Waxy Esters Research Articles

Biowaxes from Palm Oil as Promising Candidates for Cosmetic Matrices and Pharmaceuticals for Human Use.

The production of waxes from vegetable oils, such as palm oil, for use as a base material in products for human applications is an alternative to those derived from petroleum and animals. Seven palm oil-derived waxes, called biowaxes (BW1-BW7) in this work, were obtained by catalytic hydrotreating of refined and bleached African palm oil and refined palm kernel oil. They were characterized by three properties: compositional, physicochemical (melting point, penetration value, and pH), and biological (sterility, cytotoxicity, phototoxicity, antioxidant, and irritant). Their morphologies and chemical structures were studied by SEM, FTIR, UV-Vis, and 1H NMR. The BWs presented structures and compositions similar to natural biowaxes (beeswax and carnauba). They had a high concentration of waxy esters (17%-36%) with long alkyl chains (C, 19-26) per carbonyl group, which are related to high melting points (<20-47.9 °C) and low penetration values (2.1-3.8 mm). They also proved to be sterile materials with no cytotoxic, phototoxic, antioxidant, or irritant activity. The biowaxes studied could be used in cosmetic and pharmacological products for human use.

Biowax Production from the Hydrotreatment of Refined Palm Oil (RPO)

In this study, conditions were determined to obtain a solid wax with a waxy ester content of more than 25% from the hydrotreating of palm oil. The experiments were conducted in a pilot-scale fixed-bed reactor. The influence of temperature, liquid hourly space velocity (LHSV), and pressure on the conversion of triglycerides were evaluated using a nickel molybdenum catalyst (NiMo/Al2O3). The variables were evaluated between 240 and 260 °C, 1 and 2 h−1 and 41 and 55 bar, respectively. Based on these results, the best conditions were T:240–260 °C; P: 90 bar; LHSV: 1.5 h−1; hydrogen/oil ratio 472 LN/L with a conversion around 60 wt%; and a selectivity towards waxy esters of 40 wt%. These conditions were then validated with a second catalyst (NiMoB/Al2O3), yielding a triglyceride conversion of about 60 wt% and a waxy ester concentration of around 30 wt%.

Application of Thin-Layer Chromatography-Flame Ionization Detection (TLC-FID) to Total Lipid Quantitation in Mycolic-Acid Synthesizing Rhodococcus and Williamsia Species.

In addition to cell membrane phospholipids, Actinobacteria in the order Corynebacteriales possess a waxy cell envelope containing mycolic acids (MA). In optimized culture condition, some species can also accumulate high concentrations of intracellular triacylglycerols (TAG), which are a potential source of biodiesel. Bacterial lipid classes and composition alter in response to environmental stresses, including nutrient availability, thus understanding carbon flow into different lipid classes is important when optimizing TAG synthesis. Quantitative and qualitative analysis of lipid classes normally requires combinations of different extraction, derivatization, chromatographic and detection methods. In this study, a single-step thin-layer chromatography-flame ionization detection (TLC-FID) technique was applied to quantify lipid classes in six sub-Antarctic Corynebacteriales strains identified as Rhodococcus and Williamsia species. A hexane:diethyl-ether:acetic acid solvent system separated the total cellular lipids extracted from cells lysed by bead beating, which released more bound and unbound MA than sonication. Typical profiles included a major broad non-polar lipid peak, TAG and phospholipids, although trehalose dimycolates, when present, co-eluted with phospholipids. Ultra-performance liquid chromatography-tandem mass-spectrometry and nuclear magnetic resonance spectroscopy detected MA signatures in the non-polar lipid peak and indicated that these lipids were likely bound, at least in part, to sugars from cell wall arabinogalactan. Waxy esters were not detected. The single-solvent TLC-FID procedure provides a useful platform for the quantitation and preliminary screening of cellular lipid classes when testing the impacts of growth conditions on TAG synthesis.

The Role of Diet in Shaping the Chemical Signal Design of Lacertid Lizards.

