Monounsaturated Hydrocarbons Research Articles

Chemical Composition of Essential Oil from Four Sympatric Orchids in NW-Italy.

Orchidaceae is a flowering plant family worldwide distributed known for producing volatile organic compounds (VOCs) which can act as olfactory signals for pollinators. Despite the importance of VOCs in the different reproductive strategies, in the literature there are only a few publications on the characterization of orchids’ volatile profiles. In this study, the essential oils from fresh inflorescences of sympatric orchids Anacamptis morio, Himantoglossum robertianum, Ophrys sphegodes and Orchis purpurea, naturally growing in Piedmont (Italy) were isolated by steam distillation and characterized by GC/FID and GC/MS. A number of compounds were identified, with a peculiar distribution in the species: alcohols (range 16.93–50.60%), from which p-cresol (range 12.75–38.10%) was the most representative compound; saturated hydrocarbons (range 5.81–59.29%), represented by pentacosane (range 2.22–40.17%) and tricosane (range 0.78–27.48%); long-chain monounsaturated hydrocarbons (range 0.29–5.20%) represented by 9-pentacosene, 11-tricosene, and 1-heneicosene. The structure of positional isomers in linear alkenes was elucidated by derivatization with dimethyl disulfide and MS fragmentation patterns. Coumarin (68.84%) was the dominant compound in O. purpurea and was detected in lower concentrations (range 0.21–0.26%) in the other taxa. These volatile compounds may represent a particular feature of these plant species and play an essential role in pollinator interaction.

Chemical Composition of the Essential Oils From Leaves and Flowers of Passiflora sexocellata and Passiflora trifasciata

The chemical composition of the essential oils of Passiflora sexocellata and Passiflora trifasciata (Passifloraceae, subgenus Decaloba) were studied for the first time. Essential oils were obtained by steam distillation of fresh leaves and flowers. The chemical composition was assessed by using GC/FID and GC/MS. For P. sexocellata leaves, the optimized analytical procedure allowed the identification of 33 compounds (75% of the total oil composition) and 29 (74% of the total oil composition) in flowers. Regarding P. trifasciata, 35 compounds (76% of the total oil composition) were detected in leaves and 32 (71% of the total oil composition) in flowers. Terpenes and mono unsaturated hydrocarbons were quantified as major constituents of the volatile fraction in flowers (17.0 to 52.6%) and (13.7 to 20.0%). Organic acids were detected in both leaves and flowers with a percentage ranging from 3.3% to 32.0%. Aldehydes were also detected in leaves (12.6 to 41.4%) and in flowers (1.4 to 5.1%). The GC/MS analyzes allowed alcohols to be detected in leaves (20.6 to 42.9%) and in flowers (8.2 to 18.1%). These compounds represent the most important feature of the large Passiflora family. Moreover, a critical role in the coevolved mechanisms of pollinators' interaction has been investigated.

Composition of Volatile Fraction from Inflorescences and Leaves of Dendrobium moschatum (Orchidaceae)

The volatile fractions from fresh inflorescences and leaves of Dendrobium moschatum (Buchanan-Hamilton) Swartz (Orchidaceae) were isolated by steam distillation with a yield of 0.498% and 0.041% (weight/fresh weight basis), respectively. From GC/FID and GC/MS analyses, coumarin was identified to be the most abundant constituent and quantified as 48.8% and 47.8% of the total volatiles from inflorescences and leaves, respectively. Hydrocarbons, ketones, esters, acids and aldehydes were also detected. Long chain mono unsaturated hydrocarbons were quantified in higher amount in leaves and their structures were elucidated by GC/MS of their dimethyl disulfide derivatives. These compounds together with long chain ethyl esters and methyl ketones may represent a particular feature of this plant species and can play a critical role in the interaction with pollinator insect.

