UV-visible Spectroscopic Methods Research Articles

Design, Synthesis and Antimicrobial Evaluation of Novel Benzimidazoleincorporated Naphthalimide Derivatives as Salmonella typhimurium DNA Intercalators, and Combination Researches.

A series of novel benzimidazole-incorporated naphthalimide derivatives were designed and prepared in an effort to overcome the increasing antibiotic resistance. The target novel benzimidazole-incorporated naphthalimide derivatives were synthesized from commercial 4-bromo-1,8-naphthalic anhydride and o-phenylene diamine by aminolysis, Nalkylation and so on. The antimicrobial activity of the synthesized compounds was evaluated in vitro by a two-fold serial dilution technique. The interaction of compound 10g with Salmonella typhimurium DNA was studied using UV-vis spectroscopic methods. Compound 10g bearing a 2,4-dichlorobenzyl moiety exhibited the best antimicrobial activities in this series relatively; especially, it exhibited comparable activity against Salmonella typhimurium in comparison with the reference drug Norfloxacin (MIC = 4 μg/mL). Further research showed that compound 10g could effectively intercalate into the Salmonella typhimurium DNA to form the 10g-DNA complex, which might correlate with the inhibitory activity. Molecular docking results demonstrated that naphthalimide compound 10g could interact with base-pairs of DNA hexamer duplex by π-π stacking. Additionally, the combination of the strong active compound with clinical drugs exhibited better antimicrobial efficiency with less dosage and broader antimicrobial spectrum than the separate use of them alone. Notably, these combined systems were more sensitive to Fluconazole-insensitive M. ruber. This work provides a promising starting point to optimize the structures of benzimidazole- incorporated naphthalimide derivatives as potent antimicrobial agents.

Effects of Modulating Multivalent Ligand Binding Accessibility & Affinity on Liquid‐Liquid Phase Separation

Elucidating the molecular rules of ligand‐induced phase transitions is essential to determining the regulation of the formation and disassembly of biomolecular condensates. Ubiquitin‐binding shuttle protein Ubiquilin‐2 (UBQLN2) undergoes liquid‐liquid phase separation (LLPS) in vitro and colocalizes into stress‐induced cytoplasmic puncta in vivosuch as stress granules.[1] A recent study from our lab indicated that ubiquitin (Ub), and compact polyUb chains such as K48‐ & K11‐Ub4 can inhibit UBQLN2 LLPS by binding to phase separation‐driving UBQLN2 stickers whereas more extended chains such as K63‐ & M1‐Ub4 can promote UBQLN2 phase separation over a large Ub:UBQLN2 range by acting as a multivalent ligand scaffold.[2] Using a designed tetrameric ubiquitin construct (HOTag6‐Ub) that resembles a multi‐monoubiquitinated substrate, we further probed how alterations to the stickers and spacers of the HOTag6‐Ub ligand can modulate UBQLN2 phase behavior. Using turbidity and microscopy experiments, we obtained phase diagrams for LLPS driven by heterotypic interactions between UBQLN2 and HOTag6‐Ub. We discovered that, by changing the length and flexibility of the linker that tethers the Ub units to HOTag6, we can tune UBQLN2 LLPS. Single‐ and double‐point mutations to the Ub hydrophobic binding surface (I44 & V70 “stickers”) decreased the binding affinity between Ub and UBQLN2, thereby leading to changes in the shape of HOTag6‐Ub/UBQLN2 phase diagrams. Using nuclear magnetic resonance spectroscopy (NMR), microscopy and UV‐Vis spectroscopic methods we demonstrated that linker conformation, linker flexibility, and interactions with the Ub binding surface are driving factors of UBQLN2/HOTag6‐Ub co‐phase separation. Overall, our findings highlight how multivalent ligands can tune phase separation behavior of protein systems.[1] Dao, T. P., Kolaitis, R.‐M., Kim, H. J., O’Donovan, K., Martyniak, B., Colicino, E., Hehnly, H., Taylor, J. P., and Castañeda, C. A. (2018). Ubiquitin Modulates Liquid‐Liquid Phase Separation of UBQLN2 via Disruption of Multivalent Interactions. Mol. Cell 69, 965‐978.[2] Dao, T. P., Yang, Y., Cosgrove, M. S., Hopkins, J. B., Ma, W., Castaneda, C. A. (2021). Mechanistic insights into the enhancement or inhibition of phase separation by polyubiquitin chains of different lengths or linkages. bioRxiv 2021.11.12.467822; doi: https://doi.org/10.1101/2021.11.12.467822.

