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The subject of the study was the investigation of the chemical composition and antimicrobial activity of the essential oils (EOs) isolated from Calamintha sylvatica, C. vardarensis, C. nepetaand C. glandulosa, as well as their antibacterial activity in combination with antibiotics. The quantitative and qualitative analysis of EOs was performed using the GC/FID and GC/MS methods. The antimicrobial activity of EOs against six standard bacterial strains and one strain of yeast was tested using the broth microdilution method, while the antimicrobial activity of a combination of essential oils and gentamicin/ciprofloxacin was tested by the checkerboard method. The dominant components (> 10%) of the essential oils were: cis-piperitone epoxide and menthone (C. sylvatica), pulegone and menthone (C. vardarensis), pulegone and piperitenone (C. nepeta), pulegone, piperitenone, menthone and piperitone (C. glandulosa). EOs did not exhibit significant antimicrobial activity except the essential oil of C. vardarensiswhich was selectively active against Staphylococcus aureus(MIC - 21.25 μg/mL). The overall effect of essential oil-antibiotic combinations varied from synergistic (FICI ≤ 0.5) to antagonistic (FICI ≥ 2) depending on the bacterial strain tested.

The compositions of hydrodistillated essential oils of Laser trilobum(L.) Borkh. rhizomes and fruits from Serbia, were investigated using GC and GC/MS. In the dark-blue rhizome oil forty-six compounds (93.1% of the total oil) were identified, with α-pinene (31.5%), γ-terpinene (9.0%), p-cymene (7.9%), β-pinene (6.1%) and 1,4-dimethylazulene (6.0%) as the major components. In the colorless fruits oil, twenty components (96.8% of the total oil) were identified, and the main constituents were limonene (51.6%) and perillaldehyde (26.8%). The antimicrobial activity of the oils was tested using the broth microdilution method against nine bacterial and two fungal strains. The oils revealed significant antimicrobial effect, mainly better than that of thymol, used as a reference compound. The strongest activity was recorded for the rhizome oil against Escherichia coli, Klebsiella pneumoniaeand Candida albicans(MICs=25 μg/mL), and the fruit oil against C. albicansATCC 10259 (MIC=12.5 μg/mL).

The present study evaluated the anti-Helicobacter pyloriactivity of Alchemilla glabraNeygenf. (A.sect. Alchemilla), A. monticolaOpiz (A.sect. PlicataeS.E. Fröhner), A. fissaGünther & Schummel (A.sect. Calycinae(Buser) Buser) and A. viridifloraRothm. (A.sect. Calycinae), and identified ellagic acid and quercetin-3-O-β-D-glucoside. Anti-H. pyloriactivity was tested against ten clinical isolates and one reference strain (ATCC 43504). The methanol extracts were more active than the dichloromethane and cyclohexane extracts. The ranges of concentrations were between 4 μg/mL for methanol extracts of A. viridiflora, A. glabraand A. monticola, and 256 μg/mL for cyclohexane extracts of A. viridiflora, A. glabraand A. fissa. The best overall activity was obtained with A. monticolaextracts. No significant difference was found in the ellagic acid contents of the methanol extracts of the tested Alchemillaspecies (0.2–0.3 mg/mL), and anti-H. pyloriactivity was similar (4–32 μg/mL). Ellagic acid exhibited strong activity at very low concentrations (0.125–0.5 μg/mL), while the second identified compound, quercetin-3-O-β-D-glucoside, was also very active in concentration of 2–16 μg/mL.

The antimicrobial and cytotoxic activities of the essential oil of Satureja montanassp. pisidicafrom two localities (mountains Korab and Galičica) were studied. Forty-nine components were identified in the each sample. Oxygenated monoterpene hydrocarbons were the major compounds: carvacrol, thymol, carvacrol methyl ether and β-linalool. Both tested essential oils showed very high and similar antimicrobial activity. Minimal inhibitory concentrations ranged from 12.5 μg/mL against S. epidermidisto 50 μg/mL against P. aeruginosaand C. albicans.The cytotoxic effect of the essential oils was tested against MDA-MB-361, MDA-MB-453, HeLa, LS174 and MRC5 cells. The essential oil from Korab demonstrated significantly better results than the oil from Galičica, particularly against HeLa and MDA-MB-453 cell lines, with IC50values of 63.5 and 72.3 μg/mL, while the oil from Galičica was the most active on the human epithelial cervical cancer HeLa cells (IC5099.7 μg/mL).

The chemical composition and antimicrobial activity of the essential oil of the Balkan endemic species Seseli rigidumWaldst. & Kit. (Apiaceae) was investigated. The monoterpene α-pinene was predominant in the volatile oil from aerial parts (57.4%) and fruit (23.3%). In the essential oil of the aerial parts limonene (6.7%), camphene (5.8%) and sabinene (5.5%) were also present in high amounts, and in the fruit oil, β-phellandrene (17.4%) and sabinene (12.9%). On the contrary, the root essential oil was composed almost entirely of the polyacetylene falcarinol (88.8%). The antimicrobial activity of the root essential oil was significant against Staphylococcus aureus, S. epidermidis, Micrococcus luteusand Enterococcus faecalis(MICs 6.25–25.00 μg/mL). Volatile constituents from the root strongly inhibited the growth of methicillin-resistant strains of S. aureus(MICs 6.25–50.00 μg/mL). Anti-staphylococcal activity can be attributed to the main volatile constituent of S. rigidumroot, falcarinol.

