Investigation of Antibacterial Activity of Two Kinds of Novel Schiff Bases on Escherichia coli by Microcalorimetry

The microcalorimetric method was used to study the antibacterial activity of two newly synthesized Schiff basecompounds(H_2L~(3')and H_2L~3)on Escherichia coli,trying to obtain the action on both of multiplying bacteria andnon-multiplying bacteria at one experiment.The metabolic power-time curves of the bacteria treated with the com-pounds were obtained,and the thermokinetic parameters were analyzed,from which the antibacterial activities ofthese compounds were evaluated.The results showed that both of the two compounds have good activity on aerobicmultiplying metabolism of E.coli,with the value of IC_(50)75.8 and 168.8 mg/L respectively,but have not effectiveaction on fermentation metabolism of E.coli.The action of the compounds on the non-multiplying metabolism wasinvestigated by taking the heat output of E.coli in the stationary phase as the guideline of the activity.The value ofMSC_(50)(minimum stationary-cidal concentration 50)of them is 118 and 187.5 mg/L,respectively.So,H_2L~(3')hasstronger antibacterial action on E.coli than H_2L~3 either for multiplying bacteria or non-multiplying bacteria,andtheir activity on the aerobic multiplying bacteria of E.coli is mainly shown.It does strongly suggest that the calo-rimetric method should play an important role in the fight against the drug-resistant bacteria.     

Action of the Selenomorpholine Compounds on the Bacterium Growth by Microcalorimetry

The action of β-(N-selenomorpholine) ethyl phenyl ketone hydrochloride and 4-(N-selenomorpholine)-2-butanone hydro-chloride on Escherichia coli and Staphylococcus aureus was studied by microcalorimetry,Differences in their capacities to affect the metabolism of this bacterium were observed.The kinetics shows that the selenomorpholine compounds had action on the metabolism process of Escherichia coli and Staphylococcus aureus.The rate constant (k) of the studied bacterium in the presence of the drugs are concentration-dependant.The growth rate constants decrease with an increase in the mass of the selenomorpholine compounds ,but their relationship is different.As deduced from the rate constant(k) of the studied bacterium(in log phase )and the half inhibitory concentration (IC50),the experimental results reveal that the studied selenomorpholine compounds all have good antibiotic activity and better antibacterial activity on Staphylcoccus aureus than on Escherichia coli.     

One-pot synthesis, antibacterial and antifungal activities of novel 2,5-disubstituted-1,3,4-oxadiazoles

A series of novel 2,5-disubstituted-1,3,4-oxadiazoles have been synthesized from long-chain alkanoic and alkenoic acids. The structures of these compounds have been elucidated by elemental and spectral （IR, ^1H NMR, ^13C NMR, MS） analysis. Furthermore, compounds were screened for in vitro antibacterial activity against the representative panel of two Gram-positive and two Gram- negative bacteria. All the synthesized compounds were also tested for their inhibitory action against five strains of fungus. The various compounds show potent inhibitory action against test organisms. 2007 Abdul Rauf. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.     

Study on the synthesis and antimicrobial activity of novel cationic porphyrins

A novel series of quaternary ammonium cationic derivatives based on tetrapyridyl-porphyrin was synthesized.All the compounds were evaluated for their in vitro antibacterial activities against S.aureus,E.coli and P.aeruginosa,and antifungal activities against C.albicans,where microorganisms were exposed and unexposed to the irradiation.The results revealed that some of these compounds,especially,3a and 4a displayed satisfactory antibacterial activity against Gram-positive bacteria S.aureus and moderate an...     

Preparation and antibacterial activity of aromatic derivatives of β-aminopropionic and γ-aminobutyric acid

Ten aromatic derivatives of β-aminopropionic acid and γ-aminobutyric acid were prepared.Their compositions and structures were identified by elemental analysis,IR,and 1H NMR.They have been examined for their antibacterial action against Staphylococcua aurens and Escherichia coli.These compounds showed higher activity than the aromatic derivatives of ct-amino acid which were reported previously.The general conclusion to be drawn is that the distance between amino and carboxylic group in these molecules could affect their antibacterial activity.Furthermore,those compounds with p-methyl substituent in phenyl ring exhibit higher activity than the others,and all the compounds exhibit higher activity against Escherichia coli and against Staphylococcua aureus.     

