Polysiloxane cationic biocides with imidazolium salt (ImS) groups, synthesis and antibacterial properties

Novel polysiloxanes with pendant biocidal N,N′-dialkylimidazolium salt (ImS) groups were synthesized and compared with polysiloxanes bearing conventional biocidal quaternary ammonium salt (QAS) groups. The bacteriostatic power of these polymers was tested and compared under the same conditions in aqueous solution against two common strains of Gram positive bacteria and three strains of Gram negative bacteria. These new ImS containing polymers exhibited high antibacterial potency against all bacteria studied, similar to those substituted with QAS groups. The advantage of the imidazolium substituted polysiloxane stems from its higher thermal stability, as compared with the quaternary alkylammonium functionalized polymer, as demonstrated by thermogravimetric studies.     

Efficient separation of Cinnamomum camphora leaf essential oil and in vitro evaluation of its antifungal activity

Cinnamomum camphora leaf essential oil (CEO) was extracted using enzymatic-ultrasound pretreatment followed by microwave assisted extraction (EUP-MAE) method and simultaneously studied as a mycelial growth inhibitor against five important pathogens which cause potato dry rot. The optimum EUP-MAE conditions with a real CEO yield of 19.23 ± 0.12 mg/g were obtained through Plackett–Burman design and Box–Behnken design as follows: 3 % of enzyme dosage, 2 h of pretreatment time, 5 of pH, 210 W of ultrasound power, 50 °C pretreatment temperature, 16 mL/g of water to solid ratio, 30 min of microwave time and 500 W of microwave power. Compared to the reference methods, EUP-MAE possessed a highest CEO yield than these of ultrasound-microwave assisted extraction (U-MAE) and traditional hydrodistillation (HD). Gas chromatography-mass spectrometry (GC–MS) analysis demonstrated that eucalyptol, camphor, and α-terpineol were the three main constituents of CEO. Results from in vitro antifungal activity assay revealed that the mycelial growths of all the five tested Fusarium solani, Fusarium culmorum, Fusarium trichothecioides, Fusarium sporotrioides, and Fusarium avenaceum were apparently affected by CEO. These findings not only provide a potential paradigm for the separation of plant essential oil, but also guarantee a promising utilization of the CEO for potato protection to control the Fusarium spp.     

An efficient preparation and characterization of 1-(2-ethoxy-2-oxoethyl)imidazolium based ionic liquids derivatives as potential bioactive agents

A set of new 1-(2-ethoxy-2-oxoethyl)imidazolium-based ionic liquids (1–16) have been prepared via the alkylation reaction of ethyl 2-(1H-imidazol-1-yl)acetate with various type of substituted alkyl halides using a microwave irradiation reaction in yields above 90%. The chemical structures of the manufactured ILs (1–16) were analyzed by mass and NMR spectroscopy. The newly prepared ILs were examined for their in vitro anti-microbial activities towards different types of Gram (+) and Gram (−) bacteria, and also for their antifungal activities. The preliminary tests showed that most of the resultant ILs presented modest activities towards S. aureus and B. subtilis with IZ values ranging between 10 and 14 mm, while the E. coli activities was in the range of 16 and 20 mm. However, ILs (1–16) displayed poor activities against the C. albicans.     

New polyamides containing azobenzene unites and hydantoin derivatives in main chain: synthesis and characterization

Eight new polyamides containing azo moieties and hydantoin groups were synthesized under microwave irradiation by using a domestic microwave oven from the polycondensation reactions of 4,4^′-azodibenzoyl chloride [4,4^′-azobenzenedicarboxylic acid] 3 with eight different derivatives of 5,5-disubstituted hydantoin 4a-h in the presence of a small amount of a polar organic medium such as o-cresol. The polycondensation proceeded rapidly, compared with the bulk polycondensation and the solution polycondensation and was completed between 7-12 min, producing a series of new polyamides 5a-h in high yield, and inherent viscosity between 0.35 and 0.60 dL/g. The resulting polyamides were characterized by elemental analysis, viscosity measurements, thermal gravimetric analysis (TGA and DTG), solubility test and FT-IR spectroscopy. All of the polymers were soluble at room temperature in polar solvents such as N,N-dimethylacetamide, N,N-dimethylformamide, dimethylsulfoxide, tetrahydrofurane and N-methyl-2-pyrrolidone.     

