Zeitschrift für chemische Wissenschaften

Coffee and black tea, two common beverages, were investigated as potential electron donors to reduce Cr(VI) to Cr(III). Antioxidant capacity experiments showed that both coffee and black tea are strong antioxidants that provide electrons. When 2 grams of either fresh coffee or black tea were applied to 25 mL of 20 mg/L Cr(VI) solution, all of the Cr(VI) disappeared within 10 minutes. When, instead of using fresh coffee and black tea, residue collected after brewing was applied to the Cr(VI) solution, most of the Cr(VI) disappeared with the used black tea within 3 hours, and approximately 75% of the Cr(VI) was removed with the used coffee within the 8-hour reaction period. The research confirmed that coffee and black tea are excellent, ecofriendly natural electron donors to remediate Cr(VI)-contaminated water without any harmful chemicals. Used coffee and black tea can also be recycled as potential electron providers for Cr(VI) detoxification technology.

Pyrimidine is a prominent member of the diazine family of heterocyclics. Pyrimidine compounds have been explored for use as histamine and adenosine receptor antagonists as well as among several other biological receptors and modulators. The aim of the current research work was to synthesize a new set of tetrachloroquinazolin-2,4-dione derivatives by treatment of N-phenylsulphonyloxytetrachlorophthalimide with some primary aliphatic and aromatic amines via Lossen Rearrangement. The structures of the synthesized compounds were characterized using physical and spectral data such as IR, 1H NMR and mass spectral studies. The newly synthesized compounds were evaluated for their preliminary in vitro antibacterial activity towards Salmonella typhi, Staphylococcus aureus and Bacillus cereus. This study leads us to conclude that quinazolinediones have interesting biological and pharmacological properties towards bacteria.

The kinetics studies of the adsorption and degradation phenomena involved in the photocatalytic degradation of Metanil Yellow (MY) were investigated using a batch reactor and UV light irradiation. Experiments were performed in a suspended ZnO system at natural pH of 6.93 and catalyst concentration of 1 g L-1. The initial concentration of MY varied between 10- 50 mg L-1. The kinetic analysis of the photodecomposition of MY showed that the disappearance followed satisfactorily the pseudo first-order according to Langmuir—Hinshelwood model. From the results, the adsorption was found to be an essential factor in the photodegradability of the dye. The linear transform of the Langmuir isotherm curve was further used to determine the characteristic parameters which were: maximum absorbable dye quantity Qmax = 6.802 mg g_1 and adsorption equilibrium constant Kads = 0.168 L mg_1. The adsorption constant calculated from the linear form of this model, KLH = 0.155 L mg_1 was found reasonably similar to Kads deduced from isotherm adsorption.

The aim of our research was the isolation of the steroidal alkaloid glycosides such as anguivine and isoanguivine from the dried roots of S. anguvi and evaluation of their anti-inflammatory activity by HRBC and carrageenan induced paw edema method. The PASS programme predicts the anti-inflammatory activity of the aglycon part of spirosolenol, on the basis of a similarity structure based drug design. Molecular docking studies with human phospholipase A2 enzyme were carried outby utilizing Argus lab 4.0.1.version. The in silico study and pharmacological activity were correlated with good agreement.

Three sensitive, selective, rapid and easily reproducible spectrophotometric methods (A-C) have been developed for the determination of propranolol hydrochloride (PPH) as a hydrochloride free base propranolol (PPL) in bulk sample and in its dosage forms. These methods are based on ion-pair formation between propranolol as a hydrochloride and free base and three acidic (sulphonphthalein) dyes; namely bromothymol blue (BTB), bromocresol green (BCG) and bromocresol purple (BCP) which induces an instantaneous bathochromic shift of the maximum in the drug spectrum. The colored products are measured at 420 nm (PPL-BTB complex and PPL-BCP complex) and 425 nm (PPL-BCG complex). The reactions were extremely rapid at room temperature and the absorbance values remained constant for 90 min (method B), and over 24 hrs (method A and C). Conformity to Beer’s law in the range 0.4-7.0 μg ml-1for methods A and B and 0.5-8.4 μg ml-1for method C enabled the assay of dosage forms of the drug. The proposed methods were compared with a reference method; the results obtained were of equal accuracy and precision. In addition, these methods were also found to be specific for the analysis of PPH in the presence of excipients, which are co-formulated in the drug. Satisfactory results were obtained when applied to spiked human urine. A more detailed investigation of the propanolol hydrochloride ion pair complexes were made with respect to its composition indicated by stability constant values.

