Synthesis and structure of 6- and 7-(2-arylvinyl)pteridines

7-Hydroxy-6-styrylpteridine 9 and 7-(2-arylvinyl)-6-hydroxypteridines 10–12 were synthesized via the condensation of 5,6-diaminouracil 1 with benzylidenepyruvic acids 2–4 . The synthesis of the 2-methylthio analogue 15 is also described.     

Spectral, Magnetic, Electrical and Thermal Studies on Malonyl bis(thiosemicarbazide) Complexes

Mono- and binuclear complexes of malonyl bis(thiosemicarbazide), H₄ MBT, with VO²⁺, Co²⁺, Ni²⁺, Cu²⁺, Cd²⁺ and Pt⁴+ have been isolated. The elemental analyses, magnetic moments, spectra [u.v.–vis., i.r., e.s.r. (for Cu²⁺; VO²⁺) and mass], thermal and voltammetric measurements [for Co²⁺ and Ni²⁺] have been used to characterize the isolated complexes. The ligand behaves as binegative quadridentate with Cu²⁺, Co²⁺ and VO²⁺ ions, binegative pentadentate with Pt⁴+ and hexadentate, either as trinegative in [Cd₂(HMBT)(OC₂H₅)(C₂H₅OH)]H₂O or mononegative in [Ni₂(H₃MBT)(OAc)₃(C₂H₅OH)]. The lack of thiol and/or enol hydrogen during the complex formation was confirmed pH-metrically. The pK’s (10.70, 8.50 and 8.15) of H₄MBT reveal the removal of CSNH protons in one step and CONH in two steps. Also, the stability constants reveal a higher value for the Cu²⁺ complex and a lower one for VO²⁺. The TG analyses suggest high stability for most complexes followed by thermal decomposition in different steps. The kinetic and thermodynamic parameters for some decomposition steps in VO²⁺and Pt⁴⁺ thermograms have been calculated     

Determination of cimetidine,famotidine, and ranitidine hydrochloride in the presence of their sulfoxide derivatives in pure and dosage forms by high-performance thin-layer chromatography and scanning densitometry

A selective, precise, and accurate method was developed for the determination of cimetidine (C), famotidine (F), and ranitidine hydrochloride (R x HCl) in the presence of their sulfoxide derivatives. The method involves quantitative densitometric evaluation of mixtures of the drugs and their derivatives after separation by high-performance thin-layer chromatography on silica gel plates (10 x 20 cm) with ethyl acetate-isopropanol-20% ammonia (9 + 5 + 4, v/v) as the mobile phase for both C and F and ethyl acetate-methanol-20% ammonia (10 + 2 + 2, v/v) as the mobile phase for R x HCl; Rf values for C, F, and R x HCl and their corresponding derivatives were 0.85 and 0.59, 0.73 and 0.41, and 0.56 and 0.33, respectively. Developing time was approximately 20 min. For densitometric evaluation, peak areas were recorded at 218, 265, and 313 nm for C, F, and R x HCl, respectively. The relationship between concentration and the corresponding peak area was plotted for the ranges of 5-50 microg/spot for C and 2-20 microg/spot for F and R x HCl. Mean recoveries were 100.39 +/- 1.33, 99.77 +/- 1.30, and 100.09 +/- 0.69% for C, F, and R x HCl, respectively. The proposed method was used successfully for stability testing of the pure drugs in the presence of up to 90% of their degradates, in bulk powder and dosage forms. The results obtained were analyzed statistically and compared with those obtained by the official methods.     

A robust in vitro Anticancer,Antioxidant and Antimicrobial Agents Based on New Metal-Azomethine Chelates Incorporating Ag(I), Pd (II) and VO (II) Cations: Probing the Aspects of DNA Interaction

A novel azomethine ligand (HNAP) [HNAP = 1-(Pyridin-3-yliminomethyl)-naphthalen-2-ol] and its Ag(I), Pd (II) and VO (II) chelates have been synthesized and structurally inspected using a wide range of spectroscopic and analytical tools, including infra-red (IR), ultraviolet-visible (UV-Vis) and ¹H NMR spectroscopy techniques, CHN analysis, molar conductance, magnetic susceptibility, and thermogravimetric analysis. The molar conductance measurements reveal that the chelates are non-electrolytes. The thermal behavior of the investigated metal chelates shows that the hydrated, coordinated water molecules and the anions are removed in successive steps followed immediately by decomposition of the ligand in the subsequent steps. The activation thermodynamic parameters are calculated from the TG curves and discussed. Complexes formation study via continuous variation m molar ratio has been investigated, and results were consistent to those found in the solid complexes with a ratio of (M:L) as (1:1) or 1:2 (M:L) molar ratio for all the monolithic and bi-valent metal complexes with square planar for Pd (II), and Ag(I) cations while, square pyramidal geometry for VO (II) cation. DFT calculations for the titled different metal-chelates have been studied and showed a good correlation with the experimental data. The prepared compounds had been checked In vitro towards numerous sorts of plant pathogenic fungi and bacteria to evaluate their antimicrobial properties and compared with some known antibiotics. Significantly, all the complexes show excellent antimicrobial activity against various strains of bacteria and fungi, including both Gram-negative and Gram-positive bacteria. Besides, the complexes exhibited high cytotoxicity against various carcinoma cell lines, including HCT-116, MCF-7, and HepG-2. Moreover, the effect of the new synthesized compounds as antioxidants was determined by reduction of 1,1-diphenyl-2-picryl hydrazyl (DPPH) and compared with that of Vitamin C. Furthermore, the binding interactions of the complexes with CT-DNA were explored using UV-Vis spectroscopy, viscosity and gel electrophoreses measurements. They cooperatively bind to DNA possibly through intercalations. The binding ability of the complexes was shown as HNAPAg > HNAPPd > HNAPVO complex.     

A novel method for the synthesis of 1-aryltetrahydroisoquinolines

Carbenium ions generated from substituted benzhydryls using acid catalysis undergo smooth intramolecular trapping by pendant sulfonamide groups to provide excellent yields of 1-aryltetrahydroisoquinolines.     

Selective Densitometric Analysis of Cephalosporins Using Dragendorff’s Reagent

A simple, selective, precise, and stability-indicating thin-layer chromatographic method has been developed and validated for analysis of the cephalosporins cefpodoxime proxetil, ceftriaxone sodium, ceftazidime pentahydrate, cefotaxime sodium, cefoperazone sodium, cefazolin sodium, and cefixime in the bulk drug and in pharmaceutical formulations. TLC was performed on aluminium sheets precoated with silica gel G 60F₂₅₄ as stationary phase. The mobile phases chosen for development gave compact spots for all the drugs (R _F values 0.43–0.60). The separated compounds were visualized as orange spots by spraying with Dragendorff’s reagent. Linear regression analysis data for the calibration plots revealed good linear relationships between response and amounts of the drugs with correlation coefficients ranging from 0.9977 to 0.9998 and determination coefficients ranging from 0.9954 to 0.9996 over the concentration ranges 5–25 μg per spot for cefpodoxime proxetil, ceftriaxone sodium, and ceftazidime pentahydrate and 10–50 μg per spot for cefotaxime sodium, cefoperazone sodium, cefazolin sodium, and cefixime. The method was validated for precision, recovery, and robustness. Limits of detection and quantitation for the drugs ranged from 0.35 to 2.48 and from 1.07 to 7.50 μg per spot, respectively. The method was successfully applied to analysis of the drugs in their pharmaceutical dosage forms with good precision and accuracy. The method can also be used as a stability-indicating assay.     

Bioactive phenolic amides from Celtis africana

Nine compounds have been isolated for the first time from Celtis africana, namely trans-N-coumaroyltyramine (1), trans-N-feruloyltyramine (2), trans-N-caffeoyltyramine (3), lauric acid (4), oleic acid (5), palmitic acid (6), lupeol (7), β-sitosterol (8) and oleanolic acid (9), respectively. Their structures have been elucidated by different spectroscopic techniques. The isolated compounds were screened for their antioxidant, anti-inflammatory and acetylcholinestrease enzyme inhibitory activities. Compounds 1-3 showed significant antioxidant and anti-inflammatory activities and weak to moderate acetylcholinestrease enzyme inhibition activity.     

Synthesis of certain 2-substituted-1H-benzimidazole derivatives as antimicrobial and cytotoxic agents

A series of 2-substituted-1H-benzimidazole derivatives were synthesized and evaluated for antimicrobial, antifungal and cytotoxic activities. The results showed that all tested compounds showed potent antimicrobial activity against some species of Gram-negative bacteria (Pseudomonas aeruginosa, Escherichia coli, Salmonella typhi) and fungi (Candida albicans) with minimum inhibitory concentrations (MICs) lower than 0.016 μg/mL. In contrast, all tested compounds were inactive against Staphylococcus aureus (Gram-positive bacterium). The final targets were also tested for their antitumor activity in vitro on cervical carcinoma (HeLa) cell line. Eight of the test compounds displayed more potent cytotoxic effect than doxorubicin at nanomolar concentrations. Compounds 2c and 3c exerted the strongest cytoyoxic effect with IC(50) 15 and 13 nM, respectively.     

Use of a flow-injection system in the evaluation of the characteristic behavior of neutral carriers in lithium ion-selective electrodes

A flow-injection system based on microconduits is used to investigate electrode characteristics such as selectivity, detection limit, and response and equilibrium times of the new ionophore, N,N,N′,N′-tetraisobutyl-5,5-dimethyl-3,7-dioxanonane diamide, in lithium ion-selective electrodes. These characteristics were compared with those of the ionophore N,N′-diheptyl-N,N′,5,5-tetramethyl-3,7-dioxanone diamide. The new ionophore has superior detection limits and shorter response and equilibrium time, but the other exhibits better selectivity for lithium with respect to sodium. Values of K^Pot_LiNa for the new ionophore vary from 0.0450 to 0.566, depending on the methods of measurement and solution conditions. This phenomenon is discussed. Stop-flow experiments effectively demonstrated the response and equilibrium time differences between these two ionophore membranes.