Synthesis of Bio‐Based Polyurethanes from Jojoba Oil

Jojoba grows easily in harsh conditions and is the only plant species known to use liquid wax esters as a primary seed storage reserve. Jojoba oil is composed by two mono unsaturated hydrocarbon chains linked by an ester moiety and represents 50% of the weight of seeds. Hence, this atypical oil is, for the first time, dedicated to the synthesis of innovative polymer materials. Novel partially biobased polyurethanes materials are obtained with various structures. New biobased diol is first achieved by addition of mercaptoethanol by thiol‐ene coupling on jojoba oil and characterized by 1H NMR and 13C NMR. The functionalized oil is used to synthesize polyurethane prepolymers by catalyst‐free reaction with various diisocyanates: 1,6‐hexamethylene diisocyanate and 4,4‐methylene diphenyl diisocyanate. After the addition of chain extenders, the obtained polyurethane materials are characterized by 1H NMR, TGA, DSC, and DMA analyses. Various PUs are obtained in terms of flexibility and thermal stability.Practical Applications: The synthesized jojoba oil‐based PUs exhibit a good flexibility. Hence, these biobased PUs could replace petroleum‐based polyurethanes in industry and particularly as coatings, binders or compounds for automotive and aircraft industries.Innovative greener polyurethanes are achieved from jojoba oil with one‐step thiol‐ene reaction and various diisocyanates.

Branched chain fatty acids concentrate prepared from butter oil via urea adduction

Saturated branched chain fatty acids (BCFA) intake in the US is greater than that of other bioactive fatty acids (FA), yet little information is available on methodologies to concentrate them. We report here the effect of urea‐to‐FA (urea:FA) ratio, adduction time, and temperature on the enrichment of branched chain fatty acids (BCFA) from butter oil. Urea adducts precipitate both saturated and monounsaturated hydrocarbon chains as urea complexes, leaving solubilized polyunsaturated FA and BCFA in the non‐urea adduct fraction (NUA). The optimum urea:FA ratio was found to be 4:1 and the optimum temperature to be 4°C. Adduction time had negligible effect on BCFA enrichment. Anteiso‐15:0 was most enriched across major BCFA under all conditions of temperature, time, and urea:FA ratio studied. In our preferred embodiment, a two‐stage urea adduction procedure applied to hydrolyzed butter oil resulted in an enrichment from <2% BCFA in the starting oil to >11% BCFA, indicating an enrichment factor of >6. The best method has a first stage performed at 4°C and urea:FA ratio of 4:1, and a second stage at 30°C and lower urea:FA ratio (2:1). Overall yield of BCFA in enriched fraction was about 10% of starting BCFA for two stages.Practical applications: BCFA are constituents of the GI tract of healthy newborns and are known to prevent necrotizing enterocolitis. The average per capita BCFA intake of Americans is estimated to be about 220 mg/day from dairy whereas based on the current dietary recommendations of USDA it should be about 400 mg/day from dairy alone with total amounting to 575 mg/day including beef. Using the results of the current study, enriched BCFA concentrates can be prepared to meet the demand.Enrichment in major branched chain fatty acids (BCFA) of butter oil after two stage urea adduction. First stage (NUA‐1) and second stage (NUA‐2) were conducted using 4:1; 4°C 2 h and 2:1, 30°C 2 h of urea‐to‐fatty acids ratio (wt/wt), temperature and time of adduction, respectively.

Argentation high performance liquid chromatography on-line coupled to gas chromatography for the analysis of monounsaturated polyolefin oligomers in packaging materials and foods

Multidimensional chromatography based on two-dimensional high performance liquid chromatography on-line coupled to gas chromatography (on-line HPLC–HPLC–GC) enables the separate analysis of saturated, monounsaturated and aromatic hydrocarbons in packaging materials like polyolefins or paperboard and their migrates into foods. Since normal-phase HPLC on silica gel did not preseparate saturated from monounsaturated hydrocarbons, a separation step on a normal-phase HPLC column treated in the laboratory with an optimized amount of silver nitrate was added. The preparation of this HPLC column and the instrumental set-up are described, followed by examples showing the potential of the method. In a preliminary investigation of 11 polyolefin granulates for food contact up to 40% monounsaturated hydrocarbons among the oligomers C16–35 were determined.

