Biochemical activities of Iranian Mentha piperita L. and Myrtus communis L. essential oils

GC-MS analysis of essential oils of Iranian Mentha piperita and Myrtus communis extracted by hydrodistillation lead to identification of 26 and 32 compounds, respectively. The oils had good to excellent antimicrobial activities against Escherichia coli, Staphylococcus aureus and Candida albicans with the oil of M. piperita being more active. The findings suggest feasibility of application of M. piperita oil in treatment of the infections caused by C. albicans and E. coli. D-values on exposure to M. piperita and Myrtus communis oils were (2.14 and 2.8min), (1.4 and 12.8min) and (4.3 and 8.6min) for E. coli, S. aureus and C. albicans , respectively. The oils were screened for their possible antioxidant activities by two complementary test systems, namely DPPH free radical scavenging and beta-carotene/linoleic acid systems. M. piperirta oil exerted greater antioxidant activity than that of M. communis. Phytochemical and phytobiological characteristics of these oils may lead to extraction and production of active compounds in single or combined forms with useful applications.     

Characterization of a heat-stable protein with antimicrobial activity from Arabidopsis thaliana

A heat-stable protein with antimicrobial activity was isolated from Arabidopsis thaliana plants by buffer-soluble extraction and two chromatographic procedures. The results of MALDI-TOF analysis revealed that the isolated protein shares high sequence identity with aspen SP1. To determine the exact antimicrobial properties of this protein, a cDNA encoding the protein was isolated from an A. thaliana leaf cDNA library and named AtHS1. AtHS1 mRNA was induced by exposure to external stresses, such as salicylic acid and jasmonic acid. We also analyzed the antimicrobial activity of recombinant AtHS1 expressed in Escherichia coli. This protein inhibited pathogenic fungal strains, except for Phytophthora infestans and Phytophthora nicotianae, and it exhibited antibacterial activity against E. coli and Staphylococcus aureus. These results suggest that AtHS1 shows good potential for use as a natural material in the study of antimicrobial agents.     

莳萝蒿精油成分分析及抑菌活性机理探究

为了确定莳萝蒿精油的化学成分,并探究其抑菌活性及抑菌机理.该研究采用水蒸气蒸馏法提取莳萝蒿精油,并通过气相色谱-质谱联用法测定其化学成分.采用抑菌圈法、二倍稀释法和生长曲线法测定精油的抑菌活性,采用电导率法和扫描电镜法探究精油的抑菌机理.结果表明:(1)莳萝蒿精油的主要化学成分包括醇类(47.12％)和萜烯类(19.9...     

江西迷迭香精油的成分分析及抗氧化、抑菌活性研究

为了研究江西迷迭香精油的化学成分及抗氧化、抑菌活性,采用水蒸气蒸馏法提取迷迭香精油,利用气相色谱-质谱联用法(GC-MS)对迷迭香精油成分进行分析,通过对DPPH自由基、羟基自由基的清除活性和还原力来研究迷迭香精油的体外抗氧化活性;通过以枯草芽孢杆菌、金黄色葡萄球菌和大肠杆菌为供试菌,测定抑菌圈大小和最低抑菌浓度(MIC)来研究迷迭香精油的抑菌活性。实验结果表明,从迷迭香精油中鉴定出40种化学成分,占精油总量的99.46%,其主要化学成分有α-蒎烯(39.05%)和1,8-桉叶素(16.86%),其次是莰烯(4.22%)、D-柠檬烯(3.87%)、龙脑(3.74%)、β-石竹烯(3.11%)等,α-蒎烯的含量高于国内其他产地;迷迭香精油对DPPH、羟基自由基和还原力的半数清除率IC₅₀值分别为76.42、51.40和49.15μL/mL;精油对枯草芽孢杆菌、金黄色葡萄球菌和大肠杆菌的抑菌圈大小分别为14.40±0.66、11.41±0.19、11.70±0.27 mm,最低抑菌浓度(MIC)分别为2.50、10.00、10.00μL/mL,对枯草芽孢杆菌的抑制作用明显强于金黄色葡萄球菌和大肠杆菌。结果表明迷迭香精油具有较好的抗氧化、抑菌活性。     

