Dimethyl Disulfide Adducts Research Articles

Elucidation of double-bond positions of polyunsaturated alkenes through gas chromatography/mass spectrometry analysis of mono-dimethyl disulfide derivatives.

Derivatization with dimethyl disulfide (DMDS) followed by gas chromatography/mass spectrometry (GC/MS) analysis is a well-established method for locating double-bond position on the alkyl chain of mono-unsaturated compounds such as alkenes. For alkenes containing more than one double bond, however, the conventional DMDS derivatization approach forms poly- or cyclized DMDS adducts whose mass spectra are difficult to interpret in terms of double-bond positions. In this study, we report an efficient experimental procedure to produce mono-DMDS adducts for polyunsaturated alkenes with two to six double bonds. GC/MS analyses of these mono-DMDS adducts yield highly characteristic mass fragments, allowing unambiguous assignments of double-bond positions on the alkyl chain. We also apply our new approach (i.e., preferential formation of mono-DMDS adducts during derivatization with DMDS) to determine the double-bond positions of unsaturated alkenes produced by laboratory cultured Isochrysis litoralis, a haptophyte algal species. Alkenes from different sources were derivatized with DMDS at 25°C for 20 to 160 min. The mass spectra of mono-DMDS adducts were obtained by GC/EI-MS analysis of reaction products which contain chromatographically resolved mono-DMDS adducts. Mass spectra of corresponding mono-DMDS adducts contain prominent diagnostic ions that allow a conclusive elucidation of double-bond positions. In culture samples of Isochrysis litoralis, a series of novel mono- to tri-unsaturated C31 alkenes (9-C31:1 , 6,9-C31:2 , 6,22-C31:2 , 6,25-C31:2 , 9,22-C31:2 , 6,9,25-C31:3 ) were discovered for the first time. A highly efficient DMDS derivatization approach is developed to yield abundant mono-DMDS adducts of polyunsaturated alkyl alkenes for elucidating double-bond positions using GC/MS.

Preferential formation of mono‐dimethyl disulfide adducts for determining double bond positions of poly‐unsaturated fatty acids

AbstractDetermination of double bond positions of unsaturated lipids is fundamental for understanding their biofunctions and biosynthetic pathways. Derivatizing unsaturated lipids with dimethyl disulfide (DMDS) represents a convenient method to yield characteristic ions for determining double bond positions. However, DMDS adduction of poly‐unsaturated lipids often leads to the formation of poly‐ and/or cyclized DMDS adducts, which yield complex mass spectra that are difficult to interpret in terms of double bond positions. Here, we report a room‐temperature, convenient experimental procedure to preferentially form mono‐DMDS adducts for poly‐unsaturated fatty acid methyl esters (FAMEs) with two to five double bonds (c9, c12‐C18:2, t9, t12‐C18:2, c5, c9, c12‐C18:3, c7, c10, c13, c16‐C22:4 and c5, c8, c11, c14, c17‐C20:5). Electron‐impact ionization mass spectra of these mono‐DMDS adducts provide highly diagnostic ions for determining positions of all double bonds. Our approach overcomes the limit of traditional DMDS derivatization methods which are generally limited to mono‐unsaturated molecules. In addition, we show gas chromatography and gas chromatography–mass spectrometry analyses of mono‐DMDS adducts can also provide useful information about double bond geometry, as cis double bonds are prone to isomerize to trans isomers.

Long-chain alkenes and alkadienes of eight lichen species collected in Japan

The hydrocarbons of eight lichen species isolated in Japan were analyzed, and diverse mono-, di-, and tri-unsaturated alkenes were detected. The positions of the double bonds of C17 alkadienes (heptadecadiene) and C17–C20 alkenes were determined by mass spectrometry of their dimethyl disulfide adducts. We found that the six lichens containing green algal photobionts were distinguished by the presence of 1,8-heptadecadiene, 6,9-heptadecadiene, and 8- and 7-heptadecenes. On the other hand, 1-octadecene, 4-octadecene, and 5-nonadecene were the major alkene components of the two lichens with cyanobacterial photobionts. These alkadienes and alkenes were present in large quantities in the lichen samples. In particular, 1,8-heptadecadiene accounted for more than 90% of the total alkenes in all four lichens containing it. Our results provide new insights into the origin of C17 alkadienes and C17–C20 alkenes in environmental and geological samples, and these alkenes can potentially be applied as lichen biomarkers.

Novel methyl-branched alkenones with up to five double bonds in saline lakes

Long-chain alkenones, a class of highly specific and widely used lipid biomarkers found in ocean and lake sediments, have been so far found as straight-chain alkyl ketones with 2 to 4 double bonds. Jaraula et al. (2010) reported assignments of a series of tri- to penta-unsaturated alkenones as straight-chain C38 methyl (C38Me) and C39 ethyl (C39Et) alkenones in Lake Fryxell, Antarctica. The same series of compounds were later found in sediments from Lake Van (Randlett et al., 2014). The structure assignments by Jaraula et al (2010) were primarily based on strong ions at [M−43]+ for C38 alkenones and [M−57]+ for C39 alkenones, which were interpreted as a loss of CH3CO and CH3CH2CO groups. However, such fragmentation is atypical for common straight-chain methyl and ethyl alkenones. In this study, we reanalyzed Lake Van sediment samples. We show these new C38 and C39 alkenones elute earlier than the common straight-chain C38Me and C39Et alkenones on a mid-polarity GC column. After hydrogenation, mass spectra of these new alkenones show distinct peaks at m/z 72 or 86 caused by McLafferty rearrangement, indicating a methyl substitution at the α position of the carbonyl group in these C38 and C39 alkenones (i.e., α-methyl-branched C38Me and C39Et). Our new assignments as methyl-branched alkenones are further confirmed by the synthesis of an analog α-methyl C25 methyl ketone and comparison of mass spectra. Double bond positions for branched C38:5Me (brC38:5Me) are found to be Δ4, Δ7, Δ14, Δ21 and Δ28 based on the mass spectrum of corresponding dimethyl disulfide adducts. Analysis of Lake Van alkenone data reveals that Ubr38MeK∗ based on brC38Me shows a trend similar to U37K for the past 270 ka, suggesting that the degree of unsaturation of branched alkenones is also sensitive to temperature.

Diethyl-Ether Flower Washings of Dianthus cruentus Griseb. (Caryophyllaceae): Derivatization Reactions Leading to the Identification of New Wax Constituents.

Some carnation species (Dianthus spp., Caryophyllaceae) exhibit a strong resistance to drought stress that is connected with the increased surface wax formation. Wax composition is unknown for the majority of Dianthus spp. Herein, mass spectral and gas chromatographic data, in combination with synthesis and chemical transformations (transesterification and synthesis of dimethyl disulfide adducts), enabled the identification of 151 constituents of diethyl-ether washings of fresh flowers of Dianthus cruentus Griseb. from Serbia. The flower wax contained, along with the dominant ubiquitous long-chain n-alkanes, homologous series of n- and branched (iso- and anteiso-) long-chain hexyl alkanoates/alkenoates and alkyl/alkenyl benzoates. The branching position in the mentioned hexyl esters was probed by synthesis of esters of three isomeric hexanols that were spectrally characterized (1 H- and 13 C-NMR, IR, MS). The washings also contained long-chain (Z)- and (E)-alkenes (C23 -C35 ) with several different double bond regiochemistries. Fifty-five of these constituents (eight hexyl esters, two benzoates, and forty-five alkenes) were detected for the first time in Plantae, while ten of these represent completely new compounds. The rare occurrence of these wax constituents makes them possible chemotaxonomic markers of this particular Dianthus sp.

Preparation of Dimethyl Disulfide Adducts from the Mono-Trans Octadecadienoic Acid Methyl Esters.

The dimethyl disulfide (DMDS) adduct method is one of the more effective methods for determining double bond positions of dienoic acid. The DMDS method can be simply used to obtain the characteristic ions in which cleavage occurs between the methylthio group-added double-bond carbons as can be seen in the mass spectrum obtained using gas chromatography/electron ionization-mass spectrometry. In the case of the methylene-interrupted di-cis type and di-trans type dienoic acid, the DMDS addition reaction only occurs at one double-bond position, and cannot occur at the remaining double-bond position due to steric hindrance. As a result, two types of adducts are produced in the addition reaction. However, in the case of the methylene-interrupted mono-trans (mono-cis) type dienoic acid, the DMDS addition reaction only occurs at the cis-double bond. As a result, one type of adduct is produced in the addition reaction. In this report, we investigate the cause of the reaction selectivity by focusing on the addition reaction time.

Identification and Characterization of Phospholipids with Very Long Chain Fatty Acids in Brewer's Yeast.

