Antibacterial activity and chemical composition of Turkish propolis

The antibacterial activities of propolis samples have been examined in vitro, according to the principles accepted for the determination of a similar activity of antibiotics with the use of solid and liquid media. It has been found that propolis extracts showed antibacterial activity through a range of commonly encountered gram positive cocci (S. aureus, beta hem. Streptococus), but had weak activity against gram negative bacteria (E. coli, P. aeruginosa). GC/MS analysis showed that propolis samples contain a variety of chemical compounds including aromatic compounds, fatty acid esters and sesquiterpenes.     

Design and Synthesis of Heterocyclic Conjugated Peptides as Novel Antimicrobial Agents

Antimicrobial peptides have been recognized as a novel class of antibiotics and several candidates are currently in clinical trials. In the present study, new antimicrobial compounds were synthesized by coupling quinazolinone moiety with the fragments of elastin sequences VP, GVP, VGVP and GVGVP. They were evaluated for their antibacterial activity against both gram positive and gram negative bacterial strains. We are here reporting that heterocyclic conjugated tetra peptide and penta peptide showed enhanced antibacterial activity compare to the conventional antimicrobial drugs.     

Synthesis of novel steroidal heterocyclic derivatives as antibacterial agents

This study aimed at the synthesis of novel structurally promising steroidal heterocycles and to elucidate the potential role of these compounds as antibacterial agents. Epi-androsterone 1 reacted with CS2 and sodium hydride in dimethylsulfoxide to yield alpha-oxoketene dithiodisodium salt 2. The non-isolable salt 2 reacted with acetyl chloride, benzoyl chloride, phenacyl bromide and iodomethane to afford the corresponding alpha-oxodithioacetal derivatives 4a,b, 6 and 7, respectively. Interaction of 2 with the alkyl halide reagents 8a-d yielded the corresponding thiophene derivatives 10a-d. Alpha-oxoketene dithioacetal 7 reacted with urea and thiourea to furnish the pyrimidinoandrostane derivatives 12a,b. Compound 7 also reacted with ortho-phenylene diamine and ortho-aminophenol 13a,b to produce the dinucleophilic adducts 15a,b. The in vitro antibacterial evaluation of some newly prepared compounds showed that all compounds have high significant antibacterial activity against the used strains of gram positive and gram negative bacteria.     

Synthesis of some thiazolyl aminobenzothiazole derivatives as potential antibacterial, antifungal and anthelmintic agents

A series of 4-(6-substituted-1,3-benzothiazol-2-yl)amino-2-(4-substitutedphenyl)- amino-1,3-thiazoles, 9-24 have been synthesised from 2-chloro-N-(6-substituted-1,3-benzothiazol-2-yl)acetamides, 5-8. The structures of these compounds have been elucidated by spectral (IR, (1)H NMR, Mass) and elemental (C, H, N) analysis data. All the newly synthesised compounds (9-24) were screened for their antibacterial, antifungal and anthelmintic activities. Almost all of these compounds showed moderate to good antimicrobial activity against two gram negative bacteria (E. coli, P. aeruginosa), two gram positive bacteria (S. aureus, B. subtilis), pathogenic fungal strains (C. albicans, A. niger) and good anthelmintic activity against earthworm species (P. corethruses). Compounds 18 and 20 exhibited good antibacterial and antifungal activities, while compound 22 displayed the most significant anthelmintic activity.     

Synthesis and evaluation of new diaryl ether and quinoline hybrids as potential antiplasmodial and antimicrobial agents

Synthesis and bioevaluation of new diaryl ether hybridized quinoline derivatives as antiplasmodial, antibacterial and antifungal agents is reported. It was encouraging to discover that several compounds displayed 2–3 folds better efficacy than chloroquine in chloroquine-resistant K1 strain of Plasmodium falciparum. Further, a few members of the library displayed good antibacterial efficacy against gram positive strains of bacteria but none of the compounds displayed any significant antifungal activity.     

In vitro study of some medicinally important Mannich bases derived from antitubercular agent

Biologically active Mannich bases with heteroaromatic ring system have been synthesised employing Mannich reaction of isonicotinyl hydrazide with various sulphonamides/secondary amines. They were analysed by elemental analysis and characterized by uv, ir, 1H nmr spectroscopic studies. The Mannich bases were screened for their antibacterial activity against various gram positive and gram negative bacteria and were analyzed statistically. The results have shown that the compounds are quiet active against pathogens under study and were nontoxic.     