Crystal structure and substrate specificity of the beta-ketoacyl-acyl carrier protein synthase III (FabH) from Staphylococcus aureus

beta-Ketoacyl-ACP synthase III (FabH), an essential enzyme for bacterial viability, catalyzes the initiation of fatty acid elongation by condensing malonyl-ACP with acetyl-CoA. We have determined the crystal structure of FabH from Staphylococcus aureus, a Gram-positive human pathogen, to 2 A resolution. Although the overall structure of S. aureus FabH is similar to that of Escherichia coli FabH, the primer binding pocket in S. aureus FabH is significantly larger than that present in E. coli FabH. The structural differences, which agree with kinetic parameters, provide explanation for the observed varying substrate specificity for E. coli and S. aureus FabH. The rank order of activity of S. aureus FabH with various acyl-CoA primers was as follows: isobutyryl- > hexanoyl- > butyryl- > isovaleryl- > acetyl-CoA. The availability of crystal structure may aid in designing potent, selective inhibitors of S. aureus FabH.     

片球菌素PediocinPA-1抑菌活性检测

目的检测通过基因工程获得的片球菌素Pediocin PA-1抑菌活性。方法采用琼脂扩散法检测片球菌素Pediocin PA-1对单核细胞增生李斯特杆菌、金黄色葡萄球菌、铜绿假单胞菌、沙门菌和大肠埃希菌O157的抑菌活性。结果片球菌素Pediocin PA-1对单核细胞增生李斯特杆菌、金黄色葡萄球菌、沙门菌、铜绿假单胞菌和大肠埃希菌O157等均有抑制作用。其中对单核细胞增生李斯特杆菌、沙门菌、大肠埃希菌和金黄色葡萄球菌的抑制作用效果明显,对铜绿假单胞菌有微弱的抑制作用。结论通过基因工程获得的片球菌素Pediocin PA-1具有抑菌活性。     

Chemical composition and antimicrobial activity of the essential oil of Scutellaria barbata

The essential oil of Scutellaria barbata was obtained by hydrodistillation with a 0.3% (v/w) yield and analysed by GC and GC-MS. The main compounds in the oil were hexahydrofarnesylacetone (11.0%), 3,7,11,15-tetramethyl-2-hexadecen-1-ol (7.8%), menthol (7.7%) and 1-octen-3-ol (7.1%). The antimicrobial activity of the oil was evaluated against 17 microorganisms using disc diffusion and broth microdilution methods. The gram-positive bacteria, including methicillin-resistant Staphlococcus aureus, were more sensitive to the oil than gram-negative bacteria and yeasts.     

Antibacterial action of ether oils of some plants

Inhibitory effect of clove oil on Escherichia coli, Staphylococcus aureus, Salmonella typhimurium, Shigella dysenteriae and Candida albicans was detected. Mint ether oil had the high antibacterial action on S. aureus, however against other microorganisms mint oil had a reliably low effect then clove oil. Fennel oil had high antibacterial effect on C. albicans, and bactericidal action on S. typhimurium and S. dysenteriae.     

毛两面针挥发油化学成分及其生物活性

研究了毛两面针挥发油抑菌作用。抗菌实验结果表明,水蒸馏法提取的挥发油对金黄色葡萄球菌、白色念珠菌有明显的抑菌作用,乙醚提取的挥发油原液对金黄色葡萄球菌、大肠杆菌、绿脓杆菌、白色念珠菌有明显的抑菌作用。采用GC/MS分析了水蒸汽所得挥发油的化学成分,鉴定了20种物质,其中,主要成分是倍半萜。(-)-spathulenol、-γelemene和germacrene D等已被报道有抑菌作用的成分含量分别为12.53%、1.75%和1.44%。     

The antimicrobial activity of the appetite peptide hormone ghrelin

The present study examined the antimicrobial activity of the peptide ghrelin. Both major forms of ghrelin, acylated ghrelin (AG) and desacylated ghrelin (DAG), demonstrated the same degree of bactericidal activity against Gram-negative Escherichia coli (E. coli) and Pseudomonas aeruginosa (P. aeruginosa), while bactericidal effects against Gram-positive Staphylococcus aureus (S. aureus) and Enterococcus faecalis (E. faecalis) were minimal or absent, respectively. To elucidate the bactericidal mechanism of AG and DAG against bacteria, we monitored the effect of the cationic peptides on the zeta potential of E. coli. Our results show that AG and DAG similarly quenched the negative surface charge of E. coli, suggesting that ghrelin-mediated bactericidal effects are influenced by charge-dependent binding and not by acyl modification. Like most cationic antimicrobial peptides (CAMPs), we also found that the antibacterial activity of AG was attenuated in physiological NaCl concentration (150mM). Nonetheless, these findings indicate that both AG and DAG can act as CAMPs against Gram-negative bacteria.     

