Antibacterial activity of Thymus maroccanus and Thymus broussonetii essential oils against nosocomial infection - bacteria and their synergistic potential with antibiotics

The aim of this study was to evaluate the antibacterial effect of the association between conventional antibiotics and essential oils (EOs) of endemic Moroccan thyme species, Thymus maroccanus and T. broussonetii, on antibiotic-resistant bacteria involved in nosocomial infections. Synergistic interactions between antibiotics (ciprofloxacin, gentamicin, pristinamycin, and cefixime) and EOs, and between T. maroccanus and T. Broussonetii EOs were determined by the checkerboard test. Serial dilutions of two antimicrobial agents were mixed together so that each row (and column) contained a fixed amount of the first agent and increasing amounts of the second one. The results indicate that the oils had a high inhibitory activity against tested bacteria, except for Pseudomonas aeruginosa. In parallel with the increase of cellular killing, the release of 260nm-absorbing materials from bacterial cells, treated with EOs, increased in response to oil concentration. Out of 80 combinations tested between EOs and antibiotics, 71% showed total synergism, 20% had partial synergistic interaction and 9% showed no effect. Combination with carvacrol, the major constituent of T. maroccanus and T. broussonetii, showed also an interesting synergistic effect in combination with ciprofloxacin. The effect on Gram-positive bacteria was more important than on Gram-negative bacteria. These findings are very promising since the use of these combinations for nosocomial infections treatment is likely to reduce the minimum effective dose of the antibiotics, thus minimizing their possible toxic side effects and treatment cost. However, further investigations are needed to assess the potential for therapeutic application.     

Chemical composition and antimicrobial activity of essential oils from Scabiosa arenaria Forssk: growing wild in Tunisia

The essential oils isolated from three organs, i.e., fruits, stems and leaves, and flowers, of the endemic North African plant Scabiosa arenaria Forssk. were screened for their chemical composition, as well as their possible antibacterial, anticandidal, and antifungal properties. According to the GC-FID and GC/MS analyses, 61 (99.26% of the total oil composition), 79 (98.43%), and 51 compounds (99.9%) were identified in the three oils, respectively. While α-thujone (34.39%), camphor (17.48%), and β-thujone (15.29%) constituted the major compounds of the fruit oil, chrysanthenone (23.43%), together with camphor (12.98%) and α-thujone (10.7%), were the main constituents of the stem and leaf oil. In the case of the flower oil, also chrysanthenone (38.52%), camphor (11.75%), and α-thujone (9.5%) were identified as the major compounds. Furthermore, the isolated oils were tested against 16 Gram-positive and Gram-negative bacteria, four Candida species, and nine phytopathogenic fungal strains. It was found that the oils exhibited interesting antibacterial and anticandidal activities, comparable to those of thymol, which was used as positive control, but no activity against the phytopathogenic fungal strains was observed.     

Antioxidant and antibacterial activities of eugenol and carvacrol‐grafted chitosan nanoparticles

Essential oils are known to possess antimicrobial and antioxidant activity while chitosan is a biocompatible polymer with antibacterial activity against a broad spectrum of bacteria. In this work, nanoparticles with both antioxidant and antibacterial properties were prepared by grafting eugenol and carvacrol (two components of essential oils) on chitosan nanoparticles. Aldehyde groups were first introduced in eugenol and carvacrol, and the grafting of these oils to chitosan nanoparticles was carried out via the Schiff base reaction. The surface concentration of the grafted essential oil components was determined by X‐ray photoelectron spectroscopy (XPS). The antioxidant activities of the carvacrol‐grafted chitosan nanoparticles (CHCA NPs) and the eugenol‐grafted chitosan nanoparticles (CHEU NPs) were assayed with diphenylpicrylhydrazyl (DPPH). Antibacterial assays were carried out with a representative gram‐negative bacterium, Escherichia coli (E. coli) and a gram‐positive bacterium, Staphylococcus aureus (S. aureus). The grafted eugenol and carvacrol conferred antioxidant activity to the chitosan nanoparticles, and the essential oil component‐grafted chitosan nanoparticles achieved an antibacterial activity equivalent to or better than that of the unmodified chitosan nanoparticles. Cytotoxicity assays using 3T3 mouse fibroblast showed that the cytotoxicity of CHEU NPs and CHCA NPs were significant lower than those of the pure essential oils. Biotechnol. Bioeng. 2009; 104: 30–39 © 2009 Wiley Periodicals, Inc.     

Antimicrobial, antioxidant, and anti-inflammatory activities of essential oils from five selected herbs

Eucalyptus bridgesiana, Cymbopogon martinii, Thymus vulgaris, Lindernia anagallis, and Pelargonium fragrans are five species of herbs used in Asia. Their essential oils were analyzed by GC-MS, and a total of 36 components were detected. The results of our study indicated that, except for the essential oil of P. fragrans, all of the essential oils demonstrated obvious antimicrobial activity against a broad range of microorganisms. The C. martinii essential oil, which is rich in geraniol, was the most effective antimicrobial additive. All of the essential oils demonstrated antioxidant activities on 2,2-diphenyl-1-picrylhydrazyl radical scavenging assay, β-carotene/linoleic acid assay, and nitric oxide radical scavenging assay. Furthermore, the T. vulgaris essential oil, which possesses plentiful thymol, exhibited the highest antioxidant activity. For P. acnes-induced secretion of pro-inflammatory cytokines, the essential oils of P. aeruginosa, C. martinii, and T. vulgaris reduced the TNF-α, IL-1β, and IL-8 secretion levels of THP-1 cells.     

紫娇花挥发油成分的GC-MS分析及抗氧化能力测定

采用水蒸气蒸馏法和固相微萃取法提取紫娇花不同部位的挥发油,结合气相色谱—质谱(GC-MS)与计算机检索联用技术对其化学成分进行分析和鉴定,用面积归一化法测定各组分的相对含量,并对该挥发油清除DPPH·自由基能力和总抗氧化能力进行了研究。结果表明:紫娇花挥发油具有成分及相对含量差异大、成分较简单、化合物种类以含硫化合物为主的特点。两种方法在紫娇花不同部位挥发油中共检测出了16种化学成分,以硫醚类和含硫烃类化合物为主,相对含量占总成分在80%以上,其中Disulfide,bis(2-sulfhydrylethyl)-含量最高,其余许多成分还具有一定的药用价值。两种方法所得到的挥发油化学成分具有一定的差异性,固相微萃取法对醇类、醛类和酯类物质提取效果较好,而水蒸气蒸馏法对含硫烃类、硫醚类和萜类的提取效果更好。实验条件下紫娇花挥发油清除DPPH·自由基的IC_(50)为17.46 mg·mL~(-1),清除率可达54.86%;紫娇花挥发油在相同条件下较L-抗坏血酸具有更强的总抗氧化力。该研究结果为进一步开发利用该植物资源提供了理论依据。     

Analysis of the volatile components of Lavandula canariensis (L.) Mill., a Canary Islands endemic species,growing in Australia

The essential oil of a Canary Islands endemic species, Lavandula canariensis (L.) Mill., gathered from Australia, was extracted by hydrodistillation and solid phase micro-extraction (SPME). The oils have been studied by GC and GC–MS. A total of 38 compounds have been identified in the leaf oil extracted by hydrodistillation, the principal components being carvacrol (23.6%), β-bisabolene (20.8%), (E,E)-α-farnesene (11.3%), β-caryophyllene (7.6%) and carvacrol methyl ether (7.3%), while the oil extracted by SPME showed carvacrol (42.6%) as the principal component with moderate amounts of (E,E)-α-farnesene (9.1%), β-bisabolene (7.5%), cis-hex-3-en-1-ol (5.6%) and carvacrol methyl ether (4.6%). SPME extracts indicated that carvacrol, cis-hex-3-en-1-ol and linalool were in greater concentration in the head space vapours than in the oil. This is the first report describing the essential oil composition of this species.     

Chemical composition and in vitro evaluation of antioxidant effect of free volatile compounds from Satureja montana L

As a part of an investigation of natural antioxidants from Dalmatian aromatic plants, in this paper we report a study of the antioxidant activity related to the chemical composition of savory free volatile compounds. Twenty-one compounds were identified in the essential oil without fractionation, representing 97.4% of the total oil. The major compound was phenolic monoterpene thymol (45.2%). Other important compounds were monoterpenic hydrocarbons p-cymene (6.4%) a nd gamma-terpinene (5.9%)and oxygen-containing compounds carvacrol methyl ether (5.8%), thymol methyl ether (5.1%), carvacrol (5.3%), geraniol (5.0%) and borneol (3.9%). The evaluation of antioxidant power was performed in vitro by the beta-carotene bleaching and thiobarbituric acid (TBA) methods. As determined with both methods, the total savory essential oil as well as different fractions or pure constituents containing hydroxyl group exhibited relatively strong antioxidant effect. The hydrocarbons, when isolated as CH fraction, showed the poorest effectiveness in spite the fact that this fraction contained gamma-terpinene, alpha-terpinene, p-cymene and terpinolene which previously were identified as potential antioxidants.     

