Sci. Pharm., Volume 72, Issue 2 (June 2004) – 6 articles

A series of quinoxaline derivatives has been synthesized by reacting 3-hydrazinoquinoxalines 1a,b with many bifunctional reagents. Reaction of 1a,b with chloroacetyl chloride and ethyl chloroacetate afforded 1-chloromethyl[1,2,4]tnazoIo[4,3-a]quinoxalines 2a,b and dihydro[1,2,4]triazino[4,3-a]quinoxalin-2-ones 3a,b respectively. Condensation of 1a,b with ethyl acetoacetate and acetylacetone yielded 2-quinoxalinylhydrazonobutanoates 4a,b and 2-quinoxalinylhydrazono-2-pentanones 5a,b respectively. Cyclization of 5a,b gave 3,5-dimethylpyrazolylquinoxalines 6a,b. Moreover, reaction of compounds 2a,b with N-phenyl piperazine derivatives afforded 4-(4-Arylpiperazin-1-yl)-1-[(4-arylpiperazin-1-yl) methyl)]triazoloquinoxalines 7a−e. The prepared compounds were screened for in vitro antibacterial and antifungal activities. None of the tested compounds showed significant activity towards Pseudomonas aeruginosa. However, remarkable activities were noticed for compounds 5a and 5b against Eschenchia coli. Staphylococcus aureus and Candida albicans. Compounds 6a and 6b lacked any antimicrobial activities against the tested microorganisms. Full article

A new simple, precise, accurate and selective high-performance thin-layer chromatographic (HPTLC) method has been developed for the simultaneous deter-mination of five mixtures: atenolol and chlorthalidone (Mix. l), enalapril maleate and hydrochlorothiazide (Mix. ll), amiloride hydrochloride and hydrochlorothiazide (Mix. lll), atenolol, chlorthalidone and amiloride hydrochloride (Mix. lV) and atenolol, hydrochlorottriazide and amiloride hydrochloride (Mix. V) in bulk powders and in pharmaceutical dosage forms. The methods consist of dissolving the drugs in methanol and spotting these solutions on a thin layer Merck HPTLC plates (0.25 mm thickness) pre-coated wrth 60 GF₂₅₄ silica gel on aluminum sheet as the stationary phase, using dioxane:acetonrtrile: 1-propanol:hexane (30:18:23:1; v/v/v/v) , ethylacetate:chlo-roform:methanol:acetic acid (11:8:7.5:1.5; v/v/v/v). ethylacetate:chloroform:1-propanol:25% ammonia solution (12:9:1:0.2; v/v/v/v), di0xan:acetonitrile:1-propanol:tetrahydrofuran (20:13:4:15; v/v/v/v) and dioxane:ethylacetate:acetonitrile:1-propanol (10:7:5.5:3 v/v/v/v) as the mobile phases for mixtures l, ll, lll, lV and V, respectively. Detection was carried out densitometrically using UV detector at 283, 266, 257, 226 and 362 for atenolol, chlorthalidone, enalapril maleate, hydrochlorothiazide and amiloride hydrochloride, respectively. Calibration curves were linear in the range 1–100 µg/ml⁻¹ with correlation coefficients not less than 0.9996. The percentage recoveries ranged from 98.3 ± 1.42 to 100.8 ± 0.79. Full article

A reversed-phase HPLC method with spectrophotometric detection was developed for the simultaneous determination of labetalol (LBT) and hydrochloro-thiazide (HCD). The chromatographic separation was performed using a Microbondapak C₁₈ column (4.6 i.d. x 250 nm) and paracetamol as internal standard. A mobile phase consisting of 0.05 M phosphate buffer/acetonitrile of pH 4 (7:3) at a flow rate of 0.7 ml/min was used. The detection was affected spectrophotornetrically at 302 nm. The working concentration range was 0.3–10 µg/ml with detection limits of 0.05 µg/ml for both drugs. The lower quantitation limit was 0.25 µg/ml in the two cases. The method was successfully applied to tablets, the % recoveries were 99.45 ± 0.68 for LBT and 99.79 ± 0.75 for HCD. The method was extended to the in-vitro determination in spiked human plasma. The % recoveries were 91.12 ± 0.33 for LBT and 91.37 ± 0.40 for HCD. The interday and intraday precision and accuracy were evaluated in plasma by calculating the % RSD (n=5) and the % error and were found to be in the ranges of 1.18–4.1% and 0.38–0.36% for both drugs, respectively. Full article

The anodic behaviour of isradipine was studied using cyclic voltammetry (CV), direct current (DC_t) and differential-pulse (DPP) polarography. lsradipine exhibited well-defined anodic polarographic waves over the pH range of 4–8 in Britton-Robinson buffer (BRb). At pH 6, the analytical pH, the diffusion-current constant (Id) was 2.12 ± 0.42 (n = 4). The oxidation potential is −0.10 V vs AgIAgCl reference electrode with correlation coefficients of 0.9977 and 0.9948 in the DC_t and DPP modes, respectively. The current-concentration plots were rectilinear over the ranges 5–14 µg/ml and 2.4–12 µg/ml using the DC_t and DPP modes, respectively. The lower detection limit was 1.12 µg/ml (3.02 x 10⁻⁶ M) adopting the DPP mode. The proposed method was applied to commercial tablets and capsules, the % recoveries were 100.52 ± 1.267 and 99.4 ± 0.87 (n = 6) for the tablets and 101.3 ± 1.57 and 100.7 ± 2.10 (n = 6) for the capsules adopting both DC_t and DPP modes, respectively. The number of electrons involved in the electrode process was accomplished and a proposal of the electrode reaction was presented. Full article

A new simple, accurate and reasonably sensitive spectrophotometric method is described for the determination of reserpine based on the oxidation with sodium metaperiodate in the presence of acetic acid and coupling with 3-methyl-2-benzo thiazolinone hydazone hydrochloride (MBTH) to form highly blue coloured product showing maximum absorbance at 630 nm. Beer's law is obeyed in the range 0.2–1.6 µg ml⁻¹. The relative standard deviation was found to be less than 1%. The proposed method can be applied for the estimation of reserpine in tablets with no evidence of interference from excipients. Full article