Structures of Dimers Produced from Methyl Linoleate during Initial Stage of Autoxidation

A structural investigation on the main fraction of dimers formed during the induction period of autoxidation in methyl linoleate (ML) was carried out. The dimeric fraction (A₂), which was isolated from the autoxidized ML (POV= 18) by various Chromatographic techniques and gave a single spot on TLC, was further separated into four major components (components 1–4) by high performance liquid chromatography (HPLC). The mean molecular weights of these components were found to be 643–655 and component 4 gave the parent peak 652 on an FD-mass spectrum which corresponded to 2 × ML + 4O. The reduced products of each component with stannous chloride were identified in common as methyl 9- or 13-hydroxy octadecadienoate and methyl 9,13-dihydroxy octadecenoate by GC-MS. These results show that all of these dimers contained a peroxide bridge linking between a pair of MLs across C-9 or C-13 on one of the MLs and C-9 or C-13 on the other, with a hydroperoxy group.     

Free radical oxidation of coriolic acid (13-(S)-hydroxy-9Z,11E-octadecadienoic acid)

The reaction of (13S,9Z,11E)-13-hydroxy-9,11-octadecadienoic acid (1a), one of the major peroxidation products of linoleic acid and an important physiological mediator, with the Fenton reagent (Fe(2+)/EDTA/H(2)O(2)) was investigated. In phosphate buffer, pH 7.4, the reaction proceeded with >80% substrate consumption after 4h to give a defined pattern of products, the major of which were isolated as methyl esters and were subjected to complete spectral characterization. The less polar product was identified as (9Z,11E)-13-oxo-9,11-octadecadienoate (2) methyl ester (40% yield). Based on 2D NMR analysis the other two major products were formulated as (11E)-9,10-epoxy-13-hydroxy-11-octadecenoate (3) methyl ester (15% yield) and (10E)-9-hydroxy-13-oxo-10-octadecenoate (4) methyl ester (10% yield). Mechanistic experiments, including deuterium labeling, were consistent with a free radical oxidation pathway involving as the primary event H-atom abstraction at C-13, as inferred from loss of the original S configuration in the reaction products. Overall, these results provide the first insight into the products formed by oxidation of 1a with the Fenton reagent, and hint at novel formation pathways of the hydroxyepoxide 3 and hydroxyketone 4 of potential (patho)physiological relevance in settings of oxidative stress.     

Effect of 1-n-Decylimidazole on Gibberellin Biosynthesis in Tan-ginbozu,a Dwarf Variety of Rice

Previous structural studies of less-polar dimers in autoxidized methyl linoleate (ML) have been extended to polar dimers. After isolation by successive silicic acid and gel permeation chromatography, the dimeric fraction of linoleate was separated into two major fractions, A₁ and A₂, according to their polarities. The polar dimers (A₁) were further fractionated by HPLC either directly or after reduction with triphenyl phosphine on a micro silica column. Isolated subfractions were characterized by UV, IR, GC-MS and FD-MS after suitable derivatizations. FD-MS of all these dimers showed a molecular ion peak which corresponds to 2 × ML + 6 × O and the reduction of each subfraction with stannous chloride gave equimolar amounts of 9 and 13-hydroxy octadecadienoate, and 9, 10, 13 and/or 9, 12, 13-trihydroxy octadecenoate. These results combined with others show that the A₁ dimers are composed of isomeric mixtures containing a peroxide bridge linking a methyl octadecadienoate and a 9, 12 and/or 10, 13-dihydroperoxy octadecenoate across C-9 and/or 13 on each of them.     

Secondary products of lipid oxidation

In the last decade, a multitude of secondary products have been identified from the radical and photosensitized oxidations of polyunsaturated lipids. These secondary products consist of oxygenated monomeric materials including epoxy-hydroperoxides, oxo-hydroperoxides, hydroperoxy epidioxides, dihydroperoxides, hydroperoxy bis-epidioxides, and hydroperoxy bicycloendoperoxides. More recently, higher molecular weight dimeric compounds have been identified from autoxidized methyl linoleate and linolenate. Decomposition of these oxidation products form a wide range of carbonyl compounds, hydrocarbons, furans, and other materials that contribute to the flavor deterioration of foods and that are implicated in biological oxidation. The interaction of some of these degradation products with DNA may be involved in cell-damaging reactions.     

Increased levels of monohydroxy metabolites of arachidonic acid and linoleic acid in LDL and aorta from atherosclerotic rabbits.

