Microwave-assisted Conditions Research Articles

Fungal Chitosan-Derived Biomaterials Modified with Kalanchoe pinnata as Potential Hemostatic Agents-Development and Characterization.

Massive blood loss is still a great challenge for modern medicine. To stop the hemorrhage during the surgery or after injury apart from suturing or electrocoagulation, the most efficient method of hemostasis restoration is the use of hemostatic agents. Although there are numerous products on the market, there is still a need for biomaterials that are capable of fast and efficient bleeding management without affecting wound closure or embolism. Chitosan is known for its hemostatic activity; however, its quite poor mechanical properties and heterogenous chemical composition still needs some improvements to become superior compared to biological adhesives. The following study deals with the preparation and evaluation of chitosan-derived natural biomaterials containing Kalanchoe pinnata extract with the potential application as a blood-clotting agent. The materials were obtained under microwave-assisted conditions in two different forms (granules/dressing), whose chemical structure and morphology were studied. Their antioxidant properties have been proven. The chitosan-derived hemostatic agents exhibited superior blood sorption abilities and lack of cytotoxicity to L929 mouse fibroblasts. The study also showed the differences in biological properties depending on their preparation method. The potential mechanism of action was proposed as well as their potential in hemostasis revival.

Synthesis and characterization of new potential high-energy materials based on fullerene soot nanoparticles and nitroaryl diazonium ions

In this study, synthesis and characterization of new potential high-energy materials based on fullerene soot nanoparticles and nitroaryl diazonium ions were reported. Synthesis was carried out using reaction of fullerene soot with nitroaryl diazonium ions in acetonitrile or solvent free under thermal or microwave-assisted conditions. The nitroaryl diazonium ions were prepared insitu using reactions of 2-nitroaniline, 4-nitroaniline and 2,4-dinitroaniline with isoamyl nitrite. The spectroscopic and instrumental analytical methods such as Fourier transform infrared (FT-IR), Raman, ultraviolet–visible (UV–Vis), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX), elemental map and thermogravimetric analysis (TGA) were used to characterize the fullerene soot functionalized with nitroaryl groups. The differential thermal analysis (DTA) was applied to verify the energy releasing property of these compounds. The obtained results clearly confirmed the successful functionalization of fullerene soot nanoparticles by nitroaryl diazonium ions.

Catalyst-Free Microwave Digestion and Estimation of Nitrogen and Phosphorus Contents in Chicken Manure Adopting Competitive Analytical Methods

ABSTRACT For enhanced soil fertility, the application of animal manure has been recognized as an alternative mean to synthetic fertilizers. A major issue in current manure application practices is the rapid, reliable estimation of nutrients, such as nitrogen (N) and phosphorus (P). Estimation of N and P in manure involves the use of harsh chemicals and conditions, and considerable analytical time. In this work, microwave-assisted digestion condition is being reported for N and P estimation into chicken fermentation slurry. At comparative lower temperature 200°C and duration 1 h, digestion involves the use of half of the amount of acid and that too without the aid of a catalyst. Furthermore, N and P contents were determined from automatic Kjeldahl (AKj), manual Kjeldahl (MKj) and flow injection methods (FIA). The advantage of FIA is that it provides simultaneous detection of P and N. Additionally; P contents were analyzed and compared by colorimeter (Clr). To obtain a clear view of the performance of competing analytical procedures, a single sample analysis (SSA) time was measured. Thus, for N estimation; the SSA by AKj was superior, i.e.,, AKj ˃ MKj ˃ FIA which was 6:10:70 mins, respectively, and for P; Clr˃FIA which was 30:70 mins, respectively. However, when the adoptive methods were judged on the basis of effectiveness or by overall performance/ease in handling, the order of competing methods for N became AKj ˃ FIA ˃ MKj and for P it was FIA ˃ Clr. Statistical evaluations from the analytical data were also in accordance.

Synthesis of amides and esters containing furan rings under microwave-assisted conditions

Abstract In this work, we present a novel method for the synthesis of ester and amide derivatives containing furan rings (furfural derivatives) under mild synthetic conditions supported by microwave radiation. N-(Furan-2-ylmethyl)furan-2-carboxamide and furan-2-ylmethyl furan-2-carboxylate were produced using 2-furoic acid, furfurylamine, and furfuryl alcohol. The reactions were carried out in a microwave reactor in the presence of effective coupling reagents: DMT/NMM/TsO− or EDC. The reaction time, the solvent, and the amounts of the substrates were optimized. After crystallization or flash chromatography, the final compounds were isolated with good or very good yields. Our method allows for the synthesis of N-blocked amides using N-blocked amino acids (Boc, Cbz, Fmoc) and amine. As well as compounds with a monoamide and ester moiety, products with diamides and diester bonds (N,N-bis(furan-2-ylmethyl)furan-2,5-dicarboxamide, bis(furan-2-ylmethyl) furan-2,5-dicarboxylate, and furan-3,4-diylbis(methylene) bis(furan-2-carboxylate)) were synthesized with moderate yields in the presence of DMT/NMM/TsO– or EDC, using 2,5-furandicarboxylic acid and 3,4-bis(hydroxymethyl)furan as substrates.

