Zapriana Denkova

Correlation of Antimicrobial Activities of Various Essential Oils and Their Main Aromatic Volatile Constituents

Abstract The pure aromatic volatiles p-cymene, carvacrol, eugenol and thymol as well as commercial essential oils of Cinnamomum zeylanicum, Origanum vulgare, Pimenta dioica, Pimenta racemosa, Satureja hortensis, Syzygium aromaticum, Thymus vulgaris and Trachyspermum ammi were investigated concerning antimicrobial activities. Therefore, these samples and, as reference substances, synthetic antibiotics and the natural antimicrobial components carveol, m-, o- and p-cresol were tested against strains of two Gram-positive and five Gram-negative bacteria and the yeast Candida albicans using agar dilution and agar diffusion methods. The analysis of the chemical composition of the essential oils by means of GC and GC/MS focusing on aromatic volatiles produced the following results: C. zeylanicum: eugenol (74.9%); O. vulgare: carvacrol (66.1%) and p-cymene (9.2%); P. dioica: eugenol (76.0%); P. racemosa: eugenol (45.6%); S. hortensis: carvacrol (41.5%), p-cymene (10.7%) and thymol (8.7%); S. aromaticum: eugenol (76.8%); T. vulgaris: thymol (43.4%), p-cymene (23.5%) and carvacrol (4.1%); T. ammi: thymol (43.7%) and p-cymene (17.7%). All investigated aromatic volatiles and essential oils exhibited strong effects against the yeast Candida albicans and medium to strong antimicrobial activity against the Gram-positive bacteria Staphylococcus aureus and Enterococcus faecalis and the Gram-negative bacteria Escherichia coli, Klebsiella pneumoniae, Proteus vulgaris, and Salmonella sp., whereas weaker effects were observed against Pseudomonas aeruginosa.

Purity, Antimicrobial Activities and Olfactoric Evaluations of Geraniol/Nerol and Various of Their Derivatives

Abstract Commercially available geraniol and nerol, as well as some derivatives, were analyzed for their purity using GC and GC/MS. The olfactoric quality of the samples was evaluated by professional perfumers. Antimicrobial testings using an agar dilution and an agar diffusion method were done to obtain information about their activities against some Gram-(+) and Gram-(−) bacteria, as well as the yeast Candida albicans. The effects were compared with those of the phenolic compound eugenol and some synthetic antibiotics. Most of the investigated compounds were found to have a characteristic, pleasant odor and a high activity against all strains of microorganisms used.

Antimicrobial Testings and Gas Chromatographic Analyses of Aroma Chemicals

Abstract In continuation of our scientific work in the field of combined and sytematical investigation of antimicrobial activities (by means of agar dilution and agar diffusion methods) and structural properties (using gas chromatographic analyses: GC and GC/MS with chiral and achiral columns) of different aroma compounds in various samples (pure chemicals, essential oils, extracts, etc.), further odor-active hydrocarbons (2-carene, 3-carene, limonene and β-caryophyllene) and oxygenated mono- and sesquiterpenes (1,8-cineole, linalool, carvone, camphor and linalyl acetate as well as santalol) were used. Only in the case of (+)-3-carene, (+)-carvone, (-)-linalool and racemic linalool antimicrobial activities were found against all used strains (Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Klebsielle pneumonia and Candida albicans). Detailed results of both, antimicrobial activities and structural properties of the investigated aroma compounds will be presented in this paper.

Antimicrobial activities of essential oils of mint and peppermint as well as some of their main compounds.

Abstract The oil of peppermint (Mentha x piperita L.) from the USA, a dementholized cornmint oil (M. canadensis L.), and a fraction of the dementholized cornmint oil were analyzed by GC-FID and GC/MS. The main constituents of the three samples analyzed were menthone (23.4%, 20.4% and 58.3%, respectively) and menthol (40.7%, 41.2% and 12.3%, respectively). The two oils, the cornmint oil fraction and seven mint oil compounds [(-)-menthol, (-)-menthone, (+/-)-menthyl acetate, 1,8-cineole, limonene, β-pinene and β-caryophyllene] were investigated for their antimicrobial effects against two Gram-positive bacteria (Staphylococcus aureus and Enterococcus faecalis), five Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa, Proteus vulgaris, Klebsiella pneumoniae and Salmonella sp.) and the yeast Candida albicans using a modifed agar dilution and agar diffusion method. Medium to high antimicrobial effects were found for both oils, the dementholized cornmint oil fraction, and the target-compounds against all Gram-positive bacteria, whereas against the Gram-negative bacteria and the yeast, one or more samples showed only weak or no activity.

Chemical composition, antimicrobial activities and olfactive evaluation of a Salvia officinalis L. (Sage) essential oil from Egypt

Abstract The chemical composition of a Salvia officinalis L. (sage) essential oil from Egypt has been analyzed by GC and GC/MS. Twenty-eight volatiles were identified, and camphor (25.1%), α-thujone (22.2%) and β-thujone (17.7%) were found as main compounds. These analytical results were correlated with olfactoric evaluations for quality control of this sage oil. Furthermore, the oil, some of its terpene components, a reference compound and two commercial antibiotics were screened against several microorganisms to determine the antimicrobial activity of S. officinals from Egypt.

