Proficiency‐testing scheme for essential oils

The present study was conducted to evaluate the in vitro antimicrobial and antioxidant properties of thyme and rosemary essential oils. The chemical compositions of hydro distilled essential oils were analyzed by GC/MS system. A total of 30 constituents representing of thyme oil were identified: thymol (39.44%), P-cymene (23.6%), γterpinene (12.51%), ledol (2.24%) and Aromadenrrene (2.12%) were the main components comprising 79.91% of the oil. While 37 constituents representing of rosemary oil were identified: borneol (24.13%), α – pinene (9.72%), αcaryophyllene (8.35%), ledol (6.42%), eucalyptol (5.11%), camphor (5.01%), γ – terpinene (5.005), Dverbenone (4.17%), limonene (2.29%) and methyl jasmonate (2.24) were the main components comprising 72.445 % of the oil. Antioxidant effects of essential oils from thyme and rosemary were determined on flaxseed and sesame oils. These essential oils were added to the oils at concentrations of 0.25% and 0.5%, besides the control groups for comparison. The samples were stored 65° C in darkness for 14 days. The antioxidant activity of the essential oils was determined by measuring peroxide values (meq O2/kg oil). On the basis of peroxide value assay, the essential oils showed stronger antioxidant effect when compared to control groups. Amongst the investigated essential oils, the thyme oil was the most effective on retarding lipid oxidation of crude oils, which was followed by rosemary oil. On the other hand in the present investigation antimicrobial activity of two essential oils has been evaluated. After bioassays, most of the essential oils were found susceptible to Gram-positive bacteria such as Staphylococcus aureus, Bacillus subtilis, and didn't showed any activity against Gram-negative bacteria Pseudomonas aueginosa, Escherichia coli. For screening of antimicrobial susceptibility in each essential oil, both positive and negative controls were set to determine growth inhibition zone diameters and MIC (minimum inhibitory concentration).Among two essential oils thyme oil was found to be highly antimicrobial, as it has shown high growth inhibition zone diameter in comparison to rosemary oil except against Aspergillus niger.

Background: Essential oils of Lemon (Citrus limon) and Lemongrass (Cymbopogon citratus) are commonly used in therapeutic contexts including stress-reduction. There is paucity of detailed phytochemical research on chemical constituents of Citrus limon and Cymbopogon citratus essential oils to delineate their therapeutic potentials including reduction of stress. There is also dearth of comparative studies focusing on their phytochemical composition and their efficacy substantiating stress management. Objective: This study aims to authenticate and compare the chemical composition of essential oils of Citrus limon and Cymbopogon citratus and understand their potential in reduction of stress. Methodology: Leaves of Citrus limon and Cymbopogon citratus were collected, authenticated and hydrodistillation was conducted to produce Essential oils. The essential oils were analyzed qualitatively using Gas Chromatography-Mass Spectrometry (GC-MS). The efficacy in reduction of stress was carried-out utilizing structured questionnaire and observational schedule. Results: GC-MS analysis of essential oils from Citrus limon and Cymbopogon citratus revealed 52 (C.limon) and 82 (C.citratus) compounds, respectively. Essential oils of Citrus limon and Cymbopogon citratus exhibited appreciable composition of monoterpenes and sesquiterpenes with therapeutic potency. Conclusion: The phytochemical composition of essential oils of Citrus limon and Cymbopogon citratus confirmed their therapeutic eminence, especially in reduction of stress. The reported chemical profile of essential oils of Citrus limon and Cymbopogon citratus affirms their efficacy in selective human therapy including aromatherapy. Recommendation: There is dearth of clinical research studies on essential oils of Citrus limon and Cymbopogon citratus substantiating their therapeutic efficacy in reduction of stress. Prevalence of stress and syndromes of anxiety related therapeutic developments are the dire needs of the present generation and therefore, concerted research efforts are worthy to substantiate their value in clinical therapeutics. Future predictive studies on variation in their chemical composition with strict attention on geographical and climatic variations are envisaged.

