Antimicrobial activity and chemical composition of Origanum glandulosum Desf. essential oil and extract obtained by microwave extraction: Comparison with hydrodistillation

Origanum glandulosum Desf. essential oils obtained by hydrodistillation (HD), solvent-free microwave extraction (SFME) and the extract obtained by microwave-assisted extraction (MAE) were investigated by capillary gas chromatography and gas chromatography/mass spectrometry. The main components of both oils obtained by HD and SFME were thymol (41.6–81.1%) followed by γ-terpinene (27.0–3.1%), p-cymene (17.1–4.0%) and carvacrol (2.2–4.4%), respectively. In the same way, thymol (65.4%), γ-terpinene (13.1%), p-cymene (7.2%) and carvacrol (3.5%) were the main components of the extract obtained by hexane microwave extraction. The SFME method was most selective for the extraction of thymol. The examination of the antimicrobial activity of both essential oils against 10 bacteria, two yeasts and four moulds revealed that O. glandulosum oil is more antifungal than antibacterial. To our knowledge, the antifungal activity of the O. glandulosum oil obtained by HD and both antimicrobial and antifungal activities of O. glandulosum SFME oil were not yet reported. Our study suggests that O. glandulosum essential oil has the potential to be used as a food preservative and to prevent the growth of nosocomial bacteria.     

Phytochemical composition and antimicrobial activities of the essential oils from Satureja subspicata Vis. growing in Croatia

The present study describes the phytochemical profile and antimicrobial activity of Satureja subspicata Vis. essential oils, collected in Dalmatia (Croatia). Three samples of essential oils were obtained from the aerial parts of the plant by hydrodistillation and analyzed by GC–MS. From the 24 compounds representing 97.47% of the oils, carvacrol (16.76%), α-pinene (13.58), p-cymene (10.76%), γ-terpinene (9.54%) and thymol methyl ether (8.83%) appear as the main components. The oils also contained smaller percentages of myrcene, linalool, β-caryophyllene, limonene, geranyl acetate, 1-Octen-3-ol, nerol, thymol and borneol. Furthermore, antimicrobial activity of the oil was evaluated using agar diffusion and broth microdilution methods. The antimicrobial test results showed that the oils had a great potential antimicrobial activity against all 13 bacteria and 9 fungal strains. Gram-positive bacteria are more sensitive to the investigated oil, with a range of 0.09 to 6.25 μl/ml than Gram-negative bacteria in the range which is significantly higher from 1.56 to 25.00 μl/ml. Results presented here may suggest that the essential oil of S. subspicata possesses antimicrobial properties, and is therefore a potential source of antimicrobial ingredients for the food and pharmaceutical industry.     

Phytochemical composition of the essential oils from three Apiaceae species and their antibacterial effects on food-borne pathogens

Essential oils (EOs) of three Apiaceae species, including Bunium persicum, Cuminum cyminum and Carum copticum, extracted by hydrodistillation, were analyzed by gas chromatography (GC) and GC/mass spectrometry. The main components of EOs of B. persicum were γ-terpinene (44.2%), cuminaldehyde (16.9%), γ-terpinen-7-al (10.5%), and ρ-cymene (8%). The major constituents of Cu. cyminum were cuminaldehyde (30.2%), ρ-cymene (14.1%), γ-terpinene (12.8%), and safranal (9.4%), while those of Ca. copticum were thymol (48.4%), ρ-cymene (21.8%) and γ-terpinene (21.3%). The antibacterial effects of the EOs were assessed on several food-borne pathogens, namely Staphylococcus aureus, Bacillus cereus, Escherichia coli O157:H7, Salmonella enteritidis, and Listeria monocytogenes. The ranges of minimum inhibitory concentration (MIC) of the oils were 0.03–0.5, 0.18–3.0, and 0.37–3.0 mg/ml, respectively, for Ca. copticum, B. persicum and Cu. cyminum. Moreover, the combination of B. persicum and Cu. cyminum EOs confirmed synergistic and additive activities against the pathogens.     

Chemical composition and antioxidant activity of the essential oil of Clinopodium vulgare L.

