Wax Ester Composition Research Articles

Distinctive lipid composition of the copepod Limnocalanus macrurus with a high abundance of polyunsaturated fatty acids.

We studied the copepod Limnocalanus macrurus for seasonal variation in the composition of fatty acids, wax esters and sterols in large boreal lakes, where it occurs as a glacial-relict. Vast wax ester reserves of Limnocalanus were accumulated in a period of only two months, and comprised mono- and polyunsaturated fatty acids (PUFA) and saturated fatty alcohols. In winter, the mobilization of wax esters was selective, and the proportion of long-chain polyunsaturated wax esters declined first. PUFA accounted for >50% of all fatty acids throughout the year reaching up to ca. 65% during late summer and fall. Long-chain PUFA 20:5n-3 and 22:6n-3 together comprised 17-40% of all fatty acids. The rarely reported C24 and C26 very-long-chain PUFA (VLC-PUFA) comprised 6.2 ± 3.4 % of all fatty acids in August and 2.1 ± 1.7% in September. The VLC-PUFA are presumably synthesized by Limnocalanus from shorter chain-length precursors because they were not found in the potential food sources. We hypothesize that these VLC-PUFA help Limnocalanus to maximize lipid reserves when food is abundant. Sterol content of Limnocalanus, consisting ca. 90% of cholesterol, did not show great seasonal variation. As a lipid-rich copepod with high abundance of PUFA, Limnocalanus is excellent quality food for fish. The VLC-PUFA were also detected in planktivorous fish, suggesting that these compounds can be used as a trophic marker indicating feeding on Limnocalanus.

Wax Ester Variation in Olive Oils Produced in Calabria (Southern Italy) During Olive Ripening

AbstractThe wax ester composition of pressed olive oil and its variation during olive ripening were investigated by column chromatography/GC‐on column technique. Six compounds were identified: C36, C38, C40, C42, C44 and C46 wax esters, which were grouped as total detected wax esters (TDWEs). The European Union (EU) includes C40, C42, C44 and C46 waxes (TEWEs) as a distinctive characteristic between different categories, with a maximum total content ≤250 mg/kg for an extra virgin olive oil. The International Olive Council (IOC) includes C42, C44 and C46 waxes (TIOCWEs) as a purity parameter, with a maximum total content ≤150 mg/kg for an extra virgin olive oil. The analytical technique proposed by EU and IOC do not separate the wax esters from fatty acids esters with diterpenic alcohols (phytol and geranylgeraniol) that interfere with detected peaks. Although the examined cultivars were grown in the same geographical area and the same agricultural practices were applied to the trees, ANOVA analysis found significant differences among the oils extracted with the same machinery. The oil produced from the Itrana cultivar showed the lowest content in TEWEs (25.00–39.00 mg/kg) and in TIOCWEs (5.67–9.00 mg/kg). Wax content in Leccino and Pendolino cultivars showed a significant tendency to decrease during olive maturation, and a tendency to increase in all other cultivars from the first to the last harvest date when olive pigmentation changed from green to black.

Wax ester profiling of seed oil by nano-electrospray ionization tandem mass spectrometry

BackgroundWax esters are highly hydrophobic neutral lipids that are major constituents of the cutin and suberin layer. Moreover they have favorable properties as a commodity for industrial applications. Through transgenic expression of wax ester biosynthetic genes in oilseed crops, it is possible to achieve high level accumulation of defined wax ester compositions within the seed oil to provide a sustainable source for such high value lipids. The fatty alcohol moiety of the wax esters is formed from plant-endogenous acyl-CoAs by the action of fatty acyl reductases (FAR). In a second step the fatty alcohol is condensed with acyl-CoA by a wax synthase (WS) to form a wax ester. In order to evaluate the specificity of wax ester biosynthesis, analytical methods are needed that provide detailed wax ester profiles from complex lipid extracts.ResultsWe present a direct infusion ESI-tandem MS method that allows the semi-quantitative determination of wax ester compositions from complex lipid mixtures covering 784 even chain molecular species. The definition of calibration prototype groups that combine wax esters according to their fragmentation behavior enables fast quantitative analysis by applying multiple reaction monitoring. This provides a tool to analyze wax layer composition or determine whether seeds accumulate a desired wax ester profile. Besides the profiling method, we provide general information on wax ester analysis by the systematic definition of wax ester prototypes according to their collision-induced dissociation spectra. We applied the developed method for wax ester profiling of the well characterized jojoba seed oil and compared the profile with wax ester-accumulating Arabidopsis thaliana expressing the wax ester biosynthetic genes MaFAR and ScWS.ConclusionsWe developed a fast profiling method for wax ester analysis on the molecular species level. This method is suitable to screen large numbers of transgenic plants as well as other wax ester samples like cuticular lipid extracts to gain an overview on the molecular species composition. We confirm previous results from APCI-MS and GC-MS analysis, which showed that fragmentation patterns are highly dependent on the double bond distribution between the fatty alcohol and the fatty acid part of the wax ester.

