Antibacterial activity of disodium succinoyl glycyrrhetinate,a derivative of glycyrrhetinic acid against Streptococcus mutans

Streptococcus mutans is a cariogenic bacterium that localizes in the oral cavity. Glycyrrhetinic acid (GRA) is a major component of licorice extract. GRA and several derivatives, including disodium succinoyl glycyrrhetinate (GR‐SU), are known to have anti‐inflammatory effects in humans. In this study, the antimicrobial effect of GRA and its derivatives against the S. mutans UA159 strain were investigated. Minimum inhibitory concentrations (MICs) of GRA and GR‐SU showed antibacterial activity against the S. mutans strain, whereas other tested derivatives did not. Because GR‐SU is more soluble than GRA, GR‐SU was used for further experiments. The antibacterial activity of GR‐SU against 100 S. mutans strains was evaluated and it was found that all strains are susceptible to GR‐SU, with MIC values below 256 µg/mL. A cell viability assay showed that GR‐SU has a bacteriostatic effect on S. mutans cells. As to growth kinetics, sub‐MICs of GR‐SU inhibited growth. The effect of GR‐SU on S. mutans virulence was then investigated. GR‐SU at sub‐MICs suppresses biofilm formation. Additionally, GR‐SU greatly suppresses the pH drop caused by the addition of glucose and glucose‐induced expression of the genes responsible for acid production (ldh and pykF) and tolerance (aguD and atpD). Additionally, expression of enolase, which is responsible for the carbohydrate phosphotransferase system, was not increased in the presence of GR‐SU, indicating that GR‐SU suppresses incorporation of sugars into S. mutans. In conclusion, GR‐SU has antibacterial activity against S. mutans and also decreases S. mutans virulence.     

Antibacterial activity from Penicillium corylophilum Dierckx

A strain of Penicillium corylophilum isolated from Brazilian soil sample was submitted to different culture conditions to investigate the production of secondary metabolites with antimicrobial activity. The largest number of conidia was obtained after 5 days of incubation in oat medium and the highest level of antimicrobial activity was produced when the fungus culture was developed in the Czapek medium. The activity against Staphylococcus aureus was found only in the chloroform extract from Czapek culture broth, which also showed activity against Micrococcus luteus. Fumiquinozoline F was isolated from the active chloroform extract by using chromatographic methods. The minimal inhibitory concentration (MIC) values for M. luteus and S. aureus were 99 μg/mL and 137 μg/mL, respectively.     

甾体C7-羟基化研究进展

生物羟基化被用作研究甾体代谢机制和制备羟基甾体的工具,许多真菌微生物菌具有甾体C7-羟基化能力,而C7-羟基甾体具有许多重要的生物活性。在分子水平上,人们已经发现了7α-羟基化酶及其基因。就以上几个方面做一简单综述,并对此领域的发展趋势进行展望。     

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。     

Antibacterial activity of different honeys against pathogenic bacteria

To study the antimicrobial activity of honey, 60 samples of various botanical origin were evaluated for their antimicrobial activities against 16 clinical pathogens and their respective reference strains. The microbiological quality of honeys and the antibiotic susceptibility of the various isolates were also examined. The bioassay applied for determining the antimicrobial effect employs the well-agar diffusion method and the estimation of minimum active dilution which produces a 1 mm diameter inhibition zone. All honey samples, despite their origin (coniferous, citrus, thyme or polyfloral), showed antibacterial activity against the pathogenic and their respective reference strains at variable levels. Coniferous and thyme honeys showed the highest activity with an average minimum dilution of 17.4 and 19.2% (w/v) followed by citrus and polyfloral honeys with 20.8 and 23.8% respectively. Clinical isolates of Staphylococcus aureus subsp. aureus, Escherichia coli, Salmonella enterica subsp. Enterica, Streptococcus pyogenes, Bacillus cereus and Bacillus subtilis were proven to be up to 60% more resistant than their equal reference strains thus emphasizing the variability in the antibacterial effect of honey and the need for further research.     