Identification and Synthesis of D. athabasca Cuticular Hydrocarbons

We are investigating the role of chemical signals on courtship behavior of Drosophila. The chemical signals of Drosophila athabasca are cuticular hydrocarbons, derived from fatty acids, spanning 20‐40 carbons in length with variations in saturation and branching patterns. Drosophila athabasca has three distinct races that are geographically overlapping but reproductively isolated: WestNorthern, Eastern A, and Eastern B. We have identified several pheromones of Drosophila athabasca that may influence the sexual selection that necessarily precedes speciation. Using Gas Chromatography tandem Mass Spectrometry and dimethyl disulfide derivatization (DMDS), we have characterized the pheromone composition of several isofemale lines. Synthesis of the major pheromones was completed to confirm identity of the cuticular hydrocarbons. Synthesis of monounsaturated hydrocarbons utilized cis‐directed Wittig reactions, while diene hydrocarbon synthesis employed substitution chemistry with acetylenes followed by a cis‐selective reduction. Purification and isomeric separations of hydrocarbons was completed using silica followed by argentation chromatography. Behavioral studies using synthetic pheromones are underway and may provide insight into the relationship between cuticular hydrocarbons and mate discrimination.

Identification and characterisation of a novel mono-unsaturated highly branched isoprenoid (HBI) alkene in ancient Arctic sediments

The occurrence of a novel C25 highly branched isoprenoid (HBI) mono-unsaturated hydrocarbon in Arctic marine sediments from the Fram Strait is described. The structure was determined following synthesis from a closely related diene and NMR spectroscopic analysis. The position of the double bond was confirmed by oxidation (RuO4) and comparison of the mass spectrum of the resulting C19 ketone with that of an authentic sample synthesised previously. The same C19 ketone was also present following oxidation of the Fram Strait sediment extracts. The source of the novel HBI monoene biomarker is not known, but is believed to be certain marine diatoms on the basis of structural similarities with other HBIs from such sources. It does not, however, appear to be biosynthesised by Arctic sea ice diatoms, unlike its regio isomer, IP25, an established proxy for Arctic sea ice. Alternatively, it may represent a diagenetic product of the sea ice diatom biomarker IP25; this seems unlikely, however, on the basis of their respective structures. Since the new HBI monoene and IP25 possess similar gas chromatographic and mass spectral properties, but probably have contrasting sources, we suggest that future paleo sea ice reconstruction studies based on the occurrence of IP25 should pay further attention to the rigorous assignment of this biomarker in marine sediment extracts. Some suggestions for achieving this, based on analytical purification and mass spectrometric measurements, are provided.

Aliphatic Hydrocarbon Spectra by Helium Ionization Mass Spectrometry (HIMS) on a Modified Atmospheric-Pressure Source Designed for Electrospray Ionization

Chemical-ionization techniques that use metastable species to ionize analytes traditionally use a flat pin or a sharp solid needle onto which the high potential needed to generate the discharge plasma is applied. We report here that direct analysis of samples containing volatile and semivolatile compounds, including saturated and unsaturated aliphatic hydrocarbons, can be achieved on any electrospray-ionization mass spectrometer by passing helium though the sample delivery metal capillary held at a high potential. In the helium plasma ionization source (HPIS) described here, the typical helium flow required (about 20-30 mL/min), was significantly lower than that needed for other helium-ionization sources. By this procedure, positive ions were generated by nominal hydride ion removal from molecules emanating from heated saturated hydrocarbons as large as tetratetracontane (C(44)H(90)), at capillary voltages ranging from 2.0 to 4.0 kV. Unsaturated hydrocarbons, on the other hand, underwent facile protonation under much lower capillary voltages (0.9 to 2.0 kV). Although saturated and monounsaturated hydrocarbons bearing the same number of carbon atoms generate ions of the same m/z ratio, a gas-phase deuterium exchange method is described to ascertain the identity of these isomeric ions originating from either protonation or hydride abstraction mechanisms. Moreover, mass spectrometric results obtained by exposing unsaturated hydrocarbons to D(2)O vapor in an HPIS-MS instrument confirmed that the proton donor for ionization of unsaturated hydrocarbons is protonated water.