The conductivity of sodium dodecyl sulphate (SDS) and sodium dodecylbenzenesulphonate (SDBS) has been studied in varying concentrations (0-5 mM) of aqueous KCl solution at 25ºC. Data analysis was based on the conventional treatment of conductivity-concentration data, differential, and integration methods with the aim of knowing the best method. As expected, the conductivity increased with an increase in surfactant concentration; the plot of which showed a kink at critical micelle concentration, cmc (i.e. point of aggregation). The results showed no apparent relationship between the degree of counterion binding, β and [KCl]; and an inverse relationship between the cmc values and [KCl]. β was within 0.4-0.6 for SDS and 0.1-0.3 for SDBS. The cmc of SDS decreased from ca. 8 to 6 mM and that of SDBS from ca. 2 to 1 mM as the [KCl] increased from 0-5 mM. These values are in mutual agreement irrespective of the method used. It was confirmed that in the absence of KCl, values obtained from the integration method were more consistent with those reported in the literature; therefore this method is recommended as the best method for determination of micellisation parameters provided the process is followed by conductivity measurements.

A kinetics investigation of catalysed oxidation of D-(+)dextrose by cerium(IV) have been studied in acidic medium in the temperature range 308-333 K. The reaction has been found to be first order with respect to dextrose in the presence of Rh(III) catalysed. The rate follows first order kinetics in Rh(III) catalysed oxidation reaction. The effect of [HSO4-] has also been observed. A 1:2 stoichiometry is observed in the oxidation. From the effect of temperature on the rate of reaction, the Arrhenius equation and various activation parameters have been computed. A suitable mechanism has been proposed and a rate law explaining the experimental observations is derived.

Useful coating products may be obtained by chemical valorization (glycolysis) of post consumed poly (ethylene terephthalate) (PET) wastes. Glycolysis of PET waste was carried out using poly (propylene glycol) (PPG) of molecular weight 2000. The depolymerized oligoesters obtained were trans-esterified with Castor oil and Jatropha oil which results in the formation of saturated hydroxyl-functional polyester polyols. Two-pack coating systems were formulated using these resins as base component and melamine formaldehyde resins as hardener component. Cured films were tested for their hardness, chemical and corrosion resistance performances. The glycolysis of PET using PPG and polyester polyol formation was characterized using Fourier transform infrared spectroscopy

Methyl 4,6-O-benzylidene-α-D-glucopyranoside (1) was selectively converted to methyl 4,6-O-benzylidene-2-O-(2,6-dichlorobenzoyl)-α-D-glucopyranoside (2) by reaction with 2,6-dichlorobenzoyl chloride using direct method in good yield. Using a wide variety of acylating agents, a series of 3-O-acyl derivatives (2-10) of this 2-substitution product were also prepared. These synthesized derivatives were screened for in vitro antimicrobial activity against ten human pathogenic bacteria and three fungal phytopathogens. The study revealed that the acylated derivatives exhibit promising antibacterial and antifungal activities. The acylated derivatives were found to be more effective against the fungal strains than those of the bacterial pathogens. However, a good number of methyl 4,6-O-benzylidene-α-D-glucopyranoside derivatives exhibited better antimicrobial activity than the standard antibiotics.