Summary Introduction: Solanum sodomaeum L. has been observed to have several medicinal properties, in particular, in the treatment of several types of human skin cancer. Objective: The influence of the maturation stage of S. sodomaeum fruits on the total lipid contents, fatty acid profiles, essential oil yields and compositions, as well as the antibacterial and antioxidant activities of the essential oils, was investigated. Methods: The fatty acid and essential oil constituents were identified using gas chromatography (GC) and GC–mass spectrometry (GC–MS). The antioxidant properties of essential oil and vegetal oil were assessed using 1,1-diphenyl-2-picryl-hydrazyl (DPPH) scavenging and reducing power assays. The antibacterial activity of essential oil was tested using the disc diffusion assay for resistance in human pathogenic bacteria. Results: Mature fruits showed higher total lipid content (17%) and were characterised by polyunsaturated fatty acids (53.87%), represented mainly by linoleic acid (53.11%). Similar yields of essential oils were detected for immature (0.43%) and mature (0.45%) fruits. Tetrahydronaphthalene (41.79%) was detected as the major essential oil component at the immature stage versus dihydrocoumarin pentane (18.27%), hexadecanoic acid (17.43%) and 2-undecanone (13.20%) in mature fruits. The DPPH test showed that essential oils had better antioxidant properties; however, the vegetal oils showed better performance in the reducing power assay. Moreover, the essential oil of S. sodomaeum mature fruits was active against bacterial strains. Conclusions: S. sodomaeum fruits could be a valuable source of natural antioxidants and antibacterial agents.

Essential oil of Piper betle L. leaves: Chemical composition, anti-acetylcholinesterase, anti-β-glucuronidase and cytotoxic properties

Comparison of essential oil composition and phenolic acid content of selected Salvia species measured by GC–MS and HPLC methods

Variability in the essential oil content and composition of 26 Iranian landraces of coriander (Coriandrum sativum L.), cultivated in a common environment, were studied in the present study. Production of essential oil was considerably differed (0.4 % to 1.6 % of the fruits dry weights) among the local landraces in question with a mean value of 0.84 %. Out of thirty-three identified components representing about 94.2 % to 99.8 % of the all oil samples, linalool was the prevalent constituent with the highest (89.8 %) and lowest (69.7 %) amounts in the oils from Khorram Abad and Zarand landraces, respectively. α-Terpinene (0.1–13.2 %), α-pinene (0.0–7.8 %), neryl acetate (1.3–9.1 %) and (2E)-dodecanal (0.0–10.6 %) constituted other major components of essential oils. Interrelations studies among the main constituents of essential oils and oil content of fruits by calculation of Pearson correlation coefficients revealed significant negative correlations of linalool with p-cymene (r=-0.503), λ-terpinene (r=-0.554) and (2E)-dodecanal (r=-0.435) and p-cymene with neryl acetate (r=-0.467). In contrast, α-pinene positively correlated with p-cymene (r=0.566) and λ-terpinene (r=0.406) and there were no significant correlations between the oil content of fruits and important essential oils components. Because variation observed in the chemical composition of studied landraces can mainly attributed to their genetic background, selection of landraces with special aroma and/or activities is possible and they could be further exploited for use in relevant industries or as starting material for use in the breeding programs of this plant.

This review provides an overview of the emerging trends in analysis of essential oils and indicates future trends. Since early human history the essential oils have been used in folk medicine, food and cosmetic industries in various parts of the world. GC-FID is the traditional method for essential oils quantification while GC-MS is the most common analytical method for qualitative analysis. Chiral GC allowed the identification of a great number of chiral essential oil constituents. An alternative to GC analysis is HPLC chromatography. The use of hyphenated techniques, such as LC-MS-MS provides important information about the structure of essential oils constituents. However, only a comparatively small number of reports on essential oil analyses by HPLC can be found in the literature. Multidimensional chromatography is an approach capable of providing greater resolution.13C-NMR spectroscopy is a complementary tool for analysis of essential oils. Advantage of this method compared to mass spectrometry is identification of stereoisomers and thermally unstable compounds while its disadvantage is inability to identify the minor oils constituents. 1H-NMR as an online tool for GC analysis showed promising results but requires further research to be applied on the analysis of essential oils. The range of information obtained from essential oils analysis enables the application of chemometrics.

