[Validation of an HPLC method for the analysis of decomposition products in injectable diazepam]. / Validácia HPLC metódy na analýzu rozkladných produktov diazepamu v injekciách diazepamu.

Diazepam is an important drug from the group of benzodiazepines, used in clinical practice for its sedative, hypnotic, anticonvulsive, myorelaxant, and primarily anxiolytic effects. Several kinetic studies have been published which show that diazepam is a drug sensitive to hydrolysis both in acid and alkaline media. The present study aimed to elaborate and validate a simple and rapid HPLC/UV method for simultaneous analysis of three decomposition products of diazepam in the presence of diazepam and to apply it also on the control of stability of the injectional solution of diazepam. The optimization of chromatographic conditions resulted in the use of the high-performance chromatographic column Zorbax ODS, the mobile phase represented by a mixture of acetonitrile/water in a ratio of 60/40 (w/w, %), flow rate 1.5 ml/min, and spectrophotometric detection at 242 nm. The elaborated method and the employed chromatographic system were successfully validated and they can be used in practice in the control of stability of injection solution of diazepam.

[A study of the stability of dioxopromethazine in aqueous solutions and ophthalmic instillation]. / Stúdium stability dioxoprometazínu vo vodných roztokoch a v ocnej instilácii metódou HPLC.

Dioxopromethazine began to be used in therapy as a modern antihistamine agent in the 1970s. A dioxopromethazine-containing ophthalmic instillation and a gel were employed until the end of the 1990s. The paper deals with the examination of the stability of the drug dioxopromethazine in aqueous solutions and the ophthalmic instillation Promefrin stored under different conditions. High-performance liquid chromatography with spectrophotometrical and electrochemical detection and HPLC connected on-line with mass spectrometry were employed for analysis. Dioxopromethazine in aqueous solutions and in ophthalmic instillations stored in direct sunlight was found not to be stable. However, the cover of the ophthalmic instillation, a brown-glass prescription bottle, and observation of storing conditions sufficiently protect the active ingredient from decomposition processes.

[Validation of the HPLC method in the determination of dioxopromethazine and phenylephrine in eye drops]. / Validácia HPLC metódy pre stanovenie dioxoprometazínu a fenylefrínu v ocnej instilácii.

The present paper introduces a rapid HPLC method for the determination of dioxopromethazine and phenylephrine in eye drops. The method uses a modified C18 stationary phase optimized for the separation of basic compounds and a methanol/1.5 mM phosphoric acid (60/40 v/v, pH 3.02) mobile phase. The flow rate is set to 2 ml/min, sample volume 20 microliters, and compounds are detected at 275 nm. Prior to analysis, the eye drops are diluted with water in a ratio of 1:50. The elaborated HPLC method and the chromatographic system were validated according to the procedure for the validation of chromatographic systems and methods.

[Determination of residual trifluralin in the herbal drug Mentha piperita L]. / Stanovenie rezíduí trifluralinu v droge Mentha piperita L.

A HPLC/UV method was worked out to determine the residues of the herbicide trifluralin in the vegetable drug of the peppermint (M. piperita L.). The yield of the method, determined in model samples, was at least 70%, the determination limit of the method being 0.07 mg.kg-1. The content of trifluralin residues in the vegetable drug of the peppermint plant after application of the preparation Treflan 48 EC (in a dose of administration of 2 kg.ha-1) for the treatment of the growth in a small-plot experiment was below the detection limit of the analytical method.

Effect of native and oxidized low-density lipoprotein on endothelial nitric oxide and superoxide production : key role of L-arginine availability.

BACKGROUND: Native and oxidized LDLs (n-LDL and ox-LDL) are involved in the atherogenic process and affect endothelium-dependent vascular tone through their interaction with nitric oxide (NO). METHODS AND RESULTS: In this study we evaluated directly, by using a porphyrinic microsensor, the effect of increasing lipoprotein concentrations on endothelial NO and superoxide (O(2)(-)) production. We investigated where lipoproteins may affect the L-arginine-NO pathway by pretreating cells with L-arginine, L-N-arginine methyl ester (L-NAME), and superoxide dismutase. Bovine aortic endothelial cells were exposed for 1 hour to increasing concentrations of n-LDL (from 0 to 240 mg cholesterol/dL) and ox-LDL (from 0 to 140 mg cholesterol/dL). A stimulated (calcium ionophore) NO concentration decreased to 29% of the control at n-LDL concentration of 80 mg cholesterol/dL and to 15% of the control at 20 mg cholesterol/dL of ox-LDL. L-Arginine partially neutralized the inhibitory effect of n-LDL and ox-LDL on the NO generation. Superoxide dismutase pretreatment did not modify NO production, whereas L-NAME blunted NO generation at all LDL concentrations. O(2)(-) production was increased at low n-LDL and very low ox-LDL concentrations; this was reversed by L-arginine. CONCLUSIONS: These findings confirm the inhibitory role of n-LDL and ox-LDL on NO generation and suggest that lipoproteins may induce a decreased uptake of L-arginine. The local depletion of the L-arginine substrate may derange the NO synthase, leading to overproduction of O(2)(-) from oxygen, the other substrate of NO synthase.