Yeast lipids and fatty acids (FA) were analyzed in Saccharomyces pastorianus from seven breweries and in the dietary yeast supplement Pangamin. GC-MS identified more than 30 FA, half of which were very-long chain fatty acids (VLCFA) with hydrocarbon chain lengths of ≥22 C atoms. Positional isomers ω-9 and ω-7 were identified in FA with C18-C28 even-numbered alkyl chains. The most abundant ω-7 isomer was cis-vaccenic acid. The structure of monounsaturated FA was proved by dimethyl disulfide adducts (position of double bonds and cis geometric configuration) and by GC-MS of pyridyl carbinol esters. Ultra-high performance liquid chromatography-tandem mass spectrometry with negative electrospray ionization identified the phospholipids phosphatidylethanolamine, phosphatidylinositol and phosphatidylcholine, with more than 150 molecular species. Wild-type unmutated brewer's yeast strains conventionally used for the manufacture of food supplements were found to contain VLCFA.

Mass Spectrometry of Aliphatic Macrolides, Important Semiochemicals or Pheromones.

Macrolides are a relatively common structural motif prevalent in Nature. However, the structures of these large ring lactones have been relatively difficult to elucidate via NMR spectroscopy due to the minute amounts of compounds that are sometimes obtainable from natural sources. Thus, GC-MS analysis of individual macrolactones has become the method of choice for the structural identification of these compounds. Here we discuss the mass spectrometric behavior of aliphatic macrolides, evaluating spectra from numerous compounds of various ring size, including derivatives containing methyl branches as well as double bonds. The specific fragmentation of these macrolactones under electron impact conditions allows for the development of a general rule set aimed at the identification of similar compounds by mass spectrometry. In addition, the mass spectra of dimethyl disulfide adducts of unsaturated macrolides are discussed. The mass spectra of almost 50 macrolides are presented.

Fatty Acids from a Glass Sponge Aulosaccus sp. Occurrence of New Cyclopropane-Containing and Methyl-Branched Acids.

In order to identify new structures, the free fatty acids from an extract of a glass sponge Aulosaccus sp. (from the north-west Pacific) belonging to one of the least chemically investigated classes (Hexactinellida), were fractionated by RP-HPLC and analyzed by NMR spectroscopy and GC-MS of their pyrrolidine derivatives, methyl(ethyl) esters and their dimethyl disulfide adducts. One hundred and twenty-three C12-C31 acids (including nine new compounds) were detected, one hundred and ten of these compounds have not been found previously in glass sponges. The levels of common methylene-interrupted polyenes, monoenes of the (n-7) family and less common branched-chain components proved to be high. New acids were shown to be 5,13-dimethyl-tetradec-4-enoic, cis-10,11-methylene-heptadecanoic, 10,12-dimethyl-octadecanoic, cis-12,13-methylene-nonadecanoic, (14E)-13-methyl-eicos-14-enoic, 19-methyl-eicos-13-enoic, cis-20,21-methylene-heptacosanoic, 27-methyl-octacos-21-enoic and (22Z)-nonacos-22-enoic. Some important mass spectrometric characteristics of pyrrolidides of homologous cyclopropane fatty acids are reported and discussed.

Identification of a Novel Moth Sex Pheromone Component from Chilecomadia valdiviana.

Chilecomadia valdiviana (Philippi) (Lepidoptera: Cossidae) is an insect native to Chile. The larval stages feed on the wood of economically important fruit tree species such as apple, pear, olive, cherry, and avocado, and also on eucalyptus. This causes weakening and, in case of severe infestation, death of the tree. We report identification of the sex pheromone produced by females of this species. Hexane extracts of the abdominal glands of virgin females were analyzed by gas chromatography (GC) with electroantennographic detection, GC coupled with mass spectrometry, and GC coupled to infrared spectroscopy. The major pheromone component was identified as (7Z,10Z)-7,10-hexadecadienal (Z7,Z10-16:Ald), and minor components present in the extracts were (Z)-7-hexadecenal and (Z)-9-hexadecenal, hexadecanal, and (9Z,12Z)-9,12-octadecadienal. Structural assignments were carried out by comparison of analytical data of the natural products and their dimethyl disulfide adducts with those of authentic reference samples. In field tests, traps baited with Z7,Z10-16:Ald captured significantly more males than control traps.

Determination of Double Bond Positions and Geometry of Methyl Linoleate Isomers with Dimethyl Disulfide Adducts by GC/MS.