Rosemary (Rosmarinus officinalis L.) is an important medicinal plant that contained a wide range of secondary metabolites such as rosmarinic acid. In this study, essential oil content and composition and rosmarinc acid were determined at three phenological stages (before flowering, full flowering and fruit set stages). Hydro distillation method was used for essential oil extraction and GC and GC/MS was used for essential oil composition. On the basis of the obtained results rosemary plants in full flowering stage had higher amount of essential oil (1.99 ml/100 g dry weight) than in before flowering and fruit set stages (1.2 and 1.01 ml/100 per g dry weight, respectively). The extracted essential oil was contained 1,8-cineole, α-pinene, verbenone, camphor, geraniol, borneol acetae, camphene and linalool as major constituents. These constituents were affected by phenological stages. Before flowering, 1,8-cineole, α-pinene and verbenone (13.68%), in full flowering, 1,8-cineole (17.90%) and in fruit set α-pinene (21.77%) were the main constituents of the reosemary essential oil. Using HPLC analysis on leaf extract showed that the highest amount of rosmarinic acid (25.92mg/g DW) was observed in the fruit set stage. In conclusion, for essential oil content full flowering stage can be recommended for harvesting of Rosmarinus officinalis L. and for rosmarinic acid, fruit set stage can be the best time for harvesting of this medicinal plant.

This study highlighted the chemical composition of Tunisian Aleppo pine (Pinus halepensis) essential oil and its biological activities as allelopathic, antioxidant and antibacterial capacities depending on the collection region. The highest essential oil yield was obtained in Boukornine (0.67%) followed by Bizerte (0.50%) and Djerissa (0.25%). The analysis of the chemical composition of Aleppo pine essential oils showed considerable qualitative variability of major components, namely β-caryophyllene (12.27-14.26%), myrcene (11.51-14.26%), p-cymene (8.07-10.57%) and α-pinene (6.57-9.37%). The essential oil of Djerissa had stronger allelopathic effect against Triticum aestivum than Bizerte and Boukornine owing to its richness in monoterpenes, especially myrcene. However, the essential oils of Bizerte and Boukornine had higher antioxidant and antibacterial capacities than Djerissa which could be related to the synergistic property associated with the high level of the sesquiterpene β-caryophyllene with the other essential oil constituents. These results suggested that Aleppo pine essential oil could give a hope toward production of eco-friendly bio-herbicides at least against Triticum aestivum and also as a source of natural antioxidant and antibacterial agents that could be used as food additives.

The compositions of mountain pine (Pinus uncinata) and peat-bog pine (P. uliginosa) needle essential oils were investigated. Enantiomeric compositions of selected monoterpene hydrocarbons were also examined. Respectively, fifty-three and seventy-six components of the essential oils were identified using GC-MS and retention indexes. The main group of essential oil components of mountain pine needles were monoterpenes, and bornyl acetate constituted approximately 30% (46.3 g/100 g) of the oil. In peat-bog pine essential oil, monoterpenes and sesquiterpenes exhibited a similar content (ca. 40%). Bornyl acetate and α-pinene were the main constituents of both essential oils. In the essential oil of P. uncinata needles, limonene, camphene, myrcene and (E)-β-caryophyllene were also noticeable, while in the essential oil of P. uliginosa needles, Δ-car-3-ene, (E)-β-caryophyllene, germacrene D, δ-cadinene, germacrene D 4-ol and α-cadinol were present in notable quantities. In both essential oils, borneol propionate, isobutyrate, 2-methylbutyrate and isovalerate were detected. Their presence was confirmed by synthesis and analysis of the standards; retention indexes on a non-polar column are published herein.

Essential oils are aromatic and volatile liquids extracted from plants. The chemicals in essential oils are secondary metabolites, which play an important role in plant defense as they often possess antimicrobial properties. The interest in essential oils and their application in food preservation has been amplified in recent years by an increasingly negative consumer perception of synthetic preservatives. Furthermore, food-borne diseases are a growing public health problem worldwide, calling for more effective preservation strategies. The antibacterial properties of essential oils and their constituents have been documented extensively. Pioneering work has also elucidated the mode of action of a few essential oil constituents, but detailed knowledge about most of the compounds’ mode of action is still lacking. This knowledge is particularly important to predict their effect on different microorganisms, how they interact with food matrix components, and how they work in combination with other antimicrobial compounds. The main obstacle for using essential oil constituents as food preservatives is that they are most often not potent enough as single components, and they cause negative organoleptic effects when added in sufficient amounts to provide an antimicrobial effect. Exploiting synergies between several compounds has been suggested as a solution to this problem. However, little is known about which interactions lead to synergistic, additive, or antagonistic effects. Such knowledge could contribute to design of new and more potent antimicrobial blends, and to understand the interplay between the constituents of crude essential oils. The purpose of this review is to provide an overview of current knowledge about the antibacterial properties and antibacterial mode of action of essential oils and their constituents, and to identify research avenues that can facilitate implementation of essential oils as natural preservatives in foods.

