Antimicrobial activity of sesquiterpenes from the essential oil of Juniperus thurifera

Chemical analysis of the essential oil of Juniperus thurifera wood led to the identification of fifty-eight sesquiterpene compounds, of which twenty-eight have been isolated, two of them being new natural cedrane derivatives (1 and 2). Their structures were established on the basis of 1D NMR and 2D NMR spectra. The antimicrobial activities of different pure compounds of this oil were tested against nine microorganisms (Gram-positive and Gram-negative bacteria, and yeasts). Seven of the tested compounds exhibited a relevant activity, with the known alpha- and beta-cedrenes and sesquithuriferol showing minimum inhibitory concentrations of 3.06 microg/mL against Bacillus subtilis and Proteus sp.     

Antimicrobial activity and chemical composition of the essential oil of Lippia graveolens from Guatemala

The composition and the antimicrobial activity of the essential oil of Lippia graveolens H.B.K. collected in Guatemala were studied. Two samples of essential oils were obtained from the aerial parts of the plant by hydrodistillation and analyzed by GC and GC-MS. The oils were characterized by their high content of monoterpenes (70.0-87.2 %). Important differences between the major constituents were found, particularly for carvacrol (0.2 vs. 44.8 %), thymol (18.1 vs. 7.4 %) and p-cymene (6.8 vs. 21.8 %). Both oils showed significant activity against all tested Gram-positive and Gram-negative bacteria, as well as against fungi. Nevertheless, the oil with the higher carvacrol content was found to be more active than the thymol type, with MICs ranging from 0.25 to 0.83 microL/mL and 0.12 to 0.27 microL/mL for bacteria and fungi, respectively.     

Antimicrobial activity of the essential oil and some isolated sulfur-rich compounds from Scorodophloeus zenkeri

The essential oil and several pure sulfur compounds isolated from Scorodophloeus zenkeri were tested for their antibacterial and antifungal activity using a paper disc method, the poisoned food technique, a microatmosphere method and the measurement of cellular ATP content. The essential oil completely inhibited the growth of all fungi tested including yeasts, with the exception of Aspergillus flavus, and was active against the Gram-positive bacteria studied, but not the Gram-negative organisms. 2,4,5,7-Tetrathiaoctane, 2,4,5,6,8-pentathianonane, 2,3,4,6,8-pentathianonane, 2,3,5,6,8,10-hexathiaundecane, 2,3,5-trithiahexane 5-oxide, 2,4,5,7-tetrathiaoctane 2-oxide, 2,3,5,7-tetrathiaoctane 3,3-dioxide and 2,3,5-trithiahexane 3,3-dioxide differed in their effects on the strains studied with respect to both growth and synthesis of cellular ATP. 2,3,5-Trithiahexane, 2,3,4,6-tetrathiaheptane, methyl methanethiosulfonate and bis-methyl-sulfonylmethane exhibited no antimicrobial activity.     

Antimicrobial activity and chemical composition of the essential oil of Hofmeisteria schaffneri

Objectives The aims of this study were to establish the antimicrobial potential of Hofmeisteria schaffneri essential oil and its chemical composition. Methods The essential oils of Hofmeisteria schaffneri harvested at flowering (batches I and IV) and non‐flowering (batches II and III) seasons were prepared by hydrodistillation and analysed by GC and GC‐MS. The aqueous and organic (CH₂Cl₂‐MeOH 1 : 1) extracts were prepared by using infusion and maceration techniques, respectively. The in‐vitro antimicrobial activity of the preparations and compounds against Candida albicans and some bacteria (Gram‐negative and Gram‐positive) was assessed using the broth dilution method in 96‐microplate wells. Key findings Forty‐four compounds, representing ～90% of the total constituents, were identified in the essential oil of Hofmeisteria schaffneri collected in flowering (batches I and IV) and non‐flowering (batches II and III) seasons. In all cases, several thymol analogues were the major components of the oils (～65%); some small differences in the relative proportions of these constituents were observed. The infusion exhibited an antibacterial activity against Staphylococcus aureus and Bacillus subtilis, with a MIC value of 64 µg/ml in each case. The essential oil batches were active against Staphylococcus aureus, with MIC ranging from 48 to 192 µg/ml. They were, however, inactive against Gram‐negative bacteria, including Pseudomonas aeruginosa, Escherichia coli and Salmonella typhi (MIC > 1024 µg/ml). On the other hand, the infusion of the plant as well as the oil from batch I displayed anti‐Candida albicans activity, with MIC of 128 and 192 µg/ml, respectively. Finally, the organic extract did not displayed significant activity against the tested microorganisms (MIC ≥ 1024 µg/ml). Some of the compounds isolated from the plant were also tested. Compounds 8 and 38, which were present in the essential oils, displayed the best antibacterial effect against Gram‐positive bacteria (MIC ranging between 32 and 64 µg/ml). Compounds 6 (present in the infusion) and 10 (present in all preparations) showed higher activity against the yeast (MIC = 128 µg/ml) than the remaining compounds, with MIC values ranging from 256 to 512 µg/ml. Conclusions The composition and antimicrobial activity of the oils changed slightly from flowering to non‐flowering seasons. The results of the present investigation provide in‐vitro scientific support for the use of the plant against skin infections in Mexican folk medicine.     

