Green Synthesis and Antibacterial Properties of Silver Nanoparticles from Eugenia uniflora Fruit Extract

The synthesis of nanoparticles by biological methods using microorganisms, enzymes, or plant extracts has been suggested as a possible ecofriendly alternative to chemical and physical methods that involve the use of harmful reducing agents. Green synthesis of silver nanoparticles (AgNPs) was achieved using Eugenia uniflora ripe fruit extract, which was characterized by phytochemical screening revealing the presence of polyphenols (quinones, flavonoids, and tannins), reducing compounds, and terpenes. These excellent antioxidants reduced silver nitrate to give the AgNPs, which were characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), and ζ potential analysis. The diameter of the AgNPs ranged from 10.56 ± 1.2 nm to 107.56 ± 5.7 nm. The antibacterial activity of the AgNPs was evaluated using a modification of the Kirby-Bauer technique with Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. The inhibition halos were 11.12 ± 0.02 mm, 13.96 ± 0.07 mm, and 11.29 ± 0.76 mm, respectively. The synthesis using E. uniflora is an ecofriendly and low cost method of obtaining silver nanoparticles that could be used in health sciences because of their activity against bacteria with antibiotic resistance.

Synthesis and Antibacterial Effect of New Alkylenedibiguanides

Seven new alkylenedibiguanides were synthesized and comfirmed by 1H NMR, MS and elemental analyses. The preliminary test in vitro showed that some of them had potential antibacterial activities.

Synthesis and Antibacterial Activity of (S)-5-(Heterocycle Methylene) -3-(3-Fluoro-4-morpholin-4-yl-phenyl)-Oxazolidin-2-one Derivatives

Aim To study the structure-activity relationship of antibacterial oxazolidinone derivatives. Methods Seven （S） -5- （ heterocycle methylene） -3- （3-fluoro-4-morpholin-4-yl-phenyl） -oxazoli- din-2-ones were synthesized by the substitution of （S）-[ 3-（3-fluoro-4-morpholin-4-yl-phenyl）-oxazohdin-2-one-5-yl]-methanol mesylate with some secondary amines and the structures of the product were confirmed by ^1H NMR and elemental analyses or MS. Results None of the seven compounds showed potent activity against the tested 20 strains of bacteria in vitro. Conclusion The replacement of 5- acetylaminometyl of Linezolid by 5-（heterocycle methylene） lost the antibacterial activity.

Green Synthesis of Silver Nanoparticles Using Aqueous Orange and Lemon Peel Extract and Evaluation of Their Antimicrobial Properties

Green synthesis of silver nanoparticles (AgNPs) using aqueous extracts of orange and lemon peels, as a reducing agent, and silver nitrate salts as a source of silver ions is a promising field of research due to the versatility of biomedical applications of metal nanoparticles. In this paper, AgNPs were synthetized at different reaction parameters such as the type and concentration of the extracts, metal salt concentration, temperature, speed stirring, and pH. The antibacterial properties of the obtained silver nanoparticles against E. coli, as well as the physical and chemical characteristics of the synthesized silver nanoparticles, were investigated. UV-Vis spectroscopy was used to confirm the formation of AgNPs. In addition to green biogenic synthesis, chemical synthesis of silver nanoparticles was also carried out. The optimal temperature for extraction was 65˚C, while for the synthesis of AgNPs was 35˚C. The synthesis is carried out in an acidic environment (pH = 4.7 orange and pH = 3.8 lemon), neutral (pH = 7) and alkaline (pH = 10), then for different concentrations of silver nitrate solution (0.5 mM - 1 mM), optimal time duration of the reaction was 60 min and optimal stirring speed rotation was 250 rpm on the magnetic stirrer. The physical properties of the synthesized silver nanoparticles (conductivity, density and refractive index) were also studied, and the passage of laser light through the obtained solution and distilled water was compared. Positive inhibitory effect on the growth of new Escherichia coli colonies have shown AgNPs synthesized at a basic pH value and at a 0.1 mM AgNO3 using orange or lemon peel extract, while for a 0.5 mM AgNO3 using lemon peel extract.

Synthesis and Antibacterial Activities of Erythromycin Derivatives

Aim To synthesize 4″-carbamate derivatives of erythromycin and test their antibacterial activities in vitro. Methods New erythromycin antibacterial agents containing 4″-carbamate group were designed and synthesized from azithromycin via protection, aminoformylation, amination and deprotection. Their antibacterial activities against Staphylococcus aureus strains were tested. Results Nine compounds were synthesized. Their structures were confirmed by MS, IR, ~ 1 H NMR and ~ 13 C NMR, and the synthetic conditi...

