Synthesis and Antibacterial Activity of New Cephalosporin Compounds

The fourth generation cephalosporin cefepime I exhibited potent antibacterial activity with board antibacterial spectrum1,2.Based on the structure of cefepime,we synthesized its analogs Ia having fluoro atom at the aminothiazolyl oxime moiety at the7-position of the cephem nucleus,and Ib possessing1-(2-fluoroethyl)pyrrolidium methyl group at the3-position.It was reported that cephalosporin derivatives with a quaternary ammonium moiety at the3-position of the cephem nucleus,showed enhanced ant…     

Synthesis and Antibacterial Activity of New Tetracycfic Triazolothiadiazino Fluoroquinolones

A series of novel 9-fluoro-10-(4-methylpiperazin-l-yl)-3-substituted-8-oxo-8H-[1,2,4] triazolo[3,4-b]thiadiazino[6,5,4-ij]quinoline-7-carboxylic acids was prepared by a facile synthetic method and the in vitro antibacterial activity against Gram-postive (G^ ) and Gram negative (G^-) bacteria was primarily evaluated.     

Synthesis and Antibacterial Activity of New Tetracyclic Triazolo-thiadiazino Fluoroquinolones

Since nalidixic acid1 was first clinically used as a potent antibacterial agent, many analogues, such as bicyclic ciprofloxacin2, tricyclic ofloxacin3, have become an important class of therapeutical compounds. Recently, novel tetracyclic fluoroquinolones having a thiazolooxazine ring with potent antibacterial activity against both G+ and G- have been reported4. In order to find better antibacterial agents for our urgent research of the multidrug resistant (MDR)5, we herein describe a facil…     

Engineering Antibacterial Activities and Biocompatibility of Hyperbranched Lysine-based Random Copolymers

Antimicrobial peptides(AMPs) have been considered as an alternative to small molecule antibiotics since they are difficult to develop antimicrobial resistance. Hyperbranched polylysine(HPL), an AMP mimics, has gained attention due to its broad-spectrum antibacterial activities,but it also suffers from high toxicity. Here we report a facile strategy to engineer the toxicity of HPL by copolymerizing lysine(K) with a hydrophobic amino acid, e.g., alanine(A), tryptophan(W) or phenylalanine(F), to af...     

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.     

Synthesis of New N-Sulfonyl Monocyclic β-Lactams and the Investigation of Their Antibacterial Activities

New monocyclic β-lactams 4–6 were synthesized by a ketene-imine [2+2] cycloaddition reaction. The prepared monocyclic β-lactams 4–6 were cleaved by ceric ammonium nitrate (CAN) to give NH-β-lactams 7–9. The NH-β-lactams were converted to N-sulfonyl β-lactams 10–21 by treatment with four different sulfonyl chlorides in the presence of Et₃N and 4-N,N-dimethylaminopyridine (DMAP). Some of these monocyclic β-lactams were active against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Pseudomonas aeruginosa.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Chemical Constituents and Antibacterial and Antifungal Activities of Two Aglaia Species

In the course of searching bioactive natural products from the plant genus Aglaia, we selected two species, A. cordata and A. testicularis, for further chemical study. Totally twenty natural compounds were obtained and structurally elucidated with which eleven of them were discovered for the first time. Among these compounds, lignans, rocaglamides,aglains and bisamides were the main constituents of the two plant species. The results from a bioactive screening indicated that some of the lignans possess potent antibacterial and antifungal activity.     

Synthesis and Antibacterial Activity of Selenium-functionalized Poly(ε-caprolactone)

A selenium-functionalizedε-caprolactone was synthesized by introducing a phenyl selenide group at the 7-position.A polymer was obtained through the ring-opening polymerization of this monomer in a base/thiourea binary organocatalytic system.A living polymerization process was achieved under mild conditions.The resulting polymers had a controlled molecular weight with a narrow molecular weight distributions and high end-group fidelity.Random copolymers could be obtained by copolymerizing this monomer withε-caprolactone.The thermal degradation temperature of the obtained copolymers decreased with the increasing molar ratio of selenide functionalized monomer in copolymers,while the glass transition temperature increased.In addition,the phenyl selenide side group could be further modified to a polyselenonium salt,which resulted in a polymer with good antibacterial properties.The survival rate of E.coli and S.aureus was only 9%with a polymer concentration of 62.5μg/mL.     