Antimicrobial activity of essential oil and various extracts of fruits of greater cardamom

Greater cardamom (Amomum subulatum Roxb. Zingiberaceae) commonly known as "Bari ilaichi" is a well known plant used in Ayurvedic and Unani medicine. It has been used for the treatment of various diseases and disorders like gastric ulcer. Therefore antimicrobial activity of petroleum ether, methanol and aqueous extracts from leaves and roots, essential oil and isolated vasicine from A. vasica were tested against various microorganisms. Antimicrobial activity was done by disc diffusion method. The zone of inhibition observed was compared with that of standard drugs, ciprofloxacin and fluconazole. Minimum inhibitory concentration was determined against microorganisms used in the study. The results of this study reveal that methanol extract of fruits of A. subulatum shows remarkable antimicrobial activity against Escherichia coli whereas in case of other microorganisms used it was found inferior to the standard drug used. Methanol extract of rind showed good antimicrobial activity against Staphylococcus aureus. It was found that the essential oil isolated was effective against majority of microorganisms used viz. Bacillus pumilus, Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, Saccharomyces cerevisiae.     

Antimicrobial and antibiofilm activity of Baccharis psiadioides essential oil against antibiotic-resistant Enterococcus faecalis strains

Context: Baccharis psiadioides (Less.) Joch. Müller (Asteraceae) is considered as a producer of bioactive essential oils and is used in south Brazilian folk medicine for its proprieties as stimulant, antipyretic, anti-inflammatory and as an antidote for snake bites.

Objective: To verify the antimicrobial and antibiofilm activities of the essential oil of B. psiadioides (EOBP) against antibiotic-resistant Enterococcus faecalis.

Materials and methods: The initial evaluation of EOBP activity was conducted by the agar and microdilution methods against 13 antibiotic-resistant E. faecalis strains. The antibiofilm effect was determined by the application of EOBP in the earlier adherent cells or to the stabilized biofilm for 24?h and was evaluated by crystal violet, viability and scanning electron microscopy (SEM) assays. Chemical composition of EOBP was determined by gas chromatography (GC/FID – GC/MS).

Results: The MIC values for EOBP were at least 1.25% and 4–16% for agar and microdilution assays, respectively. The EOBP reduced the microbial adherence and the viability of the cells, but did not cause the complete disruption of biofilms. SEM images indicate that EOBP influences the adherence of cells to a surface. The monoterpene β-pinene was the major constituent identified in EOBP.

Conclusion: This research shows the ability of EOBP to control resistant E. faecalis strains and to reduce the biofilm amount attached to abiotic surfaces, indicating its role as a promising new natural antimicrobial agent. Moreover, these results further contribute to the growing number of studies of plant natural products which suggest that these compounds can combat resistant microorganisms.     

Antimicrobial activity of juniper berry essential oil (Juniperus communis L., Cupressaceae)

Juniper essential oil (Juniperi aetheroleum) was obtained from the juniper berry, and the GC/MS analysis showed that the main compounds in the oil were alpha-pinene (29.17%) and beta-pinene (17.84%), sabinene (13.55%), limonene (5.52%), and mircene (0.33%). Juniper essential oil was evaluated for the antimicrobial activity against sixteen bacterial species, seven yeast-like fungi, three yeast and four dermatophyte strains. Juniper essential oil showed similar bactericidal activities against Gram-positive and Gram-negative bacterial species, with MIC values between 8 and 70% (V/V), as well as a strong fungicidal activity against yeasts, yeast-like fungi and dermatophytes, with MIC values below 10% (V/V). The strongest fungicidal activity was recorded against Candida spp. (MIC from 0.78 to 2%, V/V) and dermatophytes (from 0.39 to 2%, V/V).     

Toxicity of Australian essential oil Backhousia citriodora (Lemon myrtle). Part 1. Antimicrobial activity and in vitro cytotoxicity.

The antimicrobial and toxicological properties of the Australian essential oil, lemon myrtle, (Backhousia citriodora) were investigated. Lemon myrtle oil was shown to possess significant antimicrobial activity against the organisms Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Candida albicans, methicillin-resistant S. aureus (MRSA), Aspergillus niger, Klebsiella pneumoniae and Propionibacterium acnes comparable to its major component-citral. An in vitro toxicological study based on the MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) cytotoxicity assay was performed. In vitro cytotoxicity testing indicated that both lemon myrtle oil and citral had a very toxic effect against human cell lines: HepG2 (a hepatocarcinoma-derived cell line); F1-73 (a fibroblast cell line derived from normal skin) and primary cell cultures of human skin fibroblasts. Cytotoxicity IC50 (50% inhibitory concentration) values ranged from 0.008 to 0.014% (w/v) at 4 h to 0.003-0.012% (w/v) at 24 h of exposure. The no-observed-adverse-effect level (NOAEL) for lemon myrtle oil was calculated as 0.5 mg/l at 24 h exposure and the RfD (reference dose) was determined as 0.01 mg/l. A product containing 1% lemon myrtle oil was found to be low in toxicity and could potentially be used in the formulation of topical antimicrobial products.     