Biogenic synthesis of silver nanoparticles: Antibacterial and cytotoxic potential

In green chemistry, the application of a biogenic material as a mediator in nanoparticles formation is an innovative nanotechnology. Our current investigation aimed at testing the cytotoxic potential and antimicrobial ability of silver nanoparticles (AgNPs) that were prepared using Calligonum comosum roots and Azadirachta indica leaf extracts as stabilizing and reducing agents. An agar well diffusion technique was employed to detect synthesized AgNPs antibacterial ability on Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus bacterial strains. Furthermore, their cytotoxic capability against LoVo, MDA-MB231 and HepG2 ca cells was investigated. For phyto-chemical detection in the biogenic AgNPs the Fourier-transform infrared spectroscopy (FT-IR) was considered. Zeta sizer, TEM (Transmission Electron Microscope) and FE-SEM (Field Emission Scanning Electron Microscope) were used to detect biogenic AgNPs’ size and morphology. The current results showed the capability of tested plant extract for conversion of Ag ions to AgNPs with a mean size ranging between 90.8 ± 0.8 and 183.2 ± 0.7 nm in diameter. Furthermore, prepared AgNPs exhibited apoptotic potential against HepG2, LoVo, and MDA-MB 231cell with IC₅₀ ranging between 10.9 and 21.4 μg/ml and antibacterial ability in the range of 16.0 ± 0.1 to 22.0 ± 1.8 mm diameter. Activation of caspases in AgNPs treated cells could be the main indicator for their positive effect causing apoptosis. The current investigation suggested that the green production of AgNPs could be a suitable substitute to large-scale production of AgNPs, since stable and active nanoparticles could be obtained.     

Plantaricin 163对热杀索丝菌的抗菌活性及其作用机制

【背景】热杀索丝菌(Brochothrix thermosphacta)为鲫鱼在4°C贮藏过程中的主要腐败菌,Plantaricin 163是由植物乳杆菌产生的一种新型广谱细菌素,能明显延长鲫鱼的贮藏期。【目的】研究Plantaricin163对热杀索丝菌的抗菌活性和作用机制。【方法】通过测定最小抑菌浓度(Minimuminhibitoryconcentration)和杀菌动力学了解Plantaricin163对热杀索丝菌的抗菌效果,并从电导率的变化、核酸和蛋白的泄露、流式细胞实验、扫描电镜和透射电镜观察等4个方面探讨Plantaricin 163对热杀索丝菌的作用机制。【结果】Plantaricin 163对热杀索丝菌的的最小抑菌浓度为32μg/mL,优于Nisin的作用效果,作用方式为杀菌模式,6 h内能完全杀死热杀索丝菌。Plantaricin163能够通过增加热杀索丝菌细胞膜的通透性,增加胞外电导率,进而破坏细胞膜完整性,导致内容物泄漏,并影响细胞的外部形态和内部结构,从而导致菌体细胞瓦解死亡。【结论】Plantaricin 163可以破坏热杀索丝菌的细胞膜和内部结构,发挥抗菌活性。     

7-Oxo-24ξ(28)-dihydrocycloeucalenol,a potent inhibitor of plant sterol biosynthesis

Cycloeucalenol-obtusifoliol isomerase from higher plant cells catalyses the opening of the cyclopropane ring of cycloeucalenol yielding obtusifoliol. 7-Oxo-24ξ(28)-dihydrocycloeucalenol was not a substrate but behaved like a potent inhibitor of the isomerase. The inhibition was reversible and highly specific; the inhibitor needed the presence of the 7-oxo group, the cyclopropane ring and the absence of a 4β-methyl group to be active. Other enzymes involved in plant sterol biosynthesis such as 2, 3-oxidosqualene-cycloartenol cyclase and S-adenosyl methionine cycloartenol C-24 methyltransferase were not inhibited by 7-oxo-24ξ(28)-dihydrocycloeucalenol. In vivo treatment of a suspension of bramble cells growing in a liquid medium with 7-oxo-24ξ(28)-dihydrocycloeucalenol resulted in a strong accumulation of 9β 19-cyclopropyl sterols confirming that the main cellular target of the inhibitor is the cycloeucalenol-obtusifoliol isomerase.     