This study was designed to examine the chemical composition and in vitro antioxidant activity of the essential oil of Clinopodium vulgare. GC–MS analysis of the oil resulted in the identification of 40 compounds, representing 99.4% of the oil; thymol (38.9%), γ-terpinene (29.6%) and p-cymene (9.1%) were the main components. The samples were subjected to a screening for their possible antioxidant activity by using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and β-carotene-linoleic acid assays. In the first case, IC₅₀ value of the C. vulgare essential oil was determined as 63.0 ± 2.71 μg/ml. IC₅₀ value of thymol and γ-terpinene, the major compounds of the oil, was determined as 161 ± 1.3 μg/ml and 122 ± 2.5 μg/ml, respectively, whereas p-cymene did not show antioxidant activity. In β-carotene-linoleic acid system, C. vulgare essential oil exhibited 52.3 ± 1.19% inhibition against linoleic acid oxidation. In both systems, antioxidant capacities of BHT, curcumine and ascorbic acid were also determined in parallel experiments.     

Gas Chromatography-Mass Spectrometry Analyses for Detection and Identification of Antioxidant Constituents of Achillea tenuifolia Essential Oil

The present work was designed to study the antioxidant activity and to identify the main active components of the essential oil of Achillea tenuifolia aerial parts. Gas chromatography-mass spectrometry analyses of the essential oil showed the presence of 22 compounds. The main constituents of the oil were thymol (15%), α-pinene (10.11%), Camphene (9.41%), β-pinene (7.54%), α-terpinene (7.21%), p-cymene (4%), 1,8-cineole (2.31%), γ-terpinene (7%), linalool (10%), and carvacrol (20.43%). The antioxidant and free radical scavenging activities of Achillea tenuifolia oil was evaluated by using 2,20-diphenyl-1-picrylhydrazyl assays. The oil exhibited a considerable dose-dependent antioxidant activity. Thymol showed clearly a higher activity (IC50 = 10.04 ± 0.1 μg/ml) followed by Achillea tenuifolia essential oil (15.12 ± 0.4 μg/ml). Antioxidant activity guided fractionation of the oil was carried out by the thin layer chromatography-bioautography screening and fractionation resulted in the separation of the main antioxidant compound which was identified as thymol (80%).     

Liposomal incorporation of carvacrol and thymol isolated from the essential oil of Origanum dictamnus L. and in vitro antimicrobial activity

The chemical composition of the essential oils from Origanum dictamnus L. (wild and organic cultivated plant) was analysed by GC–MS. Carvacrol, thymol, p-cymene, and γ-terpinene were identified as major constituents and isolated from both samples. The above components were successfully encapsulated in phosphatidyl choline-based liposomes and the possible improvement of their antioxidant and antimicrobial activities was tested against selected microbia. The antimicrobial properties of the oils were tested by a diffusion technique against four Gram positive and four Gram negative bacteria and three human pathogenic fungi, as well as the food-borne pathogen, Listeria monocytogenes. The percentage of the encapsulated carvacrol, the major component of the oil, was determined by GC–FID. In order to investigate any possible synergistic or antagonistic effect between carvacrol/thymol and carvacrol/γ-terpinene, the antimicrobial activities of the mixtures, were also determined before and after encapsulation in liposomes. All tested compounds presented enhanced antimicrobial activities after the encapsulation. Finally, in all cases, their antioxidant activity using differential scanning calorimetry was studied, in order to gain knowledge about their oxidation stability.     

Influence of drying and extraction methods on yield and chemical composition of the essential oil of Satureja hortensis