Essential oil production in shoot cultures versus field-grown plants of Thymus caespititius

Thymus caespititius Brot. is an important aromatic species, due to synthesis and production of essential oils for the pharmaceutical and food industries. In the present study, levels of essential oils from two chemotypes, including carvacrol/thymol (CT) and sabinene/carvacrol (SC), were evaluated in proliferating shoot cultures (6–12 subcultures following establishment) and compared to those from field-grown plants. The essential oils were isolated by hydrodistillation and analysed by gas chromatography (GC) and GC–mass spectrometry (GC–MS). Cultures grown under in vitro culture conditions, evaluated over six subcultures, were found to maintain stable composition of essential oils. For the CT chemotype, carvacrol (42 %) and thymol (23 %) were the main essential oil components detected in field-grown plants; in proliferating shoot cultures the levels detected attained 17–25 % in the case of carvacrol and 18–23 % in that of thymol, closely followed by carvacryl acetate (15–23 %) and thymyl acetate (11–15 %). For the SC chemotype, carvacrol (13–28 %), sabinene (18–45 %), and thymol (9–12 %) were the main essential oil components detected in both field-grown and proliferating shoot cultures. Our experiments showed that the essential oil composition in proliferating shoot cultures was not only stable, but also qualitatively similar to that of field-grown plants, notwithstanding minor quantitative differences.     

Chemical Composition and Antimicrobial Activity of Essential Oils from Scabiosa arenaria Forssk. Growing Wild in Tunisia

The essential oils isolated from three organs, i.e., fruits, stems and leaves, and flowers, of the endemic North African plant Scabiosa arenaria Forssk . were screened for their chemical composition, as well as their possible antibacterial, anticandidal, and antifungal properties. According to the GC‐FID and GC/MS analyses, 61 (99.26% of the total oil composition), 79 (98.43%), and 51 compounds (99.9%) were identified in the three oils, respectively. While α‐thujone (34.39%), camphor (17.48%), and β‐thujone (15.29%) constituted the major compounds of the fruit oil, chrysanthenone (23.43%), together with camphor (12.98%) and α‐thujone (10.7%), were the main constituents of the stem and leaf oil. In the case of the flower oil, also chrysanthenone (38.52%), camphor (11.75%), and α‐thujone (9.5%) were identified as the major compounds. Furthermore, the isolated oils were tested against 16 Gram‐positive and Gram‐negative bacteria, four Candida species, and nine phytopathogenic fungal strains. It was found that the oils exhibited interesting antibacterial and anticandidal activities, comparable to those of thymol, which was used as positive control, but no activity against the phytopathogenic fungal strains was observed.     

Chemical Composition and In Vitro Evaluation of Antioxidant Effect of Free Volatile Compounds From Satureja montana L.

As a part of an investigation of natural antioxidants from Dalmatian aromatic plants, in this paper we report a study of the antioxidant activity related to the chemical composition of savory free volatile compounds. Twenty-one compounds were identified in the essential oil without fractionation, representing 97.4% of the total oil. The major compound was phenolic monoterpene thymol (45.2%). Other important compounds were monoterpenic hydrocarbons p-cymene (6.4%) and γ-terpinene (5.9%) and oxygen-containing compounds carvacrol methyl ether (5.8%), thymol methyl ether (5.1%), carvacrol (5.3%), geraniol (5.0%) and borneol (3.9%). The evaluation of antioxidant power was performed in vitro by the β-carotene bleaching and thiobarbituric acid (TBA) methods. As determined with both methods, the total savory essential oil as well as different fractions or pure constituents containing hydroxyl group exhibited relatively strong antioxidant effect. The hydrocarbons, when isolated as CH fraction, showed the poorest effectiveness in spite the fact that this fraction contained γ-terpinene, α-terpinene, p-cymene and terpinolene which previously were identified as potential antioxidants.     