Photosensitizer–Antibiotic Conjugates: A Novel Class of Antibacterial Molecules

Bacterial resistance to a variety of antibiotics has led to intensive research into the effect of photosensitizers as a cytotoxic agent against bacterial cells. In this study, we synthesized the following conjugates with or without a linker: rose bengal-penicillanic acid (RBPA), rose bengal-linker-penicillanic acid (RBLPA) and rose bengal-linker-kanamycin (RBLKAN). The antibacterial activity of these conjugates was examined on Staphylococcus aureus and Escherichia coli. Exposure of the cultures to 100 J cm⁻² showed that the minimum inhibitory concentration (MIC) of RBPA, RBLPA and RBLKAN on S. aureus was 0.195, 0.156 and 0.004 μm, respectively. The MIC of RBPA, RBLPA and RBLKAN on E. coli was 1.56, 2.5 and 0.156 μm, respectively. In dark control experiments, the MIC of these conjugates was not detected until a concentration that was 16-fold that of the MIC found in the light experiments. RBPA and RBLPA as well as RBLKAN are bactericidal for both bacterial cells. Total eradication of S. aureus and E. coli was observed with RBLKAN (0.078 and 20 μm 16 J cm⁻², respectively). Under these conditions, scanning electron microscopic analysis showed significant damage to these bacteria. However, the photosensitizer and antibiotics individually were not effective.     

Antibacterial Activity of Novel 18β-Glycyrrhetinic Hydrazide or Amide Derivatives

Through a facile structural modification on the natural bioactive ingredient 18β-glycyrrhetinic acid(GA), a series of novel GA hydrazide or amide derivatives was obtained, and their final molecular frameworks were characterized by NMR and HRMS analysis. Antibacterial bioassays revealed that some of the GA hydrazide or amide derivatives were able to suppress the growth of three tested plant pathogens. Particularly, compound 3c exhibited excellent in vitro activity against Xanthomonas oryzae pv. Oryzae (Xoo), Pseudomonas syringae pv. actinidiae(Psa), and Xanthomonas axonopodis pv. citri(Xac), providing the EC₅₀ values of 5.89, 16.1, and 3.64 μg/mL, respectively. The data were better than those of the positive controls thiodiazole copper(92.7, 77.8, and 89.9 μg/mL, respectively) and bismerthiazol(31.1, 125.6, and 77.4 μg/mL, respectively). In addition, in vivo experiments suggested that, compared with thiodiazole copper(41.93% and 39.73%, respectively), compound 3c exerted prominently curative and protective activities against rice bacterial leaf blight at 200 μg/mL with the control effects of 52.36% and 51.40%, respectively. Given these obtained results, GA hydrazide or amide derivatives could serve as the feasible leads for exploring highly bioactive substrates.     

Purification and Characterization of an Antibacterial Peptide from Rana Temporaria Chensinensis Skin

ＩｎｔｒｏｄｕｃｔｉｏｎＩｎａｄｄｉｔｉｏｎｔｏｔｈｅｈｉｇｈｌｙｓｐｅｃｉｆｉｃｃｅｌｌ－ｍｅｄｉａｔｅｄｉｍｍｕｎｅｓｙｓｔｅｍ，ｖｅｒｔｅｂｒａｔｅｓａｎｄｏｔｈｅｒｏｒｇａｎｉｓｍｓｈａｖｅａｄｅｆｅｎｓｅｓｙｓｔｅｍｍａｄｅｕｐｏｆｄｉｓｔｉｎｃｔｇｒｏｕｐｓｏｆｂｒｏａｄ－ｓｐｅｃｔｒｕｍａｎｔｉｂａｃｔｅｒｉａｌｐｅｐｔｉｄｅｓ［１—３］．Ａｎｔｉｂａｃｔｅｒｉａｌｐｅｐｔｉｄｅｓｃａｎｂｅｃｌａｓｓｉｆｉｅｄｉｎｔｏｔｗｏｇｒｏｕｐｓｂａｓｅｄｏｎｈａｖｉｎｇｄｉｓｕｌ－ｆｉｄｅ…     

A New and Efficient Synthetic Method and Antibacterial Activities of Oxazolidinone Analogues

A series of novel oxazolidinone analogues were prepared by a new and efficient synthetic method and their antibacterial activities were determined. These compounds wer echaracterized by LC-MS and ^1H NMR.     

A Convenient Synthesis of Antibacterial Linezolid from （S）-Glyceraldehyde Acetonide

Oxazolidinones as a new class of synthetic antimicrobial agents are active against numerous multidrug-resistant Gram-positive organisms1. Linezolid 1 as the promising candidate of this family works effectively against numerous serious Gram-positive human …     

Antibacterial modification of cellulose fibers by grafting β-cyclodextrin and inclusion with ciprofloxacin

Antibacterial-modified cellulose fiber was prepared by covalently bonding β-cyclodextrin (β-CD) with cellulose fiber via citric acid (CA) as crosslinking agent, followed by the inclusion of ciprofloxacin hydrochloride (CipHCl) as antibiotic. Effects of reaction time, temperature, concentration of β-cyclodextrin citrate (CA-β-CD) and pH on the grafting reaction were investigated, and the grafting ratio of β-CD onto cellulose fibers was 9.7 % at optimal conditions; the loading and releasing behaviors of CipHCl into/from β-CD grafted cellulose fibers were also revealed, the load amount of CipHCl into grafted cellulose fibers increased remarkably, and the release of CipHCl from the grafted cellulose fibers was prolonged. The microstructure, phase and thermal stability of modified cellulose fibers were characterized by FT-IR, ¹³C CPMAS NMR, X-ray diffraction and TGA. Considerably longer bacterial activity against E. coli and S. aureus was observed for grafted fibers loading CipHCl compared to virgin ones. Optical and mechanical properties of the paper sheets decreased generally with more antibacterial-modified fibers added.     

