Identification of long-chain fatty acids and alcohols from human cerumen by the use of picolinyl and nicotinate esters

Mass Spectrometric Interrogation of Earwax: Toward the Detection of Ménière's Disease

Many diseases remain difficult to identify because the occurrence of characteristic biomarkers within traditional matrices such as blood and urine remain unknown. Disease diagnosis could, therefore, benefit from the analysis of readily accessible, non-traditional matrices that have a high chemical content and contain distinguishing biomarkers. One such matrix is cerumen (i.e., earwax), whose chemical complexity can pose challenges when analyzed by conventional methods. A combination of cerumen chemical profiles analyzed by gas chromatography-mass spectrometry (GC-MS) and direct analysis in real time-high-resolution mass spectrometry (DART-HRMS) were investigated to ascertain the possible presence of the rare otolaryngological disorder Ménière's disease. This illness is currently identified via "diagnosis by exclusion" in which the disease is distinguished from others with overlapping symptoms by the process of elimination. GC-MS revealed a chemical profile difference between those with and without a Ménière's disease diagnosis by a visually apparent diminution of the compounds present in the Ménière's disease samples. DART-HRMS revealed that the two classes could be differentiated using three fatty acids: cis-9-hexadecenoic acid, cis-10-heptadecenoic acid, and cis-9-octadecenoic acid. These compounds were subsequently quantified by GC-MS and overall, the amounts of these fatty acids were decreased in Ménière's disease patients. The average levels for non-Ménière's disease samples were 7.89 μg/mg for cis-9-hexadecenoic acid, 0.87 μg/mg for cis-10-heptadecenoic acid, and 4.94 μg/mg for cis-9-octadecenoic acid. The average levels for Ménière's disease samples were 1.70 μg/mg for cis-9-hexadecenoic acid, 0.13 μg/mg for cis-10-heptadecenoic acid, and 2.07 μg/mg for cis-9-octadecenoic acid. The confidence levels for cis-9-hexadecenoic acid, cis-10-heptadecenoic acid, and cis-9-octadecenoic acid were 98.7%, 99.9%, and 95.4%, respectively. The results suggest that assessment of the concentrations of these fatty acids could be a useful clinical tool for the more rapid and accurate detection of Ménière's disease.

Therapeutic efficacy of n-Docosanol against velogenic Newcastle disease virus infection in domestic chickens

INTRODUCTION

The control of Newcastle disease virus (NDV) infection depends solely on vaccination which in most cases is not sufficient to restrain the consequences of such a highly evolving viral disease. Finding out substances for preparing an efficient anti-ND drug would be of high value. n-Docosanol is a saturated fatty alcohol with an inhibitory effect against many enveloped viruses. In this study, we evaluated the therapeutic effect of n-docosanol on NDV infection and shedding in chickens.

METHODS

Chickens infected with a highly virulent NDV were treated with low to high concentrations of n-docosanol (20, 40, and 60 mg/kg body weight) for 4-successive days, once they showed the disease symptoms. Survival and curative rates, virus load, histopathological scoring, and virus shedding were defined.

RESULTS

Symptoms development was found to discontinue 24-72 hours post-treatment. Survival rate in the NDV-infected chickens raised 37.4-53.2% after the treatment. n-Docosanol treatment was also found to significantly reduce virus load in the digestive (26.2-33.9%), respiratory (38.3-63%), nervous (26.7-51.1%), and lymphatic (16.4-29.1%) tissues. Histopathological scoring of NDV lesions revealed prominent rescue effects on the histology of different tissues. Importantly, n-docosanol treatment significantly reduced virus shedding in oropharyngeal discharge and feces thereby allowing the restriction of NDV spread.

CONCLUSION

Our findings suggest n-docosanol as a promising remedy in the control strategy of Newcastle disease in the poultry industry.

