Search

Tyrosinase is a target enzyme to be inhibited in order to reduce excessive melanin production and prevent typical age-related skin disorders. Essential oils are complex mixtures of volatile compounds, belonging mainly to monoterpenoids and sesquiterpenoids, which have been relatively little studied as tyrosinase inhibitors. Among the monoterpenoids, citral (a mixture of neral and geranial) is a fragrance compound in several essential oils that has shown interesting tyrosinase inhibitory activity. Although citral is listed as an allergen among the 26 fragrances in Annex III of the Cosmetics Directive 2003/15/EC, it can be safely used for the formulation of topical products in amounts that are not expected to cause skin sensitization, as shown by various commercially available products.The aim of this work was to evaluate two different formulations (oil/water emulsion, oily solution) containing a new combination of essential oils ( Litsea cubeba, Pinus mugo, Cymbopogon winterianus ) applied to the skin both in nonocclusive and partially occlusive modes. The blend is designed to reduce the concentration of citral to avoid potential skin reactions while taking advantage of the inhibitory activity of citral. Specifically, the amount of citral and other bioactive compounds (myrcene, citronellal) delivered through the skin was studied as a function of formulation and mode of application.The results show that an oil/water emulsion is preferable because it releases the bioactive compounds rapidly and minimizes their evaporative loss. In addition, semi-occluded conditions are required to prevent evaporation, resulting in higher availability of the bioactive compounds in viable skin., Competing Interests: The authors declare that they have no conflict of interest., (Thieme. All rights reserved.)

Quality control of essential oils is fundamental for verifying their authenticity and conformity with quality standards, ensuring their safety and regulatory compliance, and monitoring their consistency. Companies that produce or market essential oils routinely evaluate the quality and authenticity of their products. However, they also must deal with increasing attention to environmental sustainability as well as practical considerations such as productivity, cost, and simplicity of methods. In this study, enantioselective gas chromatography (GC) was adopted to evaluate the quality of sweet and bitter orange essential oils, used as a case study. The analytical conditions were optimized and translated to fast GC to evaluate the impact of this approach on the environmental footprint of the analyses. The greenness of fast GC, compared with conventional GC, was quantitatively evaluated using a dedicated metric tool (AGREE), and important improvements have been calculated. The developed methods were applied to a set of commercial essential oils, and the data about the enantiomeric composition and relative percentage abundance were elaborated through multivariate statistics (principal component analysis). The results showed that fast chiral gas chromatography enables the classification of citrus essential oil samples and can be considered an environmentally friendly and sustainable approach for evaluating their quality.

This review is an overview of the recent advances of gas chromatography in essential oil analysis; in particular, it focuses on both the new stationary phases and the advanced analytical methods and instrumentations. A paragraph is dedicated to ionic liquids as gas chromatography stationary phases, showing that, thanks to their peculiar selectivity, they can offer a complementary contribution to conventional stationary phases for the analysis of complex essential oils and the separation of critical pairs of components. Strategies to speed-up the analysis time, thus answering to the ever increasing request for routine essential oils quality control, are also discussed. Last but not least, a paragraph is dedicated to recent developments in column miniaturization in particular that based on microelectromechanical-system technology in a perspective of developing micro-gas chromatographic systems to optimize the energy consumption as well as the instrumentation dimensions. A number of applications in the essential oil field is also included., (© 2021 Wiley-VCH GmbH.)

The quality control of essential oils (EO) principally aims at revealing the presence of adulterations and at quantifying compounds that are limited by law by evaluating EO chemical compositions, usually in terms of the normalised relative abundance of selected markers, for comparison to reference values reported in pharmacopoeias and/or international norms. Common adulterations of EO consist of the addition of cheaper EO or synthetic materials. This adulteration can be detected by calculating the percent normalised areas of selected markers or the enantiomeric composition of chiral components. The dilution of the EO with vegetable oils is another type of adulteration. This adulteration is quite devious, as it modifies neither the qualitative composition of the resulting EO nor the marker's normalised percentage abundance, which is no longer diagnostic, and an absolute quantitative analysis is required. This study aims at verifying the application of the two above approaches (i.e., normalised relative abundance and absolute quantitation) to detect EO adulterations, with examples involving selected commercial EO (lavender, bergamot and tea tree) adulterated with synthetic components, EO of different origin and lower economical values and heavy vegetable oils. The results show that absolute quantitation is necessary to highlight adulteration with heavy vegetable oils, providing that a reference quantitative profile is available.

Accurate, reliable, and informative mapping of untargeted and targeted components across many samples is here performed by combining off-line GC-Olfactometry (GC-O) and comprehensive two-dimensional gas chromatography (GC×GC) coupled to time-of-flight mass spectrometry with variable ionization energy (TOF MS featuring Tandem Ionization™). In particular, untargeted and targeted (UT) features patterns are processed by chromatographic fingerprinting, giving differential priority to potent odorants' retention-times regions. Distinguishing peppermint essential oil (EO) from Piedmont (Italy - Mentha × piperita L. var. Italo-Mitcham - Menta di Pancalieri EO), with its unique sensory fingerprint (i.e., freshness and long-lasting sweetness), from high-quality peppermint EOs produced in other areas poses a great challenge. Chromatographic UT fingerprinting provided a great chemical dimensionality by mapping more than 350 peak-regions at 70 eV and 135 at 12 eV. From them, 95 components were identified and responses compared to available literature. Then, potent odorants, detected by GC-O using the aroma extraction dilution analysis (AEDA), were tracked over the chromatographic space and tentatively identified. With the highest flavor dilution (FD), 1,8-cineole (eucalyptus, fresh, camphoraceous); menthone (minty, herbaceous); and menthofuran (minty, musty, petroleum-like) were highlighted. Responsible for creamy and coumarinic notes were the diasteroisomers of (3,6)-dimethyl-4,5,6,7-tetrahydrobenzo[b]-furan-2(3H)-one (i.e., menthofurolactones), detected in higher relative abundance in Pancalieri EOs. By prioritizing the investigation of volatiles on higher LogFD retention regions, including 131 untargeted/targeted features, Pancalieri EOs were separately clustered from United States samples. Besides pre-targeted analytes, additional untargeted features were post-processed for identification within marker chemicals. Myrtenyl methyl ether, ethyl 3-methyl butanoate, propyl-2-methylbutanoate, and (E)-2-hexenal were putatively identified. Of the "unknown - knowns" with diagnostic roles, all metadata were collected including low energy spectra at 12 eV, which were found to be highly complementary to 70 eV spectra., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021. Published by Elsevier B.V.)

A novel chemical profile essential oil, distilled from the aerial parts of Clinopodium taxifolium (Kunth) Govaerts (Lamiaceae), was analysed by Gas Chromatography-Mass Spectrometry (GC-MS, qualitative analysis) and Gas Chromatography with Flame Ionization Detector (GC-FID, quantitative analysis), with both polar and non-polar stationary phase columns. The chemical composition mostly consisted of sesquiterpenes and sesquiterpenoids (>70%), the main ones being ( E )- β -caryophyllene (17.8%), α -copaene (10.5%), β -bourbonene (9.9%), δ -cadinene (6.6%), cis -cadina-1(6),4-diene (6.4%) and germacrene D (4.9%), with the non-polar column. The essential oil was then submitted to enantioselective GC analysis, with a diethyl- tert -butyldimethylsilyl- β -cyclodextrin diluted in PS-086 chiral selector, resulting in the following enantiomeric excesses for the chiral components: (1 R ,5 S )-(-)- α -thujene (67.8%), (1 R ,5 R )-(+)- α -pinene (85.5%), (1 S ,5 S )-(-)- β -pinene (90.0%), (1 S ,5 S )-(-)-sabinene (12.3%), ( S )-(-)-limonene (88.1%), ( S )-(+)-linalool (32.7%), ( R )-(-)-terpinen-4-ol (9.3%), ( S )-(-)- α -terpineol (71.2%) and ( S )-(-)-germacrene D (89.0%). The inhibition activity against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) of C. taxifolium essential oil was then tested, resulting in selective activity against BChE with an IC 50 value of 31.3 ± 3.0 μg/mL (positive control: donepezil, IC 50 = 3.6 μg/mL).