The aerial parts of Satureja hortensis, cultivated in Iran (Research Station of Alborz, Karaj), were collected at the full-flowering stage and dried by three different drying methods (sun-drying, shade-drying and oven-drying at 45 °C). The essential oils of every treatment were obtained by hydro-distillation of the aerial parts. In addition, the essential oil of shade-dried sample was obtained by two other distillation methods (water- and steam-distillation and direct steam-distillation). The oils were analyzed by capillary GC and GC–MS. Statistical analysis showed no significant difference between oil yield (w/w) of the oven-dried sample (1.06%) compared to shade-dried (0.94%) and sun-dried (0.87%). The oil content of the shade-dried sample, obtained by hydro-distillation, was higher (0.94%) than that of the steam-distilled (0.27%). Twenty-three components were identified in the oil of S. hortensis in the different drying methods, including carvacrol (46.0–48.1%) and γ-terpinene (37.7–39.4%) as main components. Seventeen compounds were characterized in the oils of different distillation methods, including carvacrol (12.3–46%) and γ-terpinene (37.7–70.4%). Although the drying methods had no significant effect on oil composition of S. hortensis, the distillation changed the percentage of main components sharply (significant at 1%). The steam-distillation method produced the lowest amount of carvacrol and highest amount of γ-terpinene. The results showed that extraction by hydro-distillation gave the best results for S. hortensis, based on oil yield and carvacrol percentage.     

In vitro activity of the essential oils of Origanum vulgare, Satureja montana and their main constituents in peroxynitrite-induced oxidative processes

The essential oil obtained from aerial parts of Satureja montana L. and Origanum vulgare L. (Labiatae) along with four of its main components, p-cymene, carvacrol, thymol and γ-terpinene were tested in models of in vitro peroxynitrite-induced formation of both 3-nitrotyrosine and malondialdehyde, two biomarkers of the oxidative stress of recognised pathological and toxicological significance. The essential oils showed a significant activity, thus decreasing 3-nitrotyrosine formation (IC₅₀ values of 43.9 μg/ml for S. montana and 19.2 μg/ml for O. vulgare), and also inhibited the peroxynitrite induced malondialdehyde formation (IC₅₀ values of 27.2 μg/ml and 17.0 μg/ml respectively). Thymol and carvacrol inhibited 3-nitrotyrosine formation (IC₅₀ values of 81.3 μM and 106.3 μM; ascorbic acid IC₅₀ = 400 μM) and reduced malondialdehyde formation (IC₅₀ values of 43.9 μM and 70.1 μM respectively; trolox IC₅₀ = 240 μM). On the contrary, p-cymene and γ-terpinene were completely inactive in both assays under the concentration of 300 μg/ml. These results support, in particular for origanum, the nutraceutical value of these spices and the potential of thymol and carvacrol in preventing the formation of toxic products by the action of reactive nitrogen species.     

Essential oil composition,antimicrobial and antioxidant properties of Mosla chinensis Maxim

The essential oil of Mosla chinensis Maxim was analysed by gas chromatography/mass spectrometry, and its main components are carvacrol (57.08%), p-cymene (13.61%), thymol acetate (12.68%), thymol (6.67%), and γ-terpinene (2.46%). The essential oil exhibited great potential antimicrobial activity against all eight bacterial and nine fungal strains. Antioxidant activity was also tested, the essential oil showing significantly higher antioxidant activity than that of the methanol extract. In addition, the amounts of total phenol components in the plant methanol extract (47.3 ± 0.4 μg/mg) and the oil (80.7 ± 0.5 μg/mg) were determined. The results presented here indicate that the essential oil of M. chinensis has antimicrobial and antioxidant properties, and is therefore a potential source of antimicrobial and antioxidant agents for the food and pharmaceutical industries.     

Chemical composition of the essential oil and supercritical CO2 extracts of Zataria multiflora Boiss

Essential oil of Zataria multiflora Boiss, cultivated in Iran, was isolated by steam distillation and compared with supercritical fluid CO₂ extracts. The oils and extracts were analyzed by capillary gas chromatography, using flame ionization and mass spectrometric detection. Different parameters, such as temperature, pressure, extraction period (dynamic) and modifier (methanol) concentration were employed to maximize the SFE efficiency. The results showed that, under optimum conditions (P=30.4 MPa, T=55 °C, t_dynamic=20 min and V_modifier=0 μl) extraction of Z. multiflora Boiss was more efficient. Chemical analysis revealed that components extracted under different SFE conditions possessed widely different percentages of constituents [thymol (14.2–67.6%), λ-terpinene (0.1–19.5%) and ρ-cymene (3.6–12.0%)]. The amounts, of co-extracted cuticular waxes varied too. Oil obtained by steam distillation was also compared to the SFE extracts. The results showed that the major components of Z. multiflora Boiss were thymol (44.6%), λ-terpinene (21.5%) and ρ-cymene (13.7%), based on steam distillation.     

