Humeida A. El-Obeid

A Selective Colorimetric Method for the Determination of Penicillins and Cephalosporins with α-Aminoacyl Functions

A simple, sensitive and selective colorimetric method is described for the assay of ampicillin, amoxicillin, cephalexin, cefadroxil and cefaclor in their pharmaceutical preparations. The method is based on measuring the color obtained when the alkaline degradation products of these agents are allowed to react with ascorbic acid. The factors affecting the color generation and determination were studied and optimized. The reaction is selective to β-lactam antibiotics having amino acid side-chains with free amino functions and thus allow interference-free quantitation of some preparations containing these agents in combination with other β-lactam agents. The procedure is also successfully adopted as stability-indicating method for cephalosporins. A tentative mechanism of the color reaction is proposed.

Colorimetric Method for the Determination of Ampicillin and Amoxicillin

A simple colorimetric procedure is described for the quantitation of ampicillin and amoxicillin in their pharmaceutical preparations. The color production is based on the reaction of the oxidation product of ascorbic acid, dehydroascorbic acid, with the corresponding penicillenic acids obtained by the degradation of the antibiotics after heating under acidic conditions. The reaction demonstrated selectivity towards the penicillins having amino acid side chains and thus allowed interference-free quantitation of ampicillin and amoxicillin in combination with cloxacillin or clavulenic acid. The procedure showed good accuracy and precision and offers advantages over the official and many other reported analytical procedures.

Synthesis and Pharmacological Activity of N- Alkyl-1,2-Diphenylethanolamines

A series of N-alkyl-l,2-diphenylethanolamines were synthesized and their pharmacological activities evaluated on various mammalian organs and sytems. All compounds produced a generalized inhibitory effect on smooth and cardiac muscles and an increase in coronary flow as well as a brief reduction in rabbit blood pressure. The latter effect was not prevented by pretreatment of the animals with atropine, propranolol, or metoprolol. The compounds were devoid of local anesthetic activity and their inhibitions of the contraction of the isolated rabbit intestine and perfused heart were reversed by exogenous calcium ions. It is proposed that the compounds produce their effects through calcium-channel blockade. The inhibitory effects of some of these compounds were comparable to those of a known calcium-channel blocker.

Effects of alkali and simulated gastric and intestinal fluids on danazol stability.

The degradation kinetics of methanolic solution of danazol (0.020% w/v) in aqueous buffers and sodium hydroxide was investigated using stability-indicating HPLC method. The drug degrades in alkaline medium through a base-catalysed proton abstraction rather than via an oxidative mechanism involving oxygen species. The degradation followed pseudo-first-order kinetics. The rates pH-profile exhibited specific base catalysis. The stability of the drug was found to be dependent on pH, buffer concentration, buffer species (acetate, borate, phosphate) and temperature. The ionic strength did not affect the stability of the drug. The energy of activation according to Arrhenius plot was estimated to be 22.62 kcal mol(-1) at pH 12 and temperatures between 30 and 60 degrees C. The effect of simulated gastric and intestinal fluids on the drug stability was also investigated. Two major hydrolytic degradation products were separated and identified by IR, NMR and mass spectrometry and the degradative pathway suggested.

PMR Assay of Essential Oils. IV. Assay of Carvone in Caraway and Dill Oils

Abstract A new assay procedure has been developed for the quantitation of carvone as a pure compound and in essential oils using PMR technique. The average recovery of pure carvone in standard mixtures using benzophenone as an internal standard is 100.11 + 0.56% w/w. Using the same procedure for the determination of carvone contents in Caraway and Dill oils, mean values of 61.7 + 0.59% w/w and 63.3 + 0.26% w/w, respectively, are obtained. The results are comparable to those obtained using a reported method. Beside its simplicity and accuracy, the technique may provide a mean for detection of impurities in the oil.

Synthesis and antimicrobial activity of new furan derivatives

Abstract5-Nitrofuran derivatives were synthesized and their antibacterial activity was investigated using standard bacterial strains and clinical isolates. The compounds showed inhibitory effects on both Gram-positive and Gram-negative organisms.