Influence of harvest year and cultivar on wax composition of olive oils

AbstractOlive oils extracted from Italian cultivars grown in the Region of Calabria, Southern Italy were analyzed for their wax ester composition, for three successive harvest years. Three autochthonous cultivars from Calabria: Cassanese, Ottobratica, and Sinopolese and seven allochtonous cultivars: Coratina, Itrana, Leccino, Nocellara Messinese, Nociara, Pendolino, and Picholine were considered. This work demonstrates the presence of significant differences (ANOVA) for the different wax ester compounds present in these olive oils, taking into consideration the cultivar and the harvest year. The studied olive oils present a good wax ester composition according to both EU and IOC regulations. The cultivar Ottobratica showed the highest wax ester content, whereas Itrana presented the lowest content.Practical applications: Wax esters are naturally present on the drupe cuticle and are transferred into olive oil by means of mechanical extraction and especially by solvent extraction on an industrial scale. They are a legal parameter contained in the European Union regulation and in the International Olive Oil Council regulation. Wax esters are a quality indicator for olive oil evaluation, especially to detect a fraudulent admixture of pomace olive oil in labeled extra virgin olive oil or in labeled monocultivar extra virgin olive oil. The adaptability of allochthonous cultivars in a different geographical area is also demonstrated.

Composition of wax esters is linked to diapause behavior of Calanus finmarchicus in a sea loch environment

We studied the seasonal lipid dynamics of Calanus finmarchicus from Loch Etive, a semi‐enclosed fjordic environment on the west coast of Scotland, in relation to the diapause behavior of this species. Levels of total lipid and triacylglycerol in individual copepodid stage V (CVs) exhibited clear seasonal trends, with highest levels in June and progressively decreasing through late summer to winter. Wax esters in CVs were more variable, but followed a similar pattern. An index of the level of unsaturation of wax esters, effectively an indicator of the levels of polyunsaturated fatty acids in the wax ester reserves, were highest in midsummer and declined progressively through autumn and winter. Fatty acid analysis of total lipid in the CVs confirmed that the amounts of polyunsaturated fatty acids in the wax esters decreased, while amounts of saturated and monounsaturated fatty acids remained comparatively stable. Polyunsaturated wax esters are selectively catabolized by C. finmarchicus during diapause. Previous studies have linked unsaturation of wax esters in calanoid copepods to the initiation of diapause and buoyancy control, and we hypothesize that selective catabolism of polyunsaturated wax esters is linked to the processes of diapause termination and ascent to surface waters.

Phase transitions of wax esters adjust buoyancy in diapausing Calanoides acutus

We study the composition and biophysical properties of wax esters extracted from the Antarctic copepod, Calanoides acutus, to explore if these factors adjust buoyancy in diapausing copepods. Levels of wax ester in the copepods were correlated with depth, with deeper animals containing higher amounts. An unsaturation index was used to determine the proportions of polyunsaturated wax esters in the oil sac of the copepods. The proportion of polyunsaturated wax ester in copepods that had descended to depth was always close to 50% and attributable to high amounts of the diatom biomarker fatty acid 20:5(n‐3) contained in these storage lipids. High‐pressure differential scanning calorimetry indicated that wax esters with such high levels of unsaturation exhibited unusual properties, changing from a liquid to a solid phase at pressures and temperatures below 500 m in the ocean. The dense, solid wax esters reduce the overall buoyancy of the lipid‐rich copepods at depth and help facilitate neutral buoyancy. The composition of wax esters is a key factor in buoyancy control in these organisms during diapause.