Lipid peroxidation results in the formation of peroxy and hydroperoxy metabolites of polyunsaturated fatty acids which can directly or indirectly affect many cellular processes. Lipid hydroperoxides are rapidly metabolized to the corresponding monohydroxy products by various cellular peroxidases. We have measured the amounts of monohydroxy metabolites of linoleic acid (18:2) and arachidonic acid (20:4) in lipids derived from aorta and LDL from rabbits fed a diet enriched in cholesterol and peanut oil for either 8 or 15 weeks. Increased amounts of the 9-hydroxy, and, to a lesser extent, the 13-hydroxy metabolite of 18:2 were observed in aorta and LDL from cholesterol-fed rabbits at both 8 and 15 weeks. The amounts of esterified 11-, 12- and 15-hydroxy metabolites of 20:4 in aortae from cholesterol-fed rabbits were similar to controls after 8 weeks, but about 3-fold higher after 15 weeks. These monohydroxy metabolites of 20:4 were also detected in LDL lipids in cholesterol-fed rabbits. The greater amounts of hydroxy-18:2 in the cholesterol-fed group could be explained by an approx. 2-4-fold increase in 18:2 in aorta and LDL. In contrast, the amounts of 20:4 in aortic lipids were lower in cholesterol-fed rabbits than in controls. Thus, the percentage of esterified 20:4 which had been oxidized to its 11, 12, and 15-hydroxylated metabolites was about 5-times higher in the cholesterol-fed group. Our results would be consistent with the hypothesis that increased amounts of peroxidized 18:2 and 20:4 in lipids could be involved in the development of atherosclerotic lesions in cholesterol-fed rabbits.     

Studies on Moss Spores. IV. Mass Spectrometric Identification of Saturated and Monoenoic Long Chain Fatty Acids in the Triglyceride Fraction of Polytrichum commune Spores

The saturated long chain fatty acid methyl esters of the triglyceride fraction of Polytrichum commune spores were separated by silver nitrate TLC and identified by a combination of gas chromatographic-mass spectrometric technique. The saturated fatty acid methyl esters were straight-chained, and even-numbered with carbon numbers ranging from 12 to 26 or odd-numbered with carbon numbers ranging from 13 to 25. The major components of the fraction containing saturated fatty acid methyl esters were methyl palmitate and methyl stearate. The fatty acid methyl esters of the monoenoic fraction isolated by silver nitrate TLC were converted to TMSO derivates which were analysed by gas chromatography-mass spectrometry. The analysis gave evidence of positional isomers. The fraction contained the following straight chain monoenoic fatty acid methyl ester isomers: methyl 7-cis-hexadecenoate, methyl 9-cis-hexadecenoate, methyl 9-cis-heptadecenoate, methyl 9-cis-octadecenoate, methyl 11-cis-octadecenoate, and methyl 11-cis-eicosenoate. The major components were methyl 9-cis-octadecenoate and methyl 7-cis-hexadecenoate.     

Photolysis of unsaturated fatty acid hydroperoxides. 3. Products from the aerobic decomposition of methyl 13(S)-hydroperoxy-9(Z),11(E-octadecadienoate dissolved in methanol

In the presence of oxygen, UV-irradiation of a solution of methyl 13(S)-hydroperoxy-9(Z), 11(E)-octadecadienoate (13-HPOD) in methanol yields stereoisomers of methyl 9,13-dihydroxy-10-methoxy-11-(E)-octadecenoate and methyl 9,13-dihydroxy-12-methoxy-10(E)-octadecenoate as major products. The reaction pathway to the products was established by photolysis experiments with labeled 13-HPOD and with intermediates of the reaction route. When methanol was substituted by water in the reaction system, the corresponding trihydroxyoctadecenoic acids were formed. This was confirmed by aerobic photolysis of 13-HPOD (free acid) dissolved in water. Threo and erythro methyl 12, 13-epoxy-11-hydroxy-9(Z)-octadecenoates belong to the minor compounds formed during aerobic photolysis of the 13-HPOD in methanol. Labeling experiments indicated that the threo compound resulted mainly from a rearrangement of the 13-HPOD while the erythro compound is mainly formed via secondary hydroperoxidation.     