5H-furan-2-ones from fungal cultures of Aporpium caryae

Four furanones 1-4 with an unusual skeleton containing an acetylene unit, named aporpinones, were isolated from the culture of the basidiomycete Aporpium caryae and their structures were elucidated by spectroscopic methods. Compounds 3 and 4 showed weak to moderate antibacterial activity against Bacillus subtilis, Staphylococcus aureus and Escherichia coli.     

Oxidative stress involved in the antibacterial action of different antibiotics

Staphylococcus aureus and Escherichia coli sensitive to chloramphenicol incubated with this antibiotic suffered oxidative stress with increase of anion superoxide (O2-). This reactive species of oxygen was detected by chemiluminescence with lucigenin. S. aureus, E. coli, and Enterococcus faecalis sensitive to ciprofloxacin exhibited oxidative stress when they were incubated with this antibiotic while resistant strains did not show stimuli of O2-. Other bacteria investigated was Pseudomonas aeruginosa, strains sensitive to ceftazidime and piperacillin presented oxidative stress in presence of these antibiotics while resistant strains were not stressed. Higher antibiotic concentration was necessary to augment O2- in P. aeruginosa biofilm than in suspension, moreover old biofilms were resistant to oxidative stress caused by antibiotics. A ceftazidime-sensitive mutant of P. aeruginosa, coming from a resistant strain, exhibited higher production of O2- than wild type in presence of this antibiotic. There was relation between antibiotic susceptibility and production of oxidative stress.     

Antibacterial action of a heat-stable form of L-amino acid oxidase isolated from king cobra (Ophiophagus hannah) venom

The major l-amino acid oxidase (LAAO, EC 1.4.3.2) of king cobra (Ophiophagus hannah) venom is known to be an unusual form of snake venom LAAO as it possesses unique structural features and unusual thermal stability. The antibacterial effects of king cobra venom LAAO were tested against several strains of clinical isolates including Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Escherichia coli using broth microdilution assay. For comparison, the antibacterial effects of several antibiotics (cefotaxime, kanamycin, tetracycline, vancomycin and penicillin) were also examined using the same conditions. King cobra venom LAAO was very effective in inhibiting the two Gram-positive bacteria (S. aureus and S. epidermidis) tested, with minimum inhibitory concentration (MIC) of 0.78μg/mL (0.006μM) and 1.56μg/mL (0.012μM) against S. aureus and S. epidermidis, respectively. The MICs are comparable to the MICs of the antibiotics tested, on a weight basis. However, the LAAO was only moderately effective against three Gram-negative bacteria tested (P. aeruginosa, K. pneumoniae and E. coli), with MIC ranges from 25 to 50μg/mL (0.2-0.4μM). Catalase at the concentration of 1mg/mL abolished the antibacterial effect of LAAO, indicating that the antibacterial effect of the enzyme involves generation of hydrogen peroxide. Binding studies indicated that king cobra venom LAAO binds strongly to the Gram-positive S. aureus and S. epidermidis, but less strongly to the Gram-negative E. coli and P. aeruginosa, indicating that specific binding to bacteria is important for the potent antibacterial activity of the enzyme.     