Wax ester composition influences the diapause patterns in the copepod Calanoides acutus

Many calanoid copepods inhabiting high latitude environments overwinter at depth in the water column in a state of diapause and the large wax ester reserves that they contain are central to this process. Here we compare the abundance, depth distribution, lipid content and wax ester composition of individual CV Calanoides acutus collected from the Southern Ocean at depth horizons ranging from the surface to 1000 m. Abundances of CV C. acutus varied considerably between locations, ranging from 44 to 1256 m −2. Levels of total lipid in the copepods increased with depth at a rate of around 100 μg per 100 m depth between 200 and 1000 m. Fatty acid composition of the wax esters reflected that of the local prey community, with a spectrum of diatom to flagellate dominated profiles corresponding to different microplankton environments. Copepods with highest levels of total lipid also contained highest levels of the highly unsaturated diatom fatty acid biomarker 20:5(n-3), and occupied the deepest depths during diapause. In addition, unsaturation levels of both the fatty acid and fatty alcohol moieties of the wax esters in the copepods increased with depth. This has implications for the buoyancy of these organisms: higher unsaturation makes the lipid likely to change from liquid to solid state at overwintering depths, increasing their specific gravity. These findings emphasise functional role of n-3 fatty acids in the diapause life-phase of calanoid copepods and in particular the importance of fatty acids from diatoms for overwintering.

Wax ester composition of monovarietal olive oils from Designation of Origin (DO) “Campos de Hellin”

The wax ester composition of six monovarietal olive oils (Arbequina, Benizal, Cornicabra, Cuquillo, Manzanilla, and Picual) from Designation of Origin (DO) “Campos de Hellin” (Spain) were analysed, to obtain a more complete characterisation of these varietal oils. The analyses were carried out by on-line liquid chromatography–gas chromatography (LC–GC) using the Through Oven Transfer Adsorption Desorption (TOTAD) interface. The oil made with Arbequina variety had the highest content of total wax ester (84.4 ± 4.3 mg/kg) and Picual oil the lowest (35.5 ± 3.7 mg/kg). The data obtained were analysed statistically; significant differences in C40, C44, C46 and total wax esters were found, with a level of confidence of 95%.

Seasonal and growth stage changes in lipid and fatty acid composition in the multigeneration copepodDrepanopus pectinatusfrom Iles Kerguelen

AbstractChanges in adult weight, lipid and fatty acid composition per lipid class were studied over a complete seasonal cycle inDrepanopus pectinatusBrady. This copepod displayed a strong seasonality in adult individual weight and total lipid content. Stages C3 to adult from a summer cohort were compared in terms of lipid and fatty acid structure. Changes in lipid content were related to wax esters and polar lipids (PL) while triacylglycerols (TAG) and cholesterol remained minor constituents except at the end of winter. Changes in fatty acid composition of different lipid classes showed that food limitation in winter was high enough to affect 22:6n-3 (DHA) content in PL, and provoke accumulation of maximal percentages of bacterial marker as branched acids. Composition of TAG followed closely the changes in trophic interactions as diatom and flagellate markers dominated in spring and summer while bacterial and detritus particle markers dominated in late winter. The composition of wax esters followed the same seasonal succession but with a lower level of turn over time and shifted characteristics (bacterial markers) from winter to spring individuals when compared to TAG. Ontogenetic changes showed high triacylglycerols content in younger C3 stages and increasing wax esters with increasing developmental stages. Fatty acid composition of PL showed low percentages of EPA and DHA in stage C3, and recovery of high levels of DHA for stage C4 or 20:5n-3 (EPA) at stage C5. The same trend was observed for 18:4n-3. The reverse pattern was noted for the n-6 polyunsaturated acids (PUFA) suggesting a greater requirement in younger stages. Fatty acid partitioning between neutral and PL suggested essential fatty acids selective incorporation from neutral classes into membrane lipids.

