Chemical and Olfactory Analysis of the Volatile Fraction of Ocimum gratissimum Concrete from Madagascar

The chemical composition of the volatile fraction of Ocimum gratissimum concrete (romba) from Madagascar has been determined for the first time by GC/MS and GC-FID. A methyl cinnamate chemotype has been determined for this material, along with a set of compounds typical in essential oils and extracts from plants of the Ocimum genus. Variability was mostly observed on terpenes and terpenoids components. GC-O-MS was also used for a sensory evaluation of this material performed by a master perfumer. The chemical composition of this O. gratissimum extract was then compared with literature data to assess subtle differences between chemotypes of the same species and other species of the same genus within natural variability. A mapping illustrates the occurrence of the cinnamate chemotype in Eastern Africa, India and now Madagascar, while other origins generally present eugenol, thymol, camphor, or linalool chemotypes.

Determination of Major, Minor and Chiral Components as Quality and Authenticity Markers of Rosa damascena Oil by GC-FID

Rose oil is traditionally produced by the water distillation of Rosa damascena and is of high economic value due to the low essential oil yield. It is therefore a common target for adulteration, which can cause harm to consumers. Current standards for authenticity control only consider the analysis of major components and overlook minor quality markers as well as the enantiomeric ratio of terpenes, which have proven useful in originality determination. The aim of this study was the development of two analytical GC-FID methods for the analysis of 21 and 29 rose oil analytes including major, minor and chiral components on a DB-wax and BGB 178 30% CD (chiral) capillary column, respectively. The total run time for both methods was within 60 min. For all target analytes, the % bias at the lower and upper calibration range varied from -7.8 to 13.2% and -13.1 to 5.2% analysed on the DB-wax column and 0.5 to 13.3% and -6.9 to 7.0% analysed on the chiral column. The chiral analysis successfully separated the enantiomers (+/-)-camphene, (+/-)-rose oxide, (+/-)-linalool, (+/-)-citronellol and (+/-)-citronellyl acetate, as well as the diastereomers of citral and β-damascenone. Both methods were applied to the analysis of 10 authentic rose oil samples and the enantiomeric/diastereomeric ratios, as well as the content of major and minor components, were determined. The identity of the analysed components in the authentic samples was further confirmed by GC-MS.

Authenticity control of pine sylvestris essential oil by chiral gas chromatographic analysis of α-pinene

Numerous terpenes present in essential oils (EOs) display one or more chiral centers. Within the same genus the enantiomeric ratio of these compounds can be different. Thus, the determination of enantiomers is a valuable tool to evaluate authenticity and quality of EOs. In here, the terpene profile of primary and commercial pine EOs was analyzed by conventional and chiral gas chromatography coupled to a flame ionization detector. The enantiomeric excess of ( ±)-α-pinene was determined and significant differences between primary and commercially available EOs were observed. Primary EOs of Pinus sylvestris L. showed a positive enantiomeric excess of (+)-α-pinene whereas commercial EOs labeled as P. sylvestris L. exhibited an enantiomeric excess of (−)-α-pinene. Thus, chiral analysis provides useful information on the authenticity of pine EOs and allows to uncover possible mislabeling, the use of the wrong herbal substance and sources of adulteration in pine oil.

Type and magnitude of non-compliance and adulteration in neroli, mandarin and bergamot essential oils purchased on-line: potential consumer vulnerability

Thirty-one samples of essential oils used both in perfumery and aromatherapy were purchased to business-to-consumers suppliers and submitted to standard gas chromatography-based analysis of their chemical composition. Their compliance with ISO AFNOR standards was checked and revealed, although ISO AFNOR ranges are relatively loose, that more than 45% of the samples analyzed failed to pass the test and more than 19% were diluted with solvents such as propylene and dipropylene glycol, triethyl citrate, or vegetal oil. Cases of non-compliance could be due to substitution or dilution with a cheaper essential oil, such as sweet orange oil, blending with selected compounds (linalool and linalyl acetate, maybe of synthetic origin), or issues of aging, harvest, or manufacturing that should be either deliberate or accidental. In some cases, natural variability could be invoked. These products are made available to the market without control and liability by resellers and could expose the public to safety issues, in addition to commercial prejudice, in sharp contrast with the ever-increasing regulations applying to the sector and the high demand of consumers for safe, controlled and traceable products in fragrances and cosmetic products.