The dimethyl disulfide (DMDS) adduct method is one of the convenient and effective methods for determining double bond positions of unsaturated fatty acid methyl esters (FAME) except conjugated FAME. When analyzed using gas chromatography/electron ionization-mass spectrometry (GC/EI-MS), unsaturated FAME with DMDS added to the double bonds yields high intensity MS spectra of characteristic ions. The MS spectra of characteristic ions can then be used to easily confirm double bond positions. Here we explore the GC/EI-MS analysis of the DMDS adducts of methyl linoleate geometrical isomers isolated by high performance liquid chromatography (HPLC) with a silver nitrate column. For C18:2-c9, c12 and C18:2-t9, t12, DMDS randomly formed adducts with double bonds at either carbon 9-10 or carbon 12-13, but not both at the same time due to steric hindrance. For C18:2-c9, t12 and C18:2-t9, c12, however, DMDS only formed adducts with the double bond in the cis configuration. Consequently, when analyzing fatty acids with methylene interrupted double bonds, with one double bond in the cis and one in the trans configuration, double bond positions cannot be completely confirmed.

(Z)-13-Hexadecenyl Acetate: a Novel Moth Sex Pheromone Component from Herpetogramma submarginale (Lepidoptera: Crambidae).

The sex pheromone of Herpetogramma submarginale (Swinhoe) was studied by gas chromatography (GC) with electroantennographic detection and GC coupled with mass spectrometry. Two pheromone candidates detected in the gland extracts of females were identified as (Z)-13-hexadecenyl acetate (Z13-16:OAc) and (E)-13-hexadecenyl acetate (E13-16:OAc) in a ratio of 87:13 by mass spectral analysis of the natural pheromone components and their dimethyldisulfide adducts. In field tests, Z13-16:OAc alone attracted H. submarginale males and caught significantly more males than live virgin females. Addition of E13-16:OAc did not enhance the attractiveness of Z13-16:OAc. Derivatives of Z13-16:OAc also were tested as potential pheromone components. Addition of (Z)-13-hexadecen-1-ol significantly reduced the number of males captured, and (Z)-13-hexadecenal had no effect on the attractiveness of the lure. These results suggest that the female-produced sex pheromone of H. submarginale is Z13-16:OAc. This hexadecenyl acetate is a novel moth sex pheromone component.

N-Nonacosadienes from the marine haptophytes Emiliania huxleyi and Gephyrocapsa oceanica

The hydrocarbons in cultures of marine haptophytes Emiliania huxleyi NIES837 and Gephyrocapsa oceanica NIES1315 were analyzed, and nonacosadienes and hentriacontadienes were detected as the major compounds in both strains. C29 and C31 monoenes and di-, tri- and tetra-unsaturated C33 alkenes were also detected as minor compounds but not C37 and C38 alkenes. The positions of the double bonds in the C29 and C31 alkenes were determined by mass spectrometry of their dimethyl disulfide (DMDS) adducts. Among the four C29 alkenes identified, the most abundant isomer was 2,20-nonacosadiene, and the other three compounds were 1,20-nonacosadiene, 3,20-nonacosadiene and 9-nonacosene, respectively. Hitherto, 2,20-nonacosadiene and 3,20-nonacosadiene were unknown to be natural products. The double bond at the n-9 (ω9) position in these C29 alkenes is hypothesized to be derived from precursors of unsaturated fatty acids possessing an n-9 double bond, such as (9Z)-9-octadecenoic acid. Nonacosadienes have the potential for being used as distinct haptophyte biomarkers.

Non‐methylene Interrupted and Hydroxy Fatty Acids in Polar Lipids of the Alga Grateloupia turuturu Over the Four Seasons

