Design,Synthesis, in vitro and in silico Characterization of 2-Quinolone-L-alaninate-1,2,3-triazoles as Antimicrobial Agents

Due to the ever-increasing antimicrobial resistance there is an urgent need to continuously design and develop novel antimicrobial agents. Inspired by the broad antibacterial activities of various heterocyclic compounds such as 2-quinolone derivatives, we designed and synthesized new methyl-(2-oxo-1,2-dihydroquinolin-4-yl)-L-alaninate-1,2,3-triazole derivatives via 1,3-dipolar cycloaddition reaction of 1-propargyl-2-quinolone-L-alaninate with appropriate azide groups. The synthesized compounds were obtained in good yield ranging from 75 to 80 %. The chemical structures of these novel hybrid molecules were determined by spectroscopic methods and the antimicrobial activity of the compounds was investigated against both bacterial and fungal strains. The tested compounds showed significant antimicrobial activity and weak to moderate antifungal activity. Despite the evident similarity of the quinolone moiety of our compounds with fluoroquinolones, our compounds do not function by inhibiting DNA gyrase. Computational characterization of the compounds shows that they have attractive physicochemical and pharmacokinetic properties and could serve as templates for developing potential antimicrobial agents for clinical use.     

Pyrazole Derived Cationic Surfactants and their Tin and Copper Complexes: Synthesis,Surface Activity,Antibacterial and Antifungal Efficacy

Five membered heterocyclic cationic 3-pyrazolium surfactants namely: 2-[2-(alkyloxy)-2-oxoethyl]-3-methyl-5-oxo-1-phenyl-4,5-dihydro-1H-3-pyrazolium bromide (decyl-; dodecyl-) and their copper and tin complexes were synthesized, their structures were confirmed using different spectroscopic tools. The IR spectra of the metal complexes showed that these compounds exhibit a tetrahedron structure with the transition metal ion (M²⁺) at the center and the cationic ligands arranged in the apexes, while the halide ions in the center. The synthesized compounds were evaluated as biocides against different types of bacteria and fungi. The biological activity data showed that the cationic surfactants exhibit moderate to high efficacy against the tested microorganisms (either bacteria or fungi). While, complexation of these cationic surfactants with Cu (II) and Sn (II) ions the antimicrobial activity was strongly increased. The surface activity of these compounds were discussed and correlated to their chemical structure and the type of substituents on the heterocyclic moiety. Meanwhile, the antimicrobial assay was correlated to the surface activities of the synthesized compounds.     

Synthesis and antimicrobial activity of quaternary ammonium-functionalized POSS (Q-POSS) and polysiloxane coatings containing Q-POSS

An array of quaternary ammonium-functionalized POSS (Q-POSS) compounds were synthesized and their antimicrobial properties toward the Gram-negative bacterium, Escherichia coli, and the Gram-positive bacterium, Staphylococcus aureus, determined in aqueous solution. Using Q-POSS compositions that exhibited broad spectrum antimicrobial activity in solution, the utility of the Q-POSS compounds as an antimicrobial additive for polysiloxane coatings was determined. The results of the investigation showed that Q-POSSs possessing a relatively low extent of quaternization and longer alkyl chain lengths provided the highest antimicrobial activity in solution. For polysiloxane coatings containing Q-POSS molecules as an antimicrobial additive, coating surface energy, surface morphology, and antimicrobial properties were found to be strongly dependent on Q-POSS composition. Coatings based on Q-POSSs possessing the lowest extent of quaternization displayed antimicrobial activity while analogous coatings produced using Q-POSSs possessing the highest extent of quaternization showed no antimicrobial activity. The lack of antimicrobial activity exhibited by coatings possessing Q-POSSs with a relatively high extent of quaternization was attributed to agglomeration of Q-POSS molecules through the formation of intermolecular interactions involving the quaternary ammonium moieties. Agglomeration would be expected to reduce diffusivity and inhibit interaction of the Q-POSS molecules with microbial cells.     

Sugar-Based Ester Quaternary Ammonium Compounds and Their Surfactant Properties

Two sugar‐based ester quaternary ammonium compounds were synthesized and their surface behavior and antimicrobial activity were investigated. The compatibility with anionic surfactant sodium dodecyl sulfate (SDS) was further studied. Results indicated that the synthesized cationic surfactants showed high surface activity and good synergistic effects with SDS.     