Hydrostatic pressure affects membrane and storage lipid compositions of the piezotolerant hydrocarbon‐degrading Marinobacter hydrocarbonoclasticus strain #5

A new piezotolerant alkane-degrading bacterium (Marinobacter hydrocarbonoclasticus strain #5) was isolated from deep (3475 m) Mediterranean seawater and grown at atmospheric pressure (0.1 MPa) and at 35 MPa with hexadecane as sole source of carbon and energy. Modification of the hydrostatic pressure influenced neither the growth rate nor the amount of degraded hexadecane (approximately 90%) during 13 days of incubation. However, the lipid composition of the cells sharply differed under both pressure conditions. At 0.1 MPa, M. hydrocarbonoclasticus #5 biosynthesized large amounts ( approximately 62% of the total cellular lipids) of hexadecane-derived wax esters (WEs), which accumulated in the cells under the form of individual lipid bodies. Intracellular WEs were also synthesized at 35 MPa, but their proportion was half that at 0.1 MPa. This lower WE content at high pressure was balanced by an increase in the total cellular phospholipid content. The chemical composition of WEs formed under both pressure conditions also strongly differed. Saturated WEs were preferentially formed at 0.1 MPa whereas diunsaturated WEs dominated at 35 MPa. This increase of the unsaturation ratio of WEs resembled the one classically observed for bacterial membrane lipid homeostasis. Remarkably, the unsaturation ratio of membrane fatty acids of M. hydrocarbonoclasticus grown at 35 MPa was only slightly higher than at 0.1 MPa. Overall, the results suggest that intracellular WEs and phospholipids play complementary roles in the physiological adaptation of strain #5 to different hydrostatic pressures.

Variability of Wax Ester Fermentation in Natural and Bleached Euglena gracilis Strains in Response to Oxygen and the Elongase Inhibitor Flufenacet

Euglena gracilis is able to synthesize adenosine triphosphate under anaerobic conditions through a malonyl-independent fatty acid synthesis leading to wax ester fermentation. Mitochondrial fatty acid synthesis uses acetyl-CoA and propionyl-CoA as C2- and C3-donors for de novo synthesis of even- and odd-numbered fatty acids, respectively. Euglena's wax ester fermentation has only been described in the E. gracilis strain 1224-5/25 Z. Here we investigate eight E. gracilis strains isolated in 1932-1958 from different localities in Europe and two bleached substrains of E. gracilis 1224-5/25, obtained by treatment with streptomycin and ofloxacin, and examine their anaerobic growth, wax ester fermentation, and wax ester composition. Under ambient oxygen levels, all strains accumulated wax esters in concentrations between 0.3% and 3.5% of the dry weight, but the strains revealed marked differences in wax ester accumulation with respect to anaerobic growth. Most fermenting strains tested showed increased wax ester synthesis under anaerobic conditions as well as the increased synthesis of odd-numbered fatty acids and alcohols suggesting an activation of the mitochondrial fatty acid biosynthesis pathway. Addition of the elongase inhibitor flufenacet to the growth medium specifically reduced the accumulation of odd-numbered fatty acids and alcohols and tended to increase the overall yield of anaerobic wax esters.

Occurrence and Carbon Metabolism of Green Nonsulfur-like Bacteria in Californian and Nevada Hot Spring Microbial mats as Revealed by Wax Ester Lipid Analysis

Green nonsulfur-like bacteria (GNSLB) in Yellowstone hot spring microbial mats have been extensively studied and are thought to operate both as photoheterotrophs and photoautotrophs. Here we studied the occurrence and carbon metabolisms of GNSLB by analyzing the distribution and isotopic composition of their characteristic wax ester lipids in four Californian and Nevada hot spring microbial mats at a range of temperatures (37–96°C). The distribution of wax esters varied strongly with temperature. At temperatures between 50–60°C the wax ester composition in each of the four hot spring microbial mats was dominated by C30 to C36 wax esters, consisting of mixtures of C15-C18 n-alkyl and branched fatty acids and alcohols, typical for GNSLB. Stable carbon isotopic analysis showed that these wax esters were only depleted by 5 to 10‰ compared to dissolved inorganic carbon in the overlying water, suggesting that these GNSLB were mainly autotrophic. However, analysis of different depth layers of one microbial mat showed that these GNSLB wax esters were increasingly depleted in 13C with depth, suggesting that photoautotrophy mainly occurred in the top layer of the mat. 13C-depleted C36-C44 wax esters were found in one hot spring at high temperatures (77–96°C) and are likely derived from allochtonous plant waxes. At several lower temperature sites (35–40°C) the wax esters were predominantly composed of C28, C30 and C32 wax esters consisting of mixtures of C14-C16 fatty acids and n-alkanols and were depleted in 13C by 15–20‰ relative to dissolved inorganic carbon, suggesting they may be derived from heterotrophic organisms. Our results indicate that autotrophic GNSLB occur widely in hot springs and that diverse groups of organisms contribute to the pool of wax ester lipids in hot spring environments.