紫穗槐种子提取物的抑菌活性研究

目的研究紫穗槐种子提取物的抑菌活性。方法将紫穗槐种子乙醇提取物分别通过石油醚、乙酸乙酯和正丁醇萃取,选择金黄色葡萄球菌和肺炎克雷伯杆菌为供试菌,采用试管二倍稀释法测定紫穗槐种子提取物的最小抑菌浓度（MIC）和最小杀菌浓度（MBC）,涂布平板法绘制杀菌曲线,电镜下观察药物对细菌超微结构的影响。结果紫穗槐种子提取物经乙酸乙酯萃取后对供试菌抑制作用较强,其中对金黄色葡萄球菌的MIC和MBC分别为2．5、5．0mg／mL;对肺炎克雷伯杆菌的MIC和MBC分别为5．0、10．0mg／mL;杀菌曲线结果表明,药物对供试菌的抑制作用存在浓度和时间依赖性;电镜结果说明,药物的作用可能与破坏菌体细胞壁、改变细胞膜通透性有关。结论紫穗槐种子提取物具有显著的抗菌活性。     

杨梅果实不同溶剂提取物抑菌特性的研究

目的探讨4种溶剂杨梅果实提取物对14种致病菌的抑菌作用,并对其中活性成分的含量进行测定和比较。方法利用常压浸提法制备杨梅果实的水、乙醇、乙酸乙酯和丙酮提取物;采用管碟法、琼脂平板稀释法测定各种杨梅提取物的抑菌活性,采用常规含量测定方法对各提取物中的主要成分及含量进行研究。结果4种杨梅果实提取物对革兰阴性和阳性菌均表现出了较强的抑菌活性,其中水提取物的抑菌活性最强。含量测定结果表明4种提取物的主要成分中总酚、黄酮含量以及总酸度相差较大,单宁含量差异较小。结论推测提取物中的主要抑菌成分为单宁类物质并确定杨梅果实的最佳提取溶剂为水。     

Antibacterial activity of cardiotoxin-like basic polypeptide from cobra venom

Antibacterial activity of the three-finger toxins from cobra venom, including cytotoxin 3 from N. kaouthia, cardiotoxin-like basic polypeptide A5 from N. naja (CLBP), and alpha-neurotoxin from N. oxiana venom, was investigated. All toxins failed to influence Gram-negative bacteria. The most pronounced activity against Bacillus subtilis was demonstrated by CLBP. The latter is ascribed to the presence of additional Lys-residues within the membrane-binding motif of this toxin.     

碳量子点抗菌活性的研究进展

碳量子点（Carbon quantum dots,CQDs）是一种新型碳纳米材料,具有独特的性质,逐渐得到广泛关注。由于CQDs主要是通过“自下而上”的方法制备,其表面具有更加丰富多样的基团,因此更容易衍生化和功能化,进而更容易得到具有特殊性质和功能的CQDs。同时,CQDs在水溶性、可修饰性、耐光漂白等方面具有明显的优势,并且还兼具低生物毒性和良好的生物相容性,使其在生物成像、生物传感和生物分子/药物传递等方面具有潜在的应用价值。随着CQDs研究的增多,各种不同功能化的CQDs得到发展,并被越来越多地用于抗菌方面。根据CQDs目前在医学领域的发展,本文对CQDs在抗菌方面的最新研究进展作一综述。     