Two simple and selective spectrophotometric methods are described for the determination of propranolol hydrochloride (PPH) as base form (PPL) in bulk drug, and in tablets and capsules. The methods are based on the molecular charge-transfer complexation of propranolol base (PPL) with either 2,4,6-trinitrophenol (picric acid; PA) or 2,4-dinitrophenol (DNP). The yellow colored radical anions formed on dissociation, are quantitated at 425 nm (PA method) or 415 nm (DNP method). The assay conditions were optimized. Beer\\\'s law is obeyed in the concentration ranges 2.4-42.0 μg ml-1 in PA method and 9.0-126.0 μg ml- 1in DNP method, with respective molar absorptivity values of 4.97 × 103 and 1.66 × 103 l mol-1 cm-1. The reaction stoichiometry in both methods was evaluated by Job’s method of continuous variations and was found to be 1:1 (PPL:PA, PPL:DNP). The developed methods were successfully applied to the determination of PPL in pure form and commercial tablets/capsules with good accuracy and precision. Statistical comparison of the results was performed using Student\\\'s t-test and F-ratio at 95% confidence level and the results showed no significant difference between the reference and proposed methods with regard to accuracy and precision. Further, the accuracy and reliability of the methods were confirmed by recovery studies via standard addition technique

The present paper describes a simple and sensitive spectrophotometric method for the determination of olanzapine (OLZ) and orphenadrine (ORP) in pure and in dosage forms. The developed method is based on ternary complex formation of drugs under investigation with eosin and lead(II) using methyl cellulose as surfactant. The formed ternary complex which shows maximum absorbance (λmax) at 540 nm for both drugs OLZ and ORP, respectively. The optimum experimental conditions for the ternary complex formation were established. The Beer’s law is obeyed in the concentration ranges, 0.0-35.0 and 0.0-55 μg/mL for both methods. The molar absorptivity values for methods A and B were found to be 1.03 × 104 and 0.51 × 104 L mol-1 cm-1, respectively with the corresponding Sandell’s sensitivity values 0.0303 and 0.0602 μg cm-2. The proposed methods were further applied to the determination of OLZ and ORP in bulk and in pharmaceutical preparations via standard addition technique. No interference was observed from the common adjuvants added to the tablets which are applicable for the assay of the investigated drugs in different dosage forms.

18 Ni 250 grade maraging steel is a potential high strength steel for advanced technologies such as aerospace, nuclear, and sporting goods. The corrosion inhibition of the aged 18 Ni 250 grade maraging steel in 0.67 M phosphoric acid by 3,4 dimethoxybenzaldehydethiosemicarbazone (DMBTSC) has been investigated by means of potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The effect of concentration of inhibitor and solution temperature on inhibition efficiency of the inhibitor was studied. DMBTSC inhibits corrosion even at very low concentration. Polarisation curves indicate mixed type inhibition behavior affecting both cathodic and anodic corrosion currents. The mechanism of inhibition was discussed on the basis of an adsorption isotherm, as well as calculated thermodynamic parameters. Adsorption of DMBTSC on the annealed maraging steel surface is in agreement with the Langmuir adsorption isotherm model, and the calculated Gibb’s free energy values confirm the spontaneous adsorption

One titrimetric and two spectrophotometric methods, which are simple, rapid, cost-effective and eco-friendly, are described for the determination of methdilazine hydrochloride (MDH) in bulk drug, tablet and syrup formulations based on the oxidation of MDH by Cerium (Ce) (IV). In titrimetry (method A), the acidified solution of MDH is titrated directly with Ce(IV) using ferroin as indicator. The spectrophotometric methods are based on oxidation-reduction reaction involving MDH and Ce(IV), and the resulting Ce(III) is complexed with either arsenazo(III) at pH 7.8±1.0 and absorbance measured at 620 nm (method B) or chromotrope 2R at pH 2.5±0.8 and absorbance measured at 530 nm (method C). Under optimized experimental conditions, titrimetric procedure is applicable over the range of 3-15 mg of MDH, and the reaction stoichiometry is found to be 1:2 (MDH:Ce(IV)). The spectrophotometric methods are applicable over the ranges of 0.4-10.0 μg mL-1 (method B) and 0.4-12 μg mL-1 (method C). The molar absorptivities are calculated to be 3.4×104 and 2.8×104 L mol-1cm-1 for method B and method C, respectively, and the corresponding Sandell sensitivity values are 0.0096 and 0.0118 μg cm-2. The limits of detection are calculated and found to be 0.12 and 0.38 μg mL-1 for method B and method C, respectively, with corresponding limits of quantification of 0.09 and 0.71. The methods were applied to the determination of MDH in tablets and syrup, and the results were compared statistically with those of a reference method.