The straight-chain lipid biomarker composition of plant species responsible for the dominant biomass production along two altitudinal transects in the Ecuadorian Andes

For a detailed reconstruction of historic upper forest line (UFL) positions, new proxies in addition to traditional pollen and vegetation analyses are needed. If the straight-chain lipid composition in plant leaves and roots is specific enough to allow distinction, their records in soils and peat bogs might be used for this purpose. We tested for such distinctiveness by analyzing the n-alkane, n-alcohol, n-aldehyde and wax ester composition in lipid extracts from the leaves and roots of the 19 plant species responsible for the dominant biomass input into soils and peat bogs along two altitudinal transects in the Ecuadorian Andes. We found the combined n-alkane and n-alcohol composition of the leaves of the studied plants to be unique enough in theory to allow for a distinction of the various plant species. The extractable straight-chain lipid concentrations in the roots were generally much lower than in the leaves of the same species, and were in many cases less specific. The n-fatty acids, n-aldehydes and wax ester compositions in leaves as well as roots appeared to be less suited as biomarkers, due to a lower specificity of the n-fatty acids and the absence of the n-aldehydes and wax ester from a significant number of plant species. Furthermore, using cluster analysis we found the combination of n-alkanes and n-alcohols from leaves to give the most meaningful clustering from the point of view of an UFL reconstruction, with all but one páramo grassland species and all but one peat bog species clustering separately from forest species. In addition, a large C 31/C 27 n-alkane ratio as well as a large C 26/C 30 n-alcohol ratio were found to be indicative of páramo vegetation (grasses). Both clustering and ratios can help reconstruct past UFL positions if discerning individual species from soil or peat records proves unfeasible. The preservation of the straight-chain lipid signal was tested in soil and peat samples from the study area predating 4910 ± 40 14C years B.P. and 2110 ± 40 14C years B.P., respectively, and found to be excellent.

Submersed Culture Production of Extracellular Wax Esters by the Marine Bacterium Fundibacter jadensis

Fundibacter jadensis strain T9, a marine gram-negative bacterium, was isolated from the intertidal sediment of the German North Sea coast by our group. The cells were able to produce considerable amounts of extracellular wax esters when cultivated with n-alkanes (hexadecane or tetradecane) as a carbon source. The dependence of wax ester production and the composition of the purified wax on different culture conditions (C:N:P ratio and dissolved oxygen tension) were tested. Our results show that wax ester production was not directly growth-linked. The C:N:P ratio had no significant influence on the yield of alkane-free purified wax. The dissolved oxygen tension affected the produced amount of the alkane-free purified wax and the composition of the purified wax; when lower than 2% it decreased the yield of purified wax and led to an altered wax ester composition. Tetradecane as a carbon source enhanced the spectrum of the wax ester composition.

Cuticular hydrocarbons and wax esters of the ectoparasitoid Habrobracon hebetor: Ontogenetic, reproductive, and nutritional effects.

Hydrocarbon and wax ester components of cuticular lipids of the braconid parasitoid Habrobracon hebetor Say reared at 25 degrees C on larvae of a pyralid moth have been identified by GC-MS and analyzed with respect to adult age, mating status, and diet. The hydrocarbons range in carbon number from C(21) to C(45) and consist of a homologous series of n-alkanes, 11-, 13-, and 15-methyl alkanes, 13,17-dimethyl alkanes, and Z-5, Z-7, and Z-9-alkenes. The wax esters found in the cuticular lipid fraction are a series of homologous compounds with the acid portion being short chain, unbranched, even carbon number acids from C(8) to C(20) (predominately C(8) to C(16)). The alcohol portions of the esters are secondary alcohols with carbon number from C(22) to C(25) (predominately C(23) and C(25)) with the hydroxyl function located at C(6), C(7), C(8), and C(9). Gender, age, and nutritional states were significant factors for variation in several of the individual esters, but mating status did not affect wax ester composition. Ontogenetic examinations indicated that prepupal, and early pupal cuticular lipids contain only hydrocarbons. Low levels of wax esters are detectable in late stage pupae, and somewhat greater quantities of wax esters are present on newly eclosed adults. When pharate adults emerge from the cocoon, however, their cuticular lipids consist of approximately equal amounts of hydrocarbons and wax esters, and 6d post emergence from the cocoon, wax esters are the predominant lipid component.