Two-Dimensional Gas Chromatographic and Mass Spectrometric Characterization of Lipid-Rich Biological Matrices-Application to Human Cerumen (Earwax)

Earwax is a readily accessible biological matrix that has the potential to be used in disease diagnostics. However, its semisolid nature and high chemical complexity have hampered efforts to investigate its potential to reveal disease markers. This is because more conventional methods of analysis such as gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry yield unsatisfactory results due to the presence of many nonvolatile and/or coeluting compounds, which in some cases have very similar mass spectrometric profiles. In addition, these routine methods often require the sample to be saponified, which dramatically increases the complexity of the analysis and makes it difficult to determine which compounds are actually present versus those that are produced by saponification. In this study, two-dimensional GC mass spectrometry (GC × GC-MS) was successfully applied for the characterization of the chemical components of earwax from healthy donors using nonpolar (primary) and midpolar (secondary) columns without saponification. Over 35 of the compounds that were identified are reported for the first time to be detected in unsaponified earwax. The resulting GC × GC-MS contour plots revealed visually recognizable compound class clusters of previously reported groups including alkanes, alkenes, fatty acids, esters, triglycerides, and cholesterol esters, as well as cholesterol and squalene. The application of GC × GC-MS revealed results that provide a foundation upon which future studies aimed at comparing healthy donor earwax to that from individuals exhibiting various disease states can be accomplished.

Polyunsaturated fatty acids cause physiological and behavioral changes in Vibrio alginolyticus and Vibrio fischeri

Vibrio alginolyticus and Vibrio (Aliivibrio) fischeri are Gram-negative bacteria found globally in marine environments. During the past decade, studies have shown that certain Gram-negative bacteria, including Vibrio species (cholerae, parahaemolyticus, and vulnificus) are capable of using exogenous polyunsaturated fatty acids (PUFAs) to modify the phospholipids of their membrane. Moreover, exposure to exogenous PUFAs has been shown to affect certain phenotypes that are important factors of virulence. The purpose of this study was to investigate whether V. alginolyticus and V. fischeri are capable of responding to exogenous PUFAs by remodeling their membrane phospholipids and/or altering behaviors associated with virulence. Thin-layer chromatography (TLC) analyses and ultra-performance liquid chromatography-electrospray ionization mass spectrometry (UPLC/ESI-MS) confirmed incorporation of all PUFAs into membrane phosphatidylglycerol and phosphatidylethanolamine. Several growth phenotypes were identified when individual fatty acids were supplied in minimal media and as sole carbon sources. Interestingly, several PUFAs acids inhibited growth of V. fischeri. Significant alterations to membrane permeability were observed depending on fatty acid supplemented. Strikingly, arachidonic acid (20:4) reduced membrane permeability by approximately 35% in both V. alginolyticus and V. fischeri. Biofilm assays indicated that fatty acid influence was dependent on media composition and temperature. All fatty acids caused decreased swimming motility in V. alginolyticus, while only linoleic acid (18:2) significantly increased swimming motility in V. fischeri. In summary, exogenous fatty acids cause a variety of changes in V. alginolyticus and V. fischeri, thus adding these bacteria to a growing list of Gram-negatives that exhibit versatility in fatty acid utilization and highlighting the potential for environmental PUFAs to influence phenotypes associated with planktonic, beneficial, and pathogenic associations.

Identification of volatile organic compounds in human cerumen

We report here the initial examination of volatile organic compounds (VOCs) emanating from human earwax (cerumen). Recent studies link a single nucleotide polymorphism (SNP) in the adenosine triphosphate (ATP) binding cassette, sub-family C, member 11 gene (ABCC11) to the production of different types of axillary odorants and cerumen. ABCC11 encodes an ATP-driven efflux pump protein that plays an important function in ceruminous apocrine glands of the auditory canal and the secretion of axillary odor precursors. The type of cerumen and underarm odor produced by East Asians differ markedly from that produced by non-Asians. In this initial report we find that both groups emit many of the same VOCs but differ significantly in the amounts produced. The principal odorants are volatile organic C2-to-C6 acids. The physical appearance of cerumen from the two groups also matches previously reported ethnic differences, viz., cerumen from East Asians appears dry and white while that from non-Asians is typically wet and yellowish-brown.