Lizards communicate with others via chemical signals, the composition of which may vary among species. Although the selective pressures and constraints affecting chemical signal diversity at the species level remain poorly understood, the possible role of diet has been largely neglected. The chemical signals of many lizards originate from the femoral glands that exude a mixture of semiochemicals, and may be used in a variety of contexts. We analyzed the lipophilic fraction of the glandular secretions of 45 species of lacertid lizard species by gas chromatography/mass spectrometry. The proportions of nine major chemical classes (alcohols, aldehydes, fatty acids, furanones, ketones, steroids, terpenoids, tocopherols and waxy esters), the relative contributions of these different classes ('chemical diversity'), and the total number of different lipophilic compounds ('chemical richness') varied greatly among species. We examined whether interspecific differences in these chemical variables could be coupled to interspecific variation in diet using data from the literature. In addition, we compared chemical signal composition among species that almost never, occasionally, or often eat plant material. We found little support for the hypothesis that the chemical profile of a given species' secretion depends on the type of food consumed. Diet breadth did not correlate with chemical diversity or richness. The amount of plants or ants consumed did not affect the relative contribution of any of the nine major chemical classes to the secretion. Chemical diversity did not differ among lizards with different levels of plant consumption; however, chemical richness was low in species with an exclusive arthropod diet, suggesting that incorporating plants in the diet enables lizards to increase the number of compounds allocated to secretions, likely because a (partly) herbivorous diet allows them to include compounds of plant origin that are unavailable in animal prey. Still, overall, diet appears a relatively poor predictor of interspecific differences in the broad chemical profiles of secretions of lacertid lizards.

Variations in chemical sexual signals of Psammodromus algirus lizards along an elevation gradient may reflect altitudinal variation in microclimatic conditions.

Chemical signals used in intraspecific communication are expected to evolve or to show phenotipic plasticity to maximize efficacy in the climatic conditions of a given environment. Elevational environmental gradients in mountains provide a good opportunity to test this hypothesis by examining variation in characteristics of signals in species found across different elevations with different climatic conditions. We analyzed by gas chromatography-mass spectrometry (GC-MS) the lipophilic fraction of the femoral gland secretions of male lizards Psammodromus algirus (Fam. Lacertidae) from six localities located along a 2200m elevational gradient at Sierra Nevada Mountains (SE Spain). There was elevational clinal variation in climatic variables, number of femoral pores and in the relative proportions of some classes of compounds (i.e., ethyl esters of fatty acids, waxy esters, and aldehydes) but not others. We discuss how this variation would result in different physicochemical properties of the entire femoral secretion, which might help optimize the efficacy of chemical signals under the particular microclimatic conditions at each elevation.

Genders matters: Sexual differences in chemical signals of Liolaemus wiegmannii lizards (Iguania, Liolaemidae)

Males have traditionally been the focus of study when analyzing traits involved in communication. However, intraspecific interactions often imply both sexes as signals senders. Researches have shown the relevant role that chemical communication plays in lizards. However, the knowledge about the female scents is scarce. The aim of this paper is to characterize, by using gas chromatography-mass spectrometry (GC-MS), the lipophilic fraction of precloacal gland secretions of adult males and females of the lizard Liolaemus wiegmannii and evaluate intersexual differences in composition and proportion of their chemical profiles. We identified 48 and 41 lipohilic compounds in males and females, respectively. The main compounds were steroids and waxy esters. We also found squalene, alcohols, aldehydes and carboxylic acids. Overall, we found significant differences between sexes with respect to the relative proportions of compounds. We also found differences in proportions of three of the five predominant compounds shared by both sexes (squalene, cholesta-3,5-dien and cholesta-2,4-dien). Our study describes that females of L. wiegmannii hold lipids in their precloacal secretions, which are further clearly different from those of males. Further researches are needed to understand the ecological implications of these sexual differences in precloacal secretion of L. wiegmannii.

Rapid Oxidation of Skin Oil by Ozone

The reaction of gas-phase ozone with human skin oil has been studied at room temperature. Skin oil was exposed to ozone at mixing ratios similar to those in the ambient environment and then analyzed for condensed-phase products using direct analysis in real time mass spectrometry (DART-MS). Prior to ozone exposure, skin oil gives rise to prominent mass spectral signals indicative of highly unsaturated alkenes, sterols, triglycerides, long-chain fatty acids, pyroglutamic acid, and probably waxy esters. Upon oxidation with 50 ppb ozone for 90 min, there is a rapid loss of alkene, fatty acid, and triglyceride signals resulting from efficient multiphase ozonolysis. Oxygenated products, including a variety of carboxylic acids, are identified via studies with pure compounds present in skin oil, i.e., squalene, cholesterol, and triolein. The chemistry is rapid, occurring on time scales of tens of minutes, implying that these highly oxygenated reaction products are always present on human skin both indoors and ou...