Neat reaction technology for the synthesis of 4-oxo-thiazolidines derived from 2-SH-benzothiazole and antimicrobial screening of some synthesized 4-thiazolidinones

The synthesis of 4-thiazolidinones 4a-j in a good yields from the heterocyclization reaction of 2-(benzothiazol-2-ylthio)-N’-benzylideneacetohydrazide 3a-j with SHCH₂COOH in DMF in the presence of a catalytic amount of anhydrous ZnCl₂ under microwave irradiation is described and compared with conventional synthesis methods. All structures of the newly synthesized compounds were elucidated by elemental analysis and spectral data. Some of the new compounds were tested against bacteria (Gram? ve and Gramt+ ve) and fungi.     

Clean and efficient microwave-solvent-free synthesis of 1-(2′,4′-dichlorophenacyl) azoles

Microwave induced N-alkylation of several azoles with 2,2′,4′-trichloroacetophenone (TCA) under solvent-free conditions allowed to obtain the corresponding 1-(2′,4′-dichlorophenacyl) azoles with satisfactory to good selectivities and yields. TGA and DSC measurements were achieved for the synthesized compounds and showed a close relationship between the thermal behavior and the reaction temperature under microwave heating. Non-purely thermal microwave effects were evidenced during the alkylation of pyrazole and 1H-indazole under the selected conditions.     

Poly(N-bromobenzene-1,3-disulfonamide) and N,N,N′,N′-tetrabromobenzene-1,3-disulfonamide as novel catalytic reagents for silylation of alcohols, phenols, and thiols using hexamethyldisilazane

Poly(N-bromobenzene-1,3-disulfonamide) [PBBS] and N,N,N′,N′-tetrabromobenzene-1,3-disulfonamide [TBBDA] are effective catalysts for the silylation of alcohols, phenols, and thiols in the presence of hexamethyldisilazane with, or without solvent, and also under microwave irradiation.     

The effect of preparation temperature on the mechanical and antibacterial properties of poly(vinyl alcohol)/silver nitrate films

There has been a growing interest in developing antibacterial polymeric materials. The logical consequence following development of a new material is optimisation of its processing conditions and investigation of the influence of processing parameters on functionality of a given material. The present work deals with investigation of the effect of preparation temperature on the mechanical and antibacterial properties of polymer films based on poly(vinyl alcohol) (PVA) and silver nitrate (0, 1, 3, 5, 7, 9 wt.% silver content). The mechanical properties of the films prepared at various temperatures (25, 35, 50, 60, 75 °C) were characterized by using stress-strain analysis. Antibacterial properties were determined by using an agar diffusion test and a dilution and spread plate technique against both Gram positive (Staphylococcus aureus) and Gram negative (Escherichia coli, Pseudomonas aeruginosa and Klebsiella pneumoniae). The results show significant effect of the elevated temperature on the samples properties.     

Microwave solid phase synthesis, characterization, and antimicrobial activities of one mononuclear manganese(II) complex with 4-chlorobenzoic acid 4-[3-(4-chlorophenyl)-3-hydroxyacryloyl]-3-hydroxyphenyl ester

One mononuclear complex has been designed and synthesized by a β-dikertone ligand 4-chlorobenzoic acid 4-[3-(4-chlorophenyl)-3-hydroxyacryloyl]-3-hydroxyphenyl ester (L) with MnCl₂ · 4H₂O in microwave radiation assistance. The complex was characterized by X-ray crystallography, confirming that the central manganese(II) atom was coordinated by four oxygens from two L and two oxygens from two water. The complex was assayed for in vitro antibacterial (B. subtilis, S. aureus, S. faecalis, P. aeruginosa, E. coli, and E. cloacae) activities and showed better antimicrobial activity against Gram positive strains than Gram negative strains.     

Benzylidene/2-aminobenzylidene hydrazides: Synthesis,characterization and in vitro antimicrobial evaluation

In this study a series of new mannich bases were synthesized and characterized by elemental and spectral (IR, ¹H NMR, ¹³C NMR) studies. All the synthesized compounds were evaluated for their antimicrobial activity by broth dilution method against two Gram negative strains (Escherichia coli and Pseudomonas aeruginosa), two Gram positive strains (Bacillus subtilis and Staphylococcus aureus) and fungal strain (Candida albicans and Aspergillus niger). Preliminary pharmacological evaluation revealed that the compounds (3f, 3i, 3j, and 3k) showed good activity against these strains. The result demonstrates the potential and importance of developing new mannich bases which would be effective against resistant bacterial and fungal strain.     

