In vitro antimicrobial combinatory effect of Cinnamomum cassia essential oil with 8-hydroxyquinoline against Staphylococcus aureus in liquid and vapour phase.

AIMS: The objective of the study was to evaluate the antimicrobial interactions between two volatile agents, Cinnamomum cassia essential oil (CCEO) and 8-hydroxyquinoline (8-HQ) against Staphylococcus aureus strains in liquid and vapour phases. METHODS AND RESULTS: In vitro antimicrobial effect of CCEO in combination with 8-HQ was evaluated against 12 strains of S. aureus by broth volatilization chequerboard method. Results show additive effects against all S. aureus strains for both phases. In several cases, sums of fractional inhibitory concentration values of our test combinations were lower than 0·6, which can be considered as a strong additive interaction. Moreover, composition of CCEO was analysed by gas chromatography-mass spectrometry analysis. In the CCEO, 26 compounds in total were identified, where (E)-cinnamaldehyde was the predominant compound, followed by cinnamyl acetate, α-copaene, bornyl acetate and caryophyllene. CONCLUSIONS: Results showed additive in vitro growth-inhibitory effect of CCEO and 8-HQ combination against various standard strains and clinical isolates of S. aureus. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report on antibacterial effect of 8-HQ and CCEO combination in liquid and vapour phases. Results of the study suggest these agents as potential candidates for development of new anti-staphylococcal applications that can be used in the inhalation therapy against respiratory infections.

Anticlostridial agent 8-hydroxyquinoline improves the isolation of faecal bifidobacteria on modified Wilkins-Chalgren agar with mupirocin.

UNLABELLED: The need for suitable selective cultivation media for the isolation of Bifidobacterium spp. continues to be a real concern in the field of intestinal microbiology. Isolation of bifidobacteria from human and animal faecal samples using selective agar plating may be problematic especially in samples with increased clostridial counts than bifidobacterial counts. Due to the absence of anticlostridial agents in existing selective media, clostridia can displace bifidobacteria resulting in incorrect estimation of their counts. Therefore, we supplemented the existing selective medium 'modified Wilkins Chalgren agar with mupirocin' (MWM) with 90 mg l(-1) of 8-hydroxyquinoline (8HQ), which was recently proved to act selectively against clostridia. The newly composed 'modified Wilkins-Chalgren agar with 8HQ' (MWMQ) was tested on pure bifidobacterial and clostridial strains, their mixtures, and using faecal samples of mammalian origin; its selectivity was evaluated by genus-specific identification of isolates. The results demonstrated that the presence of 8HQ in this agar eliminated the growth of nonbifidobacterial strains on MWMQ compared to that on MWM, whereas the recovery of bifidobacterial counts was at satisfactory levels. In conclusion, MWMQ could be recommended for bifidobacterial isolation from human and animal faeces especially when bifidobacteria are not numerically dominant and there are chances of clostridial contamination. SIGNIFICANCE AND IMPACT OF THE STUDY: Routine isolation of bifidobacteria from mammalian faeces does not use a reliable selective agar with an anticlostridial agent. Overgrowth of clostridia may result in incorrect estimation of bifidobacterial counts. Thus, in order to improve the selectivity of existing media for bifidobacterial isolation, we chose the modified Wilkins-Chalgren agar with mupirocin and supplemented it with 8-hydroxyquinoline (8HQ), a molecule that shows anticlostridial activity without affecting the growth of bifidobacteria. This newly composed medium showed enhanced selectivity and specificity compared to the original medium and therefore, can be recommended for the isolation of bifidobacteria from mammal faeces.

The relationship between structure and in vitro antibacterial activity of selected isoflavones and their metabolites with special focus on antistaphylococcal effect of demethyltexasin.