Chemical Variation in Essential Oils from the Oleo-gum Resin of Boswellia carteri: A Preliminary Investigation

Frankincense, the oleo-gum resin of Boswellia species, has been an important element of traditional medicine for thousands of years. Frankincense is still used for oral hygiene, to treat wounds, and for its calming effects. Different Boswellia species show different chemical profiles, and B. carteri, in particular, has shown wide variation in essential oil composition. In order to provide insight into the chemical variability in authentic B. carteri oleoresin samples, a hierarchical cluster analysis of 42 chemical compositions of B. carteri oleo-gum resin essential oils has revealed at least three different chemotypes, i) an α-pinene-rich chemotype, ii) an α-thujene-rich chemotype, and iii) a methoxydecane-rich chemotype.

Composition and Antioxidant, Antienzymatic and Antimicrobial Activities of Volatile Molecules from Spanish Salvia lavandulifolia (Vahl) Essential Oils

The current study describes the composition of Salvia lavandulifolia (Vahl) essential oils (SlEOs) obtained from plants cultivated in Murcia (Spain), as determined by gas chromatography. Relative and absolute concentrations, the enantiomeric ratios of chiral compounds and the in vitro antioxidant, antienzymatic and antimicrobial activities are described. The main components of the SlEOs were camphor, 1,8-cineole, camphene and α-pinene, and the main enantiomers were (+)-camphor and (-)-camphene. The activities against free radicals and the capacity to reduce and chelate metallic ions were measured. SlEO-3 showed the highest activity in ORAC, DPPH, ABTS and reducing power methods, while SlEO-1 exhibited the highest chelating power. The activity of lipoxygenase and acetylcholinesterase could be inhibited by all the SlEOs, being bornyl acetate and limonene the most active individual compounds against lipoxygenase and 1,8-cineole against acetylcholinesterase. SlEOs and some individual compounds inhibited Escherichia coli, Staphylococcus aureus and Candida albicans. These results increase our knowledge of SlEOs and, particularly, provide for the first time a complete characterization of SlEOs from Murcia, Spain, while proposing possible biotechnological uses for them.

Chemotypic Characterization and Biological Activity of Rosmarinus officinalis

Rosemary (Rosmarinus officinalis L.) is a popular herb in cooking, traditional healing, and aromatherapy. The essential oils of R. officinalis were obtained from plants growing in Victoria (Australia), Alabama (USA), Western Cape (South Africa), Kenya, Nepal, and Yemen. Chemical compositions of the rosemary oils were analyzed by gas chromatography-mass spectrometry as well as chiral gas chromatography. The oils were dominated by (+)-α-pinene (13.5%–37.7%), 1,8-cineole (16.1%–29.3%), (+)-verbenone (0.8%–16.9%), (−)-borneol (2.1%–6.9%), (−)-camphor (0.7%–7.0%), and racemic limonene (1.6%–4.4%). Hierarchical cluster analysis, based on the compositions of these essential oils in addition to 72 compositions reported in the literature, revealed at least five different chemotypes of rosemary oil. Antifungal, cytotoxicity, xanthine oxidase inhibitory, and tyrosinase inhibitory activity screenings were carried out, but showed only marginal activities.

Magnetically recoverable, thermostable, hydrophobic DNA/silica encapsulates and their application as invisible oil tags

A method to encapsulate DNA in heat-resistant and inert magnetic particles was developed. An inexpensive synthesis technique based on co-precipitation was utilized to produce Fe2O3 nanoparticles, which were further functionalized with ammonium groups. DNA was adsorbed on this magnetic support, and the DNA/magnet nanocluster was surface coated with a dense silica layer by sol-gel chemistry. The materials were further surface modified with hexyltrimethoxysilane to achieve particle dispersibility in hydrophobic liquids. The hydrodynamic particle sizes were evaluated by analytical disc centrifugation, and the magnetic properties were investigated by vibrating sample magnetometry. The obtained nanoengineered encapsulates showed good dispersion abilities in various nonaqueous fluids and did not affect the optical properties of the hydrophobic dispersant when present at concentrations lower than 10(3) μg/L. Upon magnetic separation and particle dissolution, the DNA could be recovered unharmed and was analyzed by quantitative real-time PCR and Sanger sequencing. DNA encapsulated within the magnetic particles was stable for 2 years in decalin at room temperature, and the stability was further tested at elevated temperatures. The new magnetic DNA/silica encapsulates were utilized to developed a low-cost platform for the tracing/tagging of oils and oil-derived products, requiring 1 μg/L=1 ppb levels of the taggant and allowing quantification of taggant concentration on a logarithmic scale. The procedure was tested for the barcoding of a fuel (gasoline), a cosmetic oil (bergamot oil), and a food grade oil (extra virgin olive oil), being able to verify the authenticity of the products.

