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Biomedical subjects

V Kmetec

Publications and source records attributed to V Kmetec.

6 recordsLinked to original sources
PubMed2004

Determination of main low molecular weight antioxidants in urinary bladder wall using HPLC with electrochemical detector.

The aim of the present work was to develop validated HPLC method using electrochemical detector for simultaneous detection of low molecular weight antioxidants (LMWA) in urinary bladder. Furthermore, the method was applied to study the distribution of LMWA in urinary bladder wall. The ascorbic acid (AA), glutathione in reduced (GSH) and oxidized (GSSG) form and uric acid (UA) were resolved by isocratic elution from C18 reversed-phase column. The bladder tissue sample preparation involved extraction with meta-phosphoric acid solution for LMWA stabilization. The AA, GSH and UA tissue peak was identified by different approaches. The obtained method validation parameters were in acceptable range: intra-day precision (<4.4%), intra-day accuracy (<8.4%), inter-day precision (<9.4%) and inter-day accuracy (<15.6%). Additionally, the method provided good linearity (r2>0.99) and recoveries (98.9-112.6%). The distribution of LMWA in urinary bladder was determined by measuring their concentration in bladder wall layers: urothelium, lamina propria, muscularis and serosa. The validated method was able to quantify the reduced form of all three LMWA in all four bladder wall layers. The LMWA concentrations were decreasing from urothelium to serosa except of UA. The developed HPLC method with electrochemical detection of LMWA is simple, fast and can be used for simultaneous quantification of LMWA in tissues, which contain low concentrations of antioxidants.

Animals↗
PubMed2001

Stability of ascorbyl palmitate in topical microemulsions.

Ascorbyl palmitate and sodium ascorbyl phosphate are derivatives of ascorbic acid, which differ in stability and hydro-lipophilic properties. They are widely used in cosmetic and pharmaceutical preparations. In the present work the stability of both derivatives was studied in microemulsions for topical use as carrier systems. The microemulsions were of both o/w and w/o types and composed of the same ingredients. The stability of the less stable derivative ascorbyl palmitate was tested under different conditions to evaluate the influence of initial concentration, location in microemulsion, dissolved oxygen and storage conditions. High concentrations of ascorbyl palmitate reduced the extent of its degradation. The location of ascorbyl palmitate in the microemulsion and oxygen dissolved in the system together significantly influence the stability of the compound. Light accelerated the degradation of ascorbyl palmitate. In contrast, sodium ascorbyl phosphate was stable in both types of microemulsions. Sodium ascorbyl phosphate is shown to be convenient as an active ingredient in topical preparations. In the case of ascorbyl palmitate, long-term stability in selected microemulsions was not adequate. To formulate an optimal carrier system for this ingredient other factors influencing the stability have to be considered.

Administration, Topical↗
PubMed2001

Optimization of HPLC method for stability testing of bacitracin.

A stability indicating HPLC assay for bacitracin has been developed and validated. The assay is based on a gradient elution, reversed phase column and UV diode array detection. On the basis of our previous analytical work several additional systematic HPLC tests for optimization of analytical method were performed. In order to achieve the highest selectivity of HPLC method, tests were conducted with extremely complex samples -- zinc bacitracin feed grade as food additive for animals. The influence of pH of mobile phase and type of columns on chromatographic separation of active (A, B(1) and B(2)) and inactive (F) polypeptide components of bacitracin were investigated in detail. It was found also that the peak B(1) comprises three and the peak F two subunits -- probably isomers. The obtained analytical procedure proved to be very selective and effective for the simultaneous determination of active polypeptide A, B(1) and B(2), impurities, known and unknown degradation products and ballast material.

Anti-Bacterial Agents↗
PubMed1999

Are calculated log P values for some guanine derivatives by different computer programs reliable?

The log P values of n-octanol/water for some guanine derivatives, acyclovir, deoxyaciclovir and their acetyl congeners, were calculated by some commercially available computer programs for log P calculation. These values were compared with those obtained by the conventional shake-flask method. It was established that the calculations of log P values for examined guanine derivatives by these computation programs do not give reliable results.

1-Octanol↗
PubMed1987

Bioavailability of piroxicam: oral and rectal multiple application in humans.

The aim of the work is to evaluate the bioequivalence of piroxicam administered orally and rectally in 20 mg dose every 24 hours. The corresponding "in vivo" study was undertaken and plasma samples were collected during the ninth dosing interval. HPLC method was used for piroxicam plasma concentrations determination. AUC and C were calculated and the obtained data were statistically analyzed. Analog-hybrid simulation was used to confirm additionally the similarity between the discussed formulations. No significant differences were observed using paired t-test and two-way analysis of variance while the methods of Hauck and Westlake, looking strictly, gave nonbioequivalence. Simulated response of one compartment model is suitable for "in vivo" data in both cases. Measured and simulated average steady state concentrations are equal and in complete accordance with those given in literature. Finally it can be concluded that oral and rectal application are bioequivalent in the sense of expected clinical effects.

Administration, Oral↗