Melaleuca alternifolia essential oil (tea tree oil) is widely used as an ingredient in skin care products because of its recognized biological activities. The European Scientific Committee on Consumer Products constantly promotes research and collection of data on both skin distribution and systemic exposure to tea tree oil components after the application of topical formulations. This study quantitatively evaluates permeation, skin layer distribution ( stratum corneum , epidermis, and dermis), and release into the surrounding environment of bioactive tea tree oil markers (i.e., α -pinene, β -pinene, α -terpinene, 1,8-cineole, γ -terpinene, 4-terpineol, α -terpineol) when a 5% tea tree oil formulation is applied at a finite dosing regimen. Permeation kinetics were studied in vitro on pig ear skin using conventional static glass Franz diffusion cells and cells ad hoc modified to monitor the release of markers into the atmosphere. Formulation, receiving phases, and skin layers were analyzed using a fully automatic and solvent-free method based on headspace solid-phase microextraction/gas chromatography-mass spectrometry. This approach affords, for the first time, to quantify tea tree oil markers in the different skin layers while avoiding using solvents and overcoming the existing methods based on solvent extraction. The skin layers contained less than 1% of each tea tree oil marker in total. Only oxygenated terpenes significantly permeated across the skin, while hydrocarbons were only absorbed at trace level. Substantial amounts of markers were released into the atmosphere., Competing Interests: The authors declare that they have no conflict of interest., (Georg Thieme Verlag KG Stuttgart · New York.)

Qualitative and quantitative determination of volatile markers in aqueous based fragrances assumes ever-increasing importance, because of both the need for quality control and the safety-regulatory limitations introduced for several compounds. This study reports and critically discusses the results of applying new water-compatible ionic-liquid (IL) GC stationary phases, based on phosphonium and imidazolium derivative cations combined with trifluoromethanesulphonate (Watercol™) to the direct quantitative analysis of aqueous samples in the perfume field with GC-MS. Narrow-bore columns of different lengths, especially prepared for this study, were adopted to minimize the amount of water reaching the MS detector after GC separation. All GC-MS analysis steps were investigated, to achieve results compatible with quality control requirements for the volatiles of interest in this field, in terms of LODs, LOQs, and repeatability. Reliability of the GC-MS results was demonstrated by determining volatile allergens in two commercial perfumes, as per EU regulations concerning no-declaration limits for leave-on (0.001%) and rinse-off (0.01%) cosmetic products., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Room-temperature ionic liquids (ILs) have been shown to be successful as stationary phases (SPs) for gas chromatography in several fields of applications because of their unique and tunable selectivity, low vapor pressure and volatility, high thermal stability (over 300 °C), and good chromatographic properties. This study has been focused on two ILs based on a phosphonium cation (trihexyl(tetradecyl)phosphonium, P 66614 ) combined with different anions, previously shown to be suitable as gas chromatography (GC) SPs. In particular, trihexyl(tetradecyl)phosphonium bis[(trifluoromethyl)sulfonyl]imide ([P 66614 + ] [NTf 2 - ]) and trihexyl(tetradecyl)phosphonium chloride ([P 66614 + ] [Cl - ]) were investigated, as the Abraham linear solvation energy relationship has shown their ability to interact with the solute(s) when tested with a set of 26-34 probe analytes. The chromatographic performance were investigated on narrow bore and conventional test columns using the following: i) Grob test, ii) a group of model mixtures of compounds characteristic of the flavor, fragrance and essential oil fields (FFMix), iii) a standard mixture of 29 volatile allergens (AlMix), and iv) two essential oils of different complexity (sage and vetiver essential oils). The columns coated with the investigated IL SPs were characterized by similar polarity (Polarity Number (PN): 37 for [P 66614 + ] [Cl - ] and 33 for [P 66614 + ] [NTf 2 - ]), high efficiency and highly satisfactory inertness. The two IL SPs also exhibited a completely different separation performance, with [P 66614 + ] [Cl - ] test columns mainly characterized by high retention and selectivity based on the analyte functional groups, and [P 66614 + ] [NTf 2 - ] test columns featured by short retention and selectivity mainly related to the analyte volatility and polarity. These results were also confirmed with the analysis of sage and vetiver essential oils., (Copyright © 2018 Elsevier B.V. All rights reserved.)

