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.

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 Activity of New Cephalosporin Compounds

Five new cephalosporin compounds were designed and synthesized, and the antibacterial activities were evaluated by the standard serial 2-fold agar dilution method in vitro. The results showed that the activities of the compounds Ia and lb against ESBL E. coli and K. pneumoniae are comparable to those of Cefepime.

The Synthesis of the Reactive Antibacterial Agents and Their Antibacterial Activities

A series of monochlorotriazine reactive antibacterial agents were synthesised by using 2,4,4’ - trichloro -2’ - hydroxydiphenyl ether as a starting material. The spectrum analyses (UV and MS) and elementary analy-ses were also carried out. These antibacterial agents can be used as the bacteria - resistance finishing agents of the cellulose fabrics. The treated fabrics possess excellent antibacterial activity and durable wash fastness. For ex-ample , the percentages of bacterial reduction of the fab-ric finished with reactive antibacterial agent 2RSDP are 98.5%, 98. 86% and 96.67% for Staphylococcus au-reus, Escherichia coli and Pseudomonas aeruginose re-spectively. After more than 100 times of washing at 60°C, the antibacterial activity still retains at a level of about 90% of the original. The relationships between the molecular structures of the reactive antibacterial finish-ing agents and their antibacterial activities are discussed.

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.

Efficient Synthesis,Crystal Structure and Antibacterial Activity of Two Novel Thieno[2,3-d]pyrimidin-4(3H)-one Derivatives

Two new thieno[2,3-d]pyrimidin-4（3H）-one derivatives,C24H22 Cl N3O2S（5a） and C25H25N3O2S（5b）,have been synthesized via a tandem aza-Wittig reaction.This tandem reaction has many attractive aspects such as easily accessible and versatile starting materials,mild conditions and high yields.Both compounds have been characterized by elemental analysis,HR-MS,IR,NMR spectra and X-ray single-crystal diffraction.Compound 5a crystallizes in monoclinic,space group P21/c with a = 9.986（3）,b = 14.263（4）,c = 15.530（5）A,β = 93.806（5）o,V = 2207.1（11） A^3,Mr = 451.96,Z = 4,Dc = 1.360 g/cm3,F（000） = 944,μ = 0.294 mm-1,Mo Kα radiation（λ = 0.71073 A）,the final R = 0.0444 and w R = 0.1219 for 3407 observed reflections with I 〉 2σ（I）.Compound 5bcrystallizes in triclinic,space group P1 with a = 8.974（4）,b = 10.766（5）,c = 12.260（6） A,β = 93.047（7）o,V = 1122.1（9） A^3,Mr = 431.54,Z = 2,Dc = 1.277 g/cm3,F（000） = 456,μ = 0.170 mm-1,Mo Kα radiation（λ = 0.71073 A）,the final R = 0.0378 and w R = 0.1072 for 3806 observed reflections with I 〉 2σ（I）.The preliminary antibacterial activities of 5a and 5b were investigated.Compound 5a showed 71.3% and 79.2% in vitro inhibition against Fusarium oxysporium and Rhizoctonia solani,respectively.Compound 5b showed 75.3% in vitro inhibition against Rhizoctonia solani.

Green Synthesis, Characterization and Antibacterial Activity of ZnO Nanoparticles

In the present study, mehendi extract (Lawsonia inermis) was used for phytosynthesis of ZnO nanoparticles using 0.1 M Zn(NO3)2 as precursor under alkaline condition using NaOH with vigorous stirring for 2 h. ZnO NPs obtained were characterized by UV-Vis spectroscopy, XRD, SEM and TEM that showed change in shape and size. Hexagonal particles were formed due to plant extract relative to the rod shaped particles in absence of plant extract. Further the antibacterial property of ZnO NP synthesized by green method was more effective than those synthesized in absence of plant extract. The antibacterial activity study of both the synthesized ZnO nanoparticles reveals that the nanoparticles synthesized using mehendi extract are more effective than the particle synthesized without mehendi extract. Thus, the use of leaf extract as capping agent would improve the antibacterial property of ZnO nanoparticle. However, bacteriocidal effect of these nanoparticles varies with respect to the organism tested.