The composition of the essential oil obtained by hydrodistillation from the aerial parts of Satureja kitaibeliifrom Rtanj mountain (Serbia), collected during three years, was studied. Thirty-nine components were identified in each sample of S. kitaibeliiessential oil, representing about 87% of the oils. p-Cymene was the most dominant compound in all three oils (27.9%, 14.7% and 24.4%, respectively). The simple formulation of a lozenge with 0.2% of S. kitaibeliiessential oil was prepared and the antimicrobial activity of the essential oil and the lozenge with essential oil was tested using a broth microdilution assay. Both essential oil and lozenge possessed strong antimicrobial activity with MIC values of 0.10-25 μg/mL, and 0.97-15.6 mg/mL, respectively.

The essential oil obtained by hydrodistillation from the roots of Anthriscus nemorosa(Bieb.) Sprengel (Umbelliferae) was analyzed by GC and GC-MS. Among sixty-two compounds identified (representing 89.0% of the total oil), the main components were: n-nonane (12.1%), n-hexadecanol (6.9%), δ-cadinene (6.4%), β-pinene (6.0%) and germacrene D (5.4%). Furthermore, the antimicrobial activity of the oil was evaluated against the Gram-positive bacteria Staphylococcus epidermidis(ATCC 12228) and Bacillus subtilis(ATCC 6633), the Gramnegative bacterium Escherichia coli(ATCC 25922), and a yeast Candida albicans(ATCC 10259 and ATCC 24433) using the broth microdilution method.

The essential oils of Stachys spruneriBoiss. (sample A and sample B) were analyzed by GC and GC-MS. (+)-Isoabienol was the dominant component (49.5 and 48.2%, respectively of the total oils) among seventy-two identified constituents. Isoabienol was separated, purified by preparative thin-layer chromatography, and further identified by means of physicochemical and spectrometric analysis. The microbial growth inhibitory properties of the essential oil and its main metabolite, the labdane diterpene isoabienol, were determined using the broth microdilution method against eight laboratory strains of bacteria (Gram- positive: Staphylococcus aureus, S. epidermidis, Micrococcus luteus, Enterococcus faecalis, Bacillus subtilis, and Gram- negative: Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and two strains of the yeast Candida albicans.Both essential oil and isoabienol showed considerable activity against all the microorganisms tested, with the isolated compound being most active.

Oil extracts of flowering tops of Hypericum richeriVill. prepared in three different ways were evaluated for chemical composition, and Anti-inflammatory and Gastroprotective activities. An HPLC method was developed for determination of two dominant flavonoids, quercetin and I3,II8-biapigenin. The carrageenan-induced rat paw edema test was used for screening the antiinflammatory activity, while indomethacin-induced rat gastric mucosa damage test was used for evaluation of gastroprotective activity. The oil extract prepared by maceration with 96% ethanol, followed by extraction with sunflower oil by heating on a water bath, exhibited the highest antiinflammatory (38.4 %) and gastroprotective activities (gastric damage score of 0.9). The same oil extract had the highest content of quercetin (49 μg/mL) and I3,II8-biapigenin (60 μg/mL). These results approve the usage of oil extracts of H. richerias an antiinflammatory and gastroprotective agent.

The composition and antimicrobial activity of the essential oil from the underground parts (roots and rhizomes) of Laserpitium zernyi Hayek (Apiaceae) were investigated. The pale blue essential oil, obtained by hydrodistillation, was analyzed by GC and GC-MS. Forty-three compounds were identified (94.3% of total oil). The main constituent, beside α-pinene (31.6%) was α-bisabolol (30.9%), so this oil may be a novel potential natural source of this sesquiterpene alcohol. The antimicrobial activity was tested using the microdilution method against Gram (+) bacteria (Staphylococcus aureus, S. epidermidis, Micrococcus luteus, Enterococcus faecalis), Gram (–) bacteria (Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli), and two strains of yeast (Candida albicans). L. zernyi oil showed significant antibacterial activity against S. epidermidis, S. aureus and M. luteus, but lower activities against the other tested strains.

The essential oil from the aerial parts of Marrubium incanumDesr. (Lamiaceae), obtained by hydrodistillation, was analyzed by GC and GC-MS. Forty-six compounds were identified, representing 96.3% of the total oil. The main components of the oil were (E)-caryophyllene (27.0%), germacrene D (26.2%) and bicyclogermacrene (11.5%). The microbial growth inhibitory properties of the isolated essential oil were determined using the agar diffusion and broth microdilution method against seven bacterial species (Staphylococcus aureusATCC 25923, S. epidermidis ATCC 12228, Micrococcus flavusATCC 10240, Enterococcus faecalisATCC 29212, Escherichia coliATCC 25922, Klebsiella pneumoniaeNCIMB 9111, and Pseudomonas aeruginosaATCC 27853), and two strains of the yeast Candida albicans(ATCC 10259 and ATCC24433). The essential oil showed activity against all the microorganisms tested, but differences in microbial susceptibility were registered.

The essential oils of the aerial parts and fruits of Chaerophyllum aureumL., collected from two mountains in Serbia, were analyzed by GC and GC/MS. Sabinene (18.5-31.6%), p-cymene (7.9-25.4%) and limonene (1.9-10.9%) were characterized as the main constituents. The oils were tested against six bacterial strains and one strain of yeast, Candida albicans. The highest antimicrobial activity was observed against the Gram-positive bacteria Staphylococcus aureus, S. epidermidisand Micrococcus luteus, while of the Gram-negative strains, Escherichia coliwas the most sensitive.