Structural variation and inhibitor binding in polypeptide deformylase from four different bacterial species

Polypeptide deformylase (PDF) catalyzes the deformylation of polypeptide chains in bacteria. It is essential for bacterial cell viability and is a potential antibacterial drug target. Here, we report the crystal structures of polypeptide deformylase from four different species of bacteria: Streptococcus pneumoniae, Staphylococcus aureus, Haemophilus influenzae, and Escherichia coli. Comparison of these four structures reveals significant overall differences between the two Gram-negative species (E. coli and H. influenzae) and the two Gram-positive species (S. pneumoniae and S. aureus). Despite these differences and low overall sequence identity, the S1' pocket of PDF is well conserved among the four enzymes studied. We also describe the binding of nonpeptidic inhibitor molecules SB-485345, SB-543668, and SB-505684 to both S. pneumoniae and E. coli PDF. Comparison of these structures shows similar binding interactions with both Gram-negative and Gram-positive species. Understanding the similarities and subtle differences in active site structure between species will help to design broad-spectrum polypeptide deformylase inhibitor molecules.     

Compositional studies and Biological activities of Perovskia abrotanoides Kar. oils

Background

Current study has been designed to evaluate the chemical composition of essential and fixed oils from stem and leaves of Perovskia abrotanoides and antioxidant and antimicrobial activities of these oils.

Results

GC-MS analysis of essential oil identified 19 compounds with (E)-9-dodecenal being the major component in stem and hexadecanoic acid in leaves. In contrast, GC-MS analysis of fixed oil showed 40 constituents with α-amyrin the major component in stem and α-copaene in leaves. The antioxidant activity showed the highest value of 76.7% in essential oil from leaves in comparison with fixed oil from stem (45.9%) through inhibition of peroxidation in linoleic acid system. The antimicrobial assay tested on different microorganisms (e.g. E. coli, S. aureus, B. cereus, Nitrospira, S. epidermis, A. niger, A. flavus and C. albicans) showed the higher inhibition zone at essential oil from leaves (15.2 mm on B. cereus) as compared to fixed oil from stem (8.34 mm on S. aureus) and leaves (11.2 mm on S. aureus).

Conclusions

The present study revealed the fact that essential oil analyzed from Perovskia abrotanoides stem and leaves could be a promising source of natural products with potential antioxidant and antimicrobial activities, as compared to fixed oil.     

Pinelloside, an antimicrobial cerebroside from Pinellia ternata

An antimicrobial cerebroside, pinelloside, was isolated from the air-dried tubers of Pinellia ternata (Thunb.) Breit. Its structure was determined as 1-O-beta-D-glucopyranosyl-(2S,3R,4E,11E)-2-(2'R-hydroxyhexadecenoylamino)-4,11-octadecadiene-1,3-diol by chemical transformation and extensive spectroscopic analyses (IR, MS, 1H and 13C NMR, DEPT as well as 2D NMR techniques HMBC, HMQC, 1H-1H COSY and NOESY). The antimicrobial assay showed that this compound was inhibitory to the growth of Bacillus subtilis, Staphylococcus aureus, Aspergillus niger and Candida albicans, with minimum inhibitory concentrations (MICs) of 20, 50, 30 and 10 microg/ml, respectively. The MICs of penicillin G against bacteria B. subtilis, S. aureus, E. coli, P. fluorescens and H. pylori were 0.80, 0.34, 0.56, 1.34 and 0.92, and those of ketoconazole against fungi A. niger, C. albicans and T. rubrum 0.90, 0.65 and 1.0 microg/ml, respectively.     

Interaction of air ions and bactericidal vapours to control micro-organisms

AIMS: The aim of this study was to investigate the antibacterial activity of candles containing specific-antibacterial compounds, such as essential oils and their constituent compounds. The importance of the ionization products from the flame and the aerial concentration of the volatile compounds were investigated. METHODS AND RESULTS: Agar plates inoculated with Escherichia coli (DH5alpha) or Staphylococcus aureus (NCTC strain number 8532) were exposed in a large air-tight chamber to candle flames combined with the volatile bactericidal compounds beta-pinene and orange oil. A steady decline in E. coli numbers was observed over time because of the effect of a candle flame. This was significantly increased by the addition of volatile oils. The number of S. aureus colonies was not reduced by a plain candle, but significant reductions were caused following exposure to beta-pinene and orange oil candles. As aerial concentration of the volatiles was increased the viability of E. coli and S. aureus declined. Ionization products from the flame made a significant contribution to the observed effects, as intercepting the ions on a grounded grid over the agar plates allowed at least 20% more cells to survive. CONCLUSIONS: This study demonstrates the antibacterial properties of ionization products from a candle flame, and that this effect can be significantly increased by the addition of specific-antibacterial compounds, such as orange oil and beta-pinene. The role of both the ionization products from the candle flame and the concentration of volatile compounds released are important to the effect. SIGNIFICANCE AND IMPACT OF THE STUDY: The technique described here offers a new and novel technique for reducing the concentration of bacteria on surfaces.     