Phospholipids (PL) and glycolipids (GL) FA in the edible Rhodophyta Grateloupia turuturu, from Brittany, France, were investigated over four seasons. The major lipid class was GL in all seasons (around 45%). More than 80FA occurred in polar lipids, with chains from C12 to C26, identified as methyl esters and N-acyl pyrrolidides by gas chromatography-mass spectrometry (GC-MS). PUFA occurred at up to 47.1% (summer) in PL, and up to 43.6% (summer) in GL. The major PUFA were 20:5n-3 (12.2% in PL and 29.0% in GL) and 20:4n-6 (25.6% in PL and 10.4% in GL). The unusual 18:3n-7 acid was identified in PL up to 2.2%. Several minor unsaturated FA were identified in PL and are previously unreported in seaweeds, namely 14-tricosenoic, 15-tetracosenoic, 5,11-octadecadienoic and 5,9-nonadecadienoic. Also unprecedented in seaweeds, ten 2-hydroxy and three 3-hydroxy FA occurred mainly in PL, 13.9% in spring with the 3-hydroxyhexadecanoic acid as the major one (8.1% winter). Three n-9 monounsaturated 2-hydroxy FA occurred in PL. The 2-hydroxy-15-tetracosenoic acid was characterized as the dimethyl disulfide adduct of its methyl ester. The 2-hydroxy-16-pentacosenoic and 2-hydroxy-17-hexacosenoic acids were identified by comparison of mass spectra and GC mobilities with those of the 2-hydroxy-15-tetracosenoic acid, and of other homogeneous FA series. These rare n-9 monounsaturated 2-hydroxy FA are unprecedented in seaweeds.

(E)-5-Hexadecenyl Acetate: A Novel Moth Sex Pheromone Component From Stathmopoda auriferella

The sex pheromone of Stathmopoda auriferella (Walker), an important pest of kiwifruit in Korea, was studied. Two candidate pheromone components detected in the gland extracts of females were identified as (E)-5-hexadecenyl acetate (E5-16:OAc) and (E)-5-hexadecenol (E5-16:OH) in a ratio of 75:25 by mass spectral analysis of natural pheromone components and dimethyldisulfide adducts, and retention index comparisons with synthetic standards. In the kiwifruit orchards, E5-16:OAc alone was attractive to S. auriferella males and caught significantly more males than live virgin females. However, addition of E5-16:OH strongly inhibited attraction to E5-16:OAc. These results suggest that the major component of the female-produced sex pheromone of S. auriferella is E5-16:OAc. This hexadecenyl acetate is a novel moth sex pheromone component.

New 2‐Methyl‐13‐Icosenoic Acid from the Temperate Calcisponge Leuconia johnstoni

The fatty acid composition of the temperate calcareous marine sponge Leuconia johnstoni Carter 1871 (Calcaronea, Calcarea) was characterized for the first time in specimens collected off the Brittany coast of France over four years from October 2005 to September 2008. Forty-one fatty acids (FA) with chain lengths ranging from C₁₄ to C₂₂ were identified as fatty methyl esters (FAME) and N-acyl pyrrolidide (NAP) derivatives by gas chromatography-mass spectrometry (GC-MS). Twenty-two saturated fatty acids (SFA) were identified accounting for 52.1-59.0% of the total FA and dimethylacetals (DMA). In addition, among the SFA, we noticed the presence of numerous methyl-branched iso and anteiso FA, suggesting a large number of associated bacteria within L. johnstoni. Thirteen monounsaturated fatty acids (MUFA, 28.0-36.0% of total FA + DMA) were also identified as well as six polyunsaturated fatty acids (PUFA, 4.0-8.2%). A noticeable DMA was detected at a high level, particularly in September 2008 (11.8%), indicating the presence of plasmalogens in this sponge species. This calcareous sponge lacked the non-methylene-interrupted FA (NMI FA) with a Δ5,9 system typical of siliceous Demosponges and Hexactinellids. The occurrence of the unusual 8,13-octadecadienoic acid was reported for the first time as a minor PUFA in a calcareous sponge. The major FA, representing 20-25% of this sponge FA, was identified as the new 2-methyl-13-icosenoic acid from mass spectra of its methyl ester and its corresponding N-acyl pyrrolidide derivatives as well as a dimethyl disulfide adduct.

Fatty Acids of Chthonomonas calidirosea, of a Novel Class Chthonomonadetes from a Recently Described Phylum Armatimonadetes