One-pot polyamidation reaction of optically active aromatic diacid containing methionine and phthalimide moieties with aromatic diamines under microwave irradiation and traditional heating

An optically active diacid containing phthalimide and l-methionine moiety was prepared in three steps, and was polymerized with several aromatic diamines to obtain a new series of optically active polyamides (PAs) through direct polyamidation using triphenyl phosphite/pyridine/N-methyl-2-pyrrolidone/CaCl₂ system as condensing agent. The polymerization reactions were carried out under both conventional heating and microwave-assisted irradiation. The data obtained by these methods indicate that, high yields and similar inherent viscosities are resulted. It is worth to mention that in the case of microwave conditions, a drastic decrease in reaction time (3 min vs. 5 h) and cleaner reaction have been achieved. These polymers are readily soluble in polar organic solvents such as N,N-dimethyacetamide, N,N-dimethyformamide, dimethyl sulfoxide. The obtained polymers were characterized by FT-IR, specific rotation measurements, elemental analysis and ¹H NMR techniques. The thermal stability of the resulting PAs were evaluated with thermogravimetric analysis and differential scanning calorimetry techniques under a nitrogen atmosphere which indicate they are moderately stable.     

Three practical approaches for the synthesis of novel 4,7-dihetarylpyrazolo[1,5-a][1,3,5]triazines

Novel 4,7-dihetarylpyrazolo[1,5-a][1,3,5]triazines were synthesized from three different approaches. The first one, involved a one-step reaction between 5-amino-3-hetaryl-1H-pyrazoles and O,S-diethyl hetaroylimidothiocarbonates or S,S-diethyl hetaroylimidodithiocarbonates under solvent-free conditions employing microwave irradiation as the energy source. In the second approach, conventional heating under reflux in DMF as solvent was used instead of the microwave irradiation; and the third one was achieved from a two-step sequence through the treatment of 5-amino-3-hetaryl-1H-pyrazoles with hetaroyl isothiocyanates and the subsequent S-alkylation and cyclization process in DMF as solvent. Some intermediates were isolated and characterized to support the regiochemistry of the studied reactions. The structures of the new compounds were unambiguously established by spectroscopic and analytical techniques.     

Molecular modeling and docking studies of new antimicrobial antipyrine-thiazole hybrids

A series of new antipyrine incorporated thiazole derivatives having phenoxyacetamide moiety as a link bridge was synthesized. The synthetic strategy involves condensation of the precursor N-(4-antipyrinyl)-2-(4-formylphenoxy)acetamide with thiosemicarbazide followed by heterocyclization of the produced thiosemicarbazone with various α-halogenated carbonyl compounds (namely; 4-chlorophenacyl bromide, ethyl bromoacetate, 3-chloroacetylacetone and ethyl 4-chloroacetoacetate). Moreover, the quantum chemical calculations at DFT/B3LYP level were used to determine the HOMO-LUMO energies and Fukui’s indices toward nucleophilic, electrophilic and radical attacks. The investigated compounds were arranged due to HOMO-LUMO energy gap as following 6 < 5 < 7 < 3 < 2 < 4 < 8. The synthesized antipyrinyl-thiazole hybrids were screened to evaluate their antibacterial and antifungal efficacies. Using Chloramphenicol as reference material, the synthesized antipyrinyl-thiazole hybrids were revealed a remarkable activity against S. aureus than B. subtilis, as example for Gram’s positive strains. The antipyrine-thiazole compounds 3, 4, 6 and 8 exhibited significant MIC values. However, the antipyrine-thiazole hybride 4 displayed reputable activities against Gram’s negative strains S. typhimurium and E. coli, respectively, in comparison with Cephalothin. Likewise, the compounds 7 and 8 were demonstrated respectable antifungal efficacy toward C. albicans in contrast to cycloheximide grade. The theoretical molecular docking studies were applied to simulate reactivity of the synthesized antipyrine-thiazole hybrids against contrasting binding sites for both of Staphylococcus aureus “Homo sapiens” (pdb: 3HUN) protein and E.coli “Homo sapiens” (PDB: 2EXB) protein. The theoretical and practical antibacterial and antifungal activities result in this work designated a proper agreement.     

Microwave-assisted guanidinylation in solid phase peptide synthesis: comparison of various reagents

The guanidinylation of a peptide chain on a polymeric support under microwave conditions using derivatives of thioureas—S-alkylisothioureas, pyrazole-carboxamidine, and guanidine as guanidinylating reagents is described. The best results are obtained with N,N′-di-Z-S-methylisothiourea and N,N′-di-Z(2-Cl)-S-methylisothiourea. It is found that guanidinylation with reagents containing Boc groups is accompanied by side reactions.     