Assessment of genetic and chemical variability in Thymus caramanicus

Thymus caramanicus is an endemic species grown in Iran with interesting pharmacological and biological properties. In the present work, essential oil compositions and inter-simple sequences repeat (ISSR) markers were used to estimate the relationships among and within seven populations of T. caramanicus, belonging to three provinces in Iran. The studied individuals were distinguished on the basis of ISSR markers and constituents of essential oil. A total of 127 band positions were produced by 12 ISSR primers, of which 105 were found polymorphic with 82.68 % polymorphism. Genetic similarity values among individuals ranged between 0.15 and 0.82 which was indicative of a high level of genetic variation. On the basis of their genetic similarities, ISSR analysis allowed to group the samples into two main clusters. One of these included populations originated from Kerman and Isfahan provinces, and the other cluster consists of populations from Semnan province. Chemical compounds of essential oils were found variable in the various individuals and all samples were principally composed of phenolic constituents (carvacrol and/or thymol). As a consequence, the plants were classified into two major chemotypes including carvacrol and thymol/carvacrol. A relationship between genetic and chemical variability and geographic distribution has been observed in studied populations of T. caramanicus.     

Essential Oil Compositions and Antibacterial and Antioxidant Activities of Five Lavandula stoechas Cultivars Grown in Thailand

The essential oils of five Lavandula stoechas cultivars grown in Thailand were characterized for their volatile compounds using GC‐FID and GC/MS methods as well as screened for antibacterial and antioxidant activities. Dried aerial parts, including flowers and stems from each cultivar, were subjected to hydrodistillation for 4 h. The essential oil yields were 0.18 %–0.82 % w/w. Of the 95 compounds detected and identified, 1,8‐cineole, fenchone, and camphor were considered the major compounds. Essential oil from each cultivar demonstrated different patterns of antibacterial activity and a variety of antioxidant properties. The highest antibacterial activity, MIC=0.39 mg mL^?1, was observed from the essential oil of L. stoechas ‘major’ (against Klebsiella pneumoniae and Salmonella typhimurium) and the essential oil of L. stoechas ‘white lavender’ (against S. typhimurium). The essential oil of L. stoechas×viridis ‘St. Brelade’ possessed the highest antioxidant capacity, as determined by the DPPH and ABTS assays (IC₅₀ of 67.65 and 89.26 mg mL^?1, respectively). The results indicated that some of these essential oils could be used as key ingredients in lavender oil products in Thailand to increase their therapeutic efficacy, depending on their intended application.     

Inhibition of oxidation of unsaturated fatty acid methyl esters by essential oils

The essential oils from 16 various spice plants were studied as natural antioxidants for the inhibition of autooxidation of polyunsaturated fatty acids methyl esters isolated from linseed oil. The content of methyl oleate, methyl linoleate, and methyl linolenoate after 1, 2, and 4 months of autooxidation were used as criteria to estimate the antioxidant efficiencies of essential oils. In 4 months, 92% of the methyl linolenoate and 79% of the methyl linoleate were oxidized in a control sample of a model system. It was found that the most effective antioxidants were essential oils from clove bud, cinnamon leaves, and oregano. They inhibited autooxidation of methyl linolenoate by 76–85%. The antioxidant properties of these essential oils were due to phenols— eugenol, carvacrol, and thymol. Essential oil from coriander did not contain phenols, but it inhibited methyl linolenoate oxidation by 38%. Essential oils from thyme, savory, mace, lemon, and tea tree inhibited methyl linolenoate oxidation by 17–24%. The other essential oils had no antioxidant properties.     

The alpha-terpenyl acetate chemotype of essential oil of Thymus pulegioides L

The composition of the essential oils of Thymus pulegioides L. plants growing wild in Vilnius district (Lithuania) with "ester", lemon and carvacrol (phenol) odours were collected in one location and investigated by GC, GC/MS and IR-spectroscopy. The essential oils with lemon and carvacrol odour belong to corresponding known citral-geraniol and carvacrol chemotypes. The essential oil of plants with "ester" odour containing 50-70% of alpha-terpenyl acetate belong to alpha-terpenyl acetate chemotype, which was not noticed earlier in Thymus pulegioides L. species.     

Influence of environmental and genetic factors on the stability of essential oil composition of Thymus pulegioides

Thymus pulegioides plants were collected from various natural habitats of Lithuania and transferred into a new uniform environment. The plants were cloned annually at controlled conditions and their essential oil composition was monitored by capillary GC and GC/MS. The geraniol/geranial/neral (G/G/N), thymol (T), linalool (L), carvacrol/γ-terpinene/p-cymene (C/γT/pC) and thymol/carvacrol/γ-terpinene/p-cymene (T/C/γT/pC) chemotypes of T. pulegioides were studied. It was found that according to the stability of essential oil composition on a sudden change of environmental conditions two types of T. pulegioides can be distinguished: (1) plants which preserve their chemical composition of the essential oils; (2) plants, which considerably change their chemical composition of the essential oils.     