Synthesis and Characterization of Silver–PVA Nanocomposite for Sensor and Antibacterial Applications

Silver–polyvinyl alcohol (PVA) nanocomposite is synthesized by a simple chemical reduction method in aqueous media and characterized by various techniques such as UV–Visible spectroscopy, transmission electron microscopy, X-ray diffraction and infrared spectroscopy. The morphology of the obtained silver nanoparticles is spherical in shape with an average diameter of 24 nm. The prepared silver–PVA nanocomposite is demonstrated to detect the concentration of heavy metal contaminant cadmium in water based on linear change in surface plasmon resonance absorption strength. The antibacterial tests show the inhibiting action of this nanocomposite against pathogenic bacteria Escherichia coli and Pseudomonas aeruginosa (gram negative), Bacillus cereus and Staphylococcus aureus (gram positive), which are found commonly in water. These observed optical and antibacterial properties, suggest the possible utilization of prepared silver–PVA nanocomposite in the water purification application.     

Two New Antibacterial Flavanones from Sophoraflavescens

The dry root of Sophora flavescens, which is a well-known Chinese herbal medicine, has been used for the treatment of diarrhea, gastrointestinal hemorrhage and eczema1. Here we report the structure elucidation of two new flavanones isolated from this plan…     

Microcalorimetric Study of Antibacterial Activity of Salicylaldehyde Glucosamine Copper(Ⅱ) Complex on E.coli

Since Schiff base and its metal complexes are of antibacterial and anticancer bioactivity, it has been a research subject of much interest. It is reported that Cu(Ⅱ)-SG could inhibite the synthesis of O₂^- markedly and could also combine with the salmn sperm DNA. The paper repored that by using microcalorimetric method The growth meloabolism of E.coli at different temperature and reacted upon by Cu(Ⅱ)-SG. The power-time curves of E.coli reacted with Cu(Ⅲ)-SG at different temperature has been determined by LKB2277 Microcalorimetric Monitor and the multiplication rate constant k, generation time G,bacterial growth inhibition ratio I,total thermogenetic quantity Q, the heat quantity of a single bacterium. Q₀ and the heat quantity of a single bacterium per minute Q₀ have also been calculated. On the basis of k~T data, the formula Lnk~1/T has graphically obtained and activation energy Ea and pre-exponential factor A have been calculated. According to the parameters of the growth metabolism of E.coli,some linear relationships have been derived. The paper provides a discussion about the growth metabolism of E.coli reacted upon by Cu(Ⅱ)-SG at different temperature, and it is found that、and t_r can be used to characterize bacterial growth metabolism and the antibacterial activity of Cu(Ⅱ)-SG at different temperature.     

Synthesis,Characterization and Antibacterial Activities Study of a Pharmaceutical Cocrystal of Artesunate and 4,4’-Bipyridine

We report here a cocrystal with artesunate as the active pharmaceutical ingredient(API) and a pharmaceutical intermediate 4,4?-bipyridine as the cocrystal former(CCF). The analysis of single-crystal X-ray diffraction demonstrates that the eutectic structural unit consists of two artesunate molecules and one 4,4?-bipyridine molecule with their ratio to be 2:1. The carboxyl group on artesunate acts as a donor, and the acceptor is N on 4,4?-bipyridine, forming an O–H···N hydrogen bond. The appearance of new diffraction peaks in the X-ray powder diffraction pattern also indicates the formation of new phases. The PXRD results indicated a pure phase for the synthesized sample. The cocrystal is slightly soluble in water. Antimicrobial activities showed that the cocrystal displayed effective inhibition of different bacteria.     

Facile Fabrication of Hyperbranched Polyacetal Quaternary Ammonium with pH-Responsive Curcumin Release for Synergistic Antibacterial Activity

In the current global crisis of antibiotic resistance, persuit of an effective multi-pathway collaborative approach to enhance antibacterial activity is urgently needed. Here, a kind of hyperbranched polyacetal quaternary ammonium(Hyper-ace-QA) with efficiently antibacterial function were synthesized by a succession of efficient click strategies. The high molecular weights can be obtained just after UV irradiation for 3 h, and the grafting ratio can be easily adjusted through controlling solvent...     

Two New Antibacterial Iridoids from Patrinia rupestris

Patrinia rupestris has long been used as Chinese folk medicine for treatment of enteritis, appendicitis and hepatitis1. The chemical studies of this plant have not been reported till now, and iridoid containing chlorine has not been isolated from Patrinia…