镇江香醋醋醅抑菌活性及机理的初步分析

【目的】评价镇江香醋醋酸发酵过程中醋醅及其主要酿醋功能微生物的抑菌活性。【方法】采用琼脂扩散法评价醋醅和功能微生物的抑菌效果,并考察加热、蛋白酶解、透析等不同处理对发酵液抑菌活性的影响。【结果】醋醅水提取液及4种酿醋功能微生物(Acetobacter pasteurianus、A.pomorum、Lactobacillus helveticus、L.plantarum)的发酵上清液对4种指示菌具有明显的生长抑制效果。发酵上清液中的抑菌活性物质具有一定耐热性和蛋白酶敏感性,分子量小于8 k D。【结论】镇江香醋醋醅及其所含醋酸杆菌和乳酸杆菌对环境微生物具有生长抑制活性,且抑菌活性物质的种类具有多样性。     

Antibacterial activity of substituted dibenzo[a,g]quinolizin-7-ium derivatives

Berberine is a substituted dibenzo[a,g]quinolizin-7-ium derivative whose modest antibiotic activity is derived from its disruptive impact on the function of the essential bacterial cell division protein FtsZ. The present study reveals that the presence of a biphenyl substituent at either the 2- or 12-position of structurally-related dibenzo[a,g]quinolizin-7-ium derivatives significantly enhances antibacterial potency versus Staphylococcus aureus and Enterococcus faecalis. Studies with purified S. aureus FtsZ demonstrate that both 2- and 12-biphenyl dibenzo[a,g]quinolizin-7-ium derivatives act as enhancers of FtsZ self-polymerization.     

2,4-二氨基喹唑啉衍生物的抑菌活性研究

喹唑啉衍生物具有广泛的生物活性,包括抗菌活性。为发现此类化合物中具有潜在抑菌活性的化合物,本研究考察了15种带有哌嗪二硫代甲酸酯侧链的2,4-二氨基喹唑啉衍生物7a~7o的抑菌活性。首先采用分子对接方法对底物与酶的结合能进行预测,并用标准2倍稀释法测定这15种化合物对多重耐药大肠埃希菌的最小抑菌浓度(minimum inhibitory concentration,MIC)。结果表明,15种化合物与阳性对照相比均具有较好的抑菌活性。化合物7a、7g和7k具有明显的抑菌活性,其MIC均≤1mg/mL。进一步采用高效毛细管电泳筛选模型对7a、7g和7k进行分子水平抑菌实验,分别测定其抑制率与半数抑制浓度(half inhibitory concentration,IC50),发现化合物7k具有最佳抑制活性(IC_(50)为4.97×10~(-2) mg/mL)。此外,对15种化合物抑菌活性构效关系的研究表明,苯环上连有吸电子基团的哌嗪二硫代甲酸酯侧链对抑菌活性有贡献。这一研究有望为抑菌药物的研发提供有效的先导化合物。     

Non-neuronal nicotinic alpha 7 receptor, a new endothelial target for revascularization

Alpha 7 nicotinic acetylcholine receptor (alpha7 nAChR) is widely expressed in the central and peripheral nervous systems, and is also found in several non-neuronal tissues, such as endothelial cells (ECs), bronchial epithelial cells, skin keratinocytes and vascular smooth muscle cells. Recent evidence suggests that alpha7 nAChR is involved in angiogenesis. Here, we investigated the feasibility of alpha7 nAChR for revascularization in ischemic heart disease. RT-PCR and immunohistochemistry were used to examine the expression of alpha7 nAChR in human umbilical vein endothelial cell (HUVECs). The cellular function was examined using MTT, fluorescence confocal microscopy and angiogenesis assay in vitro. The capillary density in the rat model of myocardial infarction (MI) was investigated using immunohistochemistry. The results showed that alpha7 nAChR agonists choline increased the expression of alpha7 nAChR mRNA and protein, the intracellular Ca 2+ concentration, proliferation and tube formation of ECs. Reverse effects were observed by using alpha7 nAChR antagonist alpha-BTX. Furthermore, in the rat model of MI, alpha7 nAChR agonist enhanced the capillary density in ischemic tissues, whereas antagonist mecamylamine and alpha-BTX inhibited the effect. Our results suggest that alpha7 nAChR is involved in the regulation of cellular function in ECs, and capillary formation in MI, which are the important steps of angiogenesis. Therefore, alpha7 nAChR on ECs may be a new endothelium target for revascularization in therapeutic angiogenesis of ischemic heart disease.     