Interspecific differences in chemical composition of femoral gland secretions between two closely related wall lizard species, Podarcis bocagei and Podarcis carbonelli

Chemical signals play an important role in intraspecific communication and social organization of many animals, but they also may be useful in interspecific recognition. In lizards, chemical signals are often contained in femoral gland secretions, of which composition may vary between species and populations. This may be especially important in recognition and reproductive isolation between closely related species. We analyzed by gas chromatography–mass spectrometry (GC–MS) the lipophilic fraction of femoral gland secretions of two closely related wall lizard species, Podarcis bocagei and Podarcis carbonelli to test for possible interspecific differences in chemical composition. We found 56 lipophilic compounds in femoral gland secretions of male P. bocagei and 60 in P. carbonelli. The main compounds were steroids and waxy esters, but we also found carboxylic acids and their esters, alcohols, amydes, aldehydes, squalene, ketones and furanones. There were significant differences between species with respect to the number and relative proportions of compounds. Differences in chemical composition might be a consequence of phylogenetic differences per se, but they could also be explained by ecological adaptation to different microclimatic conditions. These differences in chemical profiles may explain the known chemosensory interspecific recognition between these two lizards, contributing to their reproductive isolation.

Lipophilic compounds in femoral secretions of males and females of the El Hierro giant lizard Gallotia simonyi (Lacertidae)

Many lizards use femoral gland secretions in reliable intraspecific communication. Based on mass spectra, obtained by GC–MS, we found 57 lipophilic compounds in femoral secretions of males and females of El Hierro giant lizards, Gallotia simonyi (fam. Lacertidae). Compounds included steroids (mainly cholesterol) and fatty acids ranging between n-C16 and n-C22 (mainly hexadecanoic and octadecanoic acids), followed by aldehydes, alcohols, ketones, squalene and waxy esters. There were important intersexual differences in the presence, abundance and number of compounds (more numerous in males). Males had higher proportions of the most odoriferous compounds (fatty acids and aldehydes), while females had higher proportions of more stable compounds (steroids, waxy alcohols, waxy esters and terpenoids). This suggests sexual differences in function of femoral secretions. In addition, some compounds could reflect the physiological state, allowing monitoring health of lizards from secretions samples, which is especially important given the critical conservation status of this lizard.

Influence of lipid coatings on surface wettability characteristics of silicone hydrogels.

Insoluble lipids serve vital functions in our bodies and interact with biomedical devices, e.g., the tear film on a contact lens. Over a period of time, these naturally occurring lipids form interfacial coatings that modify the wettability characteristics of these foreign synthetic surfaces. In this study, we examine the deposition and consequences of tear film lipids on silicone hydrogel (SiHy) contact lenses. We use bovine meibum, which is a complex mixture of waxy esters, cholesterol esters, and lipids that is secreted from the meibomian glands located on the upper and lower eyelids of mammals. For comparison, we study two commercially available model materials: dipalmitoylphosphatidylcholine (DPPC) and cholesterol. Upon deposition, we find that DPPC and meibum remain closer to the SiHy surface than cholesterol, which diffuses further into the porous SiHy matrix. In addition, we also monitor the fate of unstable thin liquid films that consequently rupture and dewet on these lipid-decorated surfaces. This dewetting provides valuable qualitative and quantitative information about the wetting characteristics of these SiHy substrates. We observe that decorating the SiHy surface with simple model lipids such as DPPC and cholesterol increases the hydrophilicity, which consequently inhibits dewetting, whereas meibum behaves conversely.

Lubricating and Waxy Esters. VI. Effect of Symmetry about Ester on Crystallization of Linear Monoester Isomers

The crystal structure development of jojoba-like esters incorporating either 1-decenoic acid and/or 1-decenol, namely octadec-9-enyl dec-9-enoate (JLE-281), and its isomer dec-9-enyl oleate (JLE-282) was investigated to reveal the effect of symmetry about the ester group on crystallization of aliphatic fatty monoesters. The phase transformation path was investigated with temperature-time resolved X-ray diffraction during stepped isothermal crystallization, and while cooling from the melt at a fixed rate. Startling differences in phase behavior were uncovered between the isomers. When stepped isothermals were used, selective extinctions occurred at a transition temperature for JLE-281 but not for JLE-282. The extinctions, which are due to dramatic changes in the electronic density of certain families of planes, indicate a phase transition attributed to a brusque rearrangement of the oxygen atoms in the crystal subcell. The phase transition did not occur when the JLEs were cooled continuously. The crucial role played by the position of the alkyl chain and its orientation relative to the easy rotation site of the C–O bond in the phase trajectories of the JLEs was particularly highlighted.