Amount and Composition of Wax Esters in Various Tissue Lipids of Forked Hake Laemonema longipes.

The amounts and compositions of wax esters (WE) in various tissues of the forked hake Laemonema longipes were examined. Liver specimens containing copious amounts of lipids (72.9%) were composed almost entirely of WE (87.4%). Flesh and ovary samples contained small amounts of lipids (0.4% and 1.4%) with lower WE content (1.9 % and 13.1%, respectively). WE in the tissue lipids was found to consist mostly of C38, C36, C40, C34 and C42 components (85.0-90.9%) in the carbon chain lengths. Fatty alcohols originating in WE were essentially monoenoic (89.0-95.1%) with the predominant components being 22:1 (54.0-60.9%) and 20:1 (26.7-28.1%) alcohols. Each of the monoenoic fatty alcohols comprised their isomers, and the more abundant components were 22:1n-11 (49.1-54.8%) and 20:1n-11 (21.1-22.1%) alcohols. Component fatty acids in WE from liver lipids were more monoenoic (71.8%) with 18:1n-9 (20.4%), 22:1n-11 (13.4%) and 16:1n-7 (11.8%) acids. Highly purified WE was separated from liver lipids adsorbed on silicic acid or activated aluminum oxide with n-hexane.

Herpes simplex virus evasion of complement attack

The vertical flux and composition of wax esters, steryl esters, triacylglycerols, and alkyldiacylglycerols in particulate matter was determined in the equatorial Atlantic Ocean by deploying sediment traps at 389, 988, 3,755 and 5,068 m. Detailed compositional analyses of these lipids were carried out by high temperature glass capillary gas chromatography and gas chromatography/mass spectrometry.The distributions of these lipids are discussed in terms of potential biological sources. Zooplankton fecal matter and intact zooplankters may represent the most important input of these compounds to the shallower two traps, while the material in the deeper two traps appears to have been biogeochemically altered. The finding of these biochemically important compounds, often unsaturated, indicates that particle transit through the water column must be relatively fast.Wax esters were most abundant in the 389 m sediment trap and decreased with increasing trap depth. Compounds ranging from C28–C44 were present at all depths. The major homologs were C32, C34 and C36, most often monounsaturated. The dominant alcohol/acid combinations in the 389 m trap were C18:1C14:0 and C18:1C16:0, but in the 988 m sample, C16:0C18:1 was the major wax ester. A flux maximum was observed for steryl esters at 988 m. Cholesteryl esters of C14:0, C16:1 and C16:0, and C18:1C18:0 fatty acids were the dominant steryl esters. For triacylglycerols, fluxes in the 389 and 988 m traps were similar, while the deeper pair of traps contained much less triacylglycerol. C46, C48, C50 and C52 compounds were the major triacylglycerols. Constituent fatty acids in the 389 m and 988 m samples were mainly C14:0, C16:1, C16:0, C18:1 and C18:0. In the 988 m material, C20:5 and C22:6 were also dominant. A homologous series of alkyldiacylglycerols was abundant in the 389 m trap material. The alkyldiacylglycerols consisted of C46–C56 compounds composed of C16:0 alkyl moieties and C14:0, C16:0, C18:1, and C18:0 fatty acids.

Molecular analysis of intact preen waxes of Calidris canutus (Aves: Scolopacidae) by gas chromatography/mass spectrometry.

The intact preen wax esters of the red knot Calidris canutus were studied with gas chromatography/mass spectrometry (GC/MS) and GC/MS/MS. In this latter technique, transitions from the molecular ion to fragment ions representing the fatty acid moiety of the wax esters were measured, providing additional resolution to the analysis of wax esters. The C21-C32 wax esters are composed of complex mixtures of hundreds of individual isomers. The odd carbon-numbered wax esters are predominantly composed of even carbon-numbered n-alcohols (C14, C16, and C18) esterified predominantly with odd carbon-numbered 2-methyl fatty acids (C7, C9, C11, and C13), resulting in relatively simple distributions. The even carbon-numbered wax esters show a far more complex distribution due to a number of factors: (i) Their n-alcohol moieties are not dominated by even carbon-numbered n-alcohols esterified with odd carbon-numbered 2-methyl fatty acids, but odd and even carbon-numbered n-alcohols participate in approximately equal amounts; (ii) odd carbon-numbered methyl-branched alcohols participate abundantly in these wax ester clusters; and (iii) with increasing molecular weight, various isomers of the 2,6-, 2,8-, and 2,10-dimethyl branched fatty acids also participate in the even carbon-numbered wax esters. The data demonstrate that there is a clear biosynthetic control on the wax ester composition although the reasons for the complex chemistry of the waxes are not yet understood.

