Scielo RSS <![CDATA[Journal of the Chilean Chemical Society]]> vol. 66 num. 1 lang. n <![CDATA[SciELO Logo]]> <![CDATA[FIRST- DERIVATIVE SPECTROFLUORIMETRIC DETERMINATION OF ENROFLOXACIN AND CIPROFLOXACIN IN COW MILK USING ROTATING SORPTIVE EXTRACTION]]> ABSTRACT A derivative spectrofluorimetric method for simultaneous determination of enrofloxacin (EFX) and ciprofloxacin (CFX) in cow milk was developed. The sample preparation was based on rotating disk sorptive extraction (RDSE) using Oasis HLB® as extraction phase and followed by desorption of the analytes with methanol. The final extracts were evaluated by derivative spectrofluorimetry. An analyte-free cow milk was used as blank sample which was spiked with a known amount of analytes for the study of variables. The sample was treated with trichloroacetic acid in order to precipitate proteins. Furthermore, the extraction was carried out in the presence of Mc Ilvaine-EDTA 0.3M buffer to avoid any type of interference from the calcium ion. The variables involved in the RDSE process were pH and extraction time. Spectral variables were also optimized and analytical signals were evaluated at 417nm and 438nm for EFX and CFX, respectively. The limit of detection (LOD) and limit of quantification (LOQ) were 2.98 – 9.04 μg · L−1 and 2.56 – 7.75 μg · L−1, for EFX and CFX respectively. The precision levels, expressed as relative standard deviation, for EFX and CFX were 3.2% and 3.0%, respectively. The recoveries were between 98.8% to 100.5%. Commercial milks were analyzed and both antibiotics shown concentrations below to LOD in the batches analyzed. Finally, the proposed method offers advantages in terms of simplicity, efficiency and cost. Besides being friendly with the environment. <![CDATA[SIMULTANEOUS SPECTROPHOTOMETRIC QUANTITATION OF RUTIN AND CHLOROGENIC ACID IN LEAVES OF <em>Ribes uva-crispa</em> L. BY ONE-DIMENSIONAL CONTINUOUS WAVELET TRANSFORMS]]> ABSTRACT New signal processing methods based on one-dimensional continuous wavelet transforms were proposed for the simultaneous quantification of chlorogenic acid and rutin in the leaves of Ribes uva-crispa L. These methods are based on the application of continuous wavelet transforms to the absorption spectral bands of the analyzed compounds and their samples. In preliminary practices, symlets 8 and biorthogonal 4.4 continuous wavelet transforms (sym8-CWT and bior4.4-CWT) among several wavelet families were found to be optimal ones to perform a selective and sensitive chemical determination of the analytes in analyzed plant samples. Linear regression lines were obtained by measuring sym8-CWT and bior4.4-CWT amplitudes at 333.5 and 336.0 nm for chlorogenic acid and 351.5 and 350.0 nm for rutin in the spectral region 250-450 nm. Linear regression curves were found to be linear in the working range of 2.5-40.0 μg/mL for both compounds. The validation and analytical applicability of the proposed sym8-CWT and bior4.4-CWT approaches were confirmed by analyzing the synthetics mixtures and standard addition samples. It was observed that the application of both sym8-CWT and bior4.4-CWT tools is very appropriate for the simultaneous spectral quantification of chlorogenic acid and rutin in the real plant samples consisting of leaves of R. uva-crispa. <![CDATA[PHYTOCHEMICAL STUDY OF ENDEMIC COSTA RICAN ANNONACEAE SPECIES <em>Annona pittieri</em> AND <em>Cymbopetalum costaricense</em>]]> ABSTRACT Phytochemical profile of the Central American rainforest endemic Annonaceae species, Annona pittieri and Cymbonopetallum costaricense, were studied in search of novel bioactive compounds. The acetogenin squamocin (1) isolated from A. pittieri showed cytotoxic activity against human acute lymphocytic leukaemia with low activity against healthy blood cells. In addition, other eight compounds were isolated from A. pittieri, including a novel 2-azaanthraquinone alkaloid, 4-methoxybenzo[g]isoquinoline-5,10-dione (2). Furthermore, from C. costaricense three compounds were isolated including a novel 1-azaanthraquinone alkaloid, 