Synthesis and Antibacterial Activity of 8-Substituted Phenyl-1-pyridin-3-yl-5H-bis[1,2,4]triazolo[3,4-b;4′,3′-d][1,3,4] thiadiazines

To find new structural leading compounds for the research of the multidrug resistant of antibacterial agents, five novel 8-substituted phenyl-1-pyridin-3-yl-5H-bis[1, 2, 4] triazolo[3, 4-b; 4′, 3′-d] thiadiazines were prepared from the corresponding intermediates of 3-(5-substituted phenyl[1,3,4]oxadiazol-2-ylmethylsulfanyl)-5-pyridin-3-yl-[1,2,4]triazol-4-ylamines via intramole- cular cyclization and the antibacterial activity in vitro against Gram-postive (G+) and Gram negative (G-) bacteria was primarily evaluated.

Synthesis and antibacterial activities of pleuromutilin derivatives

Six new pleuromutilin derivatives were designed and synthesized, confirmed by MS, IR and ^1H NMR techniques. And the antibacterial activities were primarily evaluated in vitro. The results indicated that most of the derivatives showed more potent activities against corresponding bacterial strains than that of pleuromutilin. Especially, compounds 4d and 5b had obvious activities against salmonella compared with pleuromutilin.

Synthesis and in vitro antibacterial activities of 7-(4-alkoxyimino-3-hydroxypiperidin-1-yl)quinolone derivatives

A series of novel 7-(4-alkoxyimino-3-hydroxypiperidin-1-yl)quinolone derivatives were designed,synthesized and evaluated for in vitro antibacterial activities.Compounds 8f,8g,8i and 8j with the potencies similar to or better than those of levofloxacin and IMB against Staphylococcus aureus and Staphylococcus epidermidis,worth further investigation.

Synthesis and Antibacterial Activity of New Tetracyclic Triazolo-thiadiazino Fluoroquinolones

A series of novel 9-fluoro-10-(4-methylpiperazin-1-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, 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.

Synthesis and in vitro antibacterial activities of 7-(3-aminopyrrolo[3,4-c]pyrazol-5(2H,4H,6H)-yl)quinolone derivatives

A series of novel 7-（3-aminopyrrolo[3,4-c]pyrazol-5（2H,4H,6H）-yl）quinolone derivatives were designed, synthesized and evaluated for in vitro antibacterial activities. Compounds 6g, 7g and 7h with the potencies similar to those of gemifloxacin, moxifloxaein, gatifloxacin and levofloxacin against Gram-positive organisms, worth further investigation.

Synthesis of 6,8-dichloroquinolones utilizing new method and evaluation of their antibacterial activities

Several 6,8-dichloroquinolone analogues were synthesized from the key intermediate compound of 2,3,4,5-tetrachlorobenzene carbonyl chloride, which was obtained from the starting material of tetrachlorophthalic anhydride. Their in vitro antibacterial activities were evaluated. As a result of this study, compounds 21e and 21d were twofold more potent than ciprofloxacin （CPFX） and norfloxacin （NFLX） against Staphylococcus aureus-9, and with the same potent as CPFX and NFLX while against Escherichia coli-2, but were less potent than references in against Pseudomonas aeruginosa-17.

Novel dihydropyrazole derivatives linked with multi(hetero)aromatic ring:Synthesis and antibacterial activity

Eight novel heterocycle-substituted dihydropyrazole derivatives were synthesized and characterized by ESI-MS, ^1H NMR and ^13C NMR. All of the compounds have been screened for their antibacterial potential in vitro against Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. The results show that compounds 9b, 9g and 9h displayed significant activity with MIC values in the range of 0.39-1.562 μlmL against B. subtilis.

Synthesis and antibacterial activity of new layered perovskite compounds,Ag_xNa_(2-x)La_2Ti_3O_(10)

Three kinds of new layered perovskite compounds with Ruddlesden-Popper （R-P） phase, AgrNa2-xLa2Ti3O10 （x = 0.2, 0.3 and 0.5）, were synthesized by an ion-exchange reaction of Na2La2Ti3O10 with AgNO3 solution. The structures of the compounds were characterized by EDX and XRD, and their antibacterial activity and light-resistance property were evaluated. The results indicated that the molecular formula of AgxNa2-xLa2Ti3O10 （x = 0.2, 0.3 and 0.5） was confirmed, and that the crystalline structure of Na2La2Ti3O10 was not obviously affected by exchange of silver ion. The minimum inhibitory concentrations （MICs） of Ag0.3Na1.7La2Ti3O10 against Escherichia coli （E. coli）, Staphylococcus aureus （S. aureus） were 180 μg/mL and 240 μg/mL, respectively, while its discoloration was not observed after 24 h light ageing test.