Synthesis,characterization and antimicrobial screening of quinoline based quinazolinone-4-thiazolidinone heterocycles

In an attempt to find new pharmacologically active molecules, we report here the synthesis and in vitro antimicrobial activity of various 2-(2-chloro-6-methyl(3-quinolyl))-3-[2-(4-chlorophenyl)-4-oxo(3-hydroquinazolin-3-yl)]-5-[(aryl)methylene]-1,3-thiazolidin-4-ones. In vitro antimicrobial activity of the title compounds are screened against two Gram positive bacteria (Staphylococcus aureus, Streptococcus pyogenes), two Gram negative bacteria (Escherichia coli, Pseudomonas aeruginosa) and three strains of fungi (Candida albicans, Aspergillus niger, Aspergillus clavatus) using broth micro dilution method. Some derivatives bearing chloro or hydroxy group exhibited very good antimicrobial activity.     

Preparation of ribavirin analogues by copper- and ruthenium-catalyzed azide-alkyne 1,3-dipolar cycloaddition

In this study, we described the synthesis of 1,4- and 1,5-disubstituted-1,2,3-triazolo-nucleosides from various alkynes with 1′-azido-2′,3′,5′-tri-O-acetylribose using either copper-catalyzed azide-alkyne cycloaddition (CuAAC) or ruthenium-catalyzed azide-alkyne cycloaddition (RuAAC), respectively. Optimized RuAAC conditions were realized with the commercially available [Cp^∗RuCl(PPh₃)₂] under microwave heating, which allows a significant acceleration of the reaction times (from 6 h to 5 min). This reaction can work under water-containing system. RuAAC and CuAAC are useful tools for the synthesis of 1,2,3-triazolyl-nucleosides small libraries.     

A Facile and Efficient Synthesis of 2‐(5‐(4‐Substitutedphenyl)‐4, 5‐dihydro‐3‐phenylpyrazol‐1‐yl)‐6‐Substitutedbenzothiazoles and Their Biological Studies

A series of new 1‐substituted 3, 5‐diarylpyrazolines ( 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ) were synthesized in good yield by both conventional and microwave‐assisted synthesis from α, β‐ unsaturated ketones ( 6 , 7 , 8 , 9 ) in n‐butanol and benzothiazole hydrazines ( 2 , 3 , 4 , 5 ). All the new compounds were characterized by IR, NMR, and mass spectral data. The synthesized compounds ( 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ) were evaluated for antibacterial and anthelmintic activities. The compounds showed potent anthelmintic activity against earthworm species (Eudrilus eugeniae) and moderate antibacterial activity against bacterial strains such as Gram positive bacteria, Enterococcus faecalis, Staphylococcus aureus, and Bacillus subtilis, and Gram negative bacteria, Escherichia coli and Proteus mirabilis.     

Synthesis and antibacterial activity of four natural chalcones and their derivatives

Four natural chalcones bearing hydroxyisoprenyl or prenyl groups, named Paratocarpin E (2), Xanthoangelol D (3), Angusticornin A (4) and Kanzonol C (5), were prepared by employing the Claisen-Schmidt condensation as the key step. In an attempt to investigate the effect of the hydroxyisoprenyl group on biological activity, two of their derivatives were also prepared for antibacterial activity research. The synthesized compounds were investigated for their expected antibacterial activities against Gram positive bacteria (Bacillus subtilis, Staphylococcus aureus) as well as Gram negative bacteria (Escherichia coli, Pseudomonas aeruginosa). Paratocarpin E (2) was found to be the most potent against two Gram positive bacteria while the majority of the remaining compounds showed promising activity as well. However, all of the compounds were inactive against both Gram-negative bacteria.     

Redox-active antifungal cobalt(II) and copper(II) complexes with sterically hindered o-aminophenol derivatives

Co(II) complexes with 4,6-di(tert-butyl)-2-aminophenol (HL^I) and 2-anilino-4,6-di(tert-butyl)phenol (HL^II) have been synthesized and characterized by means of physico-chemical methods. The compounds HL^I and HL^II coordinate in their singly deprotonated forms and behave as bidentate O,N-coordinated ligands; their low-spin Co(II) complexes are characterized by CoN₂O₂ coordination modes and square planar geometry. Both the free ligands and their Co(II) and Cu(II) complexes (we have produced and characterized the latter before) exhibit a pronounced antifungal activity against Aspergillus niger, Fusarium spp., Mucor spp., Penicillium lividum, Botrytis cinerea, Alternaria alternata, Sclerotinia sclerotiorum, Monilia spp., which in a number of cases is comparable with that of Nystatin and Terbinafine or even higher. The reducing properties of the ligands and their metal(II) complexes, as well as their antifungal activities, were found to decrease in the order: Cu(L^I)₂ > Cu(L^II)₂ ? Co(L^I)₂ > Co(L^II)₂ > HL^I > HL^II.