The in vitro antioxidative properties of the essential oils and methanol extracts of Satureja spicigera (K. Koch.) Boiss. and Satureja cuneifolia ten

This study was designed to examine the in vitro antioxidant activities of the essential oil and methanol extracts of Satureja spicigera and S. cuneifolia from Turkish flora. GC and GC/MS analysis of the essential oils resulted in the identification of 40 and 29 compounds, representing the 99.4% and 99.5% of the oils, respectively. Major constituents of the oils were carvacrol (42.5% and 67.1%), γ-terpinene (21.5% and 15.2%) and p-cymene (20.9% and 6.7%), respectively. Methanol extracts were also obtained from the aerial parts of the plants. The samples were subjected to a screening for their possible antioxidant activities by using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and β-carotene–linoleic acid assays. In general, samples obtained from S. cuneifolia exerted greater antioxidant activities than did those obtained from S. spicigera. In the DPPH test system, free radical-scavenging activity of S. spicigera oil was determined to be 127 ± 1.63 μg/ml, whereas IC₅₀ value of S. cuneifolia was 89.1 ± 2.29 μg/ml. In the β-carotene–linoleic acid test system, antioxidant activities of the oil were 81.7 ± 1.14% and 93.7 ± 1.83%, respectively. Antioxidant activities of the synthetic antioxidant, BHT, ascorbic acid, curcumin and α-tocopherol were also determined in parallel experiments.     

Radical scavenging and antibacterial properties of the extracts from different Thymus pulegioides L. chemotypes

Radical scavenging and antibacterial properties of large thyme extracts isolated from five chemotypes of Thymus pulegioides L. growing wild in Lithuania were studied. The chemotypes were defined according to the main essential oil components: linalool (L), geranial/geraniol/neral (G/G/N), thymol (T), carvacrol/γ-terpinene/p-cymene (C/γT/pC) and thymol/carvacrol/γ-terpinene/p-cymene (T/C/γT/pC). The contents of phenolic compounds, flavonoids and flavonols were determined. It was found that the extracts of phenolic chemotypes containing remarkable concentrations of thymol and/or carvacrol were stronger DPPH and ABTS free radical scavengers in the model systems. The antibacterial activity of the extracts depended on the plant chemotype, extract preparation, solvent used and finally the sensitivity of bacteria. Bacillus cereus, Micrococcus luteus, Staphylococcus epidermidis and Staphylococcus aureus were the most sensitive to the all extracts applied, whereas Escherichia coli, Salmonella typhimurium and Enterobacter aerogenes remained resistant.     

Comparison of essential oil composition of Carum copticum obtained by supercritical carbon dioxide extraction and hydrodistillation methods

Essential oil of Carum copticum cultivated in Iran was obtained by hydrodistillation and supercritical (CO₂) extraction (SFE) methods. The oils were analysed by capillary gas chromatography, using flame ionization and mass spectrometric detection. The compounds were identified according to their retention indices and mass spectra (EI, 70 eV). The effects of different parameters, such as pressure, temperature, modifier volume and extraction time, on the supercritical fluid extraction of C. copticum oil were investigated. The results showed that, under pressure of 30.4 MPa, temperature 35 °C, methanol 0% and dynamic extraction time of 30 min, the method was most selective for the extraction of thymol. Eight compounds were identified in the hydrodistilled oil. The major components of C. copticum were thymol (49.0%), γ-terpinene (30.8%), p-cymene (15.7), β-pinene (2.1%), myrcene (0.8%) and limonene (0.7%). However, by using supercritical carbon dioxide under optimum conditions, only three components constituted more than 99% of the oil. The extraction yield, based on hydrodistillation was 2.8% (v/w). Extraction yield based on the SFE varied in the range of 1.0–5.8% (w/w) under different conditions. The results show that, in Iranian C. copticum oil, thymol is a major component.     