Insights from biophysical studies on the role of polyunsaturated fatty acids for function of G-protein coupled membrane receptors

The composition of the lipid matrix is critical for function of membrane proteins. Perhaps one of the best studied examples is the function of the G-protein-coupled membrane receptor (GPCR) rhodopsin which is located in membranes with high content of phospholipids with polyunsaturated docosahexaenoic acid chains (DHA, 22:6n-3). Technological advances enabled a more detailed study of structure and dynamics of DHA chains and their interaction with rhodopsin. It was established that polyunsaturated DHA differs from saturated and monounsaturated hydrocarbon chains by far more rapid structural conversions. Furthermore, DHA chains tend to have higher density near the lipid/water interface while density of saturated chains is higher in the bilayer center. The interface of rhodopsin has a small number of sites for tighter interaction with DHA. Polyunsaturated phosphatidylethanolamines accumulate preferentially near the protein. Surprisingly, the high conformational freedom of most DHA chains is not measurably reduced upon interaction with rhodopsin. While some observations point at an involvement of continuum elastic properties of membranes in modulation of rhodopsin function, there is growing evidence for a role of weakly specific DHA–rhodopsin interactions.

Unusual lipid composition of a Bacillus sp. isolated from Lake Pomorie in Bulgaria.

The lipid composition of a Bacillus sp., isolated from Lake Pomorie in Bulgaria, was unusual and consisted of 26 different fatty acids between C12 and C26, with anteiso C15-C17 saturated fatty acids predominating. The furan fatty acid, 10,13-epoxy-11-methyloctadeca-10,12-dienoic acid, was also identified, a new finding for this genus. The hydrocarbons consisted of 30 different monounsaturated hydrocarbons, between C25 and C30, with the iso-iso, iso-anteiso, anteiso-anteiso, iso-normal, and anteiso-normal methyl branching for odd-numbered chains, and the iso-iso, iso-anteiso, iso-normal, and anteiso-normal methyl branching for even-numbered chains. The double bond positions in these hydrocarbons were determined by dimethyl disulfide derivatization followed by GC-MS, and the double-bond cis configuration was confirmed by infrared spectroscopy. Some previously unknown hydrocarbons in bacteria, such as (Z)-3,21-dimethyl-9-tricosene, (Z)-3,21-dimethyl-10-tricosene, (Z)-2,24-dimethyl-11-pentacosene, and (Z)-2,25-dimethyl-13-hexacosene were identified. Sterols were detected and were based on the sitosterol nucleus.

NEXAFS and TPD studies of molecular adsorption of hydrocarbons on Cu(100): segmental correlations with the heats of adsorption

Near-edge X-ray absorption fine structure (NEXAFS) and temperature-programmed desorption (TPD) studies have been performed to establish the relationship between adsorbate structure and binding energy in a monolayer of hydrocarbons on a Cu(100) surface. Fourteen different saturated and monounsaturated hydrocarbons were studied. The activation energy for desorption of these compounds has been found to be dependent on the following factors: (1) the length of the saturated hydrocarbon linear chain; (2) the presence and location of a double bond; (3) the cyclic versus acyclic nature of the hydrocarbons; and (4) the accessibility of the CH n groups for creating van der Waals interactions with the surface. Similar to previous observations on other surfaces, our results show that an increase of the linear hydrocarbon chain length by one methylene group increases the binding energy of a hydrocarbon by 1.5 kcal/mol. Our results also indicate that the presence of a double bond in a position where overlap between π-orbitals of a hydrocarbon and d-orbitals of the metal is significant (double bond parallel to the Cu(100) surface) increase the binding energy of an olefin molecule by 0.75 kcal/mol with respect to that of the corresponding saturated hydrocarbon.