Synthesis and characterization of copper complexes of phenylpiperazine ring-based ligands and evaluation of their antimicrobial, BSA binding, computational, and molecular docking studies

This paper describes the synthesise of copper complexes of phenylpiperazine ring-based ligands and characterization via physical and spectroscopic methods. Structure of complexes has been proposed on the basis of UV-vis, IR and Mass fragmentation pattern and additionally supported by electrochemical and thermogravimetric analysis. Low molar conductance value of metal complexes in water and DMSO suggest non-ionic nature of complexes which is in agreement of proposed structure. TGA curve, where loss of coordinated solvent molecules starts early followed by loss of ligand itself also support the proposed structures. Percentage ash content analysis also indicate that only one copper metal is binding to the ligands reported here. Antibacterial activity of metal complexes has been performed by agar well diffusion method and indicated these metal complexes possess higher activity than the corresponding ligands. Binding interaction of these complexes were studied with BSA protein by UV-vis spectroscopic methods and binding constant was calculated which indicated that the complexes are having moderate affinity. Some complexes were also geometrically optimized to lowest energy ground state by using DFT calculations. Docking study of these optimized structures with BSA protein revealed these metal complexes exhibit hydrophobic interaction owing to the aromatic bulk in the ligand.

Thin Film Coatings from Aqueous Dispersion of Graphene-Based Nanocarbon and Its Hybrids with Metal Nanoparticles

Shungite carbon (ShC) nanoparticles in the form of stable aqueous dispersions represent a promising solution for optical and biomedical applications. The dispersion is an interesting phenomenon from the point of view of stabilization of ShC nanoparticles and their structural constituents up to the basic structural unit, namely a graphene fragment. Herein, we used these aqueous dispersions with easily released structural components to study laser irradiation with various durations and obtain hybrids of ShC with Ag and Au nanoparticles. The main role in the stabilization of ShC nanoparticles belongs to the graphene fragments and their stacks, which display a considerable dipole moment. Newly prepared aqueous dispersions of ShC–metal hybrid nanoparticles retained the stability inherent in the original nanoparticles both of ShC and metals. Changes in the size distribution pattern of nanoparticles in dispersions upon ablation were studied by dynamic light scattering (DLS). Raman with UV-Vis spectroscopy methods were applied to trace structural changes in ShC upon the formation of hybrid nanoparticles. Films obtained by condensation of the dispersions on glass substrates display periodic structures, as was revealed by SEM microscopy. There, the conditions under which nanoparticles lose their ability to disperse in water and retain a graphene-like structure in a film were revealed.

Synergistic Interaction and Binding Efficiency of Tetracaine Hydrochloride (Anesthetic Drug) with Anionic Surfactants in the Presence of NaCl Solution Using Surface Tension and UV-Visible Spectroscopic Methods.

Surfactants are ubiquitous materials that are used in diverse formulations of various products. For instance, they improve the formulation of gel by improving its wetting and rheological properties. Here, we describe the effects of anionic surfactants on an anesthetic drug, tetracaine hydrochloride (TCH), in NaCl solution with tensiometry and UV–visible techniques. Various micellar, interfacial, and thermodynamic parameters were estimated. The outputs were examined by using different theoretical models to attain a profound knowledge of drug–surfactant mixtures. The presence of attractive interactions among drug and surfactant monomers (synergism) in mixed micelle was inferred. However, it was found that sodium dodecyl sulfate (SDS) showed greater interactions with the drug in comparison to sodium lauryl sarcosine (SLS). The binding of the drug with surfactants was monitored with a spectroscopic technique (UV–visible spectra). The results of this study could help optimize the compositions of these mixed aggregates and find the synergism between monomers of different used amphiphiles.