6-hydroxy-9-methoxy-cleistopholine (3). <![CDATA[NANOMETER-SCALE MECHANICAL PROPERTIES OF MWCNT-MUSTARD OIL NANOFLUID AS A POTENTIAL BASE STOKE]]> ABSTRACT Nowadays, environmentally friendly lubricants are developed to meet the standards of biodegradability, toxicity and bioaccumulation potential that reduce the adverse consequences to the aquatic atmosphere compared to conventional mineral based lubricants. In this study, an attempt made to enhance the feasibility of utilizing the Mustard oil as a commercial lubricating agent by homogeneously dispersing MWCNTs as an additive. The average crystallite size, surface morphology and elements of MWCNT are characterized through XRD, SEM, EDS and FTIR techniques, respectively. The surface deformation rate of matrix material (Mg) lubricated by Mustard oil and different weight fractions of MWCNT-Mustard oil nanofluid are estimated through Nanoindentation technique. The hardness, Young's modulus and AFM topography of the interacting surface infers that the dispersed MWCNT significantly enhance the lubricating properties of Mustard oil through micro-chipping and micro-softening effect. <![CDATA[<em>IN-VITRO</em> ANTIMICROBIAL SCREENING AND COORDINATION BEHAVIOR OF METALS BASED BIDENTATE COMPOUNDS]]> ABSTRACT By condensing ethylene-1,2-diamine with different aldehydes such as benzaldehyde, 4-chloroacetophenone and 2-chlorobenzaldeyhde within 1:2 molar ratio, resulted new series of Schiff base ligands (L1)-(L3) containing bidentate nitrogen atom. Their metal complexes were synthesized by coordinating the ligands with transition metals as Co(II), Cu(II), Ni(II) and Zn(II) and exhibited octahedral geometry. Their characterization was done with the help of spectral, physical and analytical analysis. Spectral and elemental analysis of all bidentate ligands and their corresponding 3d-metal chelates was consistent with their proposed structures, signifying the high purity of these compounds. For in-vitro studies, these metal complexes along their ligands were screened against the six bacterial strains; Escherichia coli, Bacillus subtilis, Pseudomonas aeruginosa, Klebsiella pneumonia, Staphylococcus aureus and Streptococcus faecalis. Six fungal strains; Aspergillus niger, Trichophyton mentogrophytes, Epidermophyton floccosum, Trichophyton schoenleinii, Microscopum canis and Fusarium culmorum were used to study antifungal activity of the compounds. Bioactivity results exhibited that metal complexes showed higher antimicrobial potential as compared with their corresponding ligands. The enhanced activity resulted due to chelation that decreases the polarity of metal ions by complexing with bidentate ligands. <![CDATA[SYNTHESIS, CHEMICAL IDENTIFICATION, DRUG RELEASE AND DOCKING STUDIES OF THE AMLODIPINE–CHITOSAN NANOBIOPOLYMER COMPOSITE]]> ABSTRACT A new amlodipine-chitosan nanocomposite was built using amlodipine nanoparticles as primary scaffolds by spontaneous emulsification, and its complete elucidation was performed by using several spectrometric techniques. Our results indicate that the amlodipine-chitosan nanocomposite has better solubility than amlodipine at pH 7.4 with a nearly all the drug substance dissolved (97%) by the final time-point measured. The docking study support the existence of intermolecular interactions are established between amlodipine and chitosan. <![CDATA[MINOR COMPOSITION COMPOUNDS OF ALGERIAN HERBAL MEDICINES AS INHIBITORS OF SARS-CoV-2 MAIN PROTEASE: MOLECULAR DOCKING AND ADMET PROPERTIES PREDICTION]]> ABSTRACT The identification of drugs against the new coronavirus (SARS-CoV-2) is an important requirement. Natural products are substances that serve as sources of beneficial chemical molecules for the development of effective therapies. In this study, 187 natural compounds from Algerian herbal medicines were docked in the active site of SARS-CoV-2 main protease. The result indicates that Piperitol, Warfarin, cis-calamenen-10-ol and α-Cadinene are the structures with best affinity in the binding site of the studied enzyme and all of them respect the