Chemical Compounds from the Preanal Gland Secretions of the Male Tree Agama (Acanthocercus atricollis) (Fam. Agamidae)

Chemical signals have an important role in the reproductive behaviour of many lizards. However, the compounds secreted by their femoral or preanal glands, which may be used as sexual signals, are mainly known for lizard species within the Scleroglossa clade, whereas compounds in secretions of lizards within the Iguania clade are much less studied. Based on mass spectra, obtained by GC-MS, we found 60 lipophilic compounds in preanal gland secretions of the male tree agama (Acanthocercus atricollis) (fam. Agamidae), including steroids (mainly cholesterol, cholest-3-ene, and some of their derivatives), fatty acids ranging between n-C12 and n-C18 (mainly hexadecanoic and octadecenoic acids), ketones from n-C17 to n-C25, and other minor compounds, such as tocopherol, squalene, waxy esters, and furanones. We compare the compounds found with those present in other lizard species and discuss their potential function in social behaviour

Inter-island variation in femoral secretions of the Balearic lizard, Podarcis lilfordi (Lacertidae)

Many lizards use femoral gland secretions in intraspecific communication. Although there is a consistent interspecific variation in chemical composition of secretions, considerable variation is also often found between populations, which may affect conspecifc recognition and lead to speciation processes. Balearic lizards (Podarcis lilfordi) are currently distributed only in several isolated islets offshore of the main islands with different environmental conditions (vegetation, diet, density of population, etc). Also, there is a high genetic variability between populations. We examined whether there was a similar variation in the composition of the femoral secretions of male lizards, and which could be the causes of such variation. By using GC–MS analyses, we found 75 lipophilic compounds in femoral gland secretions of male P. lilfordi from three representative island populations. Main compounds were steroids (94.4%), mainly cholesterol, but we also found alkanes, ketones, waxy esters, squalene, carboxylic acids and their ethyl esters, alcohols and other minor compounds. However, there were clear differences between populations with respect to the number and relative proportions of compounds. Using the patterns of presence and abundance of compounds in secretions it is possible to predict the population of origin of a lizard. We discuss how these differences could be explained considering genetic and environmental differences between populations.

Lubricating and Waxy Esters. 4. Synthesis, Crystallization Behavior, Melt Behavior, and Flow Behavior of Linear Monoesters Incorporating 9-Decenol and 9-Decenoic Acid

Three pure jojoba wax-like esters (JLEs), i.e., octadec-9-enyl dec-9-enoate (JLE 281), dec-9-enyl oleate (JLE 282), and dec-9-enyl dec-9-enoate (JLE-20), were synthesized from fatty acids and fatty alcohols. Calorimetric, solid fat content evolution, and flow data were used to elucidate the phase behavior of the JLEs. It was clearly established that the length of the terminal alkyl chain and orientation of the linking group in the side chains of the bent-core molecules play an important role in the phase development of the JLEs and ultimately their physical properties. Measurable differences in all physical properties investigated were detected between the isomers based on the position of the ester group in the molecule, leading to informed choices on what isomer should be synthesized for similar monoesters for specific applications.

Chemical Compounds from the Preanal Gland Secretions of the Male Tree Agama (Acanthocercus atricollis) (Fam. Agamidae)

Chemical signals have an important role in the reproductive behaviour of many lizards. However, the compounds secreted by their femoral or preanal glands, which may be used as sexual signals, are mainly known for lizard species within the Scleroglossa clade, whereas compounds in secretions of lizards within the Iguania clade are much less studied. Based on mass spectra, obtained by GC-MS, we found 60 lipophilic compounds in preanal gland secretions of the male tree agama (Acanthocercus atricollis) (fam. Agamidae), including steroids (mainly cholesterol, cholest-3-ene, and some of their derivatives), fatty acids ranging between n-C12 and n-C18 (mainly hexadecanoic and octadecenoic acids), ketones from n-C17 to n-C25, and other minor compounds, such as tocopherol, squalene, waxy esters, and furanones. We compare the compounds found with those present in other lizard species and discuss their potential function in social behaviour.

Lipophilic compounds in femoral secretions of male collared lizards, Crotaphytus bicinctores (Iguania, Crotaphytidae)

Abstract In many lizards, chemical compounds from the femoral gland secretions are used in intraspecific communication, but most studies describing these chemicals are for lizard species included in the Scleroglossa clade, whereas lizards within the Iguanian clade have been much less studied, probably because these lizards were considered to rely more on visual cues. However, many iguanian lizards have abundant femoral secretions and are able of chemosensory conspecific recognition, which might be based on compounds secreted by femoral glands. By using GC–MS analyses, we found 58 lipophilic compounds in femoral gland secretions of male Great Basin collared lizard, Crotaphytus bicinctores (Iguania, Crotaphytidae). Main compounds were steroids (mainly two triunsaturated steroids and cholesterol), carboxylic acids (mainly hexadecanoic acid), waxy esters of long chain fatty acids, alcohols (mainly hexadecanol), aldehydes and other minor compounds. We compared these compounds with those found in other lizard species and discussed the potential signaling function of some compounds and how the xeric habitat of this lizard could have conditioned the composition of secretions.