多脂长喙壳菌次生代谢产物的抑菌活性研究

植物病原真菌是生态系统的重要组成部分,能够代谢产生多种生物活性物质。用纸片法检测多脂长喙壳菌(Ceratocystis adiposa)发酵提取物对13种致病细菌的抑菌活性,并对潜在抗菌活性化合物的热、酸碱和光稳定性进行检测,同时应用OSMAC策略寻找多脂长喙壳菌产抗菌化合物的最佳培养条件。结果表明:多脂长喙壳菌提取物对革兰阳性菌——蜡样芽胞杆菌(Bacillus cereus)、缓慢芽胞杆菌(Bacillus lentus)、藤黄微球菌(Micrococcus luteus)具有抗菌活性,MIC分别为6.25、3.125和1.562 5 mg/m L,抗菌化合物具有较好的耐热、耐酸碱和耐辐射性,培养基种类、培养时间和接种量会影响多脂长喙壳菌抗菌化合物的产生,为多脂长喙壳菌抗菌化合物的开发利用提供参考。     

Development of Tyrocidine A analogues with improved antibacterial activity

The development of new antibacterial therapeutic agents capable of halting microbial resistance is a chief pursuit in clinical medicine. Classes of antibiotics that target and destroy bacterial membranes are attractive due to the decreased likelihood that bacteria will be able to generate resistance to this mechanism. The amphipathic cyclic decapeptide, Tyrocidine A, is a model for this class of antibiotics. Tyrocidine A is composed of a hydrophobic and a hydrophilic face, allowing for insertion into bacterial membranes, creating porous channels and destroying membrane integrity. We have used a combination of molecular modeling and solid phase synthesis to prepare Tyrocidine A and analogues 1-8. The minimum inhibitory concentrations (MICs) of these compounds were determined for a host of gram positive species and E. coli as a representative gram negative bacterium. Analogues 2 and 5 demonstrated moderate 2- to 8-fold increases in antibacterial activity over the parent Tyrocidine A for a variety of pathogenic microbes (best MICs for E. coli 32 microg/mL and 2 microg/mL for most gram positives). Examination of the structure- activity relationship between the analogues demonstrated a preference for increased amphipathicity but did not show a clear preference for increasing hydrophilicity versus hydrophobicity in improving antibacterial activity. Of note, movement of positively charged lysine residues or neutral pentafluorophenyl residues to different positions within the cyclopeptide ring system demonstrated improvements in antibacterial activity.     

Anthraquinones from the stem bark of Stereospermum zenkeri with antimicrobial activity

Two anthraquinones, zenkequinones A and B were isolated from the stem bark of Stereospermum zenkeri together with known sterequinone-F, p-coumaric acid, sitosterol-3-O-beta-D-glucopyranoside and 3beta-hydroxyolean-12-en-28-O-beta-D-glucopyranoside. Their structures were established by spectroscopic methods. The antimicrobial activity of the isolated compounds was evaluated against six multiresistant strains of pathogens. Zenkequinone B showed the best antibacterial activity (MIC 9.50 microg/ml) against gram-negative Pseudomonas aeruginosa.     

Bernthsen synthesis,antimicrobial activities and cytotoxicity of acridine derivatives

The condensation reaction of diphenylamine with 2-oxo-2H-(substituted chromen)-4-yl acetic acid in presence of anhydrous zinc chloride afford 4-(acridine-9-ylmethyl)-2H-(substituted chromen)-2-one. The synthesized compounds were characterized by spectral studies and elemental analysis and screened for their in vitro antibacterial activity against Staphylococcus aureus, Staphylococcus pyogenes (gram +ve), Escherichia coli, Pseudomonas aeruginosa (gram ?ve) and antifungal activity against Aspergillus niger and anticancer activity (HL-60, Hep-2 & HEK293T) by MTT assay. Chloro substituted compounds showed antimicrobial and anticancer activity with IC₅₀ values in the low micromolar range.     

Extraction of chitosan from shrimp shells waste and application in antibacterial finishing of bamboo rayon

Chitosan can be best utilized as safe antibacterial agent for textiles but there is always a limitation of its durability. The chitin containing shellfish waste is available in huge quantities, but very low quantities are utilized for extraction of high value products like chitosan. In the current work chitosan was extracted from shrimp shells and then used as antibacterial exhaust finishing agent for grafted bamboo rayon. Chitosan bound bamboo rayon was then evaluated for antibacterial activity against both gram positive and gram negative bacteria. The product showed antibacterial activity against both types of bacterias which was durable till 30 washes.     