A practical synthesis of long-chain iso-fatty acids (iso-C12-C19) and related natural products

A gram-scale synthesis of terminally-branched iso-fatty acids (iso-C₁₂–C₁₉) was developed commencing with methyl undec-10-enoate (methyl undecylenate) (for iso-C₁₂–C₁₄) or the C₁₅ and C₁₆ lactones pentadecanolide (for iso-C₁₅–C₁₇) and hexadecanolide (for iso-C₁₈–C₁₉). Central to the approaches outlined is the two-step construction of the terminal isopropyl group through addition of methylmagnesium bromide to the ester/lactones and selective reduction of the resulting tertiary alcohols. Thus, the C₁₂, C₁₇ and C₁₈ iso-fatty acids were obtained in three steps from commercially-available starting materials, and the remaining C₁₃–C₁₆ and C₁₉ iso-fatty acids were prepared by homologation or recursive dehomologations of these fatty acids or through intercepting appropriate intermediates. Highlighting the synthetic potential of the iso-fatty acids and various intermediates prepared herein, we describe the synthesis of the natural products (S)-2,15-dimethylpalmitic acid, (S)-2-hydroxy-15-methylpalmitic acid, and 2-oxo-14-methylpentadecane.

Structural characterization of saturated branched chain fatty acid methyl esters by collisional dissociation of molecular ions generated by electron ionization

Saturated branched chain fatty acids (BCFA) are present as complex mixtures in numerous biological samples. The traditional method for structure elucidation, electron ionization (EI) mass spectrometry, sometimes does not unambiguously enable assignment of branching in isomeric BCFA. Zirrolli and Murphy (Zirrolli , J. A. , and R. A. Murphy. 1993. Low-energy tandem mass spectrometry of the molecular ion derived from fatty acid methyl esters: a novel method for analysis of branched-chain fatty acids. J. Am. Soc. Mass Spectrom. 4: 223-229.) showed that the molecular ions of four BCFA methyl ester (BCFAME) yield highly characteristic fragments upon collisional dissociation using a triple quadrupole instrument. Here, we confirm and extend these results by analysis using a tabletop 3-D ion trap for activated molecular ion EI-MS/MS to 30 BCFAME. iso-BCFAME produces a prominent ion (30-100% of base peak) for [M-43] (M-C₃H₇), corresponding to the terminal isopropyl moiety in the original iso-BCFAME. Anteiso-FAME yield prominent ions (20-100% of base peak) corresponding to losses on both side of the methyl branch, [M-29] and [M-57], and tend to produce more prominent m/z 115 peaks corresponding to a cyclization product around the ester. Dimethyl and tetramethyl FAME, with branches separated by at least one methylene group, yield fragment on both sides of the sites of methyl branches that are more than 6 C away from the carboxyl carbon. EI-MS/MS yields uniquely specific ions that enable highly confident structural identification and quantification of BCFAME.

Non-polar lipid components of human cerumen

Human cerumen was separated by column chromatography into the following groups of compounds: hydrocarbons, squalene, wax esters and cholesterol esters, triacylglycerols, free fatty acids, free fatty alcohols, monoacylglycerols, free cholesterol, free sterols, and free hydroxy acids. The groups of compounds obtained were examined in detail by gas chromatography and gas chromatography-mass spectrometry. In total, about one thousand compounds have been identified.

Protein isolation from ear wax made easy

Cerumen is a waxy substance with a mixture of different lipids and and not yet identified proteins. Analysing ear wax can be quite laborious because of the different and sometimes interfering components. Therefore, time-consuming techniques such as chromatography or spectrometry were used to gain informations about the components of ear wax. Conclusions were drawn from immunohistochemical detections of special proteins within the skin or the glands of the external ear canal about the existence of these proteins within the ear wax. But directly analysing the proteins within the ear wax was difficult. We, therefore, worked out a method to isolate proteins from ear wax. Ear wax was collected from 16 adults with no infections of the external ear canal. The protein isolation was conducted using the Qproteome Mammalian Protein Prep Kit by Qiagen in two different kind of ways (cell and lysat fraction). Afterwards, we performed a quantification of the total protein concentration using the BCA method. There was a statistical significant difference in the total protein concentration between the two different (cell and lysat fraction) described ways. Furthermore, it is a fast and easy method to extract proteins from ear wax. The benefit of the described method and the field of application will be discussed.

