King Faisal Specialist Hospital & Research Centre

About: King Faisal Specialist Hospital & Research Centre is a healthcare organization based out in Riyadh, Saudi Arabia. It is known for research contribution in the topics: Medicine & Detection limit. The organization has 58 authors who have published 157 publications receiving 3527 citations.

Determination of Amlodipine in pharmaceutical formulations by differential-pulse voltammetry with a glassy carbon electrode

Abstract: A differential-pulse voltammetric method was developed for the determination of amlodipine based on the oxidation of the dihydropyridine group on the surface of glassy carbon electrode under stationary and rotating conditions. The experiments were conducted in a supporting electrolyte consisting of 0.2 MKCl, 0.1 Mphosphate buffer, and 10 % (v/v) methanol during investigation of initial potential and pH effects. No adsorption effect was observed on using an initial potential of 0 mVand the supporting electrolyte solution at pH 5.5 under both stationary and rotating conditions. The factor affecting the voltammetric current was diffusional in the range of 200-1000 rpm for rotating, and 2-40 mV s(-1) for stationary conditions up to a concentration of 0.04 mg mL(-1) amlodipine. The limit of detection (LOD) and the limit of quantitative (LOQ) for the rotating and stationary techniques were found to be 0.004 and 0.0072 mg mL(-1) (for S/N = 3.3) and LOQ 0.012 and 0.022 mg mL(-1) (for S/N = 10), respectively. The proposed method was applied to the tablets containing amlodipine and according to the statistical evaluations acceptable results were obtained at the 95 % probability level.

Scavenging of reactive oxygen species by N-substituted indole-2 and 3-carboxamides

Abstract: Indole-2 and 3-carboxamides (IDs) are proposed to be selective cyclooxygenase inhibitors. Since cyclooxygenase-1 may be involved in reactive oxygen species (ROS) production, we hypothesize that these indole derivatives have antioxidative properties. We have employed chemiluminescence (CL) and electron spin resonance (ESR) spin trapping to examine this hypothesis. We report here the results of a study of reactivity of 10 selected indole derivatives towards ROS. The following generators of ROS were applied: potassium superoxide (KO2) as a source of superoxide radicals (O2·−), the Fenton reaction (Co-EDTA/H2O2) for hydroxyl radicals (HO·), and a mixture of alkaline aqueous H2O2 and acetonitrile for singlet oxygen (1O2). Hydroxyl radicals were detected as 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) spin adduct, whereas 2,2,6,6-tetramethyl-piperidine (TEMP) was used as a detector of 1O2. Using the Fenton reaction, 0.5 mmol/L IDs were found to inhibit DMPO-ȮH radical formation in the range 7–37%. Furthermore the tested compounds containing the thiazolyl group also inhibited the 1O2-dependent TEMPO radical, generated in the acetonitrile + H2O2 system. About 20% inhibition was obtained in the presence of 0.5 mmol/L IDs. 1 mmol/L IDs caused an approximately 13–70% decrease in the CL sum from the O2·− generating system (1 mmol/L). The aim of this paper is to evaluate these indole derivatives as antioxidants and their abilities to scavenge ROS. Copyright © 2004 John Wiley & Sons, Ltd.

Validated Method for Determination of α‐Lipoic Acid in Dietary Supplement Tablets by Reversed Phase Liquid Chromatography

Abstract: A rapid high performance liquid chromatographic method was developed and validated for the determination of α‐lipoic acid in pharmaceutical dosage forms. The analysis was performed using a reversed phase Supelcosil LC‐18 (150 × 4 mm, 3 µm) column. The mobile phase consisted of acetonitrile:0.05 M potassium mono‐phosphate, pH 2.5 (45:55 v/v) at a flow rate of 0.8 mL/min. The UV‐detector was set at 332 nm. The developed method showed a good linear relationship in the concentration range from 10–500 µg/mL with a correlation coefficient from 0.9999. The limit of detection and limit of quantification were 4.4 and 16.8 µg/mL, respectively. These values are high due to the low absorption coefficient of pure lipoic acid (ϵ = 150) at 332 nm. Statistical analysis proves that the method is reproducible.