Multidimensional enantio gas chromtography/mass spectrometry and gas chromatography-combustion-isotopic ratio mass spectrometry for the authenticity assessment of lime essential oils (C. aurantifolia Swingle and C. latifolia Tanaka)

Limonene Enantiomeric Ratios from Anthropogenic and Biogenic Emission Sources

Emissions from volatile chemical products (VCPs) have been identified as contributors to air quality degradation in urban areas. Limonene can be a tracer compound for VCPs containing fragrances in densely populated regions, but limonene is also emitted from conifers that are planted in urban areas. This creates challenges for using limonene to estimate VCP emissions. In this study, the -/+ enantiomeric ratios of limonene from VCP and conifer emission sources were quantified to evaluate if this measurement could be used to aid in source apportionment and emission inventory development. Samples were analyzed using a gas chromatograph equipped with a chiral column and mass spectrometry. The results demonstrate that limonene exhibits distinct enantiomeric ratios when sourced from VCPs versus conifers. (+)-Limonene was dominant in VCP sources (>97%), which was not universally true for conifer sources. The results were compared to those of air samples collected outside at two locations and indoors. The levels of (-)-limonene in outdoor air in Irvine and Portland and in indoor air were 50%, 22%, and 4%, respectively. This suggests outdoor limonene had both VCP and plant emission sources while indoor air was dominated by VCP sources. This study demonstrates the potential utility of enantiomeric analysis for improving VCP emission estimates in urban areas.

A review of recent compound-specific isotope analysis studies applied to food authentication

Compound-specific stable isotope analysis (CSIA) of food products is a relatively new and novel technique used to authenticate food and detect adulteration. This paper provides a review of recent on-line and off-line CSIA applications of plant and animal origin foods, essential oils and plant extracts. Different food discrimination techniques, applications, scope, and recent studies are discussed. CSIA δ13C values are widely used to verify geographical origin, organic production, and adulteration. The δ15N values of individual amino acids and nitrate fertilizers have proven effective to authenticate organic foods, while δ2H and δ18O values are useful to link food products with local precipitation for geographical origin verification. Most CSIA techniques focus on fatty acids, amino acids, monosaccharides, disaccharides, organic acids, and volatile compounds enabling more selective and detailed origin and authentication information than bulk isotope analyses.. In conclusion, CSIA has a stronger analytical advantage for the authentication of food compared to bulk stable isotope analysis, especially for honey, beverages, essential oils, and processed foods.

Citrus Essential Oils in Aromatherapy: Therapeutic Effects and Mechanisms

Citrus is one of the main fruit crops cultivated in tropical and subtropical regions worldwide. Approximately half (40-47%) of the fruit mass is inedible and discarded as waste after processing, which causes pollution to the environment. Essential oils (EOs) are aromatic compounds found in significant quantities in oil sacs or oil glands present in the leaves, flowers, and fruit peels (mainly the flavedo part). Citrus EO is a complex mixture of ~400 compounds and has been found to be useful in aromatic infusions for personal health care, perfumes, pharmaceuticals, color enhancers in foods and beverages, and aromatherapy. The citrus EOs possess a pleasant scent, and impart relaxing, calming, mood-uplifting, and cheer-enhancing effects. In aromatherapy, it is applied either in message oils or in diffusion sprays for homes and vehicle sittings. The diffusion creates a fresh feeling and enhances relaxation from stress and anxiety and helps uplifting mood and boosting emotional and physical energy. This review presents a comprehensive outlook on the composition, properties, characterization, and mechanism of action of the citrus EOs in various health-related issues, with a focus on its antioxidant properties.

Citrus Essential Oils: a Treasure Trove of Antibiofilm Agent

Biofilms are groups of adherent cell communities that cohere to the biotic and abiotic surfaces with the help of extracellular polymeric substances (EPS). EPS allow bacteria to form a biofilm that facilitates their binding to biotic and abiotic surfaces and provides resistance to the host immune responses and to antibiotics. There are efforts that have led to the development of natural compounds that can overcome this biofilm-mediated resistance. Essential oils (EOs) are a unique mixture of compounds that plays a key role in preventing the development of biofilm. The present overview focusses on the role of various types of citrus essential oils in acting against the biofilm, and the antibiofilm properties of natural compounds that may show an avenue to treat the multidrug-resistant bacteria.