Gas chromatography combined with mass spectrometry, flame ionization detection and elemental analyzer/isotope ratio mass spectrometry for characterizing and detecting the authenticity of commercial essential oils of Rosa damascena Mill

RATIONALE

The essential oil of Rosa damascena Mill. is known for its fine perfumery application, use in cosmetic preparations and for several pharmacological activities. Due to its high value, it can be easily adulterated with flavors or cheaper oils. This study is aimed at a detailed phytochemical characterization of commercial samples of R. damascena essential oil and at their authenticity assessment.

METHODS

Nineteen commercial samples of R. damascena essential oil of different geographic origin and an additional authentic one, directly extracted by hydro-distillation from fresh flowers, were considered. GC/MS and GC/FID techniques were applied for the phytochemical analysis of the samples. EA/IRMS (Elemental Analyzer/Isotope Ratio Mass Spectrometry) and GC/C (Combustion)/IRMS were used to determine the δ(13)C composition of bulk samples and of some specific components.

RESULTS

Citronellol (28.7-55.3%), geraniol (13.5-27.3%) and nonadecane (2.6-18.9%) were the main constituents of Bulgarian and Turkish essential oils, while those from Iran were characterized by a high level of aliphatic hydrocarbons (nonadecane: 3.7-23.2%). The δ(13)C values of bulk samples were between -28.1 and -26.9‰, typical for C3 plants. The δ(13)C values of specific components were in the usual range for natural aromatic substances from C3 plants, except for geranyl acetate, which displayed higher values (up to -18‰). These unusual δ(13)C values were explained by the addition of a natural cheaper oil from a C4 plant (Cymbopogon martinii, palmarosa), which was found to occur in most of the essential oils.

CONCLUSION

GC/C/IRMS, in combination with GC/MS and GC/FID, can be considered as an effective and reliable tool for the authenticity control of R. damascena essential oil.

Stereochemical mechanism of two sabinene hydrate synthases forming antipodal monoterpenes in thyme (Thymus vulgaris)

The essential oil of Thymus vulgaris consists of a complex blend of mono- and sesquiterpenes that provides the plant with its characteristic aromatic odor. Several chemotypes have been described for thyme. In this study, we identified two enzymes of the sabinene hydrate chemotype which are responsible for the biosynthesis of its major monoterpene alcohols, (1S,2R,4S)-(Z)-sabinene hydrate and (1S,2S,4R)-(E)-sabinene hydrate. Both TPS6 and TPS7 are multiproduct enzymes that formed 16 monoterpenes and thus cover almost the whole monoterpene spectrum of the chemotype. Although the product spectra of both enzymes are similar, they form opposing enantiomers of their chiral products. Incubation of the enzymes with the potential reaction intermediates revealed that the stereospecificity of TPS6 and TPS7 is determined by the formation of the first intermediate, linalyl diphosphate. Since TPS6 and TPS7 shared an amino acid sequence identity of 85%, a mutagenesis study was employed to identify the amino acids that determine the stereoselectivity. One amino acid position had a major influence on the stereochemistry of the formed products. Based on comparative models of TPS6 and TPS7 protein structures with the GPP substrate docked in the active site pocket, the influence of this amino acid residue on the reaction mechanism is discussed.

Increased plant volatile production affects oviposition, but not larval development, in the moth Helicoverpa armigera

It is well established that herbivorous insects respond to changes in plant odour production, but little attention has been given to whether these responses relate to direct fitness costs of plant volatile production on insect growth and survival. Here, we use transgenic Nicotiana tabacum (tobacco) plants that produce relatively large amounts of the volatile (S)-linalool to study whether the responses of egg-laying herbivorous insects to linalool production relate directly to the growth and survival of offspring. In choice tests, fewer eggs were laid on transgenic plants compared with non-transformed controls, indicating that increased linalool emissions have a deterrent effect on Helicoverpa armigera oviposition. Larval survival and larval mass after feeding on transgenic leaves, however, was comparable to non-transformed controls. (S)-linalool, whether in volatile or sequestered form, does not appear to have a direct effect on offspring fitness in this moth. We discuss how the ecology of this polyphagous moth species may necessitate a high tolerance for certain volatiles and their related non-volatile compounds, and suggest that responses by adult female H. armigera moths towards increased linalool production may be context specific and relate to other indirect effects on fitness.