Microwave assisted, sequential two-step, one-pot synthesis of novel imidazo[1,2-a]pyrimidine containing tri/tetrasubstituted imidazole derivatives.

A series of novel imidazo[1,2- a ]pyrimidine containing tri/tetrasubstituted imidazole derivatives (1-10) has been synthesized via sequential two-step, one-pot, multicomponent reaction using imidazo[1,2- a ]pyrimidine-2-carbaldehyde, benzil, primary amines, and ammonium acetate catalyzed by p -toluenesulfonic acid under microwave-assisted conditions. The results showed that target compounds can be obtained from a wide range of primary amines bearing different functional groups with moderate to good yields (46%-80%) under optimum reaction conditions. This method provides a green protocol for imidazo[1,2- a ]pyrimidine containing tri/tetrasubstituted imidazole derivatives due to ethyl alcohol as a green solvent, microwave irradiation as a greener heating method and one-pot multicomponent reaction as a green technique. The synthesized compounds have been elucidated using various spectroscopic tools such as FT-IR, 1H NMR, 13 C NMR, and MS.

Optimization of the Application of Walnut Green Peel Pigment in Wool Fiber Dying and Fixing Process under Microwave-assisted Condition

ABSTRACT In this paper, the response surface method was used to study the technology of dyeing wool fiber with walnut green peel pigment under the microwave-assisted method. The optimized pigment extraction process were: ethanol volume fraction 60%, extraction time 1 min, liquid-material ratio 24:1, microwave power 450 W, and the optimized mordant fixation process were: mordant fixation time 3 min, microwave power 270 W, amount of mordant fixing agent 7%, reducing agent dosage 22 g/L. The results showed that the use of microwave-assisted and new mordant fixing agent lanthanum chloride greatly improved the extraction efficiency of pigments, saved extraction costs, and significantly shortened the mordant fixation time, resulting in an environmentally friendly mordant fixation process.

Comparison of different optimization techniques for microwave-assisted biodiesel production

ABSTRACT Microwave-assisted biodiesel production from palm oil is becoming more and more important because of the greatly shortened reaction time and high energy-efficiency. In this novel research, an experimental study was conducted to optimize the experimental conditions of microwave-assisted biodiesel production. Response surface methodology (RSM), back propagation artificial neural network (BP-ANN) and Genetic algorithm improved BP-ANN (BPANN-GA) and were established and compared to optimize four operating parameters, including methanol/oil molar ratio (5:1–15:1), catalyst amount (0.75 –1.25 wt.%), temperature (60–70°C) and microwave time (20 –50 min). RSM, BP-ANN and BPANN-GA models were considered to be reliable in predicting biodiesel yield, BPANN-GA model (R2 = 0.9957) showed better accuracy than the RSM model (R2 = 0.9823) and BP-ANN model (R2 = 0.9867). The optimized process parameters were 14.9 methanol/oil molar ratio, 0.84 wt.% catalyst amount, 69°C temperature and microwave time of 49.3 min, the corresponding yield was 98.15%. The produced biodiesel properties were compared with ASTM D6571 standards. The results of the research are constructive for the optimization of microwave-assisted biodiesel experimental conditions when processing a small sample database.

Fe(III) Complexes in Cyclohexane Oxidation: Comparison of Catalytic Activities under Different Energy Stimuli

In this study, the mononuclear Fe(III) complex [Fe(HL)(NO3)(H2O)2]NO3 (1) derived from Nʹ-acetylpyrazine-2-carbohydrazide (H2L) was synthesized and characterized by several physicochemical methods, e.g., elemental analysis, infrared (IR) spectroscopy, electrospray ionization mass spectrometry (ESI-MS), and single crystal X-ray diffraction analysis. The catalytic performances of 1 and the previously reported complexes [Fe(HL)Cl2] (2) and [Fe(HL)Cl(μ-OMe)]2 (3) towards the peroxidative oxidation of cyclohexane under three different energy stimuli (microwave irradiation, ultrasound, and conventional heating) were compared. 1-3 displayed homogeneous catalytic activity, leading to the formation of cyclohexanol and cyclohexanone as final products, with a high selectivity for the alcohol (up to 95%). Complex 1 exhibited the highest catalytic activity, with a total product yield of 38% (cyclohexanol + cyclohexanone) under optimized microwave-assisted conditions.