Variation in lipid class composition during batch growth of Nannochloropsis salina and Pavlova lutheri

The variations over time of reactions in lipid classes of Nannochloropsis salina (Monodopsidaceae) and Pauloua lutheri (Prymnesiophyceae) during batch culture growth were studied using a thin layer chromatography-flame ionization detection (TLC-FID) system. The lag phase was marked by an abundance of hydrocarbons in both N. salina (78% of total lipids) and P. lutheri (48%), primarily polyunsaturated hydrocarbons for the former and saturated and monounsaturated hydrocarbons for the latter. The percentages of these compounds lessened rapidly during the exponential phase to reach 2.3 and 4.8% respectively of total lipids. There was no lipid storage during the exponential growth phase. By contrast, during the stationary phase lipids accounted for as much as 50% of dry weight in N. salina and for 30% in P. latheri. The triglycerides, which are primary reserve lipids, showed more rapid anabolism in N. salina (36.5 μg mm −3 biovolume d −1) than in P. lutheri (7.6 μm −3 d −1). The cellular quota of polar lipids in P. lutheri decreased (29 μg mm −3 biovolume) during the stationary phase. This phenomenon parallels the deterioration of the cells caused by nutritive deficiencies which are normal at this stage of growth. Nannochloropsis salina, however, showed no response to this factor. A significant quantity of wax and sterol esters was also found particularly during the first day in both N. salina (95 μg mm −3 biovolume) and P. lutheri (54 μg mm −3 biovolume). Other minor lipid compounds were also identified: alcohols, free fatty acids, free sterols and a pigment peak.

Biosynthesis of acyclic methyl branched polyunsaturated hydrocarbons inPseudomonas maltophilia

The hydrocarbon composition ofPseudomonas maltophilia was determined by gas chromatography-mass spectrometry. Mono-, di- and tri-unsaturated alkenes were identified with a predominance of polyunsaturated components. The carbon chains of the alkenes contained single methyl branches iniso andanteiso position and double methyl branches in theiso-iso andanteiso-anteiso configurations. The composition of the hydrocarbons from cells grown in synthetic media enriched with amino acids or volatile fatty acids demonstrated that the probable precursors incorporated into individual hydrocarbons were branched and normal fatty acid chains in the range from C3 to C16. The probable fatty acid precursors which were connected together to form the major triunsaturated hydrocarbon chains were two monounsaturated chains, whereas the major liunsaturated chains resulted from condensation of saturated and monounsaturated chains. The probable precursors for the major monounsaturated hydrocarbons were C14 (C15) and C16 (C15) fatty acids. The accumulation of hydrocarbons was not detected until the cells were in the late exponential phase of growth; the maximal levels were reached at the mid-stationary phase of growth.

A microcomputer-controlled microcalorimeter calibration circuit. II

The heats (enthalpies) of hydrogenation of three simple mono-unsaturated hydrocarbons have been determined using a new microcomputer controlled electrical calibration system. Results agree with selected (“best”) literature values to within an arithmetic mean absolute deviation of 0.32 kJ·mol−1. We believe that the total uncertainty at the 95% confidence level for determination of the enthalpy of hydrogenation of these compounds is somewhat less than 1kJ·mol−1.

Volatile hydrocarbons in the dufour's gland of the parasiteNemeritis canescens (Grav.) (Hymenoptera; ichneumonidae)

The Dufour's gland of the parasitic waspNemeritis (= Venturia) canescens (Grav.) was shown by gas chromatography and mass spectrometry to contain a mixture of C21, C23, and C25 saturated and monounsaturated hydrocarbons. The main component (62%) was (Z)-10-tricosene. The biological activity of the components is discussed.