黑眶蟾蜍皮肤抗菌肽的制备及其性质

收集黑眶蟾蜍皮肤分泌物,经Sephadex G-25去除大分子蛋白后,利用微量测定法进行抗菌活性分析。结果发现:黑眶蟾蜍皮肤分泌物对革兰氏阳性菌——金黄色葡萄球菌、枯草芽孢杆菌的抑制作用较强,对革兰氏阴性菌中的嗜水气单细胞菌也表现出较强的抑制作用,对溶藻弧菌、副溶血弧菌、河流弧菌、大肠杆菌的抑制相对较弱。利用胰蛋白酶对黑眶蟾蜍皮肤抗菌肽水解后,其抗菌活性消失。将黑眶蟾蜍皮肤抗菌肽在37~95℃和pH 2.5~5.0下保温,发现其抗菌活性成分对热及酸耐受性较强。黑眶蟾蜍皮肤分泌物在低浓度无溶血活性。     

Actinomycetes from Moroccan habitats: isolation and screening for cytotoxic activities

In our screening for actinomycetes showing cytotoxic activities, 8 samples were collected from various Moroccan habitats, 136 isolates were tested for their capacity to produce antibacterial compounds against gram positive bacteria. Thirty-seven strains of these isolates were active against Gram-positive bacteria. Using the following steps of primary screening: antibacterial activity, confrontation between the isolates and toxicity to Artemia salina; fifteen different isolates were used for further investigation. The aqueous extracts of Streptomyces sp. T5 and Streptomyces sp. AS8 were selected for their cytotoxic activity against Hep2, BSR and P815 cell lines, and two active compounds were observed on HPLC. The two isolates exhibited high activity against human cancer cell lines and were inactive on PBMC cell lines. Furthermore, the Streptomyces sp. T5 extract showed a proliferative activity.     

Antibacterial hemolymph proteins of Manduca sexta

Exclusion column fractionated immune hemolymph of the M. sexta larva contains five peaks of anti-E. coli activity with molecular weights of greater than 140 kD and approximately 91, 54, 14 and 4 kD, plus one peak of lysozyme activity with a molecular weight of 17 kD. Purification of the 54 kD peak showed that this peak consists of the previously described M18 proteins which have monomeric weights of approximately 20 kD and had antibacterial activity against certain gram negative bacteria. Approximately 80% of the total hemolymph antibacterial activity was detected in the 14 and 4 kD peaks. These proteins, which kill both gram negative and gram positive bacteria, appeared to be directly analogous to the cecropins of H. cecropia. The greater than 140 and 91 kD peaks constituted only a minor part of the total antibacterial activity.     

Bioactivity of aviprin and aviprin-3″-<Emphasis Type="Italic">O</Emphasis>-glucoside,two linear furanocoumarins from Apiaceae

Furanocoumarins are well-known natural products that occur in the most evolved genera of Apiaceae family. This compounds were found to have cytotoxic, phytotoxic, photosensitizing, insecticidal, antibacterial and high antifungal effects. Aviprin is considered as a linear furanocoumarin substituted at C8 with an oxygenated prenyl residue. In this study we found that aviprin is a bioactive compound that exhibits high antibacterial, antifungal and phytotoxic activity. The compound stunted the germination of lettuce seeds with IC₅₀ value of 0.270 mg/ml. The compound also inhibited the mycelia growth of Sclerotinia sclerotiorum. Aviprin indicated antibacterial activity against tested gram negative and positive bacteria with inhibition zone of 19–23.5 mm. Our results shown that aviprin can play an allelopatic role for plant.     

Preliminary screening for antibacterial and antimycobacterial activity of actinomycetes from less explored ecosystems

Actinomycetes from less explored ecosystems were screened for antibacterial and antimycobacterial activity. Crude bioactive compounds were produced by growing these strains by shake flask fermentation using soybean meal medium. Culture supernatant and mycelia were extracted with ethyl acetate and methanol, respectively. Antibacterial activity of crude extracts was tested by disc diffusion method against gram positive and gram negative bacteria. Actinomycete strains D10, D5, NEK5, ANS2, M104 and R2 showed prominent activity. Culture filtrates and crude extracts were tested against standard strain Mycobacterium tuberculosis H₃₇Rv and drug sensitive and drug resistant clinical isolates of M. tuberculosis by luciferase reporter phage (LRP) assay. Considerable variation was observed in antimycobacterial activity between actinomycete culture filtrates and solvent extracts. Actinomycete strains viz., D10, D5 (desert), CSA14 (forest), CA33 (alkaline soil), NEK5 (Neem plant), MSU, ANS2, R2 and M104 (marine) screened in the present study were found to be highly potent showing good antibacterial and antimycobacterial activity. Five of them such as A3, CSA1, EE9, ANS5 and R9 were exclusively active against M. tuberculosis. Secretary products of actinomycetes of rare ecosystems are meant to antagonize organisms in their respective environments. These are likely to be novel antimycobacterial compounds as they unknown to human pathogens.     