A stability-indicating LC assay method was developed for the quantitative determination of Doxazosin mesylate (DXM) in pharmaceutical dosage form in the presence of its degradation products and kinetic determinations were evaluated in acidic and alkaline degradation conditions. Chromatographic separation was achieved by use of LiChroCART-Lichrosphere100 RP-18 column (250 × 4.0 mm, 5 m). DXM degraded in acidic, alkaline and hydrogen peroxide conditions, while it was more stable in thermal and photolytic conditions. The described method was linear over a range of 1.0-300 g mL-1 for determination of DXM (r= 0.9992). The acid degradation of DXM in 1M HCl solution showed zero-order kinetics with rate constant 0.45 mole liter-1 minutes-1, while the alkaline degradation with 1M NaOH demonstrated first-order kinetics with rate constant k = 0.0044 min−1. The half-life (t0.5) and shelf life (t0.9) values were also determined for both the kinetic studies. F-test and t-test at 95% confidence level were used to check the intermediate precision data obtained under different experimental setups; the calculated value was found to be less than critical value. The developed method was found to be simple, specific, robust, linear, precise, and accurate for the determination of DXM in pharmaceutical formulations.

In recent years there has been a tremendous increase of drug resistant pathogens, especially M. tuberculosis, leading to the design and development of newer antimycobacterial compounds. The reaction of 3-amino-2-(2-chlorophenyl) quinazolin-4(3H)-one with various 2-chloro-N-(substituted phenyl)acetamide derivatives provided the target compounds. The structure of the compounds has been confirmed by IR, 1H NMR and Mass spectral data. Antitubercular and antibacterial activities were performed by microbroth dilution and cup plate method respectively. The compounds have shown significant antitubercular and moderate antibacterial activity when compared with the standard drugs.

A facile microwave assisted one-pot synthesis of novel 1-(2-hydroxyethyl)-3-alkyl/aryl/aralkyl/hydroxyethyl-5-oxo-1,2,3,4,5,6,7,8-octahydroquinazolines 3a-h and 3,3’-(alkanediyl) bis (1-(2-hydroxyethyl)-5-oxo-1,2,3,4,5,6,7,8-octahydroquinazolines) 4a-d has been devised by the cyclocondensation of cyclic enaminones 2a-b with primary amines/diamines and formaldehyde. The structures of the products have been established by spectral and analytical data. The present paper describes a one-pot, efficient, clean, simple, fast and environment friendly strategy for the synthesis of hitherto unknown octahydroquinazolines and bis-octahydroquinazolines from easily accessible starting materials in good yields with promising biological properties. The methodology reported herein is an example of multi-component reactions (MCRs).

The mononuclear Mn(II) complexes of the type [Mn(L)n(H2O)2Cl2] (where n= 1 or 2) were prepared with biologically important drugs viz. Clomiphene citrate (CPC), Imipramine hydrochloride (IMH), Diphenylpyraline hydrochloride (DPH), Embramine hydrochloride (EBH), and Dothiepin hydrochloride (DOT), and characterized by using elemental analysis, infra-red (IR), UV-visible spectra, X-ray powder diffraction studies and thermogravimetric analysis. The molar conductance measurement of all the complexes in DMF solution corresponds to non-electrolytic nature. All complexes were of the high-spin type and found to have six-coordinate octahedral geometry. The antimicrobial activity of these complexes has been screened against two gram-positive and two gram-negative bacteria. Antifungal activity against two different fungi has been evaluated and compared with standard drug. All the complexes inhibit the growth of both gram positive and gram negative bacteria to competent level.

Dinuclear complexes from salicylaldehyde and 2-aminophenol with Cu (II), Ni (II) & Co (II) were obtained by new synthetic route and characterized. Elemental and metal compositions of these complexes were obtained. Infrared, UV – visible (absorption & emission) spectroscopy and mass spectrometry data were utilized for structure elucidation. The TGA thermograms of the complexes supported proposed structure. Magnetic properties of these complexes were extensively studied using Guoy balance at room temperature and vibrating sample magnetometer at variable temperatures. Low temperature intramolecular ferromagnetism was exhibited by homodinuclear complex while the heterodinuclear complexes showed antiferromagnetic coupling. A probable mechanism for the formation of the complexes was proposed. The most stable structure was identified using molecular mechanical method.