Lubricating and Waxy Esters II: Synthesis, Crystallization, and Melt Behavior of Branched Monoesters

A comprehensive study of branched derivatives of four pure jojoba wax-like esters (JLEs), having 36, 40 (two isomers), and 44 carbons was conducted to elucidate their crystallization and melting behavior. Crystallization and melting characteristics depended strongly on the number of branches, molar mass, and symmetry. The derivatives demonstrated a very strong tendency to form glassy liquids rather than crystal phases and remain liquid-like at very low temperatures. As the number of branches increased, their crystallinity decreased drastically while their glassy phase increased concomitantly with the depression of the onset of crystallization and/or glass transition temperature. A variety of possible transformation paths, ranging from very little polymorphic activity to extremely polymorphic behavior, depending on number of branches, mass, and symmetry were revealed. It is shown that asymmetry plays a large role in the low temperature behavior, rendering the branched derivatives of the asymmetrical JLEs much better candidates for lubricant formulations.

Lubricating and waxy esters, I. Synthesis, crystallization, and melt behavior of linear monoesters

Four pure jojoba wax-like esters (JLEs), having carbon chain length of 36, 40 (two isomers) and 44, were prepared by Steglish esterification of fatty acids (or acid chlorides) with fatty alcohols at room temperature. Calorimetric and diffraction data was used to elucidate the phase behavior of the esters. The primary thermal parameters (crystallization and melting temperatures) obtained from the DSC of the symmetrical molecules correspond well with the carbon numbers of the JLEs. However, the data also suggests that carbon number is not the only factor since the symmetry of the molecule also plays a significant role in the phase behavior. Overall, the JLEs show very little polymorphic activity at the experimental conditions used, suggesting that they are likely to transform the same way during melting as well as crystallization, a characteristic which may be useful in designing new waxes and lubricants. The XRD data clearly show that the solid phase in all samples consists of a mixture of a β-phase and a β′-phase; fully distinguishable by their characteristic diffraction peaks. Subtle differences between the subcell patterns and phase development of the samples were observed. Different layering of the samples was also observed, understandably because of the chain length differences between the compounds. The long spacings were perfectly linearly proportional to the number of carbon atoms. The length of the ester layers with n carbon atoms can be calculated by a formula similar to that used for the layers in linear alkane molecules.

Behaviour of Volatile Compounds During Traditional Alembic Distillation of Fermented Muscat Blanc and Muškat Ruža Porečki Grape Marcs

J. Inst. Brew. 117(3), 440–450, 2011 To investigate the behaviour of volatile compounds during a traditional alembic distillation, large numbers of important volatile compounds were identified and quantified by GC/MS and GC/FID analysis in different fractions of grape marc distillates made from two Muscat varieties. Generally, concentrations of terpenes, C13-norisoprenoids, acids and particular waxy esters and aldehydes were found to increase, while concentrations of higher alcohols and the majority of fruity and flowery esters were found to decrease during distillation. Because of the abundance in odoriferous monoterpenes, utilization of the tail fraction as a raw material for re-distillation was considered appropriate.

Differences in chemical signals may explain species recognition between an island lizard, Podarcis atrata, and related mainland lizards, P. hispanica

Chemical signals can be the basis of interspecific recognition and speciation in many animals. The Columbretes Islands wall lizard, Podarcis atrata is very close genetically to the mainland Iberian wall lizard Podarcis hispanica. However, a previous study suggested that chemosensory interspecific recognition would avoid reproductive interactions and hybridization between these two species. These results suggested that chemicals used in intraspecific communication might differ in composition and/or proportions between these two species. In this paper, we used gas chromatography–mass spectrometry (GC–MS) to characterize the chemical composition of the lipophilic fraction from femoral gland secretions of male P. atrata and P. hispanica. The analysis showed that chemicals found in femoral secretions varied in composition and proportions between species and between populations. Seven steroids and two unidentified waxy esters, were exclusive of P. atrata lizards from the islands. In contrast, nine steroids and other six compounds were only found in mainland P. hispanica. There were also differences in proportions of shared compounds between species. Moreover, all these differences were higher between P. atrata and P. hispanica than between any population of P. hispanica. Chemical differences might be consequence of genetic differences, but they could also be explained by adaptation to different habitats with different climatic conditions or diet resources. Compounds that are specific of each species, or differences in the pattern of compounds, could explain species recognition. Therefore, these results of chemical composition and previous studies of chemosensory recognition reinforce the fact that the genetic differences between P. hispanica and P. atrata may result in an effective reproductive isolation between these two taxa.