Solubility of Bosentan in Polyethylene Glycol 400 + Water Mixtures: Experimental and Mathematical Computations

Background: To discover the optimal solvent amounts for using in a particular application, it is vital to achieve some useful information in regard with suitable neat or mixed solvent and drugs equilibrium solubility in them. It is known that the low solubility of drugs such as bosentan (BST) in water negatively effects in vitro and in vivo kinetics of dissolution, affecting in turn its bioavailability along with making several difficulties around designing its liquid formulations. Methods: Solubility of BST in some mixtures of polyethylene glycol 400 (PEG 400) and water was experimentally determined at T = (293.15 to 313.15) K by using a common shake-flask technique followed by UV-visible spectroscopic method. The experimental solubility data in PEG 400 mass fraction (w1) of 0.0 to 1.0 at 298.15 K and in w1=0.0, 0.5 and 1.0 at other temperatures were then correlated by cosolvency models including the Jouyban-Acree, the Jouyban-Acree-van’t Hoff, and the double log-log models and some un-measured solubility data were predicted based on the obtained trained models. Results: The results presented that the aqueous solubility of BST is increased by increasing mass fraction of PEG 400 as well as increasing temperature and reached the maximum value in neat PEG 400 at 313.15 K. Conclusion: The BST solubility in water improved by addition of PEG 400 into it. According to the average relative deviations obtained from the back-computed data with trained models which were < 8.0%, it concluded that the selected models were able to predict the un-measured data with high reliability.

Innovative Green Chemistry Approach to Synthesis of Sn2+-Metal Complex and Design of Polymer Composites with Small Optical Band Gaps.

In this work, the green method was used to synthesize Sn2+-metal complex by polyphenols (PPHs) of black tea (BT). The formation of Sn2+-PPHs metal complex was confirmed through UV-Vis and FTIR methods. The FTIR method shows that BT contains NH and OH functional groups, conjugated double bonds, and PPHs which are important to create the Sn2+-metal complexes. The synthesized Sn2+-PPHs metal complex was used successfully to decrease the optical energy band gap of PVA polymer. XRD method showed that the amorphous phase increased with increasing the metal complexes. The FTIR and XRD analysis show the complex formation between Sn2+-PPHs metal complex and PVA polymer. The enhancement in the optical properties of PVA was evidenced via UV-visible spectroscopy method. When Sn2+-PPHs metal complex was loaded to PVA, the refractive index and dielectric constant were improved. In addition, the absorption edge was also decreased to lower photon. The optical energy band gap decreases from 6.4 to 1.8 eV for PVAloaded with 30% (v/v) Sn2+-PPHs metal complex. The variations of dielectric constant versus wavelength of photon are examined to measure localized charge density (N/m*) and high frequency dielectric constant. By increasing Sn2+-PPHs metal complex, the N/m* are improved from 3.65 × 1055 to 13.38 × 1055 m−3 Kg−1. The oscillator dispersion energy (Ed) and average oscillator energy (Eo) are measured. The electronic transition natures in composite films are determined based on the Tauc’s method, whereas close examinations of the dielectric loss parameter are also held to measure the energy band gap.

Highly conducting nanophases of Ag2S–Se-Ge chalcogenide glassy systems: Explanations via computational descriptions

The temperature and frequency dependent AC conductivity of some Ag2S doped chalcogenides is prepared in the laboratory and experimental data have been collected. Its structural analysis is carried out with X-Ray Diffraction and UV–Vis Spectroscopic methods. The estimated values of optical band gap energy, Egare found to increase with Ag2S content and the present system may be classified as allowed indirect band gap semiconductor. The density and molar volume of as-prepared samples have also been estimated. The AC conductivity of this system has been found to obey the Meyer-Neldel (MN) rule. The decrease of Meyer-Neldel characteristic energy EMN with compositions has been observed. Higher conductivity as well as hopping frequency should be caused due to highly conducting Ag2Senanophases, which is confirmed from DFT and Density of States (DOS) spectra.