Carum copticum Benth. & Hook., essential oil chemotypes

Carum copticum Benth. & Hook is a popular spice and a traditional flavor that is used in Iran. The fruits of C. copticum have several therapeutic effects including carminative, diuretic and anti-vomiting effects. There are some reports on the chemical composition of C. copticum fruits essential oil. In our research the results of GC–MS analyses of the essential oil from C. copticum fruits and differences among various reports were described. Major constitutes of the oil were thymol (54.50%), γ-terpinene (26.10%) and p-cymene (22.10%). Comparison of the result from this study with other reports indicates that C. copticum have thymol and carvacrol chemotypes.     

Chemical composition and antioxidant and antimicrobial activity of two Satureja essential oils

Hydro-distilled volatile oils from the aerial parts of Satureja montana L., and Satureja subspicata Bartl. ex Vis., growing wild in Bosnia and Herzegovina, were analyzed by GC/MS. More than one hundred compounds were identified in both plant oils, representing 92.4–98.1% of the total oil. The major constituents of essential oils obtained from the plant material of S. montana, collected from two different localities, were thymol (31.7%), and geraniol (22.3%), respectively. The most abundant compounds in essential oils of S. subspicata, collected at two different stages of development, were thymol (28.6%), and spathulenol (37.6%), respectively. The screening of antimicrobial activity of essential oil samples was individually evaluated against Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Pseudomonas aeruginosa and Bacillus subtilis using a paper disc diffusion method. All tested microorganisms were inhibited by essential oil samples. Antioxidant activity was tested using the DPPH radical-scavenging method. All samples showed activity comparable to thymol, which was used as a positive probe.     

Inhibitory effect of thyme and basil essential oils,carvacrol, thymol,estragol, linalool and p-cymene towards Shigella sonnei and S. flexneri

There are a few reports on the antimicrobial activity of essential oils or their major constituents towards Shigella sp. The antimicrobial effect of basil and thyme essential oil and its major constituents thymol, p-cymene, estragol, linalool, and carvacrol was determined using the agar well diffusion assay. Thyme essential oil and thymol and carvacrol showed inhibition of Shigella sp. in the agar well diffusion method. The potential of thyme essential oil, thymol and carvacrol at 0.5% and 1.0% v/v for decontamination of lettuce was evaluated. A decrease of the shigellae was observed after washing with 0.5% while at 1% Shigella numbers dropped below the detection limit. However, the antimicrobial effect on a subsequent lettuce sample in the same decontamination solution was significantly decreased. In addition, application of thyme essential oil or thymol or carvacrol for decontamination is hampered by sensoric properties of the lettuce (browning, strong odour).     

Antibacterial activities of essential oils and extracts of Turkish Achillea,Satureja and Thymus species against plant pathogenic bacteria

BACKGROUND: The aims of this study were to examine the chemical composition of the essential oils and hexane extracts of the aerial parts of Satureja spicigera (C. Koch) Boiss., Thymus fallax Fisch. & CA Mey, Achillea biebersteinii Afan, and Achillea millefolium L. by GC and GC–MS, and to test antibacterial efficacy of essential oils and n‐hexane, chloroform, acetone and methanol extracts as an antibacterial and seed disinfectant against 25 agricultural plant pathogens. RESULTS: Thymol, carvacrol, p‐cymene, thymol methyl ether and γ‐terpinene were the main constituents of S. spicigera and T. fallax oils and hexane extracts. The main components of the oil of Achillea millefolium were 1,8‐cineole, δ‐cadinol and caryophyllene oxide, whereas the hexane extract of this species contained mainly n‐hexacosane, n‐tricosane and n‐heneicosane. The oils and hexane extracts of S. spicigera and T. fallax exhibited potent antibacterial activity over a broad spectrum against 25 phytopathogenic bacterial strains. Carvacrol and thymol, the major constituents of S. spicigera and T. fallax oils, also showed potent antibacterial effect against the bacteria tested. The oils of Achillea species showed weak antibacterial activity. Our results also revealed that the essential oil of S. spicigera, thymol and carvacrol could be used as potential disinfection agents against seed‐borne bacteria. CONCLUSION: Our results demonstrate that S. spicigera, T. fallax oils, carvacrol and thymol could become potentials for controlling certain important agricultural plant pathogenic bacteria and seed disinfectant. Copyright © 2009 Society of Chemical Industry     