Antibacterial poly(D,L-lactide) (PDLLA) fibrous membranes modified with quaternary ammonium moieties

<正>Antibacterial poly(D,L-lactide)(PDLLA) fibrous membranes were developed via electrospinning,followed by surface modification which involved plasma pretreatment,UV-induced graft copolymerization of 4-vinylpyridine(4VP) and quaternization of the grafted pyridine groups with hexylbromide.The success of modification with quatemized pyridinium groups on the PDLLA fibrous membranes was ascertained by X-ray photoelectron spectroscopy(XPS).The antibacterial activities of these membranes were assessed against Gram-positive Staphylococcus aureus(S.aureus) and Gram-negative Escherichia coli(E.coli).The PDLLA fibrous membranes modified with quaternized pyridinium groups showed antibacterial efficiency against both bacteria as high as 99.999%.The results demonstrated that the antibacterial activity was based on the interaction of the positive charge of pyridinium group and negatively charged cell membrane of bacteria, resulting in loss of membrane permeability and cell leakage.     

Synthesis, characterization and antibacterial properties of multifunctional hindered amine light stabilizers

A series of novel hindered amine light stabilizers containing an N-halamine moiety were designed and synthesized. Their structures were characterized by FT-IR, 1H NMR, and MS. The compounds were tested for antibacterial activity against Candida albicans, Staphylococcus aureus, and Escherichia coll. At a concentration of 0.5 mmol/L, these compounds all exhibited satisfactory antibacterial activity against all the three types of bacteria.     

Antibacterial thermoplastic polyurethane electrospun fiber mats prepared by 3-aminopropyltriethoxysilane-assisted adsorption of Ag nanoparticles

Antibacterial thermoplastic polyurethane(TPU) electrospun fiber mats were prepared by adsorption of Ag nanoparticles(Ag NPs) onto TPU/3-aminopropyltriethoxysilane(APS) co-electrospun fiber mats from silver sol. The use of APS can functionalize TPU fibers with amino groups, facilitating the adsorption of Ag NPs. The effects of p H of silver sol and APS content on Ag NP adsorption and antibacterial activity were investigated. Ag NP adsorption was evidenced by TEM, XPS and TGA. Significant Ag NP adsorption occurred at p H = 3-5. The main driving force for Ag NP adsorption is electrostatic interaction between ―NH3~+ of the fibers and ―COO-derived from the ―COOH group capped on the surfaces of Ag NPs. The antibacterial activity of the Ag NP-decorated TPU/APS fiber mats was investigated using both gram-negative Escherichia coli and gram-positive Bacillus subtilis. The antibacterial rate increases with increasing APS content up to 5% where the antibacterial rates against both types of bacteria are over 99.9%.     

Synthesis,antimicrobial, antiquorum-sensing and cytotoxic activities of new series of benzothiazole derivatives

New series of benzothiazole derivatives were designed and synthesized. The newly synthesized compounds were screened for their antibacterial activity against Escherichia coli, Staphylococcus aureus and Bacillus cereus. Compounds 6j and 6o showed the highest activity against E. coli and S. aureus. The antifungal activity of these compounds was also tested against Candida albicans and Aspergillus fumigatus293. Compounds 4c, 4g and 6j exhibited the highest activity against C. albicans. In addition, compounds4 a and 6j displayed promising activity against A. fumigatus 293. The same compounds were examined for their antiquorum-sensing activity against Chromobacterium violaceum ATCC 12472, whereas compounds4 a, 6j and 6p showed moderate activity. The in vitro cytotoxicity testing of the synthesized compounds was performed against cervical cancer(Hela) and kidney fibroblast cancer(COS-7) cell lines. Results indicated that all tested compounds have IC50 values 50 mmol/L against both cell lines. Molecular properties, toxicities, drug-likeness, and drug score profiles of compounds 4a–c, 5a, 6g,h, 6j, 6l, 6o and7 c,d were also assessed.     

Facile synthesis of benzimidazole bearing 2-pyridone derivatives as potential antimicrobial agents

A series of benzimidazole bearing 2-pyridones 5a-k were synthesized and assessed in vitro for their activity as antimicrobial agents using the conventional broth dilution method. The results of the antimicrobial study revealed that compounds 5b, 5c, Sj and 5k exhibited substantial antibacterial activity while compound 5d emerged as amore potent antifungal agent compared to the standard drugs chloramphenicol and ketoconazole, respectively. It was observed that the presence of inductively electron withdrawing groups remarkably enhance the antibacterial activity of the newly synthesized compounds. Cytotoxicity studies suggested that none of the tested compounds exhibited any significant cytotoxic effects.     