Composition and the in vitro antimicrobial activities of the essential oils of some Thymus species

The genus Thymus (Lamiaceae) is represented by 38 species (64 taxa) in Turkey, and 24 of which are endemic to Turkey. Aerial parts of Thymus longicaulis subsp. chaubardii var. chaubardii, T. zygioides var. lycaonicus, T. longicaulis subsp. longicaulis var. subisophyllus and T. pulvinatus collected from three different localities in Balikesir province were subjected to hydrodistillation to yield essential oils which were subsequently analysed by GC and GC/MS. The main constituents of the oils were identified, and antimicrobial bioassay was applied. Thymol (56.6%, 42.8%, 36.9%) was the main component in the oils of T. longicaulis subsp. chaubardii var. chaubardii (chemotype I), T. longicaulis subsp. chaubardii var. chaubardii (chemotype II) and T. zygioides var. lycaonicus respectively. The oil of T. longicaulis subsp. longicaulis var. subisophyllus contained carvacrol (60.0%) and the oil of T. pulvinatus borneol (27.9%) as main constituents.     

In-vitro antimicrobial activity and chemical composition of Sardinian Thymus essential oils

Essential oils and their components are becoming increasingly popular as naturally occurring antimicrobial agents. In this work the chemical composition and the antimicrobial properties of Thymus essential oils and of their main components were determined. Three essential oils obtained from different species of Thymus growing wild in Sardinia and a commercial sample of Thymus capitatus oil were analysed. The essential oil components were identified by GC/MS analysis. The antimicrobial activity of the oils and components was determined against a panel of standard reference strains and multiple strains of food-derived spoilage and pathogenic bacteria, using a broth microdilution method. The GC/MS analysis showed that the major constituents of the oils were monoterpene hydrocarbons and phenolic monoterpenes, but the concentration of these compounds varied greatly among the oils examined. The results of the antimicrobial assay showed that essential oils extracted from Sardinian Thymus species have an antimicrobial activity comparable to the one observed in other thyme oils. It seems also confirmed that the antimicrobial properties of thyme essential oils are mainly related to their high phenolic content. Among the single compounds tested carvacrol and thymol turned out to be the most efficient against both reference strains and food-derived bacteria. The results of this study confirmed the possibility of using thyme essential oils or some of their components in food systems to prevent the growth of foodborne bacteria and extend the shelf-life of processed foods.     

Screening the essential oil composition of wild Sicilian oregano

The qualitative and quantitative composition of the essential oils obtained from wild Sicilian oregano plants has been investigated. Samples were collected from three areas of Sicily namely Val Mazara (M), Val di Noto (N) and Val Demona (D). These areas are based on historical territorial subdivision. The essential oils were obtained by hydrodistillation and analyzed by GC-FID-MS. Seventy eight compounds were identified representing more than 98% of the compounds in the oils. All samples are thymol-chemotype with variable percentage of γ-terpinene, p-cymene, trans-sabinene hydrate, terpinen-4-ol and carvacrol. Statistical analyses were performed in order to evaluate the variability of the essential oils. Six groups were formed reflecting the compositional differences of the essential oil profiles of the wild Sicilian oregano samples.     

Chemical Variability and Biological Activities of Brassica rapa var. rapifera Parts Essential Oils Depending on Geographic Variation and Extraction Technique

In the present work, the Brassica rapa var. rapifera parts essential oils and their antioxidant and antimicrobial activities were investigated for the first time depending on geographic origin and extraction technique. Gas‐chromatography (GC) and GC/mass spectrometry (MS) analyses showed several constituents, including alcohols, aldehydes, esters, ketones, norisoprenoids, terpenic, nitrogen and sulphur compounds, totalizing 38 and 41 compounds in leaves and root essential oils, respectively. Nitrogen compounds were the main volatiles in leaves essential oils and sulphur compounds were the main volatiles in root essential oils. Qualitative and quantitative differences were found among B. rapa var. rapifera parts essential oils collected from different locations and extracted by hydrodistillation and microwave‐assisted hydrodistillation techniques. Furthermore, our findings showed a high variability for both antioxidant and antimicrobial activities. The highlighted variability reflects the high impact of plant part, geographic variation and extraction technique on chemical composition and biological activities, which led to conclude that we should select essential oils to be investigated carefully depending on these factors, in order to isolate the bioactive components or to have the best quality of essential oil in terms of biological activities and preventive effects in food.