Thin layer of stannous silicate was used to study the chromatographic behavior of 18 metal ions in surfactant mixed solvents. Effect of presence of alcohol at various concentrations, presence of strong and weak electrolytes, effect of concentration of surfactant, effect of acidity and basicity of aqueous surfactant on mobility of metal cations were also studied. By using surfactant and with various additives mixed in mobile phase, metal ions such as Cu2+ - Hg2 + and UO22+ - Ni2+ were separated from their binary mixture. Semi-quantitative determination of Ni2+ by measurement of spot area was attempted.

Three spectrophotometric methods are described for the determination of memantine hydrochloride (MTH) in bulk and tablet dosage forms. The methods are based on the formation of ion-pairs of the MTH with anionic dyes such as bromothymol blue (BTB) and solochrome black T (SBT), which are extracted into chloroform and have absorption maxima at 415 nm (BTB) and 510 nm (SBT). Regression analysis of the Beer\\\'s plots showed good correlation in the concentration ranges 2–20 and 5–25 μg/mL for BTB and SBT, respectively. The proposed methods were successfully applied to the tablet dosage forms containing the MTH. No interference from common excipients was observed.

The development of resistant pathogenic microorganism against conventional antibiotic drugs has risen to a point of global concern. New antimicrobial compounds with diverse chemical structures and novel mechanisms of action are therefore needed to curb the new and re-emerging infectious diseases. This study has identified two Phyllanthus species (Phyllanthus amarus, Phyllanthus odontadenius) sampled from Nairobi and Siaya counties in Kenya. In vitro activity of extracts of these species and correlated their efficacy was compared with the commercial extracts of P. niruri that are in the Kenyan market. Disk diffusion method was employed to screen the antimicrobial activities of both the extracts and two standard antibiotics; 0.32mg mL-1 gentamycin and 0.30 mg mL-1 Nystatin. The dichloromethane(DCM):methanol (1:1) extracts of Phyllanthus odontodenius showed the strongest activity against all the organisms both at 100 mg μL and 50 mg μL-1 followed by both the hot water and cold water methanol extracts. The solvents in comparison to antibiotics showed 80% activity for methanol, 48% for DCM:MeOH 1:1, 43% in hot water and 28% for cold water. Thin layer chromatography (TLC) showed that the compounds found in the three species were identical. This study has shown that, the two species possess significant antimicrobial activity and justifies the use of their extracts by herbalists in the treatment of many microbial diseases. Therefore, further bioassay guided fractionation, isolation and characterization studies of compounds from these extracts are needed to confirm the active components and mechanisms of action of these two species.

The micellisation behaviour of cetyltrimethylammonium bromide (CTABr) in different mass fraction (17–47) of ethylene glycol (EG), dimethylsulfoxide (DMSO), and dimethylformamide (DMF)–water mixed solvents, was investigated using electrical conductivity measurement at different temperatures (293.1–313.1 k). The critical micelle concentration and degree of counterion dissociation ( ) values increased with increase in the amount of EG, DMSO, and DMF but micellisation was found to be unfavourable in the presence of the co-solvents. The results of the thermodynamic analysis showed that addition of organic solvents, which are principally located in the bulk phase made the micellisation process less spontaneous. The London dispersion interaction represented the major attraction force for micellisation and micellisation proceeded via an exothermic process. The difference in the magnitude of o m S value between the CTAB–water and CTAB–water-co-solvent medium is a pointer to the fact that the micellisation in CTAB–water-co-solvent system is favoured by entropy gain. This indicated that the solvents still controlled the three mdimensional water matrix and the micellisation process of the studied surfactant is exothermic though the positive values of o m S , are due to the melting of flickering cluster around hydrocarbon ends of the surfactant monomer and increased the randomness of the hydrocarbon chains in the micelle core.