Study of local anaesthetics, Part 146: Correlation between local anaesthesia, coded structural information, and chromatographic properties for homologous series of alkoxysubstituted esters of phenylcarbamic acid using a neural network.

RP HPLC capacity factors were used for the characterisation of the lipophilicity of homologous series of o- and m- alkoxy-substituted pyrolidino-, piperidino-, and N-methylpiperazino esters of phenylcarbamic acid. The mathematical method of a neural network was employed for supplementing of the incomplete original data matrix and for smoothing the biological data. The dependencies of the number of carbon atoms in the alkoxy side chain (resp. LC capacity factors) on the surface anaesthesia for the homologous series have parabolic character. The surface anaesthetic activity of the o-alkoxy-substituted derivatives was higher than that of m-alkoxy-substituted derivatives. m-Alkoxy-substituted esters presented maxima of activity at 6 and o-derivatives at 7 carbon atoms in the alkoxy side chain.

Angiotensin-converting enzyme inhibition alters nitric oxide and superoxide release in normotensive and hypertensive rats.

Young (approximately 1 month old) male normotensive Wistar-Kyoto rats (n=26) and spontaneously hypertensive rats (n=38) were randomized into three groups treated via drinking water for approximately 2 years with, respectively, placebo, low doses, or high doses of an angiotensin-converting enzyme inhibitor, ramipril (10 microg x kg[-1] x d[-1], non-blood pressure-lowering dose, or 1 mg x kg[-1] x d[-1], blood pressure-lowering dose). Relative to placebo treatment in each respective rat strain, both ramipril dosages increased endothelial constitutive nitric oxide synthase expression (Western blot) and resultant synthesis of nitric oxide (porphyrinic sensor) in freshly excised carotids and thoracic aortas, respectively. Paradoxically, this activity was associated with an increased/decreased superoxide accumulation (chemiluminescence) in freshly excised aortas from 24-/22-month-old normotensive/hypertensive rats. In normotensive rats, relative to placebo treatment, the threefold increase in superoxide accumulation with antihypertensive ramipril treatment is most likely from the >300% increase in endothelial constitutive nitric oxide synthase expression (some of which may be disarranged by local insufficiencies in L-arginine or tetrahydrobiopterin). In hypertensive rats, relative to placebo treatment, the 35% increase in nitric oxide availability by long-term antihypertensive ramipril treatment may contribute to the preservation of the endothelium and prevent its dysfunction by inhibiting superoxide production. Increased nitric oxide production with concomitant decreased superoxide accumulation (approximately one third of placebo levels) correlates positively with the previously reported +40% life span extension for rats with genetic hypertension that were treated with antihypertensive doses of ramipril.

Pesticide residue analyses in plant material by chromatographic methods: clean-up procedures and selective detectors.

This paper deals with the analysis of pesticide residues by chromatographic methods in samples of plant origin. Emphasis is put on the isolation and clean-up steps of the sample preparation for GC or LC determination. The problems of the extraction solvent selection and clean-up procedures using different types of adsorption column chromatography or gel permeation chromatography are discussed. Attention is also given to alternative techniques such as supercritical fluid extraction (SFE), matrix solid-phase dispersion (extraction) (MSPD) and sweep co-distillation that are used for sample processing prior to GC and LC analysis. Currently, pesticide residue analyses are typically multi-residue procedures with highly sensitive methods. Consumption of costly and toxic solvents is being minimized and fully automated analytical procedures can be expected in the future.

Neural network approach to the prediction of the toxicity of benzothiazolium salts from molecular structure.

The prediction of the toxicity of benzothiazolium salts calculated by the neural network model is presented. The results are comparable with the previous calculations based on the Free--Wilson additivity model. The method of calculation of activity contributions of substituents is described.

Nitric oxide in the periendothelial area of femoral vein of the dog assessed in vivo by a porphyrinic sensor.

Nitric oxide concentration in the periendothelial are of the femoral vein in anaesthetized dogs was measured directly with a catheter- protected porphyrinic sensor. A 2- to 4-fold increase occurred in the basal NO concentration of 90 +/- 12 nM after acetylcholine injection (1-1.5 micrograms/kg). A linear correlation was found between femoral artery blood flow and NO concentration in the periendothelial area of the femoral vein. Noradrenaline decreased NO levels below the detection limit of the porphyrinic sensor (10 nM).

HPLC determination of polyamines in urine.

Determination of polyamines (putrescine, spermidine and spermine) in urine samples of patients was worked out using high performance liquid chromatography (HPLC) and pre-column derivatization. For HPLC separation, a method of reversed-phase chromatography with gradient elution of water-organic mobile phases, UV and fluorescence detection were applied. Special care was devoted to the preseparation step, the hydrolysis, derivatization and selective extraction of clinical samples. The optimal HPLC conditions were recommended for simultaneous determination of putrescine, spermidine and spermine in a minimal analysis time (about 15 min) and suitable chromatographic resolution values (Rij greater than 1.5). Detection limits for all polyamines were evaluated (40 pmol for putrescine, 25 pmol for spermidine and 20 pmol for spermine) for the analysis of polyamines in the urine. The urine samples of healthy people and the cancer patients were compared and the procedure or the complete analysis has been described.