The mode of antimicrobial action of the essential oil of Melaleuca alternifolia (tea tree oil)

The essential oil of Melaleuca alternifolia (tea tree) exhibits broad-spectrum antimicrobial activity. Its mode of action against the Gram-negative bacterium Escherichia coli AG100, the Gram-positive bacterium Staphylococcus aureus NCTC 8325, and the yeast Candida albicans has been investigated using a range of methods. We report that exposing these organisms to minimum inhibitory and minimum bactericidal/fungicidal concentrations of tea tree oil inhibited respiration and increased the permeability of bacterial cytoplasmic and yeast plasma membranes as indicated by uptake of propidium iodide. In the case of E. coli and Staph. aureus, tea tree oil also caused potassium ion leakage. Differences in the susceptibility of the test organisms to tea tree oil were also observed and these are interpreted in terms of variations in the rate of monoterpene penetration through cell wall and cell membrane structures. The ability of tea tree oil to disrupt the permeability barrier of cell membrane structures and the accompanying loss of chemiosmotic control is the most likely source of its lethal action at minimum inhibitory levels.     

Factors influencing potent antagonistic effects of Escherichia coli and Bacteroides ovatus on Staphylococcus aureus in anaerobic continuous flow cultures

We examined factors related to the potent antagonistic effect of Escherichia coli and Bacteroides ovatus on Staphylococcus aureus in anaerobic continuous flow cultures. In the presence of sugars fermentable by E. coli alone or both E. coli and S. aureus, motile E. coli strains exerted a potent antagonistic effect and S. aureus was expelled from the culture vessel within a few days. Conversely, in the presence of a sugar fermentable by S. aureus alone, the antagonistic effect of E. coli was diminished and S. aureus persisted at ca. 5 x 10(5) cfu/mL. B. ovatus alone exerted only a weak antagonistic effect on S. aureus in any culture conditions; however, when B. ovatus was cocultivated with E. coli and S. aureus, even in the presence of a sugar fermentable by S. aureus but not by E. coli, the potent antagonistic effect was restored. Escherichia coli showed the same level of antagonistic effect either in the presence of acetic acid (ca. 32 mM), propionic acid (4 mM), butyric acid (17 mM) and hydrogen sulfide (5 x 10(-1) mM) or when these metabolic products, except for a small amount of acetic acid (1.2 mM) were not present. In these culture conditions, S. aureus populations were lost at rates much higher than theoretical wash out rates of resting cells. These results indicate the presence of some bactericidal factors other than the volatile fatty acids and hydrogen sulfide. The bactericidal factors were not found in cultures of E. coli heated in boiling water for 10 min and in cell-free culture filtrates. Thus, the bactericidal factors seem to be associated with live E. coli cells. The nature of the bactericidal factors is not clear at present.     

The antimicrobial activity of essential oil from Dracocephalum foetidum against pathogenic microorganisms

A number of essential oils from Mongolian aromatic plants are claimed to have antimicrobial activities. The essential oil of Dracocephalum foetidum, a popular essential oil used in Mongolian traditional medicine, was examined for its antimicrobial activity. Eight human pathogenic microorganisms including B. subtilis, S. aureus, M. lutens, E. hirae, S. mutans, E. coli, C. albicans, and S. cerevisiae were examined. The essential oil of Dracocephalum foetidum exhibited strong antimicrobial activity against most of the pathogenic bacteria and yeast strains that were tested; by both the agar diffusion method and the minimum inhibitory concentration (MIC) assay (MIC range was 26-2592 microg/ml). Interestingly, Dracocephalum foetidum even showed antimicrobial activity against methicillin-resistant Staphylococcus aureus (MRSA) strains. We also analyzed the chemical composition of the oil by GC-MS and identified several major components, including n-Mentha-1,8-dien-10-al, limonene, geranial, and neral.