Design, Synthesis and Antibacterial Activity Evaluation of 4,5-Diphenyl-1<i>H</i>-Imidazoles Derivatives

Due to the continuous emergence and rapid spread of drug-resistant strains of bacteria, there is an urgent need for the development of novel antimicrobials. Along this line, the synthesis and antibacterial activity of 4,5-diphenylimidazol-2-thiol derivatives 2a-g and 6a-e are reported. The structures of the synthesized compounds were confirmed by Nuclear Magnetic Resonance (NMR) and High Resolution Mass Spectrometry (HRMS). All compounds were screened in vitro for their antibacterial activity against Pseudomonas aeruginosa and Escherichia coli (Gram-negative bacteria) and also against Staphyloccocus aureus and Enterococcus faecalis (Gram-positive bacteria). The results showed most of the synthesized compounds have no antibacterial activity. However compound 6d was two-fold potent than ciprofloxacin against Staphylococcus aureus with Minimum Inhibitory Concentration (MIC) of 4 μg/mL and 6c showed moderate biological activity against Staphylococcus aureus (16 μg/mL) and Enterococcus faecalis (16 μg/mL).

Green Synthesis of Silver Nanoparticles from Abronia villosa as an Alternative to Control of Pathogenic Microorganisms

The aim of this study was to evaluate the antibacterial and antifungal activities of eco-friendly synthesized silver nanoparticles.The silver nanoparticles were synthesized by biological method using aqueous extract of Abronia villosa.Synthesis of silver nanoparticles was confirmed by color change and characterized using UV-visible spectroscopy,scanning electron microscope(SEM),energy dispersive X-ray spectroscopy(EDX),dynamic light scattering(DLS),and zeta potential analysis.The SEM analysis revealed the presence of spherical silver nanoparticles of the size range 21 to 33 nm.Synthesized silver nanoparticles were used to evaluate their antibacterial effects at different concentrations(25,50,75 and 100μg/ml)on gram negative and gram positive bacteria.The biggest halo zone was observed at 75 and 100μg/ml concentrations of silver nanoparticles against both gram positive and gram negative bacteria.Antifungal activity of biosynthesized silver nanoparticles was evaluated against seven different phytopathogenic fungi.AgNPs showed high inhibition of radial growth toward all tested fungi.The highest inhibition of fungal growth by AgNPs was recorded against Macrophomina phaseolina(86.06±0.92%).Biosynthesized AgNPs using plant extract are a promising to use safety for various biomedical and agricultural applications.

The synthesis and activity in vitro of a series of 8-difluoromethoxy quinolones: Analogues of gemifloxacin

7-[4-（Aminomethyl）-3-（methoxyimino）pyrrolidin- 1-yl]- 1-cyclopropyl-6-fluoro-8-difluoromethoxy- 1,4-dihydro-4-oxoquino- line-3-carboxylic acid and its analogues have been prepared and evaluated for antibacterial activity in vitro.

The Synthesis and Activity in vitro of a Series of 5-Amino-8-methoxyquinolones

A series of 1-cyclopropyl-5-amino-6-fluoro-8-methoxyquinoline-3-carboxylic acidshave been prepared and evaluated for antibacterial activity in vitro.

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-(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, 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.

Synthesis and Antibacterial Activities of Erythromycin Derivatives

Ten new erythromycin antibacterial agents containing amidino group were designed and synthesized from erythromycin via oximation, reduction and condensation. Their structures were confirmed by MS and 13C NMR; the synthetic condition(reaction medium)was explored; and their in vtiro antibacterial activities were tested. Compound HMA-3 showed antibacterial activity against staphylococcus aureus, which is equivalent to that of erythromycin A. Compounds HMA-8 and HMA-4 also showed an antibacterial activitiy. But no compound showed bactericidal activity.

Synthesis, Crystal Structure and Antibacterial Activities of 3-[3-Methyl-(2-thienyl)methyl- enehydrazinocarbonyl]-(1H)-1,2,4-triazole

The title compound, C9H9N5OS, was synthesized by the reaction of 3-（1H）-1,2,4 -triazole hydrazine with 3-methyl-2-thiophenecarboxaldehyde in ethanol. The single crystal structure has been determined by X-ray diffraction analysis. The crystal belongs to monoclinic system, space group P2 1/n with a = 9.5550（10）, b = 11.9847（12）, c = 10.1074（11） A,β= 112.995（2）° V= 1065.47（19） A^3, Z = 4,μ = 0.290 mm^-1, Mr= 235.27, Dc = 1.467 g/cm^3 and F（000） = 488. The structure was solved by direct methods and refined to R = 0.0449. The crystal structure involves intermolecular hydrogen bonds of N-H…O and N-H…N as well as intramolecular hydrogen bond of N-H…N. Its biological activity has also been determined showing this type of compounds has certain antibacterial activity.