微量热研究几种新型吡啶酰胺希夫碱对大肠杆菌的抑制作用

用微量热研究一系列新型吡啶酰胺希夫碱对大肠杆菌的抑制作用, 不同的吡啶酰胺希夫碱衍生物对大肠杆菌生长的抑制作用不同. 通过热动力学模型计算得到生长速率常数(k)和抑制率(I), 我们获得了吡啶酰胺希夫碱衍生物的抗菌作用效果. 通过药物作用于细菌处于生长对数期的实验发现, 有两种化合物(F和G)对大肠杆菌生长有非常好的抑制作用, 他们的半抑制浓度(IC50)分别是0. 106 和0. 113 g/L, 但是药物对大肠杆菌的无氧发酵过程抑制作用比较差. 通过进一步分析药物结构与药物半抑制浓度, 我们发现: 希夫碱衍生物的亲水性对其抗菌活性有很大的影响, 这主要是由细菌的细胞膜结构不同所致. 对希夫碱及其碱衍物的结构与抗菌活性关系进行了初步探讨, 它们对大肠杆菌的抗菌活性顺序为: F＞G＞C＞D＞E＞B＞A.     

Antibacterial Properties of a Kind of Schiff Base and Its Neodymium(III) and Zn(II) Complex (ZnNdL) on Escherichia coli

The microcalorimetric and electronic microscopy methods were used to study the antibacterial activity of a Schiff base and its complex ZnNdL on Escherichia coli. The metabolic power‐time curves of the bacteria treated with the compounds were obtained, and the thermokinetic parameters were analyzed. The results show that the compounds (H₂L, ZnNdL) have good activity on aerobic multiplying metabolism of E. coli, with the values of IC₅₀ 57.0 and 54.4 mg·L^?1, respectively. In order to further investigate their mechanism on E. coli, transmission electronic microscopy and scanning electronic micrography were used to study the cell membrane change induced by the dibasic quadridentate Schiff base and its neodymium(III) complex. At a low concentration of the compound, the flagellum was inhibited and the cell did not show distinct changes. However, the flagella around the cell membrane were exfoliated, the morphology of E. coli was changed from a rod shape into a spherical shape or a short rod, and the flagella disappeared completely at a high concentration. The drug permeability into cell membrane was investigated by fluorescence quenching of probe dis‐C₃‐(5), which suggested that H₂L and ZnNdL could influence on the intra and extra cell membrane.     

Antibacterial Activity of a Kind of Novel Schiff Base and Its 3d,4f Complexes

The microcalorimetric method was used to study the antibacterial activity on the bacteria's multiplying metabolism and the non-multiplying metabolism. The metabolism thermogenic curves of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), under the action of the synthesized Schiff base and its 3d,4f complexes (2L, 2LZnYb), were obtained. The results showed that the multiplying metabolism and the non-multiplying metabolism of bacteria could be analyzed by the thermogenic curves using the thermokinetic equations. On the multiplying metabolism, the two compounds (2L, 2LZnYb) have strong activity for E. coli. (IC₅₀ (half-inhibitory concentration) is 6.1 and 5.1 mg·L⁻¹, respectively) and weak activity for S. aureus (IC₅₀ is 310.1 and 595.9 mg·L⁻¹, respectively). The introduction of Zn and Yb with the compound slightly increased the inhibition on the multiplying metabolism of E. coli but greatly decreased the effect on that of S. aureus. The activity of these two compounds showed great difference on the non-multiplying metabolism. Regardless of E. coli or S. aureus, 2L showed a notable inhibition and MSC₅₀ (the minimum stationary-cidal concentration 50) of 2L was 6.4 and 209.7 mg·L⁻¹ for the two microorganisms, respectively. Thus, 2L may become a novel kind of potential antibacterial candidate.     

Synthesis and Antimicrobial Evaluation of Novel Polyfused Heterocycles‐Based Quinolone

Syntheses of some new heterocyclic compounds incorporating quinolone moieties were achieved via reaction of 4‐hydroxy‐7‐methoxyquinolin‐2(1H)‐one ( 1 ) or 3‐bromo‐4‐hydroxy‐7‐methoxyquinolin‐2(1H)‐one ( 2 ) with binucleophilic reagents. The newly synthesized compounds were characterized by elemental analyses and spectral data (IR, ¹H‐NMR and mass spectra). The newly synthesized compounds were screened for their antibacterial activity against Gram‐positive bacteria (Bacillus thuringiensis) and Gram‐negative bacteria (Escherichia coli). The results showed clearly that compounds 1 and 3 are the more potent antibacterial agents against E. coli, compounds 4 , 5 , 6 and 8 , 9 , 10 , 11 , 12 , 13 exhibited moderate activities against E. coli strain, and compounds 7 and 11 exhibited weak activities compared with Gentamicin as a well known standard drug.     

一种新型希夫碱及其3d,4f配合物的抗菌活性

用微量热法研究一种新型希夫碱及其3d,4f配合物(2L, 2LZnYb)对大肠杆菌和金黄色葡萄球菌的抗菌活性, 得到了在它们作用下大肠杆菌和金黄色葡萄球菌生长代谢的产热曲线, 并且基于分析生长代谢和非生长代谢的产热曲线建立的热动力学方程, 获得了它们的抗菌活性. 结果表明, 两种化合物(ZL, 2LZnYb)对大肠杆菌的生长代谢有强的活性(IC50分别为6.1 和5.1 mg·L-1), 但对金黄色葡萄球菌的生长代谢的活性弱得多(IC50分别为310.1 和595.5 mg·L-1). Zn 和Yb的导入使化合物对大肠杆菌生长代谢的抑制作用稍微增加, 但大大降低了对金黄色葡萄球菌的抑制作用. 对于非生长代谢, 两种化合物的活性有很大的差别. 无论对大肠杆菌还是金黄色葡萄球菌, 由于配体2L的导入, 表现出显著的抑制作用, 2L的MSC50为6.4和209.7 mg·L-1. 配体2L可能成为新的抗菌先导化合物.     

Design and synthesis of novel thiourea metal complexes with controllable antibacterial properties

A new bidentate O,S donor thiourea ligand (L¹), namely N‐(2‐hydroxyethyl)‐N′‐2‐chlorobenzoylthiourea, and its oxazolidine derivative (L²) were synthesized. Derivative L² was used for the preparation of Ni(L²)₂ and Cu(L²)₂ complexes. The compounds were investigated using X‐ray crystallography and Fourier transform infrared, ¹H NMR and UV–visible spectroscopies. Single‐crystal X‐ray analysis showed strong hydrogen bonding interactions between carbonyl oxygen and N(10) ─ H in the L¹ ligand. In addition, the antibacterial activities of these compounds were evaluated against Gram‐positive and Gram‐negative bacteria, measured using the colony count method. The Cu(L²)₂ complex exhibited a significant antibacterial activity while the activity of the other compounds was much lower. Finally, the relationship between the structure and antibacterial properties of these compounds was investigated using highest occupied and lowest unoccupied molecular orbital energies calculated by density functional theory method based on the 6‐31G*/LANL2DZ basis set.     

Synthesis of New Triazole and Oxadiazole Derivatives of Quinazolin‐4(3H)‐one and Their Antimicrobial Activity

A series of new triazole derivatives of quinazolin‐4(3H)‐one and new oxadiazole derivatives of quinazolin‐4(3H)‐one were synthesized. The newly synthesized compounds were characterized by IR, ¹H NMR, ¹³C NMR and mass spectral data. All the newly synthesized compounds were screened for antibacterial activity against Staphylococcus aureus, Bacillus subtilis (gram‐positive bacteria), Escherichia coli, Pseudomonas aeruginosa (gram‐negative bacteria), and antifungal activity was carried out against Candida albicans and Aspergillus niger.     

Synthesis,characterization, and biological investigation of new mixed-ligand complexes

A novel series of mixed-ligand complexes of 5,5′-{(1E,1E′)-1,4-phenelynebis(diazene-2,1-diyl)}bis(quinolin-8-ol) (H₂L₁) as a primary ligand and 4-aminoantipyrine(L₂) as a secondary ligand with Mn(II) ion were prepared using two general formulae: [Mn₂(H₂L₁)₂(L₂)₂X₄].4Cl (X = OH₂( 1 ), ONO₂⁻( 2 ), Cl=nil; OAc( 3 ), Cl = nil) and [Mn₂(H₂L₁)(L₂)₂(O₂SO₂)₂]( 4 ). Free ligands and their complexes were characterized. Electronic absorption spectra of the mixed-ligand complexes indicate a distorted octahedral geometry around the central metal ion, and the anions X⁻ are in the axial positions for all compounds. The ligands behave in a neutral bidentate manner, through nitrogen atoms and oxygen atoms of the carbonyl group (L₂), whereas H₂L₁ coordinated through nitrogen and OH groups as a neutral bidentate ligand. All complexes do not contain coordinated water molecules, but complex ( 1 ) contains four water molecules. The water molecules are removed in a single step. The complexes exhibited magnetic susceptibility corresponding to five unpaired electrons. The antimicrobial activity of the Mn(II) mixed-ligand complexes ( 1–4 ) against two gram-positive bacteria, three local gram-negative bacteria, and three fungi species was tested. Mn(II) mixed-ligand complex ( 2 ) exhibited significant antibacterial activity against Bacillus cereus, Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, and Pseudomonas sp. Mixed-ligand complex ( 2 ) exhibited a high potential cytotoxicity against the growth of human lung cancer cells.