Amount and Composition of Wax Esters in Salted and Dried Roe from Mullet of Australia

The amounts and compositions of wax esters (WE) of salted roe and salted and dried roe ('Karasumi') of the mullet, Mugil cephalus, caught in Australia were examined. Both salted and salted and dried roes contained large amounts of lipids (TL : 30.631.6% of dry weight) comprised almost entirely of WE (82.884.3%) consisting mainly of C32 and C34 components (53.161.1%) Fatty alcohols originating from WE were essentially saturated (83.586.4%) with the predominant component of 16 : 0 alcohol (59.363.4%). Each of monoenoic fatty alcohols (11.915.0%) comprised their isomers and the most abundant component was 16 : 1n-7 alcohol (5.89.2%). Appreciable amounts of odd chain fatty alcohols with 15 : 0 alcohol (3.1-12.0%) were also present. Component fatty acids in WE were more monoenoic (56.160.6%) with 16 : 1n-7 acid (34.038.8%) and polyenoic (26.631.1%) with 20 : 5n-3, 22 : 5n-3 and 22 : 6n-3 acids. Among triacylglycerols, 16 : 0 (32.934.6%), 16 : 1n-7 (16.622.5%) and 18 : 1n-7 (7.88.7%) acids were characteristic. No oxidation of polyenoic fatty acids in different lipid classes of salted and dried roe of mullet could be detected.

Epicuticular wax ester and triacylglycerol composition in relation to aphid infestation and resistance in red raspberry ( Rubus idaeus L.)

Epicuticular waxes from two cultivars of red raspberry ( Rubus idaeus) were collected from the newly emerging crown leaves, and also from the group of four more mature leaves immediately below the crown. One cultivar, Autumn Bliss, was identified as aphid-resistant, and the other, Malling Jewel, as aphid-susceptible following bioassay with the large raspberry aphid, Amphorophora idaei, just prior to collection of the wax. Biological activity was primarily associated with the more mature leaves. Epicuticular wax esters consisted predominantly of long-chain aliphatic compounds in which even-carbon-number acids were esterified to even-carbon-number alcohols. Lesser amounts of odd-carbon-number esters were also present. The acid : alcohol combinations of the major esters were C 38: 14 : 24, 16 : 22, 20 : 18; C 40: 14 : 26, 16 : 24, 18 : 22, 20 : 20; C 42: 16 : 26, 20 : 22; 22 : 20, C 44: 20 : 24, 22 : 22, 24 : 20; C 46: 20 : 26, 22 : 24, 24 : 22; C 48: 20 : 28, 22 : 26, 24 : 24, 26 : 22; C 50: 20 : 30, 22 : 28, 24 : 26, 26 : 24, 28 : 22 and C 52: 22 : 30, 24 : 28, 26 : 26. Terpenyl esters were also present and these consisted of α- and β-amyrin and cycloartenol esterified to C 16, C 18 and C 20 acids. Compositional differences between the more mature leaves which may relate to resistance to A. idaei were higher levels of cycloartenyl esters and α-amyryl esters in wax from the resistant cultivar Bliss. There were also differences between the cultivars in the distribution of individual alkyl esters and their component acids and alcohols. Esters with longer acid : shorter alcohol combinations were more abundant in Jewel than Bliss. There were compositional differences between leaves at the different developmental stages. Alkyl esters were more abundant and cycloartenyl esters were not detected in wax from the immature leaves. Small amounts of an unusual class of triacylglycerol were found only on leaves of the aphid-susceptible cultivar, Jewel, which had been subject to bioassay with raspberry aphid. These compounds, which have a C 6 acid at C-2 of the glycerol backbone, were derived from the aphid, and are the major component in the insect’s cornicle secretions. The triacylglycerols probably arise from the presence on the leaf surface of shed aphid skins, or by incorporation of cornicle fluid into the leaf wax. The abundance of aphid triacylglycerols on the leaf surface may provide a measure of aphid-susceptibility.