What happens when chitosan meets bentonite under microwave-assisted conditions? Clay-based hybrid nanocomposites for dye adsorption

In this study, bionanocomposites were prepared with bentonite and chitosan in proportions of 50, 100, 200, and 300 % of the cation exchange capacity (CEC) of the bentonite using microwave heating at 50 °C for 15 and 30 min. The X-ray diffraction patterns indicated basal spacings in the range of 1.48–2.10 and 1.57–1.98 nm for nanocomposites obtained at 15 and 30 min of heating, respectively, suggesting the intercalation of chitosan in the interlayer space of montmorillonite. Fourier transform infrared spectra confirmed the incorporation of chitosan in bentonite. The results of the elemental analysis suggested a higher chitosan content for the nanocomposites prepared with 200 and 300 % of the CEC after 30 min of irradiation. Chitosan–bentonite nanocomposites obtained after 30 min of heating successfully adsorbed the Reactive Violet 5R dye from aqueous solutions. The influence of several factors such as the pH, adsorbent dosage, contact time, and initial dye concentration was investigated. The optimal adsorption conditions were a pH of 1.0 and a contact time of 20 min. The adsorption capacity reached 98.00, 207.71, 250.00, and 282.01 mg g−1 for nanocomposites prepared with 50, 100, 200, and 300 % of the CEC, respectively. In was demonstrated that the prepared bentonite–chitosan nanocomposites were good dye adsorbents.

The Potential of Novel Chitosan-Based Scaffolds in Pelvic Organ Prolapse (POP) Treatment through Tissue Engineering.

The growing number of female reproductive system disorders creates a need for novel treatment methods. Tissue engineering brings hope for patients, which enables damaged tissue reconstruction. For this purpose, epithelial cells are cultured on three-dimensional scaffolds. One of the most promising materials is chitosan, which is known for its biocompatibility and biodegradability. The aim of the following study was to verify the potential of chitosan-based biomaterials for pelvic organ prolapse regeneration. The scaffolds were obtained under microwave-assisted conditions in crosslinking reactions, using dicarboxylic acids and aminoacid as crosslinkers, including l-glutamic acid, adipic acid, malonic acid, and levulinic acid. The products were characterized over their physicochemical and biological properties. FT–IR analysis confirmed formation of amide bonds. The scaffolds had a highly porous structure, which was confirmed by SEM analysis. Their porosity was above 90%. The biomaterials had excellent swelling abilities and very good antioxidant properties. The cytotoxicity study was performed on vaginal epithelial VK2/E6E7 and human colon cancer HCT116 cell lines. The results showed that after certain modifications, the proposed scaffolds could be used in pelvic organ prolapse (POP) treatment.

Synthesis of 6- and 7-alkoxy-4-methylcoumarins from corresponding hydroxy coumarins and their conversion into 6- and 7-alkoxy-4-formylcoumarin derivatives

Hydroxy derivatives of 4-methyl-2H-chromen-2-one were prepared from hydroquinone and resorcinol through their reaction with ethyl acetoacetate. These hydroxy coumarins were then converted into corresponding alkoxy derivatives by reaction with alkyl halides. The yields of 6- and 7-alkoxy-4-methylcoumarins 3a–i and 4a–i were 55−95%. Oxidation of these compounds by selenium dioxide under conventional and microwave-assisted heating conditions produced corresponding 4-formyl compounds 5b–h and 6b–h with yields of 40−67% and 90−93%, respectively. Several 6- and 7-alkoxy-4-methylcoumarins 3a–i, 4a–i and nearly all 6- and 7-alkoxy-4-formylcoumarins 5b–h, 6b–h are novel compounds.