A Novel Electrochemical Sensing Platform for the Sensitive Detection and Degradation Monitoring of Methylene Blue

Methylene blue is a toxic dye that is extensively used as a colorant in textile industries. Industrial effluent containing methylene blue, when drained into water bodies without proper treatment, poses a serious threat to aquatic and human lives. In order to protect the biocycle, various methods have been established to detect and remove hazardous dyes from aqueous systems. Electrochemical methods are preferred, owing to their characteristic features of simplicity, portability, potential selectivity, cost effectiveness, and rapid responsiveness. Based on these considerations, an electrochemical sensor consisting of amino-group-functionalized, multi-walled carbon nanotubes (NH2-fMWCNTs) immobilized on a glassy carbon electrode (GCE) was developed for the sensitive detection of methylene blue in aqueous solutions. The performance of the designed sensor was analyzed by electrochemical impedance spectroscopy, cyclic voltammetry, and square wave voltammetry. The developed sensing tool demonstrated promising features of sensitivity, selectivity, stability, fast responsiveness, and the ability to work with a very small volume of the analyte, i.e., in microliters, for analysis. Amino groups rich in electrons provide a negative charge to multi-walled carbon nanotubes, which significantly enhances the electrocatalytic activity of NH2-fMWCNTs for cationic dyes such as methylene blue. Using the designed sensing platform, a linear calibration plot with a limit of detection of 0.21 nM was obtained for methylene blue under optimized conditions. The designed sensor was also employed to monitor the extent and kinetics of the degradation of methylene blue. Titania nanoparticles were used for photocatalytic degradation, and the kinetics of degradation was monitored by both UV-Visible spectroscopic and electrochemical methods. The results revealed more than 95% removal of methylene blue in a time span of just 30 min.

Instigating the In Vitro Anticancer Activity of New Pyridine-Thiazole-Based Co(III), Mn(II), and Ni(II) Complexes: Synthesis, Structure, DFT, Docking, and MD Simulation Studies.

The perchlorate salt of (4-(4-methoxy phenyl)-2-(2-(1-pyridine-2-yl)ethylidene)hydrazinyl)thiazole (PytH·ClO4) and its metal perchlorate derivatives, namely, [Co(Pyt)2]ClO4 (1), [Mn(PytH)2](ClO4)2 (2), and [Ni(PytH)2](ClO4)2 (3), have been synthesized and characterized through single X-ray crystallography and spectroscopic methods. The ligand crystallizes in a space group P21/n in a nearly planar structure. The overall geometry of the complex salts is described as a distorted octahedron with a MN6 chromophore. The ligand (PytH·ClO4) behaves as a neutral N,N,N-tridentate donor toward the "soft" Mn(II) and Ni(II) centers, whereas the deprotonated ligand stabilizes the "hard" Co(III) center. The DNA binding constant (Kb) values of PytH·ClO4, 1, 2, and 3 are determined using the UV-vis spectroscopic method, and the Kb values are 9.29 × 105, 7.11 × 105, 8.71 × 105, and 7.82 × 105 mol-1, respectively, indicating the intercalative mode of interactions with CT-DNA. All the derivatives show effective antiproliferative activity against U-937 human monocytic tumor cells with IC50 values 4.374 ± 0.02, 5.583 ± 0.12, 0.3976 ± 0.05, and 11.63 ± 0.01 μM for PytH·ClO4, 1, 2, and 3, respectively. The best apoptosis mode of cell death is shown by 2 followed by PytH·ClO4 and 1 at an equivalent concentration of IC50 values. The combined molecular docking and dynamics simulation study evaluates the binding energies of anticancer agents, providing groove binding property with DNA. The 20 ns molecular dynamics simulation study reveals the maximum DNA binding stability of 2 corroborating the experimental results. The new class of metal derivatives of pyridine-thiazole can be used for advanced cancer therapeutics.

The structural and optical properties of combustion synthesized Ag doped ZnO nanoparticles

We report the combustion synthesis of Ag (1 to 5 mol%) doped ZnO nanoparticles and their structural and optical characteristics as a function of dopant concentration in this work. The phase, purity, structure, and optical characteristics of the produced samples were thoroughly investigated using XRD and UV-Visible spectroscopy methods. The production of polycrystalline nanoparticles in their as-synthesized condition is confirmed by XRD findings. To estimate the different structural parameters and examine the structure of the produced samples, Rietveld refinement was used. The optical properties were evaluated using Tauc’s plots (band gap energy). With increasing dopant concentration, the band gap was determined to be increasing.

