New prodrugs derived from 6-aminodopamine and 4-aminophenol as candidates for melanocyte-directed enzyme prodrug therapy (MDEPT)

Two novel tyrosinase mediated drug delivery pathways have been investigated for the selective delivery of cytotoxic units to melanocytes from urea and thiourea prodrugs. The synthesis of these prodrugs is reported, as well as oximetry data that illustrate that the targets are substrates for tyrosinase. The stability of each of the prodrugs in (i) phosphate buffer and (ii) bovine serum is discussed, and the urea prodrugs are identified as lead candidates for further studies. Finally, HPLC studies and preliminary cytotoxicity studies in a melanotic and an amelanotic cell line, that illustrate the feasibility of the approach, are presented.     

Flow Injection Chemiluminescence Method for Nalbuphine Hydrochloride in Pharmaceutical Formulations Using Tris(2,2'-bipyridyl)ruthenium(II) Chloride-diperiodatocuprate(III) Reaction

Asensitive and selective method employing chemiluminescence(CL) coupled with flow injection(FI) is reported for nalbuphine hydrochloride(NAL) assay in pharmaceutical formulations. The enhancement effect of NAL on the CL reaction between tris(2,2'-bipyridyl)ruthenium(II) chloride-diperiodatocuprate(III) {Ru[(bpy)₃]²⁺-Cu(III) complex} in acidic medium is used as analytical measurement. The optimal conditions of the CL reaction were sulfuric acid 1.0×10^-3 mol/L, Ru[(bpy)₃]²⁺ 7.5×10^-5 mol/L, Cu(III)/Ag(III) complexes 4.0×10^-4/5.0×10^-4 mol/L, sample loop volume of 120 μL and flow rate of 2.5 mL/min. The sensitivities of the method in terms of detection(S/N=3) and quantification(S/N=10) limits are 5×10^-4 and 0.001 ppm(1 ppm=1 mg/L), respectively. The linear response of the instrument in the form of CL intensity with respect to NAL concentration is over the range 0.001-15.0 ppm(R²=0.9999) with relative standard deviation from 0.8% to 3.2% and injection throughput of 120 injection/h. The applications of the method include the quantitative analysis of NAL in pharmaceutical injection samples. Variations and the average results of the proposed method are not signi-ficantly different from the results of a reported method by applying F- and paired student t-test. The most likely CL reaction mechanism is written in accordance with spectrophotometric and CL studies.     

Determination of carbaryl by flow injection with luminol chemiluminescence inhibition detection

A flow-injection procedure is described for the determination of carbaryl based on its inhibition effect on luminol-cobalt(II) chemiluminescence reaction in alkaline medium in the presence of hydrogen peroxide. The calibration data over the range 5.0?×?10^?7 to 20?×?10^?6?M give a correlation coefficient (r ²) of 0.9972 with relative standard deviations (RSD; n?=?4) in the range of 1.0–2.1% with a limit of detection (3?×?blank noise) of 2.37?×?10^?7?M for carbaryl. The sample throughput was 120?h^?1. The effects of some carbamates, anions, and cations were studied on luminol CL system for carbaryl determination. The proposed method has been applied to determine carbaryl in natural waters.     

Photodegradation and flow-injection determination of simetryn herbicide by luminol chemiluminescence detection

A novel and simple flow injection chemiluminescence method is reported for the determination of simetryn, a common herbicide. The method is based on the direct oxidation of luminol by the photoproducts of the simetryn in alkaline medium in the absence of catalyst/oxidant. The linear concentration range was 0.01 - 2 microg mL(-1) simetryn with a correlation coefficient (r(2)) of 0.9997 and relative standard deviations (RSD; n = 4) in the range of 0.9 - 2.3%. The limit of detection (S/N = 3) was 7.5 ng mL(-1) with a sample throughput of 100 h(-1). The proposed method has been applied to determine simetryn in natural waters using Sep-Pak C(18) cartridges for solid phase extraction (SPE) procedure. The recoveries were in the range of 97 +/- 1 to 104 +/- 2%. The mechanism of chemiluminescence reaction has also been discussed briefly.     