Synthesis and Crystal Structure of 3-(2-Hydroxybenzly)-4-(4-Hydroxybenzylideneamino)-(1H) -1,2,4-Triazole-5-Thione and Its Antibacterial Activities

The title compound C15H12N4O2S was synthesized by the reaction of 3-（2-hydroxybenzyl）-4-amino-（1H）-1,2,4-triazole-5-thione with 4-hydroxybenzaldehyde in ethanol and characterized by IR, ^1H NMR spectra and elemental analysis. Its structure has been determined by X-ray diffraction analysis. The crystal belongs to monoclinic, space group C2/c with a = 27.990（3）, b = 13.1326（14）, c = 7.9770（8） A, β= 105.787（2）°, V = 2821.6（5）A^3, Z = 8, Mr= 312.35,μ= 0.243 mm^-1, Dc = 1.471 g/cm^3 and F（000） = 1296. The structure was solved by direct methods.and refined to a Rint value of 0.0388. The crystal structure involving in intermolecular N-H…S and O-H…S hydrogen bonds is observed, meanwhile intramolecular O-H…N hydrogen bond is also found. Their biological activities have been measured. The results show that this type of compound has certain antibacterial activity for Staphylococous aureus and Bacillus subtilis.

Synthesis, Crystal Structure and Antibacterial Activities of 3-[(2-Hydroxy-4-diethylamino-phenyl)methylenehydrazinocarbonyl]-4-hydroxy-6-methyl-2(1H)-pyridinones

The title compound C18H22N4O4 was synthesized by the reaction of 3-hydrazine-4-hydroxy-6-methyl-2（1H）-pyridinones with 2-hydroxy-4-diethylaminobenzaldehyde in ethanol and characteri- zed by IR, tH NMR and elemental analysis. The single-crystal structure has been determined by X-ray diffraction analysis. The crystal belongs to the triclinic system, space group P1^- with a = 10.1930（14）, b = 12.5200（17）, c = 15.1863（19） A, α= 96.292（3）, β= 96.450（3）, γ= 102.443（3）°, V= 1862.6（4） A^3, Z= 4, Mr = 358.40, μ = 0.092 mm^-1, D c= 1.278 g/cm^3, F（000） = 760 and R = 0.0803. The crystal structure involves intermolcular N-H…O as well as intramolcular O-H…N, O-H…O and N-H…O hydrogen bonds. The title compound shows no antibacterial activity.

Synthesis, Crystal Structure, Antibacterial Activities and Theoretical Computation of 3-(2-Hydroxybenzly)-4-(4-isopropylbenzyl- ideneamino)-(1H)-1,2,4-triazole-5-thione

The title compound C18H18N4OS has been synthesized by the reaction of 3-（2-hydroxy- benzyl）-4-amino-（1H）-1,2,4-triazole-5-thione with 4-isopropylbenzaldehyde in ethanol and characterized by IR, ^1H NMR spectra and elemental analysis. Its structure was determined by X-ray diffraction analysis. The crystal belongs to monoclinic, space group P21/c with a = 11.605（2）, b = 7.401（1）, c = 20.339（2） A, β= 103.05（2）°, V= 1701.8（4） A^3, Z = 4, Mr = 338.42,μ = 0.202 mm^-1, Dc = 1.321 g/cm^3 and F（000） = 712. The structure was solved by direct methods and refined to R = 0.0428 and wR = 0.1069. Due to the intramolecular O-H…N hydrogen bond and π-π stacking interactions between the benzene （C（1）～C（6）） and triazole rings, the two planes are essentially coplanar. Their biological activities have been measured, showing this type of compound has certain antibacterial activity for Staphylococous aureus and Bacillus subtilis. Based on the quantum chemistry calculation at the RHF/6-31G level, the frontier orbitals and electrostatic potential of the title compound were also discussed.