Hassan Y. Aboul-Enein

Analysis of Pharmaceuticals and Biological Fluids Using Modern Electroanalytical Techniques

A review of the principles and application of modern electroanalytical techniques, namely, cyclic voltammetry, linear sweep voltammetry, differential pulse voltammetry, differential pulse polarography, square wave voltammetry, square wave polarography, stripping voltammetric, and stripping polarographic techniques, is presented. The use and advantages of these techniques at different electrodes are discussed. The analytical applications of these techniques to pharmaceutical compounds in dosage forms and biological media are also discussed. Various selected studies on these subjects since 1995 are reviewed.

Chiral Separations By Liquid Chromatography And Related Technologies

Chirality and its occurrence Polysaccharide-based chiral stationary phases Cyclodextrin-based chiral stationary phases Macrocyclic glycopeptide antibotics-based chiral stationary phases Protein-based chiral stationary phases Ligand exchange-based chiral stationary phases Crown ether-based chiral stationary phases Miscellaneous types of chiral stationary phases Enantiomeric separation by the chiral mobile phase Additives.

Radical scavenging activity and antioxidant capacity of bay leaf extracts

Bay leaves (BL) (Laurus nobilis L., Family: Lauraceae) are traditionally used orally to treat the symptoms of gastrointestinal problems, such as epigastric bloating, impaired digestion, eructation, and flatulence. In this study, lyophilized extracts (both water and ethanol) of BL were studied for their antioxidant properties. The antioxidant activity, reducing power, free radical scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging and metal chelating activities were evaluated to determine the total antioxidant capacity of both BL extracts. Both extracts exhibited strong total antioxidant activity in linoleic acid emulsion. Concentrations of 20, 40, and 60 μg ml−1 showed 84.9, 95.7, 96.8, and 94.2, 97.7, and 98.6% inhibition of lipid peroxidation of linoleic acid emulsion, for water and ethanol extracts, respectively. On the other hand, 60 μg ml−1 of the standard antioxidants butylated hydroxyianisole (BHA), butylated hydroxytoluene (BHT), and α-tocopherol exhibited 96.6, 99.1, and 76.9% inhibition of lipid peroxidation in linoleic acid emulsion, respectively. In addition, the both BL extracts had effective reducing power, DPPH⋅ free radical scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging and metal chelating activities at 20, 40, and 60 μg ml−1. The total amount of phenolic compounds in each BL extract was determined as gallic acid equivalents.

High-performance liquid chromatographic enantioseparation of drugs containing multiple chiral centers on polysaccharide-type chiral stationary phases.

Enantioseparation of drugs with multiple chiral centers is challenging. This article describes resolution of some drugs with multiple chiral centers using polysaccharide-type chiral stationary phases. Also, the use of the column-switching technique is demonstrated to achieve the resolution of this type of compounds.

Macrocyclic antibiotics as effective chiral selectors for enantiomeric resolution by liquid chromatography and capillary electrophoresis

SummaryThe separation of enantiomers by liquid chromatography and capillary electrophoresis is important in pharmaceutical, environmental, and agricultural analysis. Of the different types of chiral selector used for enantiomer resolution the macrocyclic antibiotics are considered particularly effective. Only eight antibiotics, vancomycin, teicoplanin, thiostrepton, rifamycin B, kanamycin, streptomycin, fradiomycin, and ristocetin A have yet been used as chiral selectors for separation of the enantiomers of a variely of compounds by liquid chromatography and capillary electrophoresis. This review describes the chemistry of these antibiotics, the effect of chromatographic conditions on enantioselectivity, the mechanism of resolution, the applications and limitations of the compounds, and detection in liquid chromatography and capillary electrophoresis with these antibiotics as the chiral selectors.

Instrumental Methods in Metal Ion Speciation

INTRODUCTION Importance of the Environment Environmental Pollutants Metal Ions Speciation Metal Ion Speciation and the Environment Methods Of Metal Ion Speciation Detection in Chromatography and Capillary Electrophoresis METAL ION SPECIES: SOURCES AND DISTRIBUTION Sources of Contamination Distribution of Metal Ions Mechanisms of Metal Ions Contamination METAL ION SPECIES: TOXICITIES, BIOTRANSFORMATION, AND BIODEGRADATION Modes of Bioactivity and Toxicities of Metal Ions Toxicities of Metal Ions Biotransformation of Metal Ions Biodegradation of Metal Ions Essentiality versus Toxicity of Metal Ions SAMPLE PREPARATION Sampling Preservation Filtration Digestion/Homogenization Extraction Membrane Methods in Sample Preparation Enzymatic Hydrolysis Other Extraction Methods Cleanup Preconcentration SPECIATION OF METAL IONS BY GAS CHROMATOGRAPHY Applications Optimization of Metal Ion Speciation Derivatization of Metal Ions Mechanisms of Metal Ions Speciation Errors and Problems in Metal Ions Speciation SPECIATION OF METAL IONS BY REVERSED-PHASE HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY Applications Optimization of Metal Ion Speciation Derivatization of Metal Ions Mechanisms of Metal Ions Speciation SPECIATION OF METAL IONS BY ION CHROMATOGRAPHY Applications Optimization of Metal Ion Speciation Mechanisms of Metal Ions Speciation SPECIATION OF METAL IONS BY ION-PAIR, MICELLAR ELECTROKINETIC, SIZE EXCLUSION, CHIRAL, CAPILLARY ELECTRO-, AND SUPERCRITICAL FLUID CHROMATOGRAPHIC METHODS Ion-Pair Chromatography Micellar Electrokinetic Chromatography Size Exclusion Chromatography Chiral Chromatography Capillary Electrochromatography Supercritical Fluid Chromatography Mechanisms LC versus GC SPECIATION OF METAL IONS BY CAPILLARY ELECTROPHORESIS Application of Capillary Electrophoresis for the Speciation of Metal Ions Optimization of the Speciation Validation of the Methods Effect of Interfering Ions Mechanisms of Metal Ion Speciation Capillary Electrophoresis versus Chromatography SPECIATION OF METAL IONS BY SPECTROSCOPIC METHODS UV-Visible Spectroscopy Atomic Absorption Spectroscopy Inductively Coupled Plasma Spectrometry Mass Spectrometry X-Ray Spectroscopy Miscellaneous Spectroscopic Methods SPECIATION OF METAL IONS BY ELECTROCHEMICAL AND RADIOCHEMICAL METHODS Electrochemical Methods Radiochemical Methods Miscellaneous Methods PERSPECTIVES AND LEGISLATION OF METAL ION SPECIATION The Future of Speciation Risk Assessment and Legislation Metal Ion Speciation and Legislation International Scenario of Legislation *Each Chapter contains a Conclusion and References