Characteristics of Effective and Host Specific Ineffective Strains of Rhizobium japonicum

The formation of dimers in the initial stage of methyl linoleate (ML) autoxidation was demonstrated. The oxidation profile of freshly prepared ML was followed by TLC during autoxidation by aeration at 30°C for 192 hr. After 24 hr of autoxidation, the peroxide value of ML was still 0.6, and two unknown polar spots appeared besides intact ML and methyl linoleate hydroperoxides (MLHPO). These two spots were identified as dimers by successive gel and high performance liquid Chromatographic separations and by molecular weight determination. The ratio of dimers/MLHPO reached a maximum (0.74) after 96 hr of autoxidation. This result indicates that the formation of dimers in the initial stage of autoxidation was slightly less than that of MLHPO. The dimers were linked through ?C?O?O?C? bonds and contained hydroperoxy and/or carbonyl groups and conjugated dienes.     

Rat testis lipoxygenase-like enzyme characterization of products from linoleic acid

The linoleate oxidation products of the affinity chromatography-purified lipoxygenase-like enzyme isolated from rat testes microsomes were characterized. Three types of reaction products separated by thin-layer chromatography were generally present: polar byproducts (A and B) and hydroperoxides. The methyl hydroxystearates obtained from the enzymically produced hydroperoxides were analysed by gas-liquid chromatography and showed a ratio of 67% 13-hydroxy isomer to 33% 9-hydroxy isomer.The major polar byproduct was analysed by infrared spectra, nuclear magnetic resonance and mass spectrometry (of the toluene-p-sulphonyl derivative) and its structure was established as 13-hydroxy-12-oxo-octadec-cis-9-enoic acid. The possibility of the existence of a linoleate hydroperoxide isomerase in the affinity-purified preparation is discussed.     

Syntheses and reactions of methyl (Z)-9,10-epoxy-13-oxo-(E)-11-octadecenoate and methyl (E)-9,10-epoxy-13-oxo-(E)-11-octadecenoate

The syntheses and reactions of two epoxyketoacids (methyl (Z)-9,10-epoxy-13-oxo-(E)-11-octadecenoate (IV) and methyl (E)-9,10-epoxy-13-oxo-(E)-11-octadecenoate (V)) are described. The synthetic method is based on the stereoselective oxidation of linoleic acid by soybean lipoxygenase to produce the corresponding 13-hydroperoxide. Reduction of the hydroperoxide with sodium borohydride followed by oxidation, esterification and epoxidation yielded the compounds IV and V with a global yield of 14% and 3%, respectively, referred to the diasteromerically pure isolated compounds. Confirmation of the structures was carried out by reduction of the ketone group with sodium borohydride and by the opening of the oxirane ring with methanolic boron trifluoride. The reduction of compounds IV and V with hydrogen mainly yielded the tetrahydrofuranoid fatty acid, methyl 10,13-epoxyoctadecanoate. This reaction may be considered a new procedure to obtain tetrahydrofuranoid fatty acids.     

Formation of monohydroxy derivatives of arachidonic acid, linoleic acid, and oleic acid during oxidation of low density lipoprotein by copper ions and endothelial cells.

An important event in the formation of atherosclerotic lesions is the uptake of modified low density lipoprotein (LDL) by macrophages via scavenger receptors. Modification of LDL, which results in its recognition by these receptors, can be initiated by peroxidation of LDL lipids. The first step in this process is the formation of monohydroperoxy derivatives of fatty acids, which are subsequently degraded to the corresponding monohydroxy compounds, or to a variety of secondary oxidation products. In order to understand this process more completely, we have developed a mass spectrometric procedure to measure the amounts of specific hydroperoxy/hydroxy fatty acids formed by oxidation of the major unsaturated fatty acids in human LDL, oleic acid, linoleic acid, and arachidonic acid. Oxidation of human LDL in the presence of a relatively strong stimulus (20 microM CuSO4) resulted in very large increases in the amounts of the major monohydroxy derivatives of linoleic acid (9- and 13-hydroxy derivatives) and arachidonic acid (5-, 8-, 9-, 11-, 12-, and 15-hydroxy derivatives) in LDL lipids in the early stages of the reaction. After 20 h, the amounts of these products declined due to substrate depletion, but large amounts of monohydroxy derivatives of oleic acid (8-, 10-, and 11-hydroxy derivatives) were detected. Although thiobarbituric acid-reactive substances clearly increased under these conditions, the changes were not nearly so dramatic as those observed for monohydroxy fatty acids. Oxidation of LDL in the presence of endothelial cells, a much milder stimulus, resulted in 2.5- to 3-fold increases in the amounts of monohydroxy derivatives of linoleic and arachidonic acids, as well as thiobarbituric acid-reactive substances, with more modest increases in the amounts of hydroxylated derivatives of oleic acid. There was little positional specificity in the oxidation of the above fatty acids in the presence of either stimulus, suggesting that the formation of these products proceeds primarily by lipid peroxidation, rather than by catalysis by lipoxygenases. However, an important role for lipoxygenases in the initiation of these reactions cannot be excluded. In conclusion, oxidation of LDL in the presence of copper ions or endothelial cells results in the formation of a large number of monohydroxy derivatives of oleic, linoleic, and arachidonic acids. The relative amounts of products formed from each of these fatty acids depends on the strength of the stimulus as well as the incubation time.     