Development of Analytical Methods for Determination of β-Carotene in Pumpkin (Cucurbita maxima) Flesh, Peel, and Seed Powder Samples.

Vegetables are consumed worldwide in fresh as well as processed forms. Pumpkin is considered as an important vegetable due to its nutritional values. The objective of this study was to evaluate all the analytical parameters and improve the performance of the methods for the determination of β-carotene in pumpkin flesh, peel, and seed samples using UV-VIS, NIR, and FTIR methods. β-Carotene was measured at 453 nm using the UV-VIS method which showed linear range, 0.1 to 12 µg/mL; R2, 0.999; LOD, 0.034 µg/mL; LOQ, 0.1 µg/mL; RSD, 1.5% to 11%; and percent recovery, 83% to 93%. β-Carotene was also measured at 1415 nm using NIR and at 1710 cm−1 using FTIR spectroscopic methods. The NIR method exhibited linear range, 12.5 to 250 µg/mL; R2, 0.999; LOD, 3.4 µg/mL; LOQ, 10, µg/mL; RSD, 1.8% to 11%; and percent recovery, 92% to 96%, while the FTIR method exhibited linear range, 4 to 100 µg/mL; R2, 0.999; LOD, 1.3 µg/mL; LOQ, 3.9 µg/mL; RSD, 0.69% to 10%; and percent recovery, 95% to 96%. The characteristic analytical data indicated that any of the three newly developed methods could be used for the determination of β-carotene in the pumpkin flesh, peel, and seeds. Acetone was used as the extraction solvent for the UV-VIS and NIR spectroscopic methods, and acetonitrile was used as the extraction solvent for the FTIR method. Content of β-carotene was found higher in pumpkin peel (340–445 µg/g), followed by pumpkin flesh (317–341 µg/g) and pumpkin seed (12–17 µg/g) by the UV-VIS method. β-Carotene content was obtained ((376–451 µg/g) and (289–313 µg/g); (210–287 µg/g) and (102–148 µg/g)) using NIR and FTIR methods in pumpkin peel and flesh, respectively. β-Carotene was obtained higher from pumpkin peel by all the three methods than from pumpkin flesh and seed. The β-carotene content in the pumpkin seed was not detected by NIR and FTIR spectroscopic methods.

Determination of Piperine contents in pepper in Kon Tum province by UV-Vis spectroscopy method

Piperine is the most major alkaloid in pepper. It plays an important role in determining the value of pepper. Piperine content was extracted by the Soxhlet extraction method for 3.5 hours and measured at 343 nm by an UV-Vis molecular absorption spectrophotometer. After surveying, the repeatability of green and black pepper samples was from 1.76 to 2.07% and from 3.79 to 4.85%, respectively, and the laboratory’s reproducibility was from 2.0 to 2.24% for green pepper and from 3.81 to 5.48% for black pepper, the recovery was from 87.2 to 91.4% for green pepper and from 84.4 to 89.2% for black pepper. Results showed that the Piperine content in green pepper samples was from 5.23 to 10.2% and 0.77 to 5.31% for black peper.

Minimalizing Non-point Source Pollution Using a Cooperative Ion-Selective Electrode System for Estimating Nitrate Nitrogen in Soil.

Nitrate nitrogen ( -N) in the soil is one of the important nutrients for growing crops. During the period of precipitation or irrigation, an excessive -N readily causes its leaching or runoff from the soil surface to rivers due to inaccurate fertilization and water management, leading to non-point source pollution. In general, the measurement of the -N relies upon the laboratory-based absorbance, which is often time-consuming, therefore not suitable for the rapid measurements in the field directly. Ion-selective electrodes (ISEs) support the possibility of -N measurement by measuring the nitrate () ions in soil quickly and accurately due to the high water solubility and mobility of ions. However, such a method suffers from a complicated calibration to remove the influences caused by both temperature and other ions in the measured solution, thus limiting field use. In this study, a kind of all-solid ISE system combined with a temperature sensor and a pH electrode is proposed to automatically measure the concentrations of the -N. In this study, a soil water content calibration function was established, which significantly reduces a relative error (RE) by 13.09%. The experimental results showed that the stabilization time of this electrode system was less than 15 s with a slope of −51.63 mV/decade in the linear range of 10–5–10–2.2 mol/L. Both the limit of detection of 0.5 ppm of the -N and a relative SD of less than 3% were obtained together with the recovery rate of 90–110%. Compared with the UV-Vis spectroscopy method, a correlation coefficient (R2) of 0.9952 was obtained. The performances of this all-solid ISE system are satisfied for measuring the -N in the field.