In the fields of essential oils and fragrances, samples often consist of mixtures of compounds with similar structural and physical characteristics (e.g. mono- and sesquiterpenoids), whose correct identification closely depends on the synergic combination of chromatographic and mass spectral data. This sample complexity means that new GC stationary phases with different selectivities are continually being investigated. Ionic liquids (ILs) are of great interest as GC stationary phases in this field because of their selectivity (significantly different than that of currently phases) and their high temperature stability. A first generation of IL GC columns was found to be competitive when applied to these field, in terms of selectivity and efficiency, compared to conventional columns (polydimethylsiloxane, (e.g. OV-1), methyl-polysiloxane 5%-phenyl (e.g. SE-52), 7%-cyanopropyl, 7%-phenyl polysiloxane (e.g. OV-1701), and polyethylen glycol (e.g. PEG-20M). However, these columns showed significant activity towards polar or active analytes, which primarily affected their quantitative performance. A new generation of highly-inactive columns coated with three of the most widely-used ionic liquid GC stationary phases has recently been introduced; these phases are SLB-IL60i (1,12-di(tripropylphosphonium) dodecane bis(trifluoromethylsulfonyl) imide [NTf 2 ], SLB-IL76i (tri-(tripropylphosphonium-hexanamido)-triethylamine [NTf 2 ]), and SLB-IL111i (1,5-di (2,3-dimethyllimidazolium) pentane [NTf 2 ]). This study carefully tested the new inert IL columns, in view of their routine application in the fragrance and essential oil fields. They were found to have unusually high selectivity, comparable to that of first-generation IL columns, while their inertness and efficiency were competitive with those of currently-used conventional columns. The IL column performance of first and second generations was compared, through the quali-quantitative analysis of components in a group of different complexity samples; these included the Grob test, a standard mixture of "suspected" skin allergens, and the essential oils of chamomile and sandalwood., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Salvia desoleana Atzei & V. Picci is an indigenous species in Sardinia island used in folk medicine to treat menstrual, digestive and central nervous system diseases. Nowadays, it is widely cultivated for the pleasant smell of its essential oil (EO), whose antimicrobial and antifungal activities have already been screened. This study evaluated the in vitro anti-Herpes Simplex Virus-2 (HSV-2) activity of S. desoleana EO, fractions and main components: linalyl acetate, alpha terpinyl acetate, and germacrene D. Phytochemical composition of S. desoleana EO was studied by GC-FID/MS analysis and the active fraction(s) and/or compounds in S. desoleana EO were identified with a bioassay-guided fractionation procedure through in vitro assays on cell viability and HSV-2 and RSV inhibition. S. desoleana EO inhibits both acyclovir sensitive and acyclovir resistant HSV-2 strains with EC50 values of 23.72 μg/ml for the former and 28.57 μg/ml for the latter. Moreover, a significant suppression of HSV-2 replication was observed with an EC50 value of 33.01 μg/ml (95% CI: 26.26 to 41.49) when the EO was added post-infection. Among the fractions resulting from flash column chromatography on silica gel, the one containing 54% of germacrene D showed a similar spectrum of activity of S. desoleana EO with a stronger suppression in post-infection stage. These results indicated that S. desoleana EO can be of interest to develop new and alternative anti-HSV-2 products active also against acyclovir-resistant HSV-2 strains.

The solvent-enhanced headspace sorptive extraction technique aims at modifying PDMS polarity using a solvent to increase its concentration capability. In solvent-enhanced headspace sorptive extraction, a PDMS tubing closed at both ends by small glass stoppers and filled with an organic solvent is suspended in the sample headspace for a fixed time. After sampling, the sampled analytes are recovered from the PDMS tubing by thermal desorption and online transferred to a GC-flame ionization detector or GC-MS system for analysis. Cyclohexane, iso-octane, ethyl acetate, acetone, acetonitrile and methanol were tested as PDMS modifiers to sample the volatile fractions of sage (Salvia lavandulifolia Vahl.), thyme (Thymus vulgaris L.) and roasted coffee. Ethyl acetate was found to be the most effective PDMS modifier for all matrices investigated; although to a lesser extent, cyclohexane also increased component recoveries with sage and thyme. Acetone, acetonitrile and methanol did not increase PDMS recovery, while isooctane was excluded because of its interaction with the polymer. The results show that solvent-modified PDMS extends the range of sampled headspace components with different polarities, increases the recovery of many of them, improves sensitivity in trace analysis, speeds up recovery and gives repeatability comparable with that of unmodified PDMS.