Authenticity control of essential oils containing citronellal and citral by chiral and stable-isotope gas-chromatographic analysis

Enantioselective capillary GC on a Supelco beta-DEX 225 column (heptakis(2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl)-beta-cyclodextrin SPB 20poly--20% diphenyl, 80% dimethylsiloxane) and isotope-ratio mass spectrometry, coupled online with capillary GC on an HP5 column have been used for origin-specific analysis and authenticity control of essential oils, for example lemon (Citrus limon), lemongrass (Cymbopogon citratus and Cymbopogon flexuosus), citronella (Cymbopogon nardus L.--Ceylon type and Cymbopogon winterianus--Java type), Litsea cubeba, Lippia citriodora, lemon myrtle (Backhousia citriodora), lemon gum (Eucalyptus citriodora), and, especially, precious lemon balm oil (Melissa officinalis L.). Isotope data (delta13C(PDB) and delta2H(V-SMOW)) for citral (neral + geranial) and citronellal from on-line GC-C/Py-IRMS and chiral data for citronellal in these essential oils are reported. The possibility of using these data to determine the origin of these essential oils and to detect adulteration is discussed. Principal-components analysis (PCA) of specific compounds in two essential oils of lemongrass and Litsea cubeba was performed as a practical statistical method for distinguishing between these two types of oil.

Use of a superabsorbent polymer for the pre-concentration of volatile components from complex matrices

A polymeric material commonly used as a superabsorbent in the sanitary industry is proposed for the first time for analytical purposes. Specifically, we have evaluated in this work the possibility of using this material in a programmed-temperature vaporizer (PTV) injector for the introduction of large volume samples. To that end, the viability of this superabsorbent polymer as a retaining material was first studied by testing the stability of its absorption capacity in the presence of various solvents and at various temperatures. Subsequently, its effectiveness in the isolation of menthol and its isomers from Mentha piperita essential oil as well as gamma-lactones from peach essential oil was assessed. For that purpose, optimization of different variables, namely PTV temperatures during sampling, purge times, and desorption temperatures, involved in the solvent elimination was performed. Additionally, the information obtained was compared with that acquired for the adsorbent material Tenax TA. The results shown in this work proved not only the viability of using this superabsorbent polymer in analytical procedures but also demonstrated its advantages over the adsorbent Tenax TA in attaining internal GC concentration of a sample by introducing large volumes via PTV.

Enantiomeric distribution of chiral compounds in orange juices according to their geographical origins

Chiral terpenes in nonprocessed orange juices of different geographical origins were examined by two different approaches: steam distillation-solvent extraction-gas chromatography-mass spectrometry (SDE-GC-MS) and solid-phase microextraction-gas chromatography (SPME-GC). The two sample preparation techniques were compared with regard to their effectiveness in determining the enantiomeric distributions of chiral compounds. Most target compounds exhibited constant enantiomeric ratios in all juices when either of the two approaches was used. Exceptions were found for terpinen-4-ol and beta-citronellol, whose of enantiomeric purity ratios varied significantly according to the geographical origin of the sample. These results may aid in guaranteeing the authenticity and thus the quality and safety of orange juice. A comparison between the two extraction procedures revealed SPME to be more reliable for stereochemical studies, since harsh experimental conditions that can bring about racemization are not required in such studies.

Direct stereoselective assay of fluoxetine and norfluoxetine enantiomers in human plasma or serum by two-dimensional gas-liquid chromatography with nitrogen-phosphorus selective detection

A method was developed and validated for the direct enantioselective assay of fluoxetine and norfluoxetine in human plasma or serum by two-dimensional capillary gas-liquid chromatography (GC). A Rtx-1 fused-silica capillary (15 mx0.25 mm I.D., 1.0 micrometer film thickness) and a hydrodex-beta-6-TBDM fused-silica capillary (25 mx0.25 mm I.D., 0.25 micrometer film thickness) were used. A three-step liquid-liquid extraction was used for sample preparation with fluvoxamine and nisoxetine as internal standards. The method provided linear calibration between about 5 and 250 ng/ml for (R)- and (S)-fluoxetine as well as 15 and 250 ng/ml for (R)- and (S)-norfluoxetine. The limits of detection were about 1.5 and 6 ng/ml, respectively. Intra-day precision (coefficient of variation) was estimated as being between 5.4 and 12.7% at plasma levels of 25, 100 and 200 ng/ml for the four enantiomers. Inter-day precision was between 5.3 and 9.1% at 100 ng/ml. The enantioselective separation of some racemic psychopharmaceuticals was tested with various cyclodextrin GC-capillaries. Advantages and disadvantages of direct enantioselective GC are discussed for the assay of racemic psychopharmaceuticals. Samples from a patient who was treated with racemic fluoxetine were measured. In agreement with literature, plasma levels of the (R)-enantiomers of fluoxetine and norfluoxetine were considerably decreased in comparison to the (S)-enantiomers.