Characterization of cerebrosides from the thermally dimorphic mycopathogen Histoplasma capsulatum: expression of 2-hydroxy fatty N-acyl (E)-Delta(3)-unsaturation correlates with the yeast-mycelium phase transition

Cerebroside (monohexosylceramide) components were identified in neutral lipids extracted from both the yeast and mycelial forms of the thermally dimorphic mycopathogen Histoplasma capsulatum. The components were purified from both forms and their structures elucidated by 1- and 2-dimensional nuclear magnetic resonance (NMR) spectroscopy, electrospray ionization mass spectrometry (ESI-MS), and low energy tandem collision-induced dissociation mass spectrometry (ESI-MS/CID-MS). Both components were characterized as beta-glucopyranosylceramides (GlcCers) containing (4E,8E)-9-methyl-4,8-sphingadienine as the long-chain base, attached to 18-carbon 2-hydroxy fatty N-acyl components. However, while the fatty acid of the yeast form GlcCer was virtually all N-2'-hydroxyoctadecanoate, the mycelium form GlcCer was characterized by almost exclusive expression of N-2'-hydroxy-(E)-delta(3)-octadecenoate. These results suggest that the yeast-mycelium transition is accompanied by up-regulation of an as yet uncharacterized ceramide or cerebroside 2-hydroxy fatty N-acyl (E)-delta(3)-desaturase activity. They also constitute further evidence for the existence of two distinct pathways for ceramide biosynthesis in fungi, since glycosylinositol phosphorylceramides (GIPCs), the other major class of fungal glycosphingolipids, are found with ceramides consisting of 4-hydroxysphinganine (phytosphingosine) and longer chain 2-hydroxy fatty acids. In addition to identification of the major glucocerebroside components, minor components (< 5%) detectable by molecular weight differences in the ESI-MS profiles were also characterized by tandem ESI-MS/CID-MS analysis. These minor components were identified as variants differing in fatty acyl chain length, or the absence of the sphingoid 9-methyl group or (E)-delta(8)-unsaturation, and are hypothesized to be either biosynthetic intermediates or the result of imperfect chemical transformation by the enzymes responsible for these features. Possible implications of these findings with respect to chemotaxonomy, compartmentalization of fungal glycosphingolipid biosynthetic pathways, and regulation of morphological transitions in H.capsulatum and other dimorphic fungi are discussed.     

Ferric bleomycin catalyzed reduction of 10-hydroperoxy-8,12-octadecadienoic acid: evidence for homolytic O-O bond scission

10-Hydroperoxy-8,12-octadecadienoic acid (1) is reduced by ferric bleomycin in aqueous and methanol solutions to yield 10-oxo-8-decenoic acid (2) as the major product (80-90%). Trace amounts of 10-oxo-8,12-octadecadienoic acid (3) (5-10%) and 10-hydroxy-8,12-octadecadienoic acid (4) (5-10%) were also detected. The reduction product ratios remained relatively constant in the presence or absence of the reducing substrate phenol, over the pH range 6.5-8.5, in incubations from 30 s to 1 h, and over a series of ferric drug concentrations. In the presence of phenol, incubations of ferric bleomycin and 1 yielded 2,2'-biphenol and 4,4'-biphenol as oxidation products. In reactions where phenol was replaced with the drug's biological substrate DNA, 1 was found to support ferric bleomycin mediated DNA degradation. Extracts from these assays also found 2 to be the major reduction product derived from the oxidant, with trace quantities of 3 and 4 present. Control experiments demonstrated the reactions to be dependent on both 1 and ferric bleomycin. The reduction products 2 and 3 have previously been shown to originate from transient alkoxyl radicals formed by homolysis of the peroxy O-O bond. Product 4 results from heterolysis of the peroxy O-O bond [Labeque, R., & Marnett, L. J. (1987) J. Am. Chem. Soc. 109, 2828-2829]. The results of this investigation indicate that ferric bleomycin catalyzes the homolytic cleavage of the O-O bond of 1 almost exclusively while supporting various oxidative reactions.     