Determination of Diethylcarbamazine Citrate in Tablets by Proton Magnetic Resonance

Abstract A simple, specific and accurate proton magnetic resonance (PMR) procedure has been developed for the quantitative determination of diethylcarbamazine in standard mixtures and tablets. The average recovery of the pure drug in standard mixtures with maleic acid as an internal standard was 100.03 ± 0.11% w/w. Reproducible results were obtained when the drug was determined in its tablet dosage form.

Acetylcholine Chloride: Physical Profile

Publisher Summary This chapter presents the physical profile of acetylcholine chloride. The empirical formula of the acetylcholine chloride is C 7 H 16 ClNO 2 . Acetylcholine chloride is obtained as white or off-white hygroscopic crystals, or as a crystalline powder. The physical properties includes pH, solubility characteristics, crystallographic properties, thermal methods of analysis, spectroscopy and mass spectrometry are discussed. Acetylcholine chloride is freely soluble in water, alcohol, propylene glycol, and chloroform, and is practically insoluble in ether. Acetylcholine chloride is very hygroscopic and extremely soluble, giving a solution of high viscosity. For this reason, it is difficult to prepare crystals appropriate for X-ray analysis. Aqueous solutions of acetylcholine chloride are found to be unstable. Such solutions are decomposed by heat, and are incompatible with alkalis and acids. The mass spectrum of acetylcholine chloride is obtained utilizing a Shimadzu PQ-5000 mass spectrometer, with the parent ion being collided with helium carrier gas and the mass spectrum and the mass fragmentation pattern is shown in the chapter.

Acetylcholine Chloride: Analytical Profile

Publisher Summary This chapter presents several methods employed for the analysis of acetylcholine chloride. These includes titrimetric methods of analysis, electrochemical methods of analysis, spectrophotometric methods of analysis, chromatographic methods of analysis, and other methods of analysis are also discussed in the chapter. Titrimetric methods of analysis include acidimetric methods and potentiometric methods. The transfer of acetylcholine ions across the interface between the gel electrode and water is studied by cyclic voltammetry, potential-step chronoamperometry, and potentiometry. Electrochemical method of analysis includes conductimetric methods, polarographic methods, voltammetric methods, coulometric flow titration methods, flow injection method, and amperometric methods are discussed. Spectrophotometric methods of analysis include infrared spectrophotometric method, photometric methods, mass spectrometric method, colorimetric methods, fluorimetric methods, and chemiluminescence methods. Chromatographic methods of analysis include thin layer chromatography (TLC), gas chromatography (GC), and several other methods are also presented in the chapter. Various other methods, such as ion-selective method, microwave methods, and microdialysis are also discussed in the chapter for the analysis of acetylcholine chloride.

Studies on the cardiovascular depressant effects of N-Ethyl- and N-Benzyl-1,2-diphenylethanolamines in the rat : Elucidation of the mechanisms of action

The influence and mechanisms of action of N-ethyl- and N-benzyl-1,2-diphenylethanolamines (compounds E and B, respectively) on the arterial blood pressure and the heart rate of the rat together with their effects on CaCl2-induced arrhythmias in the rat were investigated. Both E and B in doses of (1.5-12 micromol/kg IV) decreased the arterial blood pressure and the heart rate in a dose-dependent manner. Studies with various receptor blockers, enzyme inhibitors and CaCl2 revealed that E-induced cardiovascular depressant effects were mainly due to CaCl2 channel blocking action and activation of cyclic guanylyl cyclase or release of NO whereas the cardiovascular effects of B seemed to involve both blockade of Ca2+ channels and activation of parasympathetic ganglia. Both compounds (12-14.5 micromol/kg) completely protected the rat against CaCl2 (60 mg kg(-1))-induced tachyarrhythmias. The B compound seemed to be several times more potent than the E compound in its cardiovascular depressant actions. The results suggest the potential usefulness of both compounds in the treatment of hypertension and supraventricular arrhythmias.