A Study on the In Vitro Antioxidant Activity of Juniper (Juniperus communis L.) Fruit Extracts

Abstract This study aimed at evaluating the in vitro antioxidant activity of water and ethanol extracts of juniper (Juniperus communis L., Family Cupressaceae) fruit. The antioxidant properties of both Juniper extracts were studied using different antioxidant assays, including reducing power, free radical scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, and metal chelating activities. Both the water and the ethanol extracts exhibited strong total antioxidant activity. The concentrations of 20, 40, and 60 µg/mL of water and ethanol extracts of juniper fruit showed 75%, 88%, 93%, 73%, 84%, and 92% inhibition on peroxidation of linoleic acid emulsion, respectively. On the other hand, 60 µg/mL of standard antioxidant such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), and α‐tocopherol exhibited 96, 96, and 61 inhibitions on peroxidation of linoleic acid emulsion, respectively. However, both extracts of juniper had effective reducing power, free radical scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, and metal chelating activities at these same concentrations (20, 40, and 60 µg/mL). Those various antioxidant activities were compared to BHA, BHT, and α‐tocopherol as standard antioxidants. In addition, total phenolic compounds in both aqueous and ethanolic juniper extracts were determined as gallic acid equivalents. Accordingly, these results indicate that juniper has in vitro antioxidant properties and these may be major reasons for the inhibition of lipid peroxidation properties.

Optimization strategies for HPLC enantioseparation of racemic drugs using polysaccharides and macrocyclic glycopeptide antibiotic chiral stationary phases

The chiral resolution by high performance liquid chromatography (HPLC) is controlled by a number of parameters. The optimization of HPLC parameters is an important issue in chiral resolution. This review discusses the optimization of HPLC conditions for the chiral resolution of racemic drugs on polysaccharides and macrocyclic glycopeptide antibiotic chiral stationary phases (CSPs). The most important parameters discussed are composition of mobile phase, pH of mobile phase, flow rate, temperature and effect of other parameters.

Improvement of water solubility and in vitro dissolution rate of gliclazide by complexation with β-cyclodextrin

Inclusion complexes of gliclazide with beta-cyclodextrin were prepared using different two methods: neutralization and recrysstalization. Host-guest interactions were studied in the solid state by X-ray diffractometry and infrared spectroscopy. The stability constant between gliclazide and beta-cyclodextrin was calculated from the phase solubility diagram. It was found that the neutralization technique and a solid complex of gliclazide with beta-cyclodextrin in a molar ratio of 1.5:1 could be used to prepare the amorphous state of drug inclusion complexes. The dissolution rates of gliclazide from the inclusion complex made by neutralization was much faster than the pure drug, physical mixture of drug and cyclodextrin, recyristalization system and also comparable to the data reported in literature. Results of this report indicate that beta-cyclodextrin could be useful for the solid gliclazide formulations as it may results in a more rapid and uniform release of the drug.

Studies on the effect of alcohols on the chiral discrimination mechanisms of amylose stationary phase on the enantioseparation of nebivolol by HPLC.

The chiral recognition mechanism of amylose CSPs has been described by achieving the enantiomeric resolution of (+/-)-nebivolol on Chiralpak AD and Chiralpak AD-RH columns with methanol, ethanol, 1-propanol, 2-propanol, 1-butanol as mobile phases at different flow rates. The energies of interactions of methanol, ethanol, 1-propanol, 2-propanol and 1-butanol with both phases were calculated. The (+)-RRRS enantiomer eluted first when using methanol, ethanol and 1-propanol, while the elution order was reversed when using 2-propanol and 1-butanol as the mobile phases. It has been concluded that the reversal elution order observed was due in part to the chiral cavities on the amylose CSP which were responsible for the bondings of different magnitude between chiral stationary phase and enantiomers, which are influenced with the type of alcohol used as mobile phase on the conformation of the 3,5-dimethyl phenyl carbamate moiety on the pyranose ring system of the amylose.