Comparative study of the dufour gland secretions of workers of four species of Myrmica ants

The Dufour gland secretions of myrmica rubra, M. ruginodis, M. sabuleti and M. scabrinodis have been studied. The most volatile portions of the secretion of workers of all four species were found to be similar, containing C 2C 4 oxygenated compounds. The less volatile portion consists of a mixture of hydrocarbons. In M. ruginodis this is chiefly a mixture of linear saturated and mono-unsaturated hydrocarbons, similar in composition to that of M. rubra, while in M. sabuleti it consists of (Z,E)-α-farnesene and its homologues, homofarnesene, bishomofarnesene and trishomofarnesene, similar in composition to that of M. scabrinodis. Workers of each species studied were attracted to the Dufour gland volatiles of all four species, these substances chiefly causing an increase in running speed, with the workers not distinguishing between conspecific and allospecific secretions, though small quantitative differences could be demonstrated between the speed and orientation reaction of workers of each species. The less volatile fraction of the Dufour gland secretion is used for territorial marking by foraging workers. This marking is specific for each species except between M. rubra and M. ruginodis.

Soldier frontal glands of the termiteMacrotermes subhyalinus: Morphology, chemical composition, and use in defense

Soldiers of the East African fungus-growing termiteMacrotermes subhyalinus (Rambur) (Termitidae: Macrotermitinae) employ both mechanical and chemical defenses. Soldiers release a chemical secretion composed of long-chain saturated and monounsaturated hydrocarbons into wounds inflicted by their powerful mandibles. Chemical analysis of the secretion shows the paraffin fraction to consist primarily ofn-tricosane,n-pentacosane, 3- and 5-methylpentacosane, and 5-methylheptacosane. The major oleflns were identified as (Z)-9-heptacosene and (Z)-9-nonacosene. The secretion originates from the frontal glands of both major and minor soldiers; however, the hypertrophied gland of the major soldiers contains 500-fold more secretion than that of the minor soldiers. This secretion appears to impair the healing of wounds in test ants, and thus could represent a valuable supplement to the mechanical defense mechanism.

Saturated and mono-unsaturated long-chain hydrocarbon profiles from mandarin juice sacs

The long-chain saturated and mono-unsaturated hydrocarbon content of the juice sacs of five mandarin cultivars (Mediterranean, Honey, Wilking, Kinnow, King) were examined. Normal homologues accounted for more than 47% of the saturated and more than 75% of the monoene hydrocarbons. In the saturated fraction the major hydrocarbon was n-C 25 but in the monoene fraction n-C 25 predominated in Kinnow and King while C 29 predominated in Mediterranean, Honey and Wilking. All five cultivars could be differentiated from each other and from other citrus species by their hydrocarbon patterns. The noticeably high normal/iso ratios of saturated C 23 and C 25 hydrocarbons previously shown to be characteristic of mandarin species, Citrus unshiu and C. reticulata, were also found in C. nobilis and C. deliciosa.

Chemical congruence of the complex odoriferous secretions from Dufour's gland in three species of ants of the genus Formica

Forty-six volatile compounds were identified in the secretions from Dufour's gland of worker ants of the species Formica nigricans, F. rufa, and F. polyctena using combined gas chromatography-mass spectrometry and capillary gas chromatography. In both methods the natural volatile material has been driven off excised glands using a precolumn technique. The composition of the secretions from the three species are very similar but there are also some distinct differences, especially between F. nigricans on the one hand and F. rufa and F. polyctena on the other. Straight-chain, saturated hydrocarbons are the quantitatively dominating compounds, with undecane as the largest individual component, followed by tridecane, pentadecane, and heptadecane. Straight-chain, monounsaturated hydrocarbons and methyl-branched, saturated hydrocarbons are also present and a few straight-chain, doubly unsaturated hydrocarbons are present in trace amounts. In the region of lower volatility two isoprenoids identified as all- trans-geranylgeraniol and the corresponding acetate all- trans-geranylgeranyl acetate, have been found together with octadecyl acetate. The relative amounts between these compounds are the main difference between the secretions from the three species. Octadecyl acetate is thus present only in trace amounts in the secretion of F. nigricans. In addition to the compounds mentioned a few aliphatic acetates and alcohols present in small amounts have been identified. The secretions are thought to have many functions which are reflected in their complex composition. This is discussed in comparison with results from other formicine ants. The species specificity in the composition of the secretion from Dufour's gland and the taxonomic value of this specificity are also discussed.