Acrylate polymers of triazine containing chalcone moiety: Synthesis, characterization, reactivity ratio and photocrosslinking studies

Acrylate monomer ((4-(3-(4-((4-(4-(3-(2,4-dichlorophenyl)-3-oxoprop-1-en-1-yl)phenoxy)-6-((4-nitrophenyl)amino)-1,3,5-triazin-2-yl)oxy)phenyl)-3-oxoprop-1-en-1-yl)phenyl acrylate (DTCP) is prepared and used to prepare poly (DTCP) and its copolymer poly (DTCP-co-HEA) and poly (DTCP-co-S) using 2-hydroxyethyl acrylate (HEA), styrene (S) by solution polymerization technique. Infrared spectroscopy (FT-IR), proton Nucleharmar Magnetic Resonance (1H NMR), and UV-Visible techniques are used to identify the synthesized polymers. Gel permeation chromatography method is used to determine the polymer’s weight average molecular weight, which is found to be around 10000 g/mol. According to the Thermo Gravimetric Analysis study, the synthesized polymers go through single stage decomposition centered at 340°C. The polymer reactivity ratio is found using well known Finemann-Ross (F-R), Kelen-Tudos (K-T), and extended Kelen-Tudos (ex.K-T) methods. The reactivity of the commercial monomers (HEA or S) is found to be higher than that of synthesized monomer, according to our findings. The photocrosslinking rate of the synthesized polymers is determined using a UV visible spectroscopic method and found to be high for polymer having HEA unit.

Effect of Fe substitution on the structural, microstructural and dielectric properties of sodium bismuth titanate

Lead free sodium bismuth titanate (NBT) is widely being studied as an emerging room temperature multiferroic and as a ferroelectric material with potential to replace toxic lead based ceramics. Various elements can be substituted in the A-site or B-site to improve its electrical and magnetic properties. In this work, pure and Fe substituted NBT having the chemical formula Na0.5Bi0.5Ti(1-x)FexO3 (x = 0.00, 0.02) were synthesized using sol gel auto ignition method to study the effect of Fe substitution on the properties of NBT. XRD analysis confirmed the rhombohedral symmetry of the synthesized samples and the crystallite size of the samples were calculated using Scherrer’s formula. The morphological property of the samples was studied from the SEM images. UV–Visible Spectroscopy method was employed to study the optical properties of the samples. The dielectric properties of the samples were measured as a function of frequency in the range 100 Hz to 1 MHz at room temperature and also as a function of temperature in the range of 298 K- 473 K using an Agilent HP4284 LCR meter. Usual dispersive behavior of dielectric constant was observed for both the samples at the studied temperature range. Study of frequency and temperature dependence of the AC conductivity suggested that the conduction process in the materials is thermally activated. Jonchers’ universal power law was used to fit the AC conductivity curves to describe the dynamics of charge carrier with suitable conduction mechanism.

Method Development and Validation of Azelnidipine Drug by Ultraviolet Visible Double Beam Spectrophotometer

Azelnidipine is a ca2 channel blocker used for treatment of patients with hypertension. The main objective was to develop UltraViolet- visible spectroscopy method for Azelnidipine which should be fast error-free exact sensitive and validate the processed method according to ICH guidelines by use of API and tablet formulations of Azelnidipine by UV-visible spectroscopy. UV-visible Spectrophotometric resolution was carried out with Thermo scientific GENESYS 10S single beam spectrophotometer. A simple rapid precise accurate and sensitive UV-visible Spectroscopy method has been developed for the determination of Azelnidipine by using acetone as a medium. The spectrum of the standard solution was run from 200-400 nm range for the determination of lambdamax and lambdamax of Azelnidipine was found at 255 nm. Different validation parameters such as Linearity Accuracy Precision LOD and LOQ and Robustness and various Quality Control tests like here evaluated as per ICH guidelines. Linearity for the UV-visible Spectroscopy was noted in the concentration range of 2-14microgml and mean correlation coefficient of 0.9993. Accuracy was found to be 98- 100. The precision demonstrates as relative standard deviation of Intraday and Interday which was 1.058-1.029 and 1.144-1.316 with RSD less than 2 and the limit of detection which was LOD and limit of Quantitation LOQ for Azelnidipine was found to be 2.086 and 8.68 microgmml respectively. The proposed UV-visible spectroscopy method and its validation according to the ICH guidelines shown that method is sensitive precise accurate and simple for the estimation of Azelnidipine API and tablet formulation.