Comparison of the site occupancies determined by combined Rietveld refinement and density functional theory calculations: example of the ternary Mo-Ni-Re σ phase

The site occupancies of the Mo-Ni-Re σ phase have been studied as a function of the composition in the ternary homogeneity domain by both experimental measurements and calculations. Because of the possible simultaneous occupancy of three elements on the five sites of the crystal structure, the experimental determination of the site occupancies was achieved by using combined Rietveld refinement of X-ray and neutron diffraction data, whereas calculation of the site occupancies was carried out by using the density functional theory results of every ordered (i.e., 3(5) = 243) configuration appearing in the ternary system. A comparison of the experimental and calculation results showed good agreement, which suggests that the topologically close-packed phases, such as the σ phase, could be described by the Bragg-Williams approximation (i.e., ignoring the short-range-order contributions). On the other hand, the atomic distribution on different crystallographic sites of the Mo-Ni-Re σ phase was found to be governed by the atomic sizes. Ni, having the smallest atomic size, showed a preference for low-coordination-number (CN) sites, whereas Mo, being the largest in atomic size, preferred occupying high-CN sites. However, the preference of Re, having intermediate atomic size, varied depending on the composition, and a clear reversal in the preference of Re as a function of the composition was evidenced in both the calculated and experimental site-occupancy results.     

Determination of total iron in fresh waters using flow injection with potassium permanganate chemiluminescence detection

A flow injection method is described for the determination of iron in fresh water based on potassium permanganate chemiluminescence detection via oxidation of formaldehyde in aqueous hydrochloric acid. Total iron concentrations are determined after reducing Fe(III) to Fe(II) using hydroxylamine hydrochloride. The detection limit (three standard deviations of blank) is 1.0 nM, with a sample throughput of 120 h⁻¹. The calibration graph was linear over the range (2–10) × 10⁻⁷ M (r ² = 0.9985) with relative standard deviations (n = 5) in the range 1.0–2.3%. The effect of interfering cations (Ca(II), Mg(II), Zn(II), Ni(II), Co(II), Fe(III), Mn(II), Pb(II), and Cu(II)) and common anions (Cl⁻, SO ₄ ²⁻ , PO ₄ ³⁻ , NO ₃ ⁻ , NO ₂ ⁻ , I⁻, F⁻, and SO ₃ ²⁻ ) was studied at their maximum admissible concentrations in fresh water. The method was applied to fresh-water samples from the Quetta Valley, and the results obtained (0.04 ± 0.001–0.11 ± 0.01 mg/L Fe(II)) were in reasonable agreement with those obtained using the spectrophotometric reference method (0.05 ± 0.01–0.12 ± 0.02 mg/L Fe(II)). The text was submitted by the authors in English.     

Equilibration in bicyclic pyroglutamates by ring opening-reclosure

Enantiopure bicyclic tetramates, readily obtained by Dieckmann ring closure on oxazolidine-derived templates, can be further converted to hydroxypyroglutamates by kinetically controlled nucleophilic additions, and some of these products are capable of equilibration via a facile retro-aldol/aldol reclosure.     

Metal contamination in Sunairi Point sediment core along Karachi coast,Pakistan

Journal of Radioanalytical and Nuclear Chemistry - This paper describes the pollution level in sediment core collected from Sunairi Point of Karachi coastal area Pakistan. The sediment was...     

Enzymatic determination of vitamin A in pharmaceutical formulations with spectrophotometric detection

An enzymatic method for the determination vitamin A (retinol) is reported using soluble and immobilized alcohol dehydrogenase, isolated from rabbit liver. The reaction is based on the oxidation of retinol and simultaneous reduction of NAD⁺ to NADH followed by spectrophotometric detection at 340 nm. The calibration graph was linear over the range of 2.0–10 μM with correlation coefficients of 0.9967 and 0.9992 (n = 5) for soluble and immobilized alcohol dehydrogenase respectively, with relative standard deviations (n = 3) in the range of 0.5–1.2%. The limit of detection was lower than 1.0 μM. The proposed method was applied to determine vitamin A in pharmaceuticals, and the results obtained were in reasonable agreement with the amount labeled. The results were compared using spectrophotometric reference method, and no significant difference was found between the results of the both methods.