Synthesis, Crystal Structure and Antibacterial Activity of 4,4'-Hydrazine-1,2- diylidenebis(methanylylidene)bis(2-ethoxyphenol)

A new Schiff base compound, 4,4′-hydrazine-1,2-diylidenebis（methanylylidene）- bis（2- ethoxyphenol） （C18H20N2O4）, has been synthesized by the condensation of 3-ethoxy-4- hydroxybenzaldehyde and 80% hydrazine hydrate in an ethanol solution. The compound was characterized by 1H NMR, MS and single-crystal X-ray diffraction. The crystal belongs to the monoclinic system, space group P21/n with a = 5.2421（5）, b = 10.3700（8）, c = 14.9906（11）A, β = 97.6030（10）°, Z = 2, V= 807.73（12） A, Dc = 1.350 g/cm3, Mr = 328.36, λ（MoKa） = 0.71073 A,μ = 0.096 mm-1, F（000） = 348, R = 0.041 and wR = 0.0136. The two benzene rings are coplanar. The molecule adopts an E,E configuration about the central C=N functional bonds. A total of 3938 unique reflections were collected, of which 1440 with I 〉 2σ（I） were observed. A different type of intermolecular hydrogen bond, O-H…N, exists in the crystal. The title complex molecules are connected through hydrogen bonds to generate a two-dimensional network. The preliminary antibacterial activity results showed that the title compound exhibits antibacterial activity against Staphylococcus aureus.

Synthesis, Structure and Antibacterial Activities of 4-BBTS Schiff Base and Its Complexes

4-Bromobenzaldehyde thiosemicarbazone Schiff base （4-BBTS） and its Cu（Ⅱ）, Zn（Ⅱ）, Co（Ⅱ） and Ni（Ⅱ） complexes were synthesized and characterized by elemental analysis, UV, IR, MS, ^1H NMR, and molar conductivity. Using disc diffusion method, the antibacterial activity tests were conducted. The results revealed that the ligand as well as all the complexes exhibits good antibacterial activities against E. Coli. and S. Aureus. Moreover, Cu（Ⅱ） complex shows the best antibacterial activity, which provides beneficial reference for studying the relationship between the structures and performances.

Studies on Condensed Heterocyclic Compounds(Ⅲ)——Synthesis and Antibacterial Activity of 3-(4-Pyridyl)-6-Alkyl/Aromatic Heterocyclyl-s-Triazolo[3,4-b]-1, 3,4-Thiadiazoles and 1,4-Bis [6-(4-Pyridyl)-s-Triazolo [3,4-b]-1, 3,4-Thiadiazol-3-yl]-n-Butane

In recent years, fused heterocycles have been reported to possess important properties in synthesis and pharmacology. Especially, s-triazolo, 3,4-thiadiazole derivatives have been attracting much attention for chemists and pharmacologists because they show broad spectra of biological activities, such as antifungal, antibacterial, hy-

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

A convenient synthesis of oxazolidinone antibacterial linezolid from readily available L-ascorbic acid is described. The key steps include reductive amination of arylamine and （S）-glyceraldehyde acetonide in the presence of NaBH4 and 4A sieve, followed by hydrolysis and regioselective cyclization.

Synthesis and antibacterial activity of 4″-O-carbamoyl analogs of clarithromycin

A series of novel 4'-O-carbamoyl analogs of clarithromycin were synthesized and evaluated for their in vitro antibacterial activity. All of the desired compounds showed excellent activity against erythromycin-susceptible S.pneumoniae.Particularly,4-fluorobenzyl carbamate 7a demonstrated potent activity against erythromycin-resistant S.pneumoniae encoded by the mef gene,and remarkably improved activity against erythromycin-resistant S.pneumoniae encoded by the erm gene,and the erm and mef genes.

Efficient Synthesis, Crystal Structure and Antibacterial Activity of Two Novel 1,3-Oxazin Derivatives

Two new 1,3-oxazin derivatives, C22H24N2O5 （3I） and C19H16N2O5（3II）, have been synthesized via an unusual cascade reaction. The attractive aspect of this cascade reaction is that the novel construction of 1,3-oxazine and the direct C-N bond formation from C-C bond can be easily achieved via pyridine-mediated acylation in a one-pot operation. Both compounds have been synthesized and characterized by elemental analysis, IR, NMR spectra and X-ray single-crystal diffraction. Compound 3I crystallizes in monoclinic, space group P21/n with α = 16.282（4）, b = 7.4117（18）, c = 17.256（5） A, β = 103.193（9）°, V = 2027.4（9） A3, Mr = 396.43, Z = 4, Dc= 1.299 g/cm3, F（000） = 840, MoKa radiation （λ = 0.71073 A）, the final R = 0.0771 and wR = 0.1582 for 3662 were observed reflections with I 〉 2σ（I）. Compound 3II crystallizes in triclinic, space group Pī with α = 7.1265（9）, b = 10.1071（13）, c = 23.529（3） A, α = 97.463（9）, β = 96.981（9）, γ = 94.345（9）°, V = 1600.5（4） A3, Z = 4, Dc = 1.409 g/cm3, F（000） = 736, CuKa radiation （λ = 1.54186 A）, the final R = 0.0515 and wR = 0.1241 for 4920 observed reflections with I 〉 2σ（I）. The preliminary antibacterial activities of 2 and 3 against E. coli and S. aureuswere investigated. The results showed that the inhibiting effect of 3 was higher than that of 2.