Amino acid conjugated sophorolipids: A new family of biologically active functionalized glycolipids

Sophorolipids (SLs) are extra cellular glycolipids produced by Candida bombicola ATCC 22214 when grown in the presence of glucose and fatty acids. These compounds have a disaccharide head group connected to a long-chain hydroxyl-fatty acid by a glycosidic bond. To explore structure-activity of modified SLs, a new family of amino acid-SL derivatives was prepared. Synthesized analogs consist of amino acids linked by amide bonds formed between their alpha-amino moiety and the carboxyl group of ring-opened SL fatty acids. Their preparation involved the following: (i) hydrolysis of a natural SL mixture with aqueous alkali to give SL free acids, (ii) coupling of free acids to protected amino acids using dicarbodiimide, and (iii) removing amino acid carboxyl protecting groups. These conjugates were evaluated for their antibacterial, anti-HIV, and spermicidal activity. All tested analogs showed antibacterial activity against both gram +ve and gram -ve organisms. Leucine-conjugated SL was most efficient. For example, the minimum inhibitory concentrations (MIC) for Moraxella sp. and E. coli were 0.83 and 1.67 mg/mL, respectively. Among the alkyl esters of amino acid conjugated SLs, the ethyl ester of leucine-SLs was most active. Against Moraxella sp., S. sanguinis, and M. imperiale, MIC values are 7.62 x 10(-4), 2.28 x 10-(3) and 1.67 mg/mL, respectively. All compounds displayed virus-inactivating activity with 50% effective concentrations (EC50) below 200 microg/mL. The EC50 of leucine-SL ethyl ester was 24.1 microg/mL, showing that it is more potent than commercial spermicide nonoxynol-9 (EC50 approximately 65 microg/mL).     

4-(Ethoxycarbonyl) phenyl-1-amino-oxobutanoic acid-chitosan complex as a new matrix for silver nanocomposite film: preparation, characterization and antibacterial activity

The present work describes the preparation of new chitosan complex with 4-(ethoxycarbonyl) phenyl-1-amino-oxobutanoic acid (ETHA), as a matrix for silver nanoparticles to obtain a nanocomposite film by solution casing method. The characterization of the prepared nanocomposite film was made by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetry (TG) and scanning electron microscopy (SEM). The optical property of nanocomposite film was analyzed by UV-Visible and photo-luminescence (PL) spectroscopy. The nanocomposite film was screen for antibacterial activity with Staphylococcus aureus (gram positive), Pseudomonas aurigionasa (gram negative) and Escherichia coli (gram negative) bacteria by adopting the disk diffusion method. The result of antibacterial study revealed that the prepared nanocomposite film may be a promising candidate for wide range of bio-medical applications.     

A simple method to tune the gross antibacterial activity of cellulosic biomaterials

A very preliminary approach for grossly tuning the antibacterial activity of cellulosic fibers has been developed and its preliminary findings are described herein. The approach is universal for cellulosic-based substrates and first involves a physico-chemical adsorption phenomenon between fatty acid methyl esters (FAMEs) and cellulose. The cellulose biomaterials were in the form of disks 2 cm in diameter that were subjected to standard agar growth plates containing a gamut of gram positive and gram negative bacteria. Zones of inhibition were measured around the biomaterials which displayed a broad spectrum of antibacterial activity. This activity could be tuned simply by grossly changing the surface area of the cellulosic surface topology as indicated by the surface fibrillation of the microfibrils and hence the bioactive availability of the fatty acids. Thus, the potential application of these materials in the biomedical field appears promising.     

Antibacterial components of honey

The antibacterial activity of honey has been known since the 19th century. Recently, the potent activity of honey against antibiotic-resistant bacteria has further increased the interest for application of honey, but incomplete knowledge of the antibacterial activity is a major obstacle for clinical applicability. The high sugar concentration, hydrogen peroxide, and the low pH are well-known antibacterial factors in honey and more recently, methylglyoxal and the antimicrobial peptide bee defensin-1 were identified as important antibacterial compounds in honey. The antibacterial activity of honey is highly complex due to the involvement of multiple compounds and due to the large variation in the concentrations of these compounds among honeys. The current review will elaborate on the antibacterial compounds in honey. We discuss the activity of the individual compounds, their contribution to the complex antibacterial activity of honey, a novel approach to identify additional honey antibacterial compounds, and the implications of the novel developments for standardization of honey for medical applications.