Constituents of the essential oil of Sideritis cretica boiss

The essential oil constituents of Sideritis cretica Boiss have been investigated by gas chromatography-mass spectrometry. Over 30 compounds were identified or partially identified in the oil which was obtained by steam distillation. The compounds reported in this work are: limonene, β-phellandrene, γ-terpinene, p-cymene, hexanol, nonanal, 1-octen-3-ol, a-copaene, linalool, octanol, 1-terpinen-4-ol, caryophyllene, pulegone, β-farnesene, terpineole, borneol, carvone, naphthalene, zingiberene, trimethyl-dihydro-naphthalene, β-cadinene, ar-curcumene, anethol, damascenone, calamene, colacorene, hexenyl benzoate, γ-decalactone, drimenol, thymol, carvacrol, diterpenes, diethyl phthalate and benzyl benzoate.     

Comparative Antibacterial,Chemical and Morphological Study of Essential Oils of Thymbra spicata var. spicata Leaves by Solvent-Free Microwave Extraction and Hydro-Distillation

The essential oils of Thymbra spicata var. spicata were obtained by both hydrodistillation and solvent-free microwave extraction methods. Chemical composition and antibacterial activity of the essential oils were examined. The main constituents of both essential oils obtained by solvent-free microwave extraction and hydrodistillation from Thymbra spicata var. spicata were carvacrol (44.8–36.1%), γ-terpinene (23.8–26.1%), and p-cymene (7.3–9.6%), respectively. The essential oil obtained from solvent-free microwave extraction contained substantially higher amounts of oxygenated compounds and lower amounts of monoterpenes than hydrodistillation. The antibacterial activities of the essential oils from solvent-free microwave extraction and hydrodistillation were evaluated by the disc diffusion method against six bacterial strains. The essential oil extracted by solvent-free microwave extraction was more effective than the essential oil extracted by hydrodistillation against the tested bacteria except for E. coli ATCC 25922- and S. aureus ATCC 25923+. Especially, S. aureus ATCC 25923+ was more sensitive against the essential oils obtained from Thymbra spicata var. spicata. Scanning electron microscopy measurements show that glands (that are filled with essential oils) were subjected to more severe thermal stresses and localized high pressure by microwave heating, the pressure build up within the glands could have exceeded their capacity for expansion and break down of cell walls. Solvent-free microwave extraction resulted in more extract release more rapidly than in hydrodestillation.     

Chemical composition and biological activities of Algerian Thymus oils

The compositions of essential oils isolated from nine samples of three Thymus species (Thymus algeriensis, Thymus pallescens and Thymus dréatensis) were analysed by GC and GC–MS, and a total of 114 components were identified. T. pallescens collected from various regions showed a great similarity in their compositions and were characterised by carvacrol (44.4–57.7%), p-cymene (10.3–17.3%) and γ-terpinene (10.8–14.2%) as the major components for four samples; only one sample was thymol-rich (49.3%) with a small amount of carvacrol (9.0%). On the other hand, T. algeriensis showed a chemical polymorphism, even for samples from the same location, and two new chemotypes for this species were proposed. Oxygen-containing monoterpenes were the predominant class (76.3%) in T. dreatensis oil, with linalool (30.4%), thymol (20.2%) and geraniol (19.6%) as the principal constituents. The oils were screened for their possible antioxidant activities by four complementary assays, namely DPPH free radical scavenging, hydroxyl radical scavenging, inhibition of lipid peroxidation and reducing power. The two new chemotypes of T. algeriensis exhibited strong hydroxyl radical scavenging (IC₅₀ = 2.2–3.3 μg/ml), but were not or only slightly active against the other radicals and exhibited a weak reducing power. Despite their chemical similarity, T. pallescens oils sometimes produced significant differences in their antioxidant activities. The essential oils were also screened for their antimicrobial activity against five bacteria (three Gram-positive and two Gram-negative) and one yeast (Candida albicans). The tested essential oils showed antimicrobial activity against the microorganisms used, in particular against two important pathogens, C. albicans and Helicobacter pylori.