Rapid UV-Vis spectroscopy methods for quantification of ranitidine tablets

Ranitidine is a histamine H2-receptor antagonist that inhibits gastric acid secretion, commonly used in the treatment and prophylaxis of peptic ulcer and gastroesophageal reflux disease. Over-the-counter ranitidine hydrochloride tablets are available in several European countries as well as the US for the relief of indigestion and heartburn. Commercial tablets containing the equivalent of 150 mg of ranitidine were analysed following extraction. Ranitidine is water-soluble, thus avoiding the use of organic solvents. Standard aqueous solutions of ranitidine hydrochloride were used to construct a calibration curve. This graduate laboratory experiment describes a simple, inexpensive, safe, and “green” procedure for the quantification of ranitidine tablets by UV spectrophotometry. The entire procedure provides an pedagogical opportunity to approach a realistic analytical scenario, typical of a quality control laboratory, by designing an attractive and engaging hands-on session. An average content of 148 ± 1 mg of ranitidine was determined using both standard addition and external calibration methods and results are in agreement with Pharmacopoeia. Keywords: Analytical chemistry, ranitidine, drugs/pharmaceuticals, quantitative analysis, UV-Vis spectroscopy

Synthesis, spectral characterization, X-ray crystallography and biological evaluations of Pd(II) complexes containing 4(N)-substituted thiosemicarbazone

Four new Pd(II) complexes have been synthesized by reacting equimolar ratio of [PdCl2(PPh3)2] and 4(N)-substituted 4,6-dimethoxysalicylaldehyde thiosemicarbazone ligands in toluene and characterized by UV-Vis, IR and NMR. Single crystal X-ray diffraction studies of 2 and 3 revealed that both the complexes have distorted square planar geometry around palladium ion, in which the ligand coordinates through NS and form five-membered rings. Interaction of complexes with calf thymus DNA (CT-DNA) has been examined by absorption titration, suggesting intercalation. Binding of complexes with Bovine serum albumin (BSA) protein using UV-Visible and fluorescence spectroscopic methods indicated strong binding of complexes to BSA. The antioxidant properties of all the complexes showed moderate activity as compared to standard BHT. The cytotoxicities of the Pd(II) complexes were investigated in vitro against both lung cancer (A549) and human breast cancer (MCF-7) cell lines by using MTT assay and by using (AO/EB and DAPI) staining method for cytological changes in cell lines.

Complexes of Transition Metals with Petroleum Porphyrin Ligands: Preparation and Evaluation of Catalytic Ability

In the present work, the first data on the catalytic activity of d-metal complexes of petroleum porphyrins obtained via two-stage re-metallization (acid demetallization with subsequent metalation) of high-purity petroleum vanadyl porphyrins are presented. During acid demetallization of petroleum vanadyl porphyrins, the highest yield (49%) and spectral purity of free petroporphyrin bases were achieved with concentrated sulfuric acid and a diluted solution of vanadyl porphyrins in chloroform. In the series of divalent cations of Mn, Fe, Co, Ni, Cu, and Zn, only the last four metals are complexed with demetallated petroporphyrins without significant changes in their component composition, whereas the interaction with Mn and Fe cations causes an evident structural transformation or even full degradation of petroporphyrin macrocycles, respectively. The composition and spectral purity of petroleum porphyrin-containing reactants and products were analyzed by FT-IR, UV-Vis, NMR, and MALDI-TOF mass spectroscopic methods. The obtained petroporphyrin-based d-metal complexes were assayed by the reaction of 2-mercaptoethanol oxidative dimerization, in which the copper porphyrins exhibited the highest catalytic activity.