Overcoming the lack of reliability associated to monodimensional gas chromatography coupled to isotopic ratio mass spectrometry data by heart-cut two-dimensional gas chromatography

The use of IRMS as a GC detector has a history going back decades, however the critical issue of wrong δ¹³C measurements resulting from impure peaks has been often underestimated. To this regard, multidimensional separation techniques are effective tools to improve the reliability of the data, with respect to those obtained after monodimensional analysis. The present research aims to draw attention to one critical issue, related to the reliability of the δ¹³C data obtained by means of monodimensional GC-C-IRMS. Although already known from the literature, such aspect has been greatly overlooked, as is reflected in the few papers reporting the use of MDGC, among the plethora of published research dealing with GC-C-IRMS applications. Hereby, a set of natural samples of complex composition were analysed to investigate the presence of minor or even undetected coelutions, and to which extent it affected the isotope ratio determination. Apart from chromatographic effects, and issues related to analytes conversion to CO₂ prior to IRMS measurement, unpredictable co-elutions with compounds, either resulting from oxidation or intentionally added in fraudulent practices, could also contribute to a shift of the δ¹³C data, up to 10‰ and higher. Last, the influence of column bleed was investigated, as affecting the determination of the δ¹³C data for compounds that were eluted at high temperatures. It was finally demonstrated by the selected key studies that implementation of MDGC separation is mandatory to prevent the aforementioned issues, aiming to guarantee accurate results. In the light of the above conclusions, and considering the level of automation of heart-cut devices nowadays available, routine practice of MDGC results highly recommendable in any IRMS applications.

Citrus essential oils: Extraction, authentication and application in food preservation

Citrus EOs is an economic, eco-friendly and natural alternatives to chemical preservatives and other synthetic antioxidants, such as sodium nitrites, nitrates or benzoates, commonly utilized in food preservation. Citrus based EOs is obtained mainly from the peels of citrus fruits which are largely discarded as wastes and cause environmental problems. The extraction of citrus oils from the waste peels not only saves environment but can be used in various applications including food preservation. The present article presents elaborated viewpoints on the nature and chemical composition of different EOs present in main citrus varieties widely grown across the globe; extraction, characterization and authentication techniques/methods of the citrus EOs; and reviews the recent advances in the application of citrus EOs for the preservation of fruits, vegetables, meat, fish and processed food stuffs. The probable reaction mechanism of the EOs based thin films formation with biodegradable polymers is presented. Other formulation, viz., EOs microencapsulation incorporating biodegradable polymers, nanoemulsion coatings, spray applications and antibacterial action mechanism of the active compounds present in the EOs have been elaborated. Extensive research is required on overcoming the challenges regarding allergies and obtaining safer dosage limits. Shift towards greener technologies indicate optimistic future towards safer utilization of citrus based EOs in food preservation.

Carbon isotope ratios of selected volatiles in Citrus sinensis and in orange-flavoured food

BACKGROUND

Twenty genuine samples of industrially cold-pressed sweet orange essential oils, were analysed by gas chromatography-combustion-isotope ratio mass spectrometry to determine the values of the carbon isotope ratios (δ(13)C(VPDB)) of selected volatiles and assess the corresponding range of authenticity. Successively, four commercial orange-flavoured products were analysed under identical conditions to evaluate the authenticity of the orange flavour. The samples were extracted by solid-phase microextraction under optimised conditions. The evaluation was performed by using an internal standard procedure to neglect the contribution due to the original environment to the isotopic abundance of (13)C. The composition of the volatile fraction of the essential oils and of the flavoured products was determined by gas chromatography coupled to mass spectrometry with linear retention indices, and by gas chromatography with a flame ionisation detector.