Synthesis of Ecofriendly Functionalized Oxadiazole,Imidazole, Triazole and Pyridine Derivatives

5-Pentadecyl-1,3,4-oxadiazol-2-amine (2) was employed as key intermediate for the synthesis of some new functionalized five and six membered heterocyclic derivatives. The synthesized compounds were reacted with propylene oxide to obtain surface active agents having good surface activity, high solubility in water and good biodegradability. Moreover, the functionalized surfactants showed good antimicrobial activity against gram negative and gram positive organisms. The new compounds are easily synthesized, economical and environmentally friendly and are expected to constitute an important class of organic compounds for medicinal purposes in the future.     

Synthetic and biological studies on mono- and bis-methylene-bridged heterocyclic sulfides and sulfones of carbostyrils

A series of new sulfides and sulfones of carbostyrils were synthesized and tested for their in vitro antimicrobial and in vivo analgesic activities. The results of a bioassay showed that these newly synthesized compounds exhibit potential antibacterial and antifungal activities. The chloro substitution at C-6 and C-7 positions of carbostyrils was found to enhance the antimicrobial activity. Similarly, halogen-substituted sulfones were found to possess potent analgesic activities. All the newly synthesized compounds were characterized by elemental analysis, IR, ¹H NMR, ¹³C NMR, ESI-MS and FAB-MS.     

Self-stratifying antimicrobial polyurethane coatings

In this work antimicrobial polyurethane coatings were prepared aiming at self-stratification. A hydroxyl end-capped liquid oligoester consisting of three equimolar diacids and an excess of 1,4-butanediol has been synthesized by a condensation reaction. A set of quaternary ammonium compounds (QACs) which are well known contact killers, was synthesized via a straightforward quaternization reaction. These synthesized precursors were later covalently bonded to the polymer network by addition of a polyisocyanate crosslinker resulting in antimicrobial polyurethane coatings. Self-stratification was confirmed by dynamic contact angle analysis and X-ray photoelectron spectroscopy. The final films showed strong antimicrobial activity against both Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli type bacteria.     

Amino-functionalized mesoporous silica as solid base catalyst for regioselective aza-Michael reaction of aryl tetrazoles

The modified MCM-41 with aminopropyl groups was synthesized, characterized and its catalytic activity was evaluated in aza-Michael addition of various aryl tetrazoles to activated olefin esters under reflux condition. The synthesized new compounds were characterized using spectroscopic and physical methods. The catalyst was reused in five consecutive experiments without obvious loss of activity. The results showed with application of aminopropylated MCM-41 only N2 alkylation occurs on tetrazole rings. However, when triethylamine was used as the base, a mixture of N1 and N2 alkylation was observed. In addition, antimicrobial studies investigated and results indicated that the products did not show considerable antimicrobial activity.     

二茂铁亚胺酯的抑菌活性研究Ⅰ——1-[1-(2-羟基苯基)乙基]- 二茂铁及其酯的合成、表征与抑菌活性

为了增加乙酰基二茂铁缩邻氨基酚席夫碱的酯溶性，对其进行结构修饰。用乙酰基二茂铁与邻氨基苯酚进行缩合，制得席夫碱（二茂铁亚胺），然后再与酰氯反应，得到二茂铁亚胺羧酯酯。对所得产物结构用元素分析，红外光谱和核磁z共振氨谱进行了表征，化合物的抑菌活性试验表明，二茂铁亚胺及其酯显示了较好的抗病原微生物作用。     

Synthesis and characterization of antimicrobial cationic surfactants: Aminopyridinium salts

Three antimicrobial 4-aminopyridinium salts were synthesized using two different processes in an effort to develop antimicrobial surface treatment agents for wool fibers. The structures of the salts were fully characterized using Fourier transform infrared, ¹H nuclear magnetic resonance (NMR), and ¹³C NMR analysis. In addition, their thermal stability was determined using differential scanning calorimetry and thermogravimetric analysis. The antimicrobial efficacy of these compounds was evaluated using minimum inhibitory concentration as an indicator. All of the synthesized aminopyridinium salts showed antimicrobial activity against gram-negative bacteria, but in different levels depending on their structures. The salts possessing longer alkyl chains demonstrated better antimicrobial function. The melting points of the salts decreases as the alkyl chain length increases.     