UNLABELLED: In this study, we tested 15 naturally occurring isoflavones and their metabolites for their possible antibacterial properties against nine Gram-positive and Gram-negative bacteria. The in vitro antibacterial activity was determined using the broth microdilution method, and the results were expressed as minimum inhibitory concentrations (MICs). 6,7,4'-trihydroxyisoflavone (demethyltexasin), 7,3',4'-trihydroxyisoflavone (hydroxydaidzein), 5,7-dihydroxy-4'-methoxyisoflavone (biochanin A), 7,8,4'-trihydroxyisoflavone (demethylretusin) and 5,7,4'-trihydroxyisoflavone (genistein) produced significant antibacterial activity (MICs ≥ 16 µg ml(-1)). The most effective compound, demethyltexasin, was subsequently tested for its growth-inhibitory effect against Staphylococcus aureus, and it exhibited significant antistaphylococcal effects against various standard strains and clinical isolates, including methicillin and tetracycline resistant ones with the MICs ranging from 16 to 128 µg ml(-1). SIGNIFICANCE AND IMPACT OF THE STUDY: The results of the structure-activity relationship (SAR) analysis identified ortho-dihydroxyisoflavones as a class of antibacterially effective compounds emphasizing the hydroxyl groups at C-5, 6 and 7 positions as crucial supposition for the antibacterial action of plant isoflavones and their metabolites. Demethyltexasin, an isoflavones' metabolite present in the human body through enterohepatic recycling of soya bean isoflavones (daidzein, genistein), showed the most potent antibacterial activity, especially against various strains of Staphylococcus aureus (including MDR and MRSA). The significance of this study is a deepening of the knowledge on isoflavones' SAR and identification of the antistaphylococcal activity of demethyltexasin, which suggest that metabolites of isoflavones can be even more potent antibacterial agents than their precursors.

Antimicrobial activity of traditional medicinal plants from Ankober District, North Shewa Zone, Amhara Region, Ethiopia.

CONTEXT: Traditional medicinal plants have long been used in Ethiopia to treat human and livestock ailments. Despite a well-documented rich tradition of medicinal plant use in the country, their direct antimicrobial effects are still poorly known. OBJECTIVE: To investigate the antimicrobial activity of 19 medicinal plant species that were selected based on the ethnobotanical information on their traditional use to treat infectious diseases in Ankober District. METHODS: About 23 different ethanol extracts of plants obtained by maceration of various parts of 19 medicinal plant species were studied for potential antimicrobial activity using a broth microdilution method against Bacillus cereus, Bacteroides fragilis, Candida albicans, Clostridium perfringens, Enterococcus faecalis, Escherichia coli, Listeria monocytogenes, Pseudomonas aeruginosa, Salmonella enteritidis, Staphylococcus aureus, Staphylococcus epidermidis, and Streptococcus pyogenes. RESULTS: Plant extracts from Embelia schimperi Vatke (Myrsinaceae) showed the strongest antibacterial activity with a minimum inhibitory concentration (MIC) value of 64 µg/ml against B. cereus, L. monocytogenes, and S. pyogenes. Growth inhibitory activities were also observed for extracts of Ocimum lamiifolium Hochst. (Lamiaceae) against S. pyogenes, and those of Rubus steudneri Schweinf. (Rosaceae) against S. epidermidis at an MIC value of 128 µg/ml. Generally, 74% of ethanol extracts (17 extracts) showed antimicrobial activity against one or more of the microbial strains tested at an MIC value of 512 µg/ml or below. DISCUSSION AND CONCLUSIONS: Results confirm the antimicrobial role of traditional medicinal plants of Ankober and warrant further investigations on promising medicinal plant species so as to isolate and characterise chemicals responsible for the observed strong antimicrobial activities.

In vitro antibacterial activity of extracts from Samoan medicinal plants and their effect on proliferation and migration of human fibroblasts.

ETHNOPHARMACOLOGICAL RELEVANCE: The prevalence of different types of chronic wounds, due to the ageing population and increase incidence of diseases, is becoming a worldwide problem. Various medicinal plants used in folk medicine have demonstrated wound healing and antimicrobial properties, and some of these species are currently used in commercial preparations. Despite the well-documented and rich tradition of the use of local herbs for the treatment of skin injuries in Samoan folk medicine, their wound healing potential has not yet been systematically studied. AIM OF THE STUDY: Investigation into the in vitro antibacterial activity of ethanol extracts from 14 medicinal plants used in Samoan traditional medicine for the healing of wounds, burns and sores, and their effects on the proliferation and migration of human fibroblasts. MATERIALS AND METHODS: The antibacterial activity of these extracts was tested against pathogens associated with infected skin injuries, using the broth microdilution method. The effect on migration, proliferation and viability of human dermal fibroblasts was evaluated using wound healing scratch assay, cell proliferation assay, and thiazolyl blue tetrazolium bromide cytotoxicity test. RESULTS: The extracts from Cerbera manghas, Commelina diffusa, Kleinhovia hospita, Mikania micrantha, Omalanthus nutans, Peperomia pellucida, Phymatosorus scolopendria, Piper graeffei, Psychotria insularum, and Schizostachyum glaucifolium inhibited the growth of Staphylococcus aureus at the minimum inhibitory concentration (MIC) of ≥4 µg/mL, whereas C. manghas and P. pellucida produced the same MIC against both Escherichia coli and Pseudomonas aeruginosa. Among the antibacterially active species, C. diffusa, K. hospita, P. scolopendria, P. insularum, and S. glaucifolium did not produce toxicity towards the standard line of normal adult human dermal fibroblasts (IC80 > 128 µg/mL). In addition, extracts from Barringtonia asiatica, C. manghas, M. micrantha, O. nutans, P. insularum, and Piper graeffei stimulated significant migration of dermal fibroblasts, while M. micrantha, O. nutans, and P. insularum did not affect cell proliferation at a concentration of 32 µg/mL. CONCLUSIONS: The results suggest that the above-mentioned species of Samoan medicinal plants can be used for the development of new wound healing agents. However, further phytochemical and pharmacological research is needed regarding the isolation and identification of their active constituents.

Comparison of chemical composition and antibacterial activity of Nigella sativa seed essential oils obtained by different extraction methods.

Nigella sativa L. seed essential oils obtained by hydrodistillation (HD), dry steam distillation (SD), steam distillation of crude oils obtained by solvent extraction (SE-SD), and supercritical fluid extraction (SFE-SD) were tested for their antibacterial activities, using the broth microdilution method and subsequently analyzed by gas chromatography and gas chromatography-mass spectrometry. The results showed that the essential oils tested differed markedly in their chemical compositions and antimicrobial activities. The oils obtained by HD and SD were dominated by p-cymene, whereas the major constituent identified in both volatile fractions obtained by SD of extracted oils was thymoquinone (ranging between 0.36 and 0.38 g/ml, whereas in oils obtained by HD and SD, it constituted only 0.03 and 0.05 g/ml, respectively). Both oils distilled directly from seeds showed lower antimicrobial activity (MICs > or = 256 and 32 microg/ml for HD and SD, respectively) than those obtained by SE-SD and SFE-SD (MICs > or = 4 microg/ml). All oil samples were significantly more active against gram-positive than against gram-negative bacteria. Thymoquinone exhibited potent growth-inhibiting activity against gram-positive bacteria, with MICs ranging from 8 to 64 microg/ml.

Antimicrobial activity of some medicinal barks used in Peruvian Amazon.

The aim of this study was to evaluate the antimicrobial activity of six barks traditionally used in Callería District (Ucayali Department, Peru) for treating conditions likely to be associated with microorganisms. Ethanol extracts of stem barks of Abuta grandifolia (Menispermaceae), Dipteryx micrantha (Leguminosae), Cordia alliodora (Boraginaceae), Naucleopsis glabra (Moraceae), Pterocarpus rohrii (Leguminosae), and root bark of Maytenus macrocarpa (Celastraceae) were tested against nine bacteria and one yeast using the broth microdilution method. All plants possessed significant antimicrobial effect, however, the extract of Naucleopsis glabra exhibited the strongest activity against Gram-positive bacteria (MICs ranging from 62.5 to 125 microg/ml), while the broadest spectrum of action was shown by the extract of Maytenus macrocarpa, which inhibited all the strains tested with MICs ranging from 125 to 250 microg/ml.

Antibacterial screening of some Peruvian medicinal plants used in Callería District.

Nine ethanol extracts of Brunfelsia grandiflora (Solanaceae), Caesalpinia spinosa (Caesalpiniaceae), Dracontium loretense (Araceae), Equisetum giganteum (Equisetaceae), Maytenus macrocarpa (Celastraceae), Phyllanthus amarus (Euphorbiaceae), Piper aduncum (Piperaceae), Terminalia catappa (Combretaceae), and Uncaria tomentosa (Rubiaceae), medicinal plants traditionally used in Calleria District for treating conditions likely to be associated with microorganisms, were screened for antimicrobial activity against nine bacterial strains using the broth microdilution method. Among the plants tested, Phyllanthus amarus and Terminalia catappa showed the most promising antibacterial properties, inhibiting all of the strains tested with minimum inhibitory concentrations (MICs) ranging from 0.25 to 16 mg/ml. The extract from aerial part of Piper aduncum was significantly more active against Gram-positive (MICs ranging from 1 to 2 mg/ml) than against Gram-negative bacteria (MICs > 16 mg/ml).