Novel ring cleavage products in the biotransformation of biphenyl by the yeast Trichosporon mucoides

The yeast Trichosporon mucoides, grown on either glucose or phenol, was able to transform biphenyl into a variety of mono-, di-, and trihydroxylated derivatives hydroxylated on one or both aromatic rings. While some of these products accumulated in the supernatant as dead end products, the ortho-substituted dihydroxylated biphenyls were substrates for further oxidation and ring fission. These ring fission products were identified by high-performance liquid chromatography, gas chromatography-mass spectrometry, and nuclear magnetic resonance analyses as phenyl derivatives of hydroxymuconic acids and the corresponding pyrones. Seven novel products out of eight resulted from the oxidation and ring fission of 3,4-dihydroxybiphenyl. Using this compound as a substrate, 2-hydroxy-4-phenylmuconic acid, (5-oxo-3-phenyl-2,5-dihydrofuran-2-yl)acetic acid, and 3-phenyl-2-pyrone-6-carboxylic acid were identified. Ring cleavage of 3,4,4'-trihydroxybiphenyl resulted in the formation of [5-oxo-3-(4'-hydroxyphenyl)-2,5-dihydrofuran-2-yl]acetic acid, 4-(4'-hydroxyphenyl)-2-pyrone-6-carboxylic acid, and 3-(4'-hydroxyphenyl)-2-pyrone-6-carboxylic acid. 2,3,4-trihydroxybiphenyl was oxidized to 2-hydroxy-5-phenylmuconic acid, and 4-phenyl-2-pyrone-6-carboxylic acid was the transformation product of 3,4,5-trihydroxybiphenyl. All these ring fission products were considerably less toxic than the hydroxylated derivatives.     

metabolism of prostaglandins of the A-type

, originally introduced as an inadvertent contaminant in solutions used for evaluating the stability of prostaglandins, proved to lead to the rapid disappearance of the cyclopentenone unit of PGA₂ (as monitored by circular dichroic spectroscopy). The cyclopentenone unit is converted, in various metabolites, to a 9-keto, 9α or 9β-hydroxy group lacking the ring unsaturation. The major EtoAc-soluble 9-hydroxy metabolite (Compound-I) was shown to be 9α, 15α-dihydroxy-2,3,4,5-tetranor-13- -prostenoic acid. Similar tetranor 9-hydroxy metabolites with one additional degree of unsaturation, and with a 9β-hydroxy group, also occur but these have not been fully characterized. Only two of the wide range of 9-keto metabolites are fully characterized by mass spectral (MS) data: 9,15-oxo-2,3,4,5-tetranorprostanoic acid and 9,15-oxo-2,3,4,5-tetranor-13- -prostenoic acid. The water soluble metabolites have not been characterized further.The fully characterized metabolites together with MS data from mixtures of minor metabolites indicate that can perform the following transformations: β-oxidation, dehydrogenation at C-15, reduction of the enone carbon-carbon double bonds (both Δ^10,11 and Δ^13,14), reduction of the 9-ketone, and possibly migration of the cyclopentyl double bond (Δ^10,11 → Δ^11,12). metabolizes 15-epimeric PGA₂ equally readily with the production of similar products. PGA₁ affords less 9-keto metabolites with compound I constituting 33% of the product by HPLC analysis. displays some enantioselectivity, PGA₂ and 15-epi-PGA₂ are each metabolized more rapidly than their enantiomers. Other prostaglandins appear to be less readily metabolized.     

Further Oxygenated Compounds Produced from Methyl Linoleate Monohydroperoxides at the Process of Autoxidation

The primary stable products, methyl linoleate monohydroperoxides (MLHPO), formed by the autoxidation of methyl linoleate were characterized by gas chromatography-mass spectrometry. MLHPO was converted into methyl hydroxy stearates which consisted of two isomers, methyl 9-hydroxy and methyl 13-hydroxy stearate. Trimethylsilyl ether derivatives of these hydroxy isomers were separated directly by gas chromatography and mass fragmentgraphy. MLHPO was degradated by incubating under aerobic condition at 37°C for a week, and the quantity of MLHPO was determined as hydroxy derivatives. Decrease of MLHPO was almost similar to that of conjugated diene structure, but the peroxide value was not appreciably decreased during the incubation. This fact based on the formation of further oxygenated compounds. After chemical reduction, these compounds were identified as methyl 9,13-hydroxy octadecenoate and methyl 9,12,13- or 9,10,13-trihydroxy octadecenoate, in which oxygen attached to the conjugated diene. The formation mechanisms of these oxygenated compounds are proposed.     