Recent developments in food characterization and adulteration detection: technique-oriented perspectives

This review covers mainly publications that appeared in Analytical Abstracts (Royal Society of Chemistry) from January 1990 to February 2001. The number of publications on this topic continues to grow, and during the past three years (1998-2000) about 150 reviews and/or overviews have been published in the area of food. Numerous techniques and food matrices or chemical components are presented and discussed in these reviews. The present review is intentionally limited to eight techniques or classes of techniques and intends to be a "technique by technique" presentation of "what was used" or "what is used" to characterize food products and to detect their possible adulteration. The present review focuses on the following techniques: microscopic analysis; HPLC; GC, GC-(MS, FTIR); UV-visible spectrophotometry; AAS/AES, ICP-(AES, MS); IRMS, GC-IRMS, GC-C-IRMS; DSC; IR, mid-IR, and NMR (202 references). Emphasis is placed as much as possible on chemometrical treatment of analytical data, which are commonly used to achieve the final objective, either food characterization or adulteration detection. Finally, a brief description is given of the new generation of analytical systems that combine powerful analytical techniques and powerful computer software for a best extraction of the information from analytical data.

Gas chromatographic technologies for the analysis of essential oils

Essential oil analysis has basically had one technical goal: to achieve the best possible separation performance by using the most effective, available technology of the day. The result achieved from this may then be used to answer the research or industrial analysis questions which necessitated the analysis. This may be for comparative purposes, where one oil is contrasted with other(s) for quality control or investigation of adulteration, to discover new components, or to characterise the chemical classes of compounds present. Clearly, today the analyst turns to chromatography as the provider of separation and then may supplement that with mass spectrometry to aid identification. The power of GC-MS means that advances in both the separation technique, and improvements in mass spectrometry detection - along with improved data handling tools - will immediately be relevant to the essential oil area. This present review outlines the developmental nature of instrumental approaches to essential oil analysis using gas chromatography. Mass spectrometry will be included to the extent that it represents the hyphenation of choice for most analysts when analysing essential oils. Thus single-column and multi-dimensional analysis will be covered, as will sample handling or introduction techniques prior to the analysis step, where these techniques provide some measure of separation. The recent demonstration of comprehensive gas chromatography will be discussed as the potentially most powerful separation method for essential oils. This brief review is not intended to be a comprehensive dissertation on the field of essential oil analysis since that would require sufficient space to occupy a book in its own right. Rather, it will outline selected considerations and developments, to help explain where new technology has been applied to advantage in this field.

Cyclodextrin derivatives as chiral selectors for direct gas chromatographic separation of enantiomers in the essential oil, aroma and flavour fields

This article reviews papers published over the period 1995-1998 dealing with the application of cyclodextrin derivatives (CDs) as chiral selector for direct enantiomer GC separation of volatile optically active components in the essential oil, extract, flavour and aroma fields. For each application, the racemate analysed, the CD employed as chiral selector and the matrix investigated are reported. The applications are grouped by analytical technique employed: capillary gas chromatography and capillary gas chromatography-mass spectrometry (GC and GC-MS); two-dimensional gas chromatography (GC x GC); capillary gas chromatography-isotope ratio-mass spectrometry (GC-IRMS); liquid chromatography-capillary gas chromatography (LC-GC).

Separation of enantiomers by capillary electrophoresis using pentosan polysulfate

Pentosan polysulfate, a semisynthetic polysaccharide, was employed as a chiral run buffer additive in capillary electrophoresis. Twenty-eight racemic analytes were resolved. The separations were successful only at low pH when the analytes were significantly protonated. This suggests that ionic interactions were the dominant associative interactions between the anionic pentosan polysulfate and the positively charged analytes. Compared to other linear, carbohydrate-based chiral selectors (i.e., chondroitin sulfates, heparin and dextran sulfate) pentosan polysulfate has some characteristics common of anionic polysaccharides; yet it has several differences in its structure and properties which account for its unusual enantioselectivity. The effects of pH, concentration of phosphate buffer, concentration of pentosan polysulfate and the type and concentration of organic modifier on the enantiomeric separations were investigated. The optimization of these separations were dependent on the nature of the analytes and could be achieved by the proper choice of experimental conditions.