RESULTS

The δ(13)C(VPDB) values of seven secondary metabolites determined here were successfully used to characterise genuine orange essential oil. These values were used to evaluate the quality of orange-flavoured products, revealing the presence of compounds of different origin, not compatible with the values of genuine orange secondary metabolites.

CONCLUSIONS

This study provides the range of authenticity of δ(13)C(VPDB) of seven different secondary metabolites in sweet orange genuine essential oil, useful for evaluating the genuineness of orange flavour. In accord with a previous study on different essential oils, the values determined here can be successfully applied for the evaluation of a large number of flavoured food stuffs and correlated with their origins.

Heart-cutting two-dimensional gas chromatography in combination with isotope ratio mass spectrometry for the characterization of the wax fraction in plant material

Gas chromatography coupled to isotope ratio mass spectrometry after on-line combustion (GC-C-IRMS) and high temperature conversion (GC-HTC-IRMS) is used for compound specific isotope ratio determination. This determination can only be performed successfully if the target solutes are fully resolved from other compounds. A new instrumental set-up consisting of heart-cutting two-dimensional GC based on capillary flow technology and a low thermal mass GC oven in combination with an isotope ratio mass spectrometer is presented. Capillary flow technology was also used in all column and interface connections for robust and leak-free operation. The new configuration was applied to the characterization of wax compounds in tobacco leaf and corresponding smoke samples. It is demonstrated that high accuracy is obtained, both in the determination of δ(13)C and δ(2)H values, allowing the study of biosynthesis and delivery mechanisms of naturally occurring compounds in tobacco.

Evaluation of Anti-Inflammatory Activity of Citrus latifolia Tanaka Essential Oil and Limonene in Experimental Mouse Models

The genus Citrus (Rutaceae) includes several species of plants that produce some of the most cultivated fruits in the world, providing an appreciable content of essential oil. In folk medicine, they are used as a cholagogue, antipyretic, anti-inflammatory, sedative, and antitoxic effects. Lemon essential oil has been used since ancient times for its antiseptic, carminative, diuretic, and eupeptic effects. In this study, we investigated the anti-inflammatory activity of Citrus latifolia Tanaka essential oil (CLEO) and its main constituent LIM. In the cell viability assay, CLEO and LIM (3, 10, 30, and 90  μ g/mL) had low cytotoxicity. In zymosan-induced peritonitis, LIM (500 mg/kg) decreased the infiltration of peritoneal exudate leukocytes and decreased the number of polymorphonuclear leukocytes. In vitro chemotaxis revealed that CLEO and LIM (1, 3, and 10 µg/mL) promoted a significant reduction of neutrophil migration toward fMLP and LTB4. LIM (500 mg/kg) also reduced TNF- α levels but did not alter IL-10 levels in the peritoneal exudate. In conclusion, this study showed that LIM isolated from CLEO had potential anti-inflammatory effects, likely by inhibiting proinflammatory mediators present in inflammatory exudate and leukocyte chemotaxis.

Evaluation of gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) for the quality assessment of citrus liqueurs

Citrus liqueurs are alcoholic beverages obtained by maceration. The European Parliament protects these alcoholic beverages, forbidding the addition of nature-identical flavoring substances. However, for economical and technological reasons, producers often add natural and/or synthetic flavors to the alcoholic syrup, obtaining artificial spirit drinks. The aim of this study is to investigate the authenticity of Italian liqueurs, of lemon, bergamot, and mandarin (locally known as "limoncello", "bargamino", and "mandarinetto"), comparing the carbon isotope ratios with values determined in genuine cold-pressed peel oils. Authenticity assessment was performed using headspace-solid phase microextraction coupled to gas chromatography-combustion-isotope ratio mass spectrometry. Additional analyses were performed by direct enantioselective gas chromatography to determine the enantiomeric distribution of selected chiral volatiles and by gas chromatography-mass spectrometry for the qualitative analyses of the samples. The method allowed confirmation of genuineness. Enantioselective gas chromatography analyses confirmed the results, demonstrating the reliability of the method.