conditions mentioned in Lipinski's rule and have acceptable ADMET proprieties; so, these compounds could have more potent antiviral treatment of COVID-19 than the studied compounds, and they have important pharmacokinetic properties and bioavailability. <![CDATA[GREEN CHEMISTRY – A NOVEL APPROACH TOWARDS SUSTAINABILITY]]> ABSTRACT A study on the emergence and twelve principles of Green chemistry has been thoroughly discussed. Syntheses of polymers and nanoparticles with the aid of greener method have been elucidated. Phase transfer catalysis is found to play Key role in the synthesis of various multistep processes to one pot cascade reaction. Ionic liquids have emerged out as alternative green solvent in synthetic chemistry replacing traditional organic ones due to environmental and health concerns. Non ionic surfactants notably due to their characteristic temperature induced clouding phenomena and subsequent phase separation above cloud point have been found potential application in the field of preconcentration and extraction of various metal ions, organic and inorganic industrial pollutants and pesticides. <![CDATA[SYNTHESIS, CRYSTAL STRUCTURE AND HIRSHFELD SURFACE ANALYSIS OF A NEW COORDINATION POLYMER: STRONTIUM BENZILATE]]> ABSTRACT A novel coordination polymer was synthesized from strontium carbonate and benzylic acid in aqueous solution and is formulated as Sr[(C6H5)4(COCOO)2·2H2O]. This compound was characterized by FTIR spectroscopy and powder X-ray diffraction. The crystal structure was determined by single-crystal X-ray diffraction. The complex crystallizes in the monoclinic P21/n space group, with unit cell parameters a = 15.0224(9) Å, b = 7.5038(6) Å, c = 25.000(2) Å, β = 94.764(2)°, V = 2808.4 Å3, Z = 4. In the structure, the metallic ion is coordinated to eight oxygen atoms, six from benzilate molecules, and two from water molecules, forming a distorted tetragonal antiprism. One of the benzilates is coordinated to the metal in a monodentate fashion (carboxylate only), while the other benzilate molecule does it in the bidentate from carboxylate and hydroxide. Strontium ions form infinite zig-zag chains along the [010] direction, which form a three-dimensional network via O--H···O hydrogen-bond interactions between the coordinated water molecules and the O atoms of the carboxylate groups. The intermolecular interactions were analyzed using Hirshfeld surface analysis. <![CDATA[EFFECTS OF CLAY CONTENT IN SOIL ON PESTICIDES SORPTION PROCESS]]> ABSTRACT Intensive application of pesticides in the agricultural sector and for domestic purposes has resulted in increased usage over the years. Pesticides are used to control pest, diseases and weeds in agricultural and urban areas, but their persistence in the environment has resulted in human poisoning, health risk problem and environmental pollution due to their ability to permeate the soil surface, groundwater systems and water surface bodies. Sorption of two organophosphorus pesticides: Diazinon and Clorpyriphos was studied in a soil (S) and in soil modified with clay addition. Soil Alhue, VI region, Chile, was spiked with 1% of either Montmorillonite (M) or Kaolinite (K) (S1). In addition, organic matter (OM), in the soil was eliminated and this soil (S2), was spiked again, with 1% of both clays. Batch sorption and kinetics experiments were conducted to obtain the retained amounts onto the soil samples. Pesticides were quantified by high performance liquid chromatography (HPLC). The results showed that for both pesticides the sorption order is: S1-M &gt; S1-K &gt; S1. For soil without OM (S2) the order is the same, although the adsorption was lower. The adsorption isotherms were expressed by the Langmuir and Freundlich models. The negative Gibb's free energy change (ΔG°) values obtained suggest that the adsorption of both pesticides, is an exothermic process. Clay addition to the soil, increased the adsorption processes, generating an increase in the amount of pesticide retained in the soil and partially avoiding possible contamination of the