Rat testis lipoxygenase-like enzyme. Characterization of products from linoleic acid.

The linoleate oxidation products of the affinity chromatography-purified lipoxygenase-like enzyme isolated from rat testes microsomes were characterized. Three types of reaction products separated by thin-layer chromatography were generally present: polar byproducts (A and B) and hydroperoxides. The methyl hydroxystearates obtained from the enzymically produced hydroperoxides were analysed by gas-liquid chromatography and showed a ratio of 67% 13-hydroxy isomer to 33% 9-hydroxy isomer. The major polar byproduct was analysed by infrared spectra, nuclear magnetic resonance and mass spectrometry (of the toluene-p-sulphonyl derivative) and its structure was established as 13-hydroxy-12-oxo-octadec-cis-9-enoic acid. The possibility of the existence of a linoleate hydroperoxide isomerase in the affinity-purified preparation is discussed.     

Vanadium-catalyzed transformation of 13(S)-hydroperoxy-9(Z), 11(E)-octadecadienoic acid: Structural studies on epoxy alcohols and trihydroxy acids

Treatment of methyl 13(S)-hydroperoxy-9(Z), 11(E)-octadecadienoate with vanadium oxyacetylacetonate led to the formation of two diastereometric α,β-epoxy alcohols, i.e. methyl 11(R), 12(R)-epoxy-13(S)-hydroxy-9(Z)-octadecenoate and methyl 11(S), 12(S)-epoxy-13(S)-hydroxy-9(Z)-octadecenoate. The epoxy alcohols underwent spontaneous hydrolysis into isomeric trihydroxyesters. The first mentioned epoxy alcohol afforded methyl 9(R), 12(S), 13(S)- and methyl 9(S), 12(S), 13(S)-trihydroxy-10(E)-octadecenoates as major hydrolysis products whereas the latter epoxy alcohol afforded methyl 9(R), 12(R), 13(S)- and methyl 9(S), 12(R)-13(S)-trihydroxy-10(E)-octadecenoates as major compounds. Smaller amounts of diastereomeric methyl 11,12,13-trihydroxy-9-octadecenoates were also formed from both epoxy alcohols. The vanadium-catalyzed conversion of 13(S)-hydroperoxy-9(Z),11(E)-octadecadienoic acid (13(S)HPOD) (methyl ester) into α,β-epoxy alcohols and their further conversion into trihydroxy derivatives offers a model system for similar transformations of certain poly-unsaturated fatty acids recently described in the fungus, Saprolegnia parasitica.     

Studies of Aedes aegypti (Diptera: Culicidae) ovipositional responses to newly identified semiochemicals from conspecific eggs

Abstract  The chemical factors influencing the selection of oviposition site by gravid females of various mosquito species have been the subject of numerous investigations. Recent studies have revealed this behaviour to be controlled by semiochemicals. Here we report studies on semiochemicals of egg origin and their effect on the ovipositional behaviour of Aedes aegypti. The compounds present in egg extracts of Ae. aegypti mosquitoes were isolated and identified by gas chromatography-mass spectrometry. They were then evaluated for their effect on ovipositional behaviour against gravid females of Ae. aegypti mosquitoes at different concentrations. Gravid female Ae. aegypti were found to be sensitive to all the identified compounds: 6-hexanolactone, methyl dodecanoate, dodecanoic acid, methyl tetradecanoate, tetradecanoic acid, methyl (Z)-9-hexadecenoate, methyl hexadecanoate (Z)-9-hexadecenoic acid, hexadecanoic acid, methyl (Z)-9-octadecenoate, methyl octadecanoate (Z)-9-octadecenoic acid and octadecanoic acid. Among them, dodecanoic and (Z)-9-hexadecenoic acids showed significant positive ovipositional response at different concentrations whereas all the esters showed deterrent/repellent ovipositional effect.     

Autoxidation and Photosensitized Oxidation of Methyl Eicosapentaenoate: Secondary Oxidation Products

Methyl eicosapentaenoate (methyl 5,8,11,14,17-eicosapentaenoate) was subjected to autoxidation and methylene blue-sensitized photooxidation. The secondary oxidation products were separated, and characterized by gas chromatography-mass spectrometry. The autoxidation products included hydroperoxy endoperoxide isomers, prostaglandin-like hydroperoxy bicyclic endoperoxide isomers and 5,18-dihydroperoxide. The photosensitized oxidation products included only dihydroperoxide isomers as the secondary products.