A simple and sensitive visible spectrophotometric method has been developed for the determination of pramipexole dihydrochloride (PPD). The method is based on the condensation of the drug with acetyl acetone and formaldehyde producing a yellow colored Hantzsch condensation product having maximum absorption at 455 nm. The method is optimized for pH, concentration of reagents (acetyl acetone and formaldehyde) required, temperature and heating time. Beer’s law was obeyed in the concentration range of 5–150 μg mL-1. Molar absorptivity, Sandell’s sensitivity, limit of detection and limit of quantification were calculated and were found to be 5.23 x 103 L mole-1 cm-1, 0.0849 μg cm-2, 0.449 μg mL-1, and 1.362 μg mL-1, respectively. The method was applied to different tablet dosage forms containing PPD. The results of the proposed method were compared with the reported UV spectrophotometric method. The new method was found to be simple, accurate (t-test), and reproducible (F-test).

The rates of hydrolysis of p-Methyl Benzyl-2-Theno Hydroxamic Acid have been studied over a wide range of acidities in hydrochloric, sulphuric, and perchloric acids in 20% (v/v) dioxane-water at 55ºC. Plots of the first order rate constant, Kobs against H+ show maxima, which are caused by protonation of the substrate. The kinetics of the hydrolysis has been analyzed by Bunnett, Bunnett Olsen and Cox-Yates excess acidity methods. The variation of reaction rate with acid concentration can be described by a two parameter equation. The mechanism of the reactions was found to be A-2, which involves two steps. A rapid protonation is followed by rate determining step in which nucleophilic attack of water at the carbonyl carbon takes place giving a tetrahedral intermediate, which rapidly changes to the hydrolytic products. Arrhenius activation parameters were also determined.

Four simple and sensitive visible spectrophotometric methods have been developed for the assay of dutasteride. Method I describes the interaction of dutasteride, as an n-electron donor, with chloranil, as a pi-acceptor, in acetonitrile to give reddish orange colored chloranil radical anion with absorption maxima at 525 nm. Method II involves the oxidative coupling reaction of dutasteride with 3-methyl-2-benzothiazolinone hydrazone hydrochloride in the presence of ferric chloride in an acidic medium, which results in a green colored product with absorption maxima at 550 nm. Methods III and IV are based on the formation of ion-pairs of dutasteride with bromothymol blue and bromophenol blue, which are extracted into chloroform and exhibit absorption maxima at 425 (bromothymol blue) and 435 nm (bromophenol blue). Regression analysis of Beer’s law plot showed good correlation in the concentration range of 2–40, 1–20, 5–50, and 2–20 μg mL−1 for Methods I, II, III, and IV, respectively. Different variables affecting the reaction were studied and the experimental conditions were optimized. The proposed methods were applied successfully to analyze dutasteride in tablets dosage forms. No interference was observed from common pharmaceutical excipients.

A facile microwave-assisted one-pot synthesis of novel 1-phenylethylhexahydro quinazolin-5 (6H)-ones 3a–j and bis-1-phenylethylhexahydro quinazolin-5 (6H)-ones 4a–f and 5a–d has been devised by the cyclocondensation of cyclic enaminones 2a–b with primary amines/diamines and formaldehyde. The structures of the products have been established with the help of spectral and analytical data.

In the present work, the copolymerization of ε-caprolactone with tetrahydrofyran using a proton exchanged Montmorillonite clay as initiator is reported. The effects of the amounts of Mag-H and the temperature on the synthesis of poly(ε-caprolactone-co-tetrahydrofuran) were studied. The copolymer obtained was characterized by 1H-NMR spectroscopy.

Marine source plays an important role in the form of pharmaceutical care and for the discovery of new molecular structures (i.e. targets). Marine organisms are a source of new therapeutics, especially for oncology, as a tremendous chemical diversity is found in marine bacteria, fungus, cyanobacteria, seaweeds, mangroves, microalgae and other halophytes. Several marine-derived compounds are currently extracted and synthesized by chemical processes for cancer treatment. By studying various papers related to marine source for new therapeutics for cancer treatment instead of other chemical enriched sources, the marine sources are largely unexplored for anti-cancer lead compounds. Hence this paper reviews results on the aspect with a view to provide basic information about the methods to produce extracts from marine organisms that are unique and different from that used by marine natural products chemists previously, yields both organic solvents and water soluble material for anti-cancer screening purpose. Chemists synthesize these compounds and their analogues in the laboratory for studying their activity towards various cancer cell lines.