Novel (+)-Neoisopulegol-Based O-Benzyl Derivatives as Antimicrobial Agents

Discovery of novel antibacterial agents with new structures, which combat pathogens is an urgent task. In this study, a new library of (+)-neoisopulegol-based O-benzyl derivatives of aminodiols and aminotriols was designed and synthesized, and their antimicrobial activity against different bacterial and fungal strains were evaluated. The results showed that this new series of synthetic O-benzyl compounds exhibit potent antimicrobial activity. Di-O-benzyl derivatives showed high activity against Gram-positive bacteria and fungi, but moderate activity against Gram-negative bacteria. Therefore, these compounds may serve a good basis for antibacterial and antifungal drug discovery. Structure–activity relationships were also studied from the aspects of stereochemistry of the O-benzyl group on cyclohexane ring and the substituent effects on the ring system.     

Antimicrobial Polychelates: Synthesis and Characterization of Transition Metal Chelated Barbituric Acid–Formaldehyde Resin

A monomeric Schiff base was prepared by the condensation reaction of salicylaldehyde and semicarbazide, which further react with formaldehyde and barbituric acid-formed polymeric Schiff base. Its metal polychelates were then formed with Mn(II), Co(II), Ni(II), Cu(II), and Zn(II). All the synthesized compounds were characterized by elemental analysis, magnetic moment, FTIR, ¹HNMR, and electronic spectroscopies. The elemental analysis data show the formation of 1:1 [M: L] metal polychelates. Thermogravimetric analysis was carried out to find the thermal behavior of all the synthesized polymeric compounds and thermal data revealed that all the metal polychelates are more thermally stable than their parent polymeric Schiff base. All the synthesized polymeric compounds were screened for antimicrobial activity against some clinically important microorganisms, such as Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, Staphylococcus aureus, Staphylococcus typhi, Candida albicans, Microsporum canis, and Aspergillus niger. In vitro antimicrobial activity was determined by the Agar Well Diffusion method and the result shows that all the metal polychelates exhibited better antimicrobial activity than their parent polymeric Schiff base.     

N-苯甲酰基苯并异噻唑-3-酮硫代甲酰胺类化合物的合成及生物活性

通过1,2-苯并异噻唑啉-2(3H)-酮和硫代异氰酸苯甲酸酐类化合物反应,合成了7种N-苯甲酰基苯并异噻唑-3-酮硫代甲酰胺类化合物,用IR、MS、1HNMR、13CNMR对其结构进行了表征;活性测试表明,浓度为0.005mol/L的该类化合物溶液对鳗孤菌、拟态孤菌、溶藻弧菌、大肠杆菌和嗜水性单胞菌的抑菌率达40.5%~100%。     

新型双季铵盐杀菌剂的合成和杀菌性能研究

本文合成了以两个吡啶环为核心,通过链桥结构联接,每个分子含有两个正电荷N 离子,及两个亲水和疏水基团的一种新型双季铵盐,通过微生物杀菌试验,表现出良好的杀菌性能。     

Chemo‐enzymatic synthesis of lipophilic ferulates and their evaluation for antioxidant and antimicrobial activities

An efficient chemo‐enzymatic synthesis of ferulic acid‐based structured lipids mimicking triacylglycerol with a pendant phenolic moiety was carried out for the first time. Initially, ferulic acid was reduced to coniferyl alcohol, followed by its esterification with fatty acids. The key step in the synthesis was dihydroxylation of the olefinic side chain of coniferyl ester, which was eventually esterified with fatty acids to generate phenolic structured lipids. Two such compounds of varying fatty acid chain lengths were synthesized in good yield. Structural confirmation of both compounds is based on IR, ¹H and ¹³C NMR, and MS techniques. The synthesized compounds were tested for in vitro antioxidant and antimicrobial activities. Both compounds exhibited moderate to good antioxidant activity. The phenolic structured lipid with only shorter‐chain fatty acids showed antibacterial activity. Both compounds did not show any antifungal activity.     