aquifers. The difference found in relation to the behavior of both clays on the soil, can be explained considering its structure and its octanol-water partition coefficient (kow). <![CDATA[PHYTOCHEMICAL CONSTITUENTS, ANTIOXIDANT, ANTIBACTERIAL AND ENZYME INHIBITION ACTIVITIES OF ESSENTIAL OIL FROM THE AERIAL PART OF <em>Achillea tomentosa</em> L. GROWN IN JORDAN]]> ABSTRACT This investigation aimed to evaluate the phytochemical constituents, antioxidant, antibacterial and α-glucosidase inhibitory activities of A. tomentosa essential oil. The essential oil extracted using steam distillation method possessed antibacterial activity for all tested bacteria. Comparing to cefaclor the percentage of relative inhibition zone diameter (RIZD) was 100.30 ± 4.73 % for Staphylococcus aureus and ranged between 79.67 ± 3.79 % and 84.33 ± 4.16 % for other bacteria. The essential oil showed considerable antioxidant activity using 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity, ferric reducing antioxidant power (FRAP) assay and metal chelating methods, the EC50 of the essential oil were 72.06 ± 3.99, 54.69 ± 4.69 and 50.39 ± 2.86 µg/ml respectively, comparing 7.34 ± 2.43, 10.87 ± 3.34 and 14.50 ± 3.46 µg/ml for positive controls (Trolox, EDTA and Quercetin respectively). The essential oil also possessed concentration dependent α-glucosidase inhibitory activity with EC50 149.20 ± 7.63 µg/ml comparing to acarabose EC50 14.50 ± 3.46 µg/ml. Forty compounds were identified depending in retention index (RI) and mass spectra (MS) that form 96.31 % of the essential oil composition. The result showed that the ratio of the identified compounds range between 0.11 % and 23.72 %, 3-Carene (23.72 %), Limonene (12.19 %) and α-Terpinyl acetate (10.22%) were found to be the major components of the essential oil. m-Cyneme (7.11 %) and Di-n-octyl phthalate (4.50 %) present in moderate quantities. The phytochemical analyzes showed that the identified compound quantitatively and qualitatively differ from the previous study that investigate the composition of A.tomentosa L. essential oil. <![CDATA[A REVIEW ON BIODIESEL FEEDSTOCKS AND PRODUCTION TECHNOLOGIES]]> ABSTRACT Biodiesel is a long-chain fatty acid ester made from renewed and biological raw materials such as used cooking, animal fat, vegetable oil, and algae. Biodiesel is a renewable and clean fuel as it reduces carbon monoxide, carbon dioxide, hydrocarbons, and particulate matter emissions compared with petroleum-based diesel fuel. Production of biodiesel from renewable resources is done through the transesterification reaction at which the organic group (alkyl) of alcohol is substituted with the organic group of a triglyceride– the main component of the feedstock –producing fatty acid alkyl ester (biodiesel) and crude glycerol. Biodiesel can be used in pure form (B100) or may be blended with petroleum diesel at any concentration if its specifications is identical to the international standard specifications provided by American standard for testing materials (ASTM) or EN14214 in the European Union for alternative fuels. In this paper, the different types of biodiesel feedstocks, feedstocks treatment methods, and biodiesel production technologies are reviewed and discussed. <![CDATA[SYNTHESIS AND CHARACTERIZATION OF COPPER NANOPARTICLES SUPPORTED IN CARBON NANOTUBES MULTIPLE WALLS PREPARED BY CLD AND SMAD]]> ABSTRACT The synthesis and characterization of copper nanoparticles supported in carbon nanotubes is reported. Copper nanoparticles were obtained by the CLD (chemical liquid deposition) method consisting of reduced pressure evaporation of metals and subsequent low-temperature condensation (77K) of these vapors, with organic solvent vapors. From the reactions obtained by this method, copper colloids of concentrations 10-3 and 10-4 were synthesized in the organic solvents 2-propanol, 2-mercaptoethanol, 2-methoxyethanol and 2-ethoxyethanol. The support of copper nanoparticles in the carbon nanotubes was made by SMAD method with 24 hours under agitation and nitrogen atmosphere before