Antifungal activity of essential oil from fruits of Indian Cuminum cyminum

The essential oil of fruits of Cuminum cyminum L. (Apiaceae), from India, was analyzed by GC and GC-MS, and its antifungal activity was tested on dermatophytes and phytopathogens, fungi, yeasts and some new Aspergilli. The most abundant components were cumin aldehyde, pinenes, and p-cymene, and a fraction of oxygenate compounds such as alcohol and epoxides. Because of the large amount of the highly volatile components in the cumin extract, we used a modified recent technique to evaluate the antifungal activity only of the volatile parts at doses from 5 to 20 µL of pure essential oil. Antifungal testing showed that Cuminum cyminum is active in general on all fungi but in particular on the dermatophytes, where Trichophyton rubrum was the most inhibited fungus also at the lowest dose of 5 µL. Less sensitive to treatment were the phytopathogens.     

Antimicrobial and antioxidant properties of the essential oil of Salvia lanigera from Cyprus

The essential oil of aerial parts of Salvia lanigera Poir. (Lamiaceae) growing wild in Cyprus was obtained by hydrodistillation and was analysed by GC and GC-MS. A total of 67 compounds, representing 93.6% of the oil, were identified, and the major components were showed to be thymol (12.1%), hexadecanoic acid (6.0%), carvacrol and α-thujone (5.7%). The essential oil was assayed for its antioxidant and antimicrobial activities. Antimicrobial activity of the oil, evaluated using the broth dilution method, resulted higher against Gram-positive bacteria than the other referenced strains tested. Antioxidant activity of the oil was evaluated by using DPPH and FRAP methods together with three antioxidant standards, l-ascorbic acid, tert-butyl-4-hydroxy toluene (BHT) and gallic acid. The activity of the sample in both methods was higher than that of all of standards used at the same dose.     

Anti-inflammatory activity of seed essential oil from Zizyphus jujuba

This study was undertaken to evaluate the effect of essential oil from seeds of Zizyphus jujuba on TPA-induced skin inflammation in experimental mice. Exposure of TPA on the ear of the BALB/c mice caused a marked increase in both ear thickness and skin water content. The ear thickness was measured for TPA-induced ear was 0.54 mm, as compared to control (0.23 mm). Treatment with 1% and 10% of essential oil caused significant decrease in ear thicknesses which were measured to be 0.30 and 0.35 mm, as well as reduce the water content about 51% and 53% in the TPA-induced skin inflammation model, respectively. Furthermore, histological analysis clearly confirmed that Z. jujuba essential oil inhibited the inflammatory responses of skin inflammation in animal model. Therefore, our findings demonstrate that the essential oil of Z. jujuba seeds might accelerate the development of new drugs for various inflammatory diseases.     

Antimicrobial activity and chemical composition of some essential oils

In this study the composition and antimicrobial properties of essential oils obtained from Origanum onites, Mentha piperita, Juniperus exalsa, Chrysanthemum indicum, Lavandula hybrida, Rosa damascena, Echinophora tenuifolia, Foeniculum vulgare were examined. To evaluate the in vitro antibacterial activities of these eight aromatic extracts; their in vitro antimicrobial activities were determined by disk diffusion testing, according to the NCCLS criteria. Escherichia coli (ATTC 25922), Staphylococcus aureus (ATCC 25923) and Pseudomonas aeruginosa (ATTC 27853 were used as standard test bacterial strains. Origanum onites recorded antimicrobial activity against all test bacteria, and was strongest against Staphylococcus aureus. For Rosa damascena, Mentha piperita and Lavandula hybrida antimicrobial activity was recorded only to Staphylococcus aureus. Juniperus exalsa, and Chrysanthemum indicum exhibited antibacterial activities against both Staphylococcus aureus and Escherichia coli. We also examined the in vitro antimicrobial activities of some components of the essential oils and found some components with antimicrobial activity.     

柠檬精油的活性成分分析

目的通过GC/MS分析LEO的活性成分。方法将LEO溶于正己烷,配成2%的溶液,每次进样1μL,流经DB-5毛细管柱,采用GC/MS技术并与NIST标准谱库进行比对确定LEO中各化学成分,按峰面积归一化法得出各组分百分含量。结果 GC/MS分析发现LEO的12种化学成分,占总LEO含量的98.85%,其中含量最高的是m-Mentha-6,8-diene,(R)-(+)-达到77.04%,其次为-Terpinen占14.90%。结论该试验建立的方法简便、快捷、准确,可为EO检测的标准操作流程提供参考,并为建立精油指纹图谱库提供可能。