A Gram-negative, aerobic, pink-pigmented, rod-shaped bacterium Chthonomonas calidirosea (strain T49(T)) with an optimal temperature for growth of 68°C, isolated from soil samples from Hell's Gate in the Tikitere geothermal system (New Zealand), was the first cultivated bacterium of the novel phylum Armatimonadetes (formerly candidate division OP10). The lipid composition of C. calidirosea presents a number of unusual features both in the fatty acids and polar lipids. This contribution reports on the fatty acid profile of C. calidirosea. Transmethylation of bacterial biomass yielded fatty acid methyl esters and hydrocarbons, including squalene, partially hydrogenated squalenes, and diploptene. The only type of unsaturation found in C. calidirosea fatty acids was cis-Δ5, as revealed by GCMS of dimethyl disulfide (DMDS) adducts, and the lack of trans-unsaturation absorbance at 960-980cm(-1) in the IR spectrum of fatty acids methyl esters. An unidentified component X with ECL 16.86 (BP1) and ECL 17.27 (BP20) was also observed, with molecular ion at m/z 282 ("17:1"). X did not form DMDS adducts, nor was affected by mild hydrogenation conditions, indicating the likely presence of a ring rather than unsaturation. The presence of a cyclopropane ring with cis-stereochemistry was confirmed by the (1)H-NMR spectrum. Hydrogenation of X in acetic acid resulted in formation of straight chain 17:0, 5-methyl- and 6-methyl-16:0 fatty acid methyl esters, thus confirming the structure of a novel 5,6-methylene hexadecanoic acid. The major fatty acids of a solid media-grown C. calidirosea were as follows (in weight % of total fatty acids): 16:0 (25.8), i17:0 (19.3), ai17:0 (13.5), 16:1∆5 (8.8), i17:1∆5 (6.8), 5,6-methylene 16:0 (5.2), i16:0 (4.4), 18:0 (3.6), 18:1∆5 (3.2).

Occurrence of all-cis-5,8,11,14,17,20,23-hexacosaheptaenoic acid (26:7n-3) in roughscale sole Clidoderma asperrimum flesh lipids

Fatty acid analysis of roughscale sole Clidoderma asperrimum flesh lipids was carried out by gas chromatography. An unidentified peak appeared in the chromatogram in the elution region of ≥C24 fatty acids. After enrichment by solvent partitioning, reversed-phase thin-layer chromatography (TLC), and argentation TLC, the peak component was subjected to structural analyses. The partially hydrogenated products after reaction with hydrazine hydrate gave seven isomers of cis-hexacosenoic acid (26:1). Gas chromatography-mass spectrometry (GC–MS) analyses of their dimethyl disulfide adducts identified the monounsaturates as 5-, 8-, 11-, 14-, 17-, 20-, and 23-26:1. The peak component was assigned to all-cis-5,8,11,14,17,20,23-hexacosaheptaenoic acid (26:7n-3). GC–MS analyses of the 4,4-dimethyloxazoline derivative and methyl ester confirmed this structure. This fatty acid is a rare, very long-chain polyunsaturated fatty acid (VLCPUFA). The concentrations of the acid found in roughscale sole were 0.69 ± 0.34% (N = 5) of total fatty acids in flesh lipids. Roughscale sole appears to be characterized by the occurrence of 26:7n-3, which is lacking in popular sources of methylene-interrupted VLCPUFA, such as vertebrate retina, spermatozoa, and herring.

Identification and field testing of sex pheromone components of a Korean population of the allium leafminer, Acrolepiopsis sapporensis

AbstractThe allium leafminer, Acrolepiopsis sapporensis Matsumura (Lepidoptera: Acrolepiidae), is a pest of Allium species (Liliaceae) in Asia and Hawaii, USA. We identified candidate sex pheromone components in pheromone gland extracts of female moths and field tested the response of male moths to blends with different components and ratios. Gas chromatographic comparison of abdominal tip extracts from both sexes showed three female‐specific components: (Z)‐11‐hexadecenal (Z11‐16:Ald), (Z)‐11‐hexadecenyl acetate (Z11‐16:OAc), and (Z)‐11‐hexadecen‐1‐ol (Z11‐16:OH). These compounds were identified by mass spectral analysis of natural pheromone components and dimethyldisulfide adducts, and retention index comparisons with synthetic standards. The average ratio of three components, Z11‐16:Ald, Z11‐16:OAc, and Z11‐16:OH, in female extract was 33:100:14. Field trapping experiments indicated that all three components were essential for maximal attraction of male moths. Traps baited with a ternary blend mimicking the blend found in the pheromone gland extracts caught significantly more males than traps baited with caged live females. Increasing doses of the pheromone blend in the lures from 0.01 to 1.0 mg increased catches of male A. sapporensis.

An Improved Method for Preparing Dimethyl Disulfide Adducts for GC/MS Analysis

AbstractDimethyl disulfide (DMDS) adducts are prepared from fatty acid methyl esters to locate the double‐bond position in monoenoic fatty acids by gas chromatography/mass spectrometry. We improved our original procedure for preparing DMDS adducts with a simple device that can be made in any laboratory using a glass pipette and silica based packing material, Extelut NT.