C-3 Substituted Lawsonemonoximates of Holmium(III): Synthesis, Characterization, and Antimicrobial Activity

A series of five new metal complexes of Ho(III) with C-3 substituted derivatives of lawsonemonexime (2-hydroxy-1,4-naphthalenediene-1-oxime) were synthesized. The compounds were characterized by melting point, elemental analysis, IR spectroscopy and magnetic susceptibility. The antimicrobial activity of the compounds were determined by disk diffusion method and broth micro-dilution techniques using Mueller Hinton medium against the following organisms: S. aureus ATCC 6538P, Klebsiella pneumoniae, NCTC 418, Pseudomonas aeruginosa ATCC 27833, Salmonella typhimurium ATCC 23564, E. coli U 1777, E. coli HB101, Proteus morganii NCIM 2860, Providencia stuartii NCIM 2799 and Acinetobacter baumannii U 24. The chelates of Ho(III) with lawsonemonoxime and Ho(III) with 3-bromolawsonemonoxime showed a variable antimicrobial activity against all organisms tested except Pseudomonas and Klebsiella spp. S. aureus was found more sensitive to all ligands and chelates tested; but the MIC values of chelates were considerably less; thus having more antimicrobial effect.     

Antibacterial activity of new dibenzoxepinone oximes with fluorine and trifluoromethyl group substituents

In this paper we present the antimicrobial activity of some newly synthesized dibenz[b,e]oxepin derivatives bearing the oximino moiety, and fluorine (F) and trifluoromethyl (CF(3)) group substituents. The chemical structure and purity of the new compounds were assessed by using elemental analysis, NMR and FTIR spectroscopy. The new compounds were screened for their antibacterial activity towards Gram-positive and Gram-negative strains, by qualitative and quantitative assays. Our results demonstrated that the CF(3) and F disubstituted compounds could be considered for the further development of novel antimicrobial drugs.     

无患子提取液制备纳米银及其协同抗菌性研究

以无患子提取液为还原剂,制备了含有纳米银的无患子复合抗菌液,考察了无患子提取液用量、温度、硝酸银摩尔浓度等因素对纳米银形貌和粒径的影响,并借助UV-Vis可见分光光谱、X射线衍射(XRD)以及透射电子显微镜(TEM)对产物进行表征;通过抑菌环法探讨了复合抗菌液对大肠杆菌的抗菌活性。由UV-Vis图谱可知,复合抗菌液等离子体共振吸收峰(SPR)在418 nm左右,说明该复合抗菌液中有纳米银的存在;XRD图表明合成的纳米银为面心立方结构;TEM图表明合成纳米银粒径为10~40 nm。由此获得的含有纳米银的无患子复合抗菌液对大肠杆菌表现出显著协同抗菌活性,抑菌圈直径变大。     

Characterization,surface properties and biological activity of some synthesized anionic surfactants

In this study, esterification reaction between four different fatty alcohols (octyl, dodecyl, hexdecyl and octadecyl alcohol) and phosphoric acid was performed. The produced compound was reacted with polyethylene glycol-400. Then, the reaction product was quenched using sodium hydroxide to form the desired anionic gemini surfactants. The chemical structures of the synthesized surfactants were recognized by FT-IR and ¹H NMR spectroscopy. The synthesized surfactants showed higher surface activity. The emulsion stability measurements showed the applicability of these surfactants as emulsifying agents. The foaming power measurements showed the synthesized surfactants have low ability to foam formation. The thermodynamic parameters showed their tendency toward adsorption at the interfaces and also micellization in the bulk of their solutions. The studied surfactants were evaluated as antimicrobial agents against pathogenic bacteria using inhibition zone diameters. The synthesized surfactants showed good antimicrobial activities against the tested microorganisms including Gram positive, Gram negative as well as fungi. The promising inhibition efficiency of these compounds against the pathogenic bacteria facilitates them to be applicable in the petroleum field as new categories of biocides.     

羟丙基壳聚糖、壳聚糖铈/银的合成、表征和抗菌性能研究

以壳聚糖和硝酸铈铵为原料,并对壳聚糖进行改性,合成了两种新型的配合物。通过红外光谱、X射线光电子能谱、差热-热重分析、透射电镜等对合成物进行表征。由透射电镜照片发现合成物由分散的纳米颗粒组成。通过抗菌实验对其抑菌效果进行研究,结果表明这两种配合物对大肠杆菌和金黄色葡萄球菌均有较强的抑菌作用,最小抑菌浓度(MIC)分别为130μg/mL,70μg/mL和75μg/mL,60μg/mL,属于广谱抗菌剂,抗菌效果明显优于单独的壳聚糖、羟丙基壳聚糖、稀土化合物。