavelengths of their minima are different fortrans,trans andcis,trans geometric isomers, which allowed determination of each individual isomer in a mixture without any separation. The derivative spectra of 2,4-hexadienes, some acetyl esters of unsaturated fatty alcohols and autoxidized linoleic acid, soybean oil and soybean lecithin are discussed.     

Sex pheromone of European grapevine moth (Lobesia botrana) its chemical transformations in sunlight and heat

Photo- and radical isomerization of (E, Z)-7,9-dodecadien-1-yl acetate (DDA) leads to an equilibrium mixture of all four possible geometric isomers of 7,9-DDA in the ratio ofE,E, 69–76%;Z,E, 11–13%;E, Z, 12–15%; andZ, Z, 1–3%. Iodine catalysis of the isomerization takes place even in dark at room temperature and is probably a radical reaction.     

Thermal‐ and Photo‐Induced Isomerization of All‐E‐ and Z‐Isomer‐Rich Xanthophylls: Astaxanthin and Its Structurally‐Related Xanthophylls,Adonirubin, and Adonixanthin

The effects of heating and photo‐irradiation on the stability of all‐E‐isomer‐rich and Z‐isomer‐rich xanthophylls, astaxanthin and its structurally related xanthophylls, adonirubin, and adonixanthin, are investigated. The xanthophylls with high Z‐isomer content are prepared from their high‐purity all‐E‐isomers by thermal isomerization and filtering techniques, that is, total Z‐isomer ratios of adonirubin, astaxanthin, and adonixanthin are 80.9%, 89.5%, and 72.5%, respectively. The all‐E‐ and Z‐isomer‐rich xanthophylls dissolved in ethanol are stored at 4, 30, and 50 °C in the dark and at 30 °C under photo‐irradiation using a fluorescent light for 21 days. In the all‐E‐isomer‐rich xanthophylls, as the storage temperature increases, the total Z‐isomer ratio becomes higher, whereas in the Z‐isomer‐rich xanthophylls, the all‐E‐isomer ratio becomes higher. Photo‐irradiation slightly promotes Z‐isomerization in (all‐E)‐xanthophylls, but highly promotes all‐E‐isomerization in Z‐isomer‐rich xanthophylls. In addition, photo‐irradiation prevents thermal Z‐isomerization of (all‐E)‐xanthophylls. Moreover, it is found that some xanthophyll Z‐isomers such as (9Z)‐astaxanthin are more stable than that of the other Z‐isomers against heating and photo‐irradiation. These findings can contribute not only to establishing suitable storage conditions for Z‐isomer‐rich xanthophylls, but also to developing control techniques for the E/Z‐isomer ratio of the xanthophylls. Practical Applications: The fundamental data on the stability of xanthophyll isomers against heating and photo‐irradiation and finding stable xanthophyll Z‐isomers are very important to develop xanthophyll materials rich in the Z‐isomers. Moreover, this study clearly shows that the heat treatment enhances the Z‐isomerization of xanthophylls, whereas the photo‐irradiation enhances the all‐E‐isomerization and prevents thermal Z‐isomerization of them. This information can be utilized in technology for arbitrarily controlling E/Z‐isomerization of xanthophylls.     

cis andtrans Analysis of fatty esters by gas chromatography: Octadecenoate and octadecadienoate isomers

A gas chromatographic method has been developed for quantitative determination of thecis andtrans percentages in octadecenoate and octadecodienoate esters. To separatecis- andtrans-monoene and diene isomers on a packed GC column, the fatty esters were stereospecifically epoxipized with peracetic acid. A simple and quantitative epoxidation procedure allows thecis- andtrans-epoxyoctadecanoates to be analyzed without prior isolation from the reaction mixture. No positional or geometric isomerization of the double bond occurred during epoxidation. Synthetic mixtures containingcis- andtrans-6,-9 and-12 octadecenoate isomers were completely separated intocis andtrans fractionstrans-15-Octadecenoate was the only isomer investigated that partially interfered in the analysis. Diene mixtures containingrans,trans-, cis,trans- andcis,-cis-9,12-octadecadienoates were also successfully analyzed by gas liquid chromatography (GLC) after epoxidation with peracetic acid. Each diene isomer formed two pairs of diepoxy diastereomers, some of which could be separated. Onecis,cis-diepoxyoctadecanoate diastereomer peak overlapped thecis,trans-diepoxyoctadecanoate peaks. The totalcis,-cis-diepoxyoctadecanoate percentages were calculated by using the ratio of the twocis,cis-diepoxyoctadecanoate diastereomers. Other positional octadecadienoate isomers were also epoxidized and analyzed by GLC. The large number of possible octadecadienoate isomers requires that some preeiminary fractionation be made before GC analysis is practical for diene isomers. Presented at the AOCS Meeting, Atlantic, City, October 1971 N. Market. Nutr. Res. Div., ARS, USDA.