Antibacterial activity of selected plant essential oils against Escherichia coli O157:H7

AIMS: To quantify the antibacterial properties of five essential oils (EO) on a non-toxigenic strain of Escherichia coli O157:H7 in the presence and absence of a stabilizer and an emulsifier and at three different temperatures. METHODS AND RESULTS: Five EOs known to exhibit antibacterial properties were screened by disc diffusion assay and the most active were selected for further study in microdilution colorimetric assays. Oregano (Origanum vulgare) and thyme (Thymus vulgaris; light and red varieties) EO had the strongest bacteriostatic and bactericidal properties, followed by bay (Pimenta racemosa) and clove bud (Eugenia caryophyllata synonym: Syzygium aromaticum) EO. Oregano oil was colicidal at 625 microl l(-1) at 10, 20 and 37 degrees C. The addition of 0.05% (w/v) agar as stabilizer reinforced the antibacterial properties, particularly at 10 degrees C, whereas 0.25% (w/v) lecithin reduced antibacterial activity. Scanning electron micrographs showed extensive morphological changes to treated cells. CONCLUSIONS: Oregano and thyme EO possess significant in vitro colicidal and colistatic properties, which are exhibited in a broad temperature range and substantially improved by the addition of agar as stabilizer. Bay and clove bud EO are less active. Lecithin diminished antibacterial properties. The bactericidal concentration of oregano EO irreversibly damaged E. coli O157:H7 cells within 1 min. SIGNIFICANCE AND IMPACT OF THE STUDY: Oregano and light thyme EO, particularly when enhanced by agar stabilizer, may be effective in reducing the number or preventing the growth of E. coli O157:H7 in foods.     

Antibacterial,tyrosinase, and DNA photocleavage studies of some triazolylnucleosides

In order to explore the biological potential, some synthesized triazolylnucleosides were evaluated for their antibacterial, tyrosinase and DNA photocleavage activities. Triazolylnucleosides (5–12) were screened against Staphylococcus aureus (ATCC 6538), gram-positive and Escherichia coli (ATCC 10536), gram-negative bacterial strains. Among the series, compound 9 exhibited a significant level of antibacterial activity against both strains at higher concentration in reference to the standard drug, Levofloxacin. Tyrosinase activity and inhibition of these compounds were also studied, and it has been found that compounds 8 and 11 displayed more than 50% inhibitory activity. In addition, six compounds (7–12) were evaluated for their DNA photocleavage activity. The compounds 8 and 12 exhibited excellent DNA photocleavage activity at a concentration of 10 μg and may be used as template for antitumor drugs in the future.     

Antibacterial and resistance modifying activity of Rosmarinus officinalis

As part of a project to characterise plant-derived natural products that modulate bacterial multidrug resistance (MDR), bioassay-guided fractionation of a chloroform extract of the aerial parts of Rosmarinus officinalis led to the characterisation of the known abietane diterpenes carnosic acid (1), carnosol (2) and 12-methoxy-trans-carnosic acid. Additionally, a new diterpene, the cis A/B ring junction isomer of 12-methoxy-trans-carnosic acid, 12-methoxy-cis-carnosic acid (5), was isolated. The major components were assessed for their antibacterial activities against strains of Staphylococcus aureus possessing efflux mechanisms of resistance. Minimum inhibitory concentrations ranged from 16 to 64 microg/ml. Incorporation of 1 and 2 into the growth medium at 10 microg/ml caused a 32- and 16-fold potentiation of the activity of erythromycin against an erythromycin effluxing strain, respectively. Compound 1 was evaluated against a strain of S. aureus possessing the NorA multidrug efflux pump and was shown to inhibit ethidium bromide efflux with an IC50 of 50 microM, but this activity is likely to be related to the inhibition of a pump(s) other than NorA. The antibacterial and efflux inhibitory activities of these natural products make them interesting potential targets for synthesis.