Novel phenethylimidazolium based ionic liquids: Design, microwave synthesis, in-silico, modeling and biological evaluation studies

An eco-friendly preparation method for the novel bioactive imidazolium ionic liquids halides (ILs) was developed under microwave-assisted conditions. Synthesized ILs were characterized by spectroscopic techniques. Selected ILs were investigated for their antimicrobial activity against highly resistant Gram-positive and Gram-negative bacterial strains. Overall, 3-(2-chlorobenzyl)-1-phenethyl-1H-imidazol-3-iumchloride (4) showed high antimicrobial activity against the Staphylococcus aureus strain in the inhibition zone tests and displayed low MIC and MBC levels against almost all tested bacteria. Furthermore, the ILs were screened in vitro against human hepatocellular carcinoma (HepG-2), human breast adenocarcinoma (MCF-7), and human colon carcinoma (Caco-2) cell lines. The screening results showed excellent to moderate anticancer activity across the ILs. Among the synthesized ILs, Overall, 3-(2-chlorobenzyl)-1-phenethyl-1H-imidazol-3-ium chloride (4) and 1-phenethyl-3-(3-phenoxypropyl)-1H-imidazol-3-ium bromide (7) were found to exhibit the most promising ant proliferative effects and had the lowest IC50 values. The docking study suggested strong interaction of ILs with DNA with binding energy ranging from −4.9 to −4.1 kcal/mol. ILs 4 and 7 were most strongly bonded with −4.9 and −4.8 kcal/mol binding energy; confirming in vitro anticancer results.

Selection of Water-Soluble Chitosan by Microwave-Assisted Degradation and pH-Controlled Precipitation.

In the field of gene therapy, chitosan (CS) gained interest for its promise as a non-viral DNA vector. However, commercial sources of CS lack precise characterization and do not generally reach sufficient solubility in aqueous media for in vitro and in vivo evaluation. As low molecular weight CS showed improved solubility, we investigated the process of CS depolymerization by acidic hydrolysis, using either long time heating at 80 °C or short time microwave-enhanced heating. The resulting depolymerized chitosan (dCS) were analyzed by gel permeation chromatography (GPC) and 1H nuclear magnetic resonance (NMR) to determine their average molecular weight (Mn, Mp and Mw), polydispersity index (PD) and degree of deacetylation (DD). We emphasized the production of water-soluble CS (solubility > 5 mg/mL), obtained in reproducible yield and characteristics, and suitable for downstream functionalization. Optimal microwave-assisted conditions provided dCS with a molecular weight (MW) = 12.6 ± 0.6 kDa, PD = 1.41 ± 0.05 and DD = 85%. While almost never discussed in the literature, we observed the partial post-production aggregation of dCS when exposed to phase changes (from liquid to solid). Repeated cycles of freezing/thawing allowed the selection of dCS fractions which were exempt of crystalline particles formation upon solubilization from frozen samples.

Synthesis of Diaryl Hydroxyl Dicarboxylic Acids from Amino Acids.

Herein we report a unique method for preparing diaryl hydroxyl dicarboxylic acids in a diastereospecific manner. The three-component reaction occurs between amino acid, aromatic aldehyde, and primary alcohol in alkaline solutions under microwave-assisted conditions. The dicarboxylic acids are isolated as sodium salts in high yields (up to 77%) by direct precipitation from the reaction solution. The experimental results suggest that the diastereospecificity originates from a [3,3]-sigmatropic rearrangement followed by a sodium-assisted hydride transfer. As further shown, the previously unreported dicarboxylic acids are easily turned into corresponding δ-lactones.

Development of C60-based labeling reagents for the determination of low-molecular-weight compounds by matrix assisted laser desorption ionization mass spectrometry (II): Determination of thiols in human serum.

Perturbation of thiol homeostasis in biological fluids are thought to be associated with several diseases, and reliable analytical methods for the determination of low molecular weight (LMW) thiols in human plasma or serum are thus required. In this study, a matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) method is described for high throughput determination of four LMW thiols (glutathione, cysteine, homocysteine and cysteinylglycine) in human serum. It is based on the use of a bromoacetyl functionalized C60 (Br-C60) as a derivatization reagent to label thiols. The Br-C60 labeling can add an 832-Da tag to thiols, which moves thiol signals to high mass region and effectively avoids the signal interference generated by the traditional MALDI matrix below 800Da. The labeling can be completed within 5min under microwave-assisted condition. Thereby, the Br-C60 labeling based MALDI-TOF MS analytical method can achieve high throughput analysis of LMW thiols in serum. Good linearities of the method for the thiols in human serum were obtained in the range of 0.5-500.0μM with correlation coefficient (R) greater than 0.9960. The limit of detection is in the range of 0.07-0.18μM for the investigated thiols in human serum with relative standard deviations of lower than 13.5% and recoveries ranging from 81.9 to 117.1%. Using the method, four thiols in microliter serum samples of breast cancer (BC) patients were determined. The result showed that the contents of the four thiols in BC serum samples significantly changed compared to the healthy control (HC).

Microwave-Assisted Synthesis and Characterization of Poly(L-lysine)-Based Polymer/Carbon Quantum Dot Nanomaterials for Biomedical Purposes.