Antimicrobial Activities of Roman Chamomile Oil From France and Its Main Compounds

Abstract The antimicrobial activity of an essential Roman chamomile flower oil from the Provence (France) was tested against various strains of Gram-positive bacteria (Staphylococcus aureus and Enterococcus faecalis) and Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa, Proteus vulgaris, Klebsiella pneumoniae and Salmonella sp.) as well as against the yeast Candida albicans using a modified agar dilution and agar diffusion method. In addition, some pure main and minor compounds (chemical composition obtained by means of GC and GC/MS measurements), such as isobutyl angelate (32.1%), 2-methylbutyl angelate (16.2%), isobutyl isobutyrate (5.3%), methyl 2-methylbutyrate (1.9%), prenyl acetate (1.4%), 2-methylbutyl 2-methylbutyrate (1.2%) and 2-methylbutyl acetate (1.2%), were also studied for their antimicrobial effects. The Roman chamomile sample showed high antimicrobial activity against all strains of tested microbes (reference compounds: eugenol and three synthetic antibiotics). A similar result was found for 2-methylbutyl 2-methylbutyrate, 2-methylbutyl acetate and prenyl acetate. Surprisingly, no antimicrobial effects against Escherichia coli by methyl 2-methylbutyrate and against Klebsiella pneumoniae by 2-methylbutyl angelate and methyl 2-methylbutyrate as well as by isobutyl isobutyrate against Staphylococcus aureus were observed. It is proposed that the very high antimicrobial activity of Roman chamomile oil from the Provence results of effects found for both main and minor constituents of this oil.

Probiotic Strain Lactobacillus Plantarum NBIMCC 2415 with Antioxidant Activity as a Starter Culture in the Production of Dried Fermented Meat Products

ABSTRACT Lactobacillus plantarum NBIMCC 2415 resistant to low and high values of pH and pepsin, and to high concentrations of bile salts was selected. It was demonstrated that Lactobacillus plantarum NBIMCC 2415 inhibited the growth of pathogenic microorganisms such as Escherichia coli ATCC 25922, Escherichia coli ATCC 8739, Proteus vulgaris G, Salmonella sp., Salmonella abony NTCC 6017, Staphylococcus aureus ATCC 25093, Staphylococcus aureus ATCC 6538 P, Listeria monocytogenes and Listeria monocytogenes I at temperature 15–18°C in the meat products. The high antioxidant activity of this strain against peroxide radicals (ORAC results) was determined. Experimental series of raw-dried meat products were produced. Reduction of the microflora of the meat raw-dried sausages and high concentration of viable cells of L. plantarum NBIMCC 2415 were observed, which makes them functional foods.

SOY MILK YOGHURT

ABSTRACT The influence of the initial dry substance of reconstituted soymilk and two types of starter cultures (single-strain and symbiotic) of Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus thermophilus on the fermentation process duration and the fermented milk quality was investigated. Witht 10% initial dry substance of the soymilk and 1% of the starter cultures for Bulgarian yoghurt the fermentation continued for 2.5 h. The soy milk yoghurt had a titratable acidity of 65–75°T and the cell titre reached 1010 cfu/cm3. The soy milk yoghurt retained its organoleptic qualities when stored for up to 3 days at temperatures of 25–30 °C and for 15 days at 4–6°

Purity, Antimicrobial Activities and Olfactory Evaluations of 2-Phenylethanol and Some Derivatives

Abstract Commercially available 2-phenylethanol and some of its derivatives were analyzed for their purity using GC and GC/MS. The olfactory quality of the samples was evaluated by professional perfumers. Antimicrobial tests using an agar dilution and an agar diffusion method were done to obtain information about their activities against some Gram-positive and Gram-negative bacteria as well as the yeast Candida albicans. The effects were compared with those of the phenolic compound eugenol and some synthetic antibiotics. Most of the investigated compounds were found to show a characteristic, pleasant odor, mostly with a sweet-floral top-note, but do not possess a high activity against many strains of microorganisms used.

In Vitro Study on the Adhesion and Colonization of Candida Albicans on Metal and Acrylic Piercings

Summary Oral/perioral piercing may provide an ideal environment for adhesion and colonization of microorganisms. The aim of this study is to perform an “in vitro” research on the capabilities of adhesion of Candida albicans on oral piercings made of plastic and metal. Acrylic and metal piercings were incubated with Candida albicans and then were observed using scanning electron microscopy under different magnifications. A lot of irregularities and roughness were observed on the surface of the plastic piercing unlike the surface of the metal one, which is not so rough. Nevertheless, the number of Candida albicans colonies was considerably larger on the scanned metal surface in comparison to the plastic surface. In vitro the metal surface of the piercing creates better environment for the adhesion and colonization of microorganisms than the acrylic. This could be attributed to the electrostatic forces that most likely attract Candida albicans to the metal piercing in the early stages of biofilm formation.