Alaa Khedr

3-Bromomethyl-propyphenazone as a new derivatization reagent for high performance liquid chromatography of captopril and hydrochlorothiazide with UV-detection.

3-Bromomethyl-propyphenazone (BMP) was used as a derivatization reagent for the detection and quantification of captopril (CAP) and hydrochlorothiazide (HCT) by high performance liquid chromatography using Zorbax C8 column, and 0.05M sodium acetate, acetonitrile, methanol (14:17:4; pH 6.5) as mobile phase system with UV-detection at 254 nm. The cited reagent reacts with the mercapto and amino groups of CAP and HCT in acetone using anhydrous potassium carbonate as hydrobromide acceptor. The reaction was completed within 30 min for CAP and 60 min for HCT with heating at 105 +/- 5 degrees C in mini-reaction vial. The linear concentration ranges for both CAP and HCT were 8 to 160 and 6 to 140 ng per injection, respectively. The derivatized captopril was synthesized and confirmed with spectral analysis. This method was applied for determination of spiked captopril in human urine after extraction with Extrelut-20 column using ethyl acetate:isopropanol (85:15 v/v) as eluant.

Biological and metabolic study of naproxen-propyphenazone mutual prodrug.

Naproxen-propyphenazone (NAP-PP) esters were synthesized as prodrugs with the aim of improving the therapeutic index through prevention of gastrointestinal irritation and bleeding. The structures of the synthesized NAP-PP hybrid esters were confirmed by IR and 1H NMR spectroscopy and their purity was established by elemental analysis, HPLC and TLC. The release of NAP as well as PP derivatives, from the ester prodrugs was studied. A validated analytical HPLC method for the estimation of the NAP, and the prodrugs was developed. Also the enzymatic hydrolysis products of the ester were identified by GC-MS and in conjugation with HPLC. The kinetics of ester hydrolysis was studied in two different non-enzymatic buffer solutions, at pH 1.2, and 7.4 as well as in liver homogenates. Study of analgesic and anti-inflammatory properties in comparison with the reference compounds has shown that both analgesic and anti-inflammatory activities were present at the same doses of the investigated compounds. The ester III was found to be less irritating to gastric mucosal membrane than the parent drugs. These results suggest that the synthesized prodrugs are characterized by better therapeutic index than the parent drugs.

Spectrophotometric determination of epinephrine and norepinephrine with sodium periodate

A simple and accurate spectrophotometric method is described for the determination of epinephrine (EP), norepinephrine (NE) and their bitartrate salts. The method is based on the development of a red colour (lambda(max) 490 nm) with sodium periodate in aqueous alcoholic medium. The colour is stable for at least 1 hr. The molar reacting ratio of EP or NE to periodate is 1:2. The proposed method is particularly suitable for routine analysis of EP and NE injections. The interference due to the sodium metabisulphite normally used as antioxidant can be overcome by addition of acetone. Results for analysis of bulk drugs and injections agree well with those of official methods.

Stereoselective metabolic study of famprofazone

Famprofazone (1) metabolites were studied in human urine after medication by 50 mg oral dose. The human urine was collected over 48 h from six volunteers at time intervals of 6, 12, 24 and 48 h. The amount of famprofazone metabolites were recovered from the urine samples by application of Extrelut extraction method. The resultant extracts were derivatized using N-methyl-N-trimethylsilytrifluoroacetamide (MSTFA) for trimethylsilylation followed by N-methyl-bis-trifluoroacetamide (MBTFA) for trifluoroacetylation. Methamphetamine (2) and 3-hydroxymethyl-propyphenazone (3), excreted in human urine, were identified as famprofazone metabolites by gas chromatography-mass spectrometry (GC-MS). The quantitative results revealed that the average amounts of 2 and 3, excreted in human urine were equal to 2.6 and 4 mg, respectively, through 48 h. However, 3 was analysed after enzymatic hydrolysis of the urine samples using beta-glucuronidase/arylsulphatase. The excreted methamphetamine enantiomers could be separated by application of indirect GC-technique using S-(-)-N-trifluoroacetylprolyl chloride (TPC) as a chiral derivatizing agent. The average amount of (-)-methamphetamine isomer excreted in the urine was found to be three fold those of the (+)-isomer.

ON-LINE PRECOLUMN DERIVATIZATION FOR HPLC DETERMINATION OF METHOTREXATE USING A COLUMN PACKED OXIDANT

A high-performance liquid chromatographic method involving on-line precolumn oxidative cleavage and fluorimetric detection was developed for the determination of methotrexate in plasma. Plasma samples were subjected to protein precipitation followed by solvent purification and then injection into the chromatographic system. Cerium (IV) trihydroxyhydroperoxide (CTH) was introduced as a packed oxidant before analytical column for the conversion of methotrexate into highly fluorescent 2,4-diaminopteridine derivatives. The oxidative cleavage of methotrexate occurs during the flow of 0.04 M phosphate buffer (pH 3.5) containing the drug through CTH column with a flow-rate of 0.2 mL/min at 40 degrees C. The separation was performed on a reversed-phase column (ODS/TM) using a mobile phase consisting of phosphate buffer (0.05 M, pH 6.6) and acetonitrile (90:10 v/v). The fluorescent products were monitored fluorimetrically at emission and excitation wavelengths of 463 and 367 nm, respectively. Validation of accuracy and precision were satisfactory for both within- and between-run assays. All coefficients of variance were less than 4% and mean relative errors were within 1.11% to 7.83%. The average recovery was found to be 93.74% to 98.11%. The proposed method is highly sensitive, specific and applicable to biological fluids.

Rapid and Specific Precolumn Extraction High-Performance Liquid Chromatographic Assay for Bupivacaine in Human Serum

A rapid and specific HPLC assay for quantiative determination of bupivacaine in human serum is described. The technique incorporates an on-line sample clean-up system followed by reversed-phase chromatography with UV detection. The proposed method uses a column-switching technique and protein-coated Lichrosorb RP-8 as a precolumn together with Lichrosorb RP-18 as an analytical column. The total run time for an injection of serum sample was 10 min. This procedure offers a sensitive assay without the need for time-consuming extractions. The average bupivacaine recoveries over a concentration range of 150-600 ng/mL ranged from 99.12 to 101.02%, and relative standard deviations ranged from 1.15 to 1.78%.