Carbon nanomaterials in the form of quantum dots have a high potential due to their luminescent properties and low cytotoxicity which allows their use in optical probes for use in bioimaging and biodetection. In this article, we present a novel type of nanomaterials and their obtainment method under microwave-assisted conditions using poly(L-lysine) as a raw material. The ready products were characterized over their chemical structure, pH-dependent fluorescence properties and cytotoxicity on human dermal fibroblasts. Moreover, their antioxidant activity as well as ability to biologically active molecules (vitamins) and heavy metal ions detection was evaluated. The results confirmed the obtainment of biocompatible nanomaterials with advanced properties and good water solubility according to sustained development principles.

Hetero-hexalanthanide Complexes: A New Synthetic Strategy for Molecular Thermometric Probes.

Reactions in solvothermal or microwave-assisted conditions between a hexanuclear rare-earth entity ([Ln6] with Ln = Eu-Dy) and m-halogeno-benzoic acids lead to three series of isostructural complexes with respective chemical formulas [Ln6(μ3-OH)2(H2O)2(NO3)2(3-cb)14]·4CH3CN, [Ln6(μ3-OH)2(H2O)2(NO3)2(3-bb)14]·6CH3CN, and [Ln6(μ3-OH)2(H2O)2(NO3)2(3-ib)14]·6CH3CN, where 3-cb-, 3-bb-, and 3-ib- represent 3-chloro-, 3-bromo-, and 3-iodo-benzoate, respectively. These three series of compounds are almost isostructural. Their luminescent properties, in the solid and solution states, have been studied in detail and compared. This study shows that hexanuclear complexes own strong intermetallic energy transfers. This makes these complexes good candidates for thermometric probes in solid state or in solution state.

P-TSA Catalyzed One-Pot Synthesis of Some Novel Bis(Hexahydroacridine-1,8-Diones) and Bis(Tetrahydrodipyrazolo[3,4-b:4′,3′-e]Pyridines) Derivatives

A simple, efficient and ecofriendly procedure has been developed for the synthesis of bis(hexahydroacridine-1,8-diones) and bis(tetrahydrodipyrazolo[3,4-b:4′,3′-e]pyridines) derivatives using p-TSA as catalyst under microwave-assisted reaction conditions as well as under conventional heating.

Synthesis of boron-containing tetrazoles under neutral microwave-assisted conditions

In this report, the mild synthetic strategies for the synthesis of two series of boron-containing tetrazoles were included. For the first series, a boron-containing isocyanide reacted with TMS-N3 to afford the desire products. The reaction took place at 60 °C in TFE for 30 min under microwave irradiation. For the second series, the Ugi four-component reaction (Ugi-4CR) was deployed to synthesize the desire products. The reaction took place simply in MeOH at ambient temperature for 2 h. The synthetic strategies included could provide access to ranges of boron-containing tetrazole libraries, which might possess unique biological properties.

Microwave-assisted efficient synthesis of 3-substituted bis-isoxazole ether bearing 2-chloro-3-pyridyl via 1,3-dipolar cycloaddition.

An efficient strategy for synthesizing of 3-substituted bis-isoxazole ether bearing 2-chloro-3-pyridyl under microwave radiation was reported. The reactive regioselectivity was improved by changing mainly the solvent and acid-binding agent. 3-(2-Chloropyridin-3-yl)-5-(((3-substituted phenyl isoxazol-5-yl)methoxy)methyl)isoxazoles were synthesized in 31-92% yields and were characterized by FT-IR, HRMS, 1H and 13C NMR spectroscopy. The single crystal of 3-(2-chloropyridin-3-yl)-5-(((3-(p-tolyl)isoxazol-5-yl)methoxy)methyl)isoxazole was obtained, and the structure of compound has also been determined by X-ray diffraction technique. Weak intra- and intermolecular C-H∙∙∙O interactions and a C-H∙∙∙π interaction link molecules into a three-dimensional network. The results showed that the synthesized compounds belonged to triclinic system, and their regioselectivity depended on the solvent and acid-binding agent. The merits of this method include the environmentally friendly, efficient, simple operation, and higher regional selectivity. An efficient synthesis of 3-substituted bis-isoxazole ethers was developed via 1,3-dipolar cycloaddition reaction starting from 3-substituted phenyl-5-((prop-2-yn-1-yloxy))methyl)isoxazoles and (Z)-2-chloro-N-hydroxynicotinimidoyl chloride using NaHCO3 as an acid-binding agent in THF solvent-dissolved trace water under catalyst-free microwave-assisted conditions.