Chemical composition and seasonality variability of the Spiranthera odoratissima volatile oils leaves

The herb, Elettariopsis triloba (Gagnep.) Loes. (syn. Amomum trilobum Gagnep. or Elettariopsis trilobum (Gagnep.), has been used ethnomedically for the treatment of rabies, inflammation and amelioration of microbial infections. We report herein the chemical constituents and antimicrobial activity of the rhizome essential oil of E. triloba from north-central Vietnam. The technique of gas chromatography (GC) and gas chromatography coupled with mass spectrometry (GC/MS) was used to analyze the oil sample while the microdilution assay was employed to determine the antimicrobial efficacy. Monoterpene compounds including camphene (23.2 %), fenchyl acetate (12.7 %), bornyl acetate (10.6 %), α-pinene (5.7 %) and limonene (5.1 %) were the main constituents of the rhizome essential oil. The essential oil displayed antimicrobial activity only towards Gram-positive bacteria of Enterococcus faecalis ATCC 299212, Staphylococcus aureus ATCC 25923 and Bacillus cereus ATCC 14579 with minimum inhibitory concentration (MIC) values of 16.0 μg/mL, 256 μg/mL and 32.0 μg/mL, respectively. The oil also inhibited the growth of the yeast, Candida albicans ATCC 10231, with a MIC value of 16.0 μg/mL. The chemical constituents and antimicrobial activity of essential oil from E. triolba were being reported for the first time and validation of the ethnomedicinal usage of the plant.

The Apiaceae family known for vegetable crops rich in essential oils, includes numerous genera of high medicinal and economic value. This study investigates the effects of red and far-red light treatments through the dark period (night-break), on the growth characteristics, essential oil quantity and composition, in Coriandrum sativum L., Anethum graveolens L., and Petroselinum crispum. Treatments began 20 days after sowing, with exposure to red or far-red light for 4 h, nightly, from 10 pm to 2 am. Control plants had no treatment. The plants shoots were harvested after 30 days of treatment. The fresh and dry weight, height, petiole length, internode length, leaf number, leaf area, and total chlorophyll of plant samples were measured. Essential oils were evaluated and then analyzed using gas chromatography–mass spectrometry. The results showed that the red and far-red light led to non-significant increase in fresh and dry weight, plant height, petiole length, leaf number, leaf area, essential oil content, and concentration of individual oil components, while the internode length and total chlorophyll showed a significant increase in all treated plants. Therefore, the controlled use of red light and far-red light may be useful for initiating a response in plants, and enhancing their nutritional value. Key words: Apiaceae, light, night-break, essential oil constituents. &nbsp

Schinus terebenthifolius popularly known as aroeira, is a plant widely used in folk medicine for the treatment of respiratory disorders, mycosis and invasive candidal infections. The chemical composition of the essential oil of S. terebenthifolius from different parts of the world is described in the literature, however, there are no comparative reports of essential oils composition from male and female individuals of this plant. In this context, this study aimed to determine the essential oil composition of leaves (male and female plants) and green and ripe fruits from S. terebenthifolius. The essential oils were extracted by hydrodistillation and chemical composition were obtained by gas chromatography at GC-MS and CG-FID systems. Regarding the chemical composition, all the essential oils showed predominance of monoterpene compounds, except the essential oil of leaves from female plant, which presented higher content of sesquiterpenes constituents. The monoterpene D-limonene (39.52-96.61 %) was presented as the main volatile component of leaves (male individual) and in green fruits. The sesquiterpene -caryophyllene (30.20 %) and the monoterpene terpinen-4-ol (64.59 %) were identified as major constituents of essential oils extracted from the leaves of the female individual and the ripe fruits, respectively. These components are reported with antioxidant, antimicrobial, anti-inflammatory, among others properties. In this sense, the chemical composition knowledge indicates that the essential oils properties should be investigated to increase the importance of these volatiles in therapeutic applications.