collecting, obtaining copper nanoparticle solids supported in carbon nanotubes by evaporating the solvent either 2-mercaptoethanol or 2-ethoxyethanol. Colloidal and solid dispersions were characterized by diverse techniques, for colloidal dispersions UV-Vis spectrophotometry, electrophoretic mobility, electron transmission microscopy (TEM), electron diffraction and stability over time was used. Far-medium infrared spectroscopy (FT-IR) and thermogravimetry (TGA) were used for solids. These analyses show that Cu colloids are relatively stable in the solvents used, the most stable dispersion was synthesized in 2-mercaptoethanol and the less stable is synthesized in 2-methoxyethanol, which is demonstrated in UV spectra. By TEM, particle sizes were studied, between 5.2 and 17.2 nm. Electron diffraction confirms the presence of copper. Analysis of active solids shows in the case of FTIR that solvents are incorporated into copper particles, and in the case of thermograms it is shown that the solids synthesized in the solvent had greater thermal stability 2-mercaptoethanol. It was impossible to obtain electron diffraction from the copper nanoparticles visualized because they are incorporated in the multiwall nanotubes. <![CDATA[POLY(4-VINYLBENZYL)TRIMETHYLAMMONIUM CHLORIDE) RESIN WITH REMOVAL PROPERTIES FOR VANADIUM(V) AND MOLYBDENUM(VI). A THERMODYNAMIC AND KINETIC STUDY]]> ABSTRACT Ion exchange resin poly(4-vinylbenzyl) trimethylammonium chloride(P(ClVBTA)) was synthesized and its removal properties toward vanadium(V) and molybdenum(VI) were evaluated and compared with those of the Amberlite IRA-402 commercial resin. The resin was characterized by FT-IR spectroscopy, TGA, and SEM. The water absorption capacity, pH effect, Langmuir and Freundlich adsorption isotherms, and kinetic model parameters were determined. All studies were conducted through a batch equilibrium procedure. Thermodynamic parameters, including enthalpy, entropy, and free energy, were determined. The P(ClVBTA) resin showed faster and higher capacity for the removal of V(V) and Mo(VI) from a water solution than the Amberlite IRA-402 commercial resin with the same ammonium salt functional group. The higher capacity of the P(ClVBTA) resin was attributed to the higher degree of swelling, the exfoliation in the monolayer, and the small particle size. <![CDATA[EFFECT OF WI-FI RADIOFREQUENCIES ON THE CONTENT OF FATTY ACID AND ERGOSTEROL, A PRECURSOR OF VITAMIN D, IN <em>IN VITRO</em> CULTURES OF THE FUNGUS <em>Serpula himantioides</em>]]> ABSTRACT In the microwave-radiofrequency spectrum, Wi-Fi is a short-range wireless broadband technology, which transmits at a frequency of 2.5 GHz. This type of technology has been positioned itself as one of the most widely used technological advances in recent years. It has been reported that direct exposition to radiofrequencies can induce physiological changes in different animals and plants species. One of the degenerative effects that Wi-Fi can cause is the production of reactive oxygen species, inducing tissue damage and DNA alterations. In fungi, the effect of exposure to electromagnetic radiation in the UV spectrum has been extensively studied, the physiological effect to radiofrequencies such as Wi-Fi is unknown. In that sense, the aim of this study was to detect the main changes in metabolism of some acid fatty and ergosterol of the fungus Serpula himantioides, using gas chromatography - mass spectrometry (GC–MS), and evaluate the antioxidant activity of metabolites obtained from in vitro cultures of S. himantioides exposed to Wi-Fi at 2.5 GHz. The results showed an increment in the content of some the fatty acids and ergosterol, in total extracts from the fungus mycelium. Antioxidant analysis revealed that the total extracts of S. himantioides culture medium showed antioxidant capacity associated with an increment in the content of phenolic compounds. Our results suggest that direct exposition to Wi-Fi radiation produces oxidative damage by modifying cellular components in the fungus S. himantioides.