In vitro growth-inhibitory effect of ethanol GRAS plant and supercritical CO2 hop extracts on planktonic cultures of oral pathogenic microorganisms.

Conventional chemical antiseptics used for treatment of oral infections often produce side-effects, which restrict their long-term use. Plants are considered as perspective sources of novel natural antiseptics. However, little is still known about their inhibitory properties against oral pathogens. The objective of this study was to test in vitro antimicrobial activities of generally recognized as safe (GRAS) species against planktonic cultures of cariogenic, periodontal and candidal microorganisms and identify active compounds of the most active extracts. Growth-inhibitory effects of ethanol extracts from 109 GRAS plant species, six Humulus lupulus cultivars and two hop supercritical CO2 extracts were evaluated using broth microdilution method. The chemical analysis was done through high-performance liquid chromatography. Best results were obtained for supercritical CO2 and ethanol extracts of H. lupulus with minimum inhibitory concentrations (MIC) ≥8 µg/mL and ≥16 µg/mL, respectively. The chemical analysis of supercritical CO2H. lupulus extracts revealed that α- and ß-acids were their main constituents. Capsicum annuum and Capsicum frutescens showed antibacterial effect against Streptococcus sobrinus and Streptococcus salivarius (MIC=64-128 µg/mL). These strains were further inhibited by Zanthoxylum clava-herculis (MIC=64-128 µg/mL) and Myristica fragrans (both MIC≥128 µg/mL). The latter also exhibited antimicrobial activity against Fusobacterium nucleatum (MIC=64 µg/mL). Punica granatum possessed inhibitory effects against Candida albicans (MIC=128 µg/mL) and F. nucleatum (MIC=64 µg/mL). The results indicate that supercritical CO2H. lupulus extracts together with ethanol extracts of C. annuum, C. frutescens, M. fragrans, P. granatum and Z. clava-herculis are promising materials for further investigation on new antiseptic agents of oral care products.

Screening of some Siberian medicinal plants for antimicrobial activity.

The antimicrobial activity of crude ethanolic extracts of 16 Siberian medicinal plants was tested against five species of microorganisms: Bacillus cereus, Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans. Of the 16 plants tested, 12 showed antimicrobial activity against one or more species of microorganisms. The most active antimicrobial plants were Bergenia crassifolia, Chelidonium majus, Rhaponticum carthamoides, Sanguisorba officinalis, and Tussilago farfara.

Ethnobotanical inventory of medicinal plants used in the Bustillo Province of the Potosi Department, Bolivia.

A survey of medicinal plants used by rural communities in the Bustillo Province of the Potosi Department in Bolivia is reported in this article. Fifty-six plant species belonging to 24 families and 46 different genera were included. Their botanical and vernacular names, plant part used, popular medicinal use, forms of preparation and applications of the herbal remedies are given.

The bifidogenic effect of Taraxacum officinale root.

The infusion of dandelion root (Taraxacum officinale) stimulated in vitro the growth of 14 strains of bifidobacteria. The utilization of oligofructans, glucose, fructose and total saccharides was determined by enzymatic and phenol-sulfuric methods. Dandelion oligofructans were important source of carbon and energy for bifidobacteria tested.

Growth inhibitory effect of grape phenolics against wine spoilage yeasts and acetic acid bacteria.

This paper investigates the in vitro antimicrobial potential of 15 grape phenolic compounds of various chemical classes (phenolic acids, stilbenes and flavonoids) using the broth microdilution method against yeasts and acetic acid bacteria frequently occurring in deteriorated wine. Pterostilbene (MICs=32-128 µg/mL), resveratrol (MICs=256-512 µg/mL) and luteolin (MICs=256-512 µg/mL) are among six active compounds that possessed the strongest inhibitory effects against all microorganisms tested. In the case of phenolic acids, myricetin, p-coumaric and ferulic acids exhibited selective antimicrobial activity (MICs=256-512 µg/mL), depending upon yeasts and bacteria tested. In comparison with potassium metabisulphite, all microorganisms tested were more susceptible to the phenolics. The results revealed the antibacterial and antiyeast effects against wine spoilage microorganisms of several highly potent phenolics naturally occurring in grapes. These findings also provide arguments for further investigation of stilbenes as prospective compounds reducing the need for the use of sulphites in winemaking.