This study reports on the compatibility of a conventional quadrupole MS (qMS) as detector for Fast-GC in terms of separation, identification, and quantitation when applied to the analysis of peppermint essential oil (e.o.), adopted as representative of this field. The influence of Fast-GC carried out on a 10 mx0.1 mm id narrow bore column with temperature programmes from 20 to 60 degrees C/min on the results of a qMS in total ion chromatograms (TIC) at different speeds (from 999 and 11 111 amu/s) and SIM modes was evaluated on ten differently abundant components characterizing peppermint e.o. Separation measure (S), peak capacity (n), and half height peak width were taken as separation parameters; match quality, number of scans per peak (NP), spectral skewing, and TIC area repeatability were used for identification. Quantitation was in SIM mode and NP, dwell time, SIM area repeatability and calibration curves, LOD, and LOQ of the selected components were measured. The results show that the peppermint e.o. markers can successfully be analysed qualitatively and quantitatively by F-GC-qMS up to temperature programmes of 60 degrees /min provided that a suitable scan speed is applied. Fast-GC-qMS reduces analysis time by a factor greater than ten and gives results that are qualitatively reliable and quantitatively comparable to those obtained by conventional GC-qMS.

Headspace-solid-phase microextraction gas chromatography-principal component analysis (HS-SPME GC-PCA) is proposed as a complementary or alternative method to essential oil (EO) GC-PCA in order to discriminate between flower-heads of chamomile of different chemotypes. Ninety-two EOs and the headspaces sampled by HS-SPME of the corresponding chamomile flower-heads were examined by conventional GC and fast GC (F-GC) and the results submitted to statistical analysis by PCA. HS-SPME F-GC-PCA showed itself to be a rapid technique by which to distinguish chamomile flower-head chemotypes a produced results in agreement with the accepted EO classification. Using this method, the analysis time was reduced from at least 4.5 h with EO conventional GC to less than 1 h with HS-SPME F-GC. This approach can thus successfully be used as an analytical decision maker in order to reduce the number of time-consuming EO conventional GC analyses by limiting them to those samples that cannot unequivocally be classified. The EO conventional GC and HS-SPME F-GC results of PCA were very uniform, but they did not provide quantitative correlations between the components as determined by the two methods. A different statistical approach and a larger number of samples will be needed in order to correlate components in the headspace sampled by SPME and those in the corresponding EO quantitatively through a function.

This study evaluates concentration capability of headspace sorptive extraction (HSSE) and the influence of sampling conditions on HSSE recovery of an analyte. A standard mixture in water of six high-to-medium volatility analytes (isobutyl methyl ketone, 3-hexanol, isoamyl acetate, 1,8-cineole, linalool and carvone) was used to sample the headspace by HSSE with stir bars coated with different polydimethylsiloxane (PDMS) volumes (20, 40, 55 and 110 microL, respectively), headspace vial volumes (8, 21.2, 40, 250 and 1000 mL), sampling temperatures (25, 50 and 75 degrees C) and sampling times (30, 60 and 120 min, and 4, 8 and 16 h). The concentration factors (CFs) of HSSE versus static headspace (S-HS) were also determined. Analytes sampled by the PDMS stir bars were recovered by thermal desorption (TDS) and analysed by capillary GC-MS. This study demonstrates how analyte recovery depends on its physico-chemical characteristics and affinity for PDMS (octanol-water partition coefficients), sampling temperatures (50 degrees C) and times (60 min), the volumes of headspace (40 mL) and of PDMS (in particular, for high volatility analytes). HSSE is also shown to be very effective for trace analysis. The HSSE CFs calculated versus S-HS with a 1000 mL headspace volumes at 25 degrees C during 4 h sampling ranged between 10(3) and 10(4) times for all analytes investigated while the limits of quantitation determined under the same conditions were in the nmol/L range.