Development of a liquid enzyme-based ceruminolytic product

Various compositions for removal of human cerumen are marketed but they are not very effective. Therefore, a proteolytic enzyme-based ceruminolytic product was developed containing the enzyme, methyl trypsin, and sodium bicarbonate. Efficacy was optimized based on in vitro testing using both human and artificial cerumen preparations. Both qualitative (visual observation) and quantitative (spectrophotometric) assessments of ceruminolytic efficacy were employed. Optimal enzyme stability was observed for the aqueous formulation at pH 4, while greater ceruminolytic efficacy was observed at pH 8. The optimal concentration range of enzyme was 150-300 absorbance U/mL based on efficacy and stability considerations. An aqueous formulation containing both methyl trypsin and sodium bicarbonate was shown to be more effective than two commercial products, Murine Ear Wax Removal Drops and Cerumenex Ear Drops. A two-part packaging system was employed to provide adequate shelf-life. Long-term stability studies confirmed that the formulation maintained >75% enzyme stability for 24 months at 5 and 25 degrees C and after reconstitution at room temperature for up to 1 day.

Retention of long-chain acetylenic hydrocarbons on non-polar stationary phases

The retention indices of methyl and trimethylsilyl esters of octadeca-, eicosa- and tricosa-ynoic fatty acids containing acetylenic bonds were measured on non-polar stationary phase (dimethylsilicone with 5% phenyl groups). An unusually large increase in retention is observed for compounds containing conjugated and methylene interrupted acetylenic bonds. The additional increase in retention index as a result of the presence of one conjugated acetylenic bond is roughly equivalent to the retention increase caused by lengthening of the hydrocarbon chain for one carbon atom. The increase in retention for methylene interrupted bonds constitutes approximately 50% increase for conjugated triple bonds. A further increase in interruption substantially decreases the effect. Based on available literature data and the results of this work, the contributions of conjugated acetylenic and olefinic bonds, and methylene interrupted acetylenic bonds to retention were estimated.

Branched chain fatty acids are constituents of the normal healthy newborn gastrointestinal tract

Vernix suspended in amniotic fluid is normally swallowed by the late term fetus. We hypothesized that branched chain fatty acids (BCFA), long known to be major vernix components, would be found in meconium and that the profiles would differ systematically. Vernix and meconium were collected from term newborns and analyzed. BCFA-containing lipids constituted about 12% of vernix dry weight, and were predominantly saturated, and had 11-26 carbons per BCFA. In contrast, meconium BCFA had 16-26 carbons, and were about 1% of dry weight. Meconium BCFA were mostly in the iso-configuration, whereas vernix BCFA contained dimethyl and middle chain branching, and five anteiso-BCFA. The mass of BCFA entering the fetal gut as swallowed vernix particles is estimated to be 180 mg in the last month of gestation whereas the total mass of BCFA found in meconium is estimated to be 16 mg, thus most BCFA disappear from the fetal gut. The BCFA profiles of vernix and meconium show that BCFA are major components of normal healthy term newborn gastrointestinal tract. BCFA are candidates for agents that play a role in gut colonization and should be considered a nutritional component for the fetus/newborn.

Investigation of age, sex and menstrual stage variation in human cerumen lipid composition by high performance thin layer chromatography

OBJECTIVE

The objective of the study was to correlate quantitative changes in the lipid composition of human cerumen with changes in age, sex and menstrual cycle stage.

DESIGN

Cerumen samples were collected from the external ear canal and analysed using sequential, one dimensional, high performance thin layer chromatography.

SUBJECTS

The following age groups of both sexes were investigated: one to 10 years; 11-18 years; 19-40 years; and 40 years and over. Additionally, cerumen samples from subjects in three stages of the menstrual cycle were compared.

RESULTS

In the cerumen samples, the peak values for wax ester and cholesterol occured between the ages of one and 10 years for both sexes. However, squalene and triglyceride content reached maximum levels at puberty. Men aged 19-40 years had a significantly greater percentage of cerumen lipid squalene content than women from the same age group; however, their cholesterol content was found to be lower. Regarding the various menstrual cycle stages, cerumen samples taken at the follicular stage from women aged 19-40 years had a significantly lower free fatty acids content, and higher cholesterol and squalene levels, compared with samples taken in the luteal or menstrual stages.

CONCLUSION

The proportions of the lipid constituents of cerumen varied with age, sex and menstrual stage. In cerumen, the main lipid constituent stimulated at puberty appears to be squalene, not wax esters as reported for sebum. The relevance of lipid constituents to cerumen's protective role is discussed.

The toxicity of behenyl alcohol. II. Reproduction studies in rats and rabbits

Behenyl alcohol is a saturated 22-carbon, long-chain aliphatic alcohol, which has potential for use in foods as an oil-structuring and -solidifying agent in fats. Previously completed studies with behenyl alcohol indicated an absence of mutagenic or genotoxic potential. In addition, subchronic toxicity studies in rats and dogs reported no adverse effects following gross and histopathological examinations. Compound-related effects were limited to the observation of pale feces in dogs treated with high doses of behenyl alcohol, and were attributable to unabsorbed behenyl alcohol. The reproductive effects of behenyl alcohol were investigated in a fertility and reproduction study, and an embryonic development study in rats and rabbits, respectively. No evidence of maternal or fetal toxicity was observed in either study. Behenyl alcohol demonstrated no effects on the fertility or reproduction of rats dosed up to 1000 mg/kg body weight. Similarly, behenyl alcohol had no reproductive effects on rabbits treated with doses up to 2000 mg/kg body weight. The observation of pale feces was the only compound-related effect reported, limited to rabbits treated with 2000 mg behenyl alcohol/kg body weight. Based on these findings, there is no evidence to suggest that behenyl alcohol is teratogenic or embryotoxic.

The toxicity of behenyl alcohol. I. Genotoxicity and subchronic toxicity in rats and dogs

The genotoxic potential of behenyl alcohol, a saturated long-chain (C22:0) fatty alcohol, was examined in the Ames Salmonella typhimurium reverse mutation assay, the gene mutation, and chromosome aberrations assays in Chinese hamster V79 cells, and the micronucleus assay in NMRI mice. Behenyl alcohol did not increase the number of revertants per plate compared to controls in the S. typhimurium assay, with or without metabolic activation. No significant increases in the number of mutant colonies or in structural chromosome aberrations were observed in Chinese hamster V79 cells. In addition, behenyl alcohol did not increase the frequency of bone marrow polychromatic erythrocyte (PCE) micronuclei in mice in vivo. In two subchronic toxicity studies, CD rats and beagle dogs were administered behenyl alcohol by oral gavage for at least 26 weeks at doses of 0, 10, 100, or 1000 mg behenyl alcohol/kg body weight/day for rats and 0, 20, 200, or 2000 mg behenyl alcohol/kg body weight/day for dogs. Adverse effects were not observed following gross and histopathological evaluations of dosed rats. Compound-related effects in dogs were limited to observations of pale feces, indicative of unabsorbed behenyl alcohol, at doses of 2000 mg/kg body weight/day. There were no histopathological changes observed in dogs dosed with behenyl alcohol. The no-observed-adverse-effect-level (NOAEL) for behenyl alcohol was 1000 mg/kg body weight/day for rats, and 2000 mg/kg body weight/day for dogs, the highest doses used in these studies.

Application of triple quadrupole tandem mass spectrometry to the analysis of pyridine-containing derivatives of long-chain acids and alcohols

An improved derivatization procedure for the preparation of nicotinate and 3-picolinyl esters from mixtures of fatty alcohols and acids has been developed. The derivatives can be analysed by capillary gas chromatography on an SE-54 type column, which affords separation of the acid and alcohol derivatives with the same carbon chain. Detection with tandem mass spectrometric techniques on a triple quadrupole instrument is feasible, and yields informative spectra devoid of coeluting interferences.

Pyridine-Containing schiff base derivatives for the struxtural determination of long-chain aldehydes by gas chromatography combined with mass spectrometry

Long-chain aldehydes, encountered as insect pheromones, were converted into Schiff bases with 3-aminopyridine, 3-(aminomethyl)pyridine, or 2-aminopyrimidine to provide derivatives suitable for revealing the alkyl chain structure by mass spectrometry. The two pyridine-containing derivatives were satisfactory in initiating a radical-induced cleavage. of the chain to give a series of fragment ions, the masses and relative abundance of which revealed the chain structure. The derivatives were applied to aldehydes having straight, branched (iso and anteiso), and unsaturated (delta-7, delta-9, delta-ll, and delta-13) structures; these all gave the fragmentation patterns that have been seen earlier for similar pyridine-containing derivatives of fatty acids (picolinyl esters) and alcohols (nicotinates).Of the two derivatives, those from 3-aminopyridine gave slightly simpler spectra. Derivatives formed from 2-aminopyrimidine were less satisfactory in revealing chain structure.