HPLC-fluorescence determination of unconjugated estrogens in pharmaceuticals

The demonstration of synergistic interaction between differentiation inducing agents and DNA synthesis inhibitors suggests that these two groups act by two different mechanisms. We prospectively studied the response rate, response duration, survival, and toxicity in 10 patients with myelodysplastic syndrome (MDS) treated with all trans retinoic acid (ATRA) and low dose cytosine arabinoside (ara-C). These patients diagnosed between October 1993 and May 1995 were treated with ATRA (45 mg/M2/day) for 90 days followed by 90 mg/M2 on alternate day till Day 275; together with Ara-C (10 mg/m2) subcutaneously twice daily for 21 days for a total of 6 cycles. These patients were analyzed for response after 3 cycles of LD Ara-C and at the time of completion of therapy. Toxicity was recorded at the end of each cycle of Ara-C. There were 6 male and 4 female patients in the age range of 24 to 76 years. The morphological diagnosis was chronic myelomonocytic leukemia in 2, refractory anemia with excess blasts in 4 and refractory anemia with excess blasts in transformation in 4. Only 1 patient achieved a complete remission and 1 patient achieved a partial response. Four patients had progressive disease on treatment. One patient died of neutropenic sepsis and 1 of resistant thrombocytopenia and intracranial hemorrhage while on treatment. One patient refused further treatment after a minor clinical response and in 1 patient treatment was stopped due to toxicity. This data in a pilot study with a limited number of patient suggests that ATRA in combination with Ara-C has little effect in MDS.     

Spectrofluorimetric determination of prenalterol hydrochloride in pharmaceutical preparations and biological fluids

A simple and highly sensitive fluorimetric method was developed for the routine determination of prenalterol hydrochloride in bulk, in dosage forms and in biological fluids. The method is based on the fluorescence induced by reaction of the nitroso-derivative of prenalterol hydrochloride with 2-cyanoacetamide in the presence of ammonia. The different experimental parameters were carefully studied and incorporated into the procedure. The fluorescence is measured at 440 nm after excitation at 368 nm. Fluorescence intensity is a linear function of prenalterol hydrochloride concentration over the range of 0.1-2.8 microg x ml(-1) in the solution finally measured. A proposal for the reaction pathway was suggested.     

Flow-injection spectrophotometric determination of diclofenac sodium in pharmaceuticals and urine samples

The localization of two salmon-type gonadotropin-releasing hormone (sGnRH) precursors, pro-sGnRH-I (short type) and pro-sGnRH-II (long type), was investigated by using in situ hybridization techniques in the brain of the landlocked sockeye salmon, Oncorhynchus nerka. We used 30-mer oligonucleotide probes complementary to pro-sGnRH-I and pro-sGnRH-II cDNA. No significant differences were observed in the localization of sGnRH neurons expressing pro-sGnRH-I and pro-sGnRH-II mRNAs; both were expressed in the olfactory nerve, the olfactory bulbs, the regions between the olfactory bulb and telencephalon, the ventral telencephalon, the preoptic area, and the hypothalamus. Almost all sGnRH neurons examined co-expressed both precursors. The expression of two sGnRH precursors in the same neuron and the wide distribution of such neurons in the brain suggest that there are no functional differences between the two precursors.     

Reversed-phase ion-pair HPLC determination of some water-soluble vitamins in pharmaceuticals

A reversed-phase ion-pair high-performance liquid chromatografic method (RP-IPC) was developed to assay some water-soluble vitamins in solution dosage forms. Vitamins of the B-group B1, B2, B3, and B6, including vitamin C were determined in Oligovit coated tablets. In Beviplex coated tablets the vitamins B1, B2, B3, B6 and p-aminobenzoic acid were analysed. Hexanesulphonic acid sodium salt and triethanolamine in water methanol were used as mobile phase with adjusting pH to 2.8 with orthophosphoric acid. Phenol was used as an internal standard. For quantitative simultaneous analysis of vitamins in pharmaceutical formulations, the method of internal standard was used. All parameters for the validation of the method are given.     

Time-resolved fluoroimmunoassay for the determination of lisinopril and enalaprilat in human serum

A solid-phase immunoassay with detection based on time-resolved fluorescence (TR-FIA) has been developed for the determination of lisinopril and enalaprilat in human serum. The immunogen was prepared by coupling lisinopril to bovine serum albumin through a two-step reaction with difluorodinitrobenzene. An antiserum specific to both lisinopril and enalaprilat was used. The assay is based on the competitive immunoassay principle in which the drug competes with biotin-labeled drug for a limited quantity of primary antibody bound via sheep anti-rabbit globulin to the wells of microtitration strips. At the end of the first incubation, the unbound biotin-labeled drug is washed away. In the second step, europium-labeled streptavidin (specific to biotin) reacts with the biotin already bound to the solid-phase antibody. After a washing step, the addition of an enhancement solution dissociates the europium ions from the labeled streptavidin into solution. The fluorescence from each sample is inversely proportional to the concentration of the drug in the sample. The assay demonstrates good accuracy, reproducibility and specificity at serum concentrations down to 0.5 ng ml-1. However, the useful concentration range of TR-FIA is much narrower than that obtained by double antibody radioimmunoassay (RIA).     

The improvement of colorimetric determination of lipid peroxide in human serum

The present work details an improved application of kit to the measurement of lipid peroxides in human serum. Kits based on the reaction of lipid hydroperoxides with a leucomethylene blue derivative in the presence of hemoglobin. Overall sensitivity was increased by taking samples 5 times larger than those indicated in product literature for the system. It was necessary, however, to compensate actual data for protein error. To do this, the following empirically obtained formula was employed: A = a/(-3.45x + 98) x 100, where A (nmol/ml) indicates compensated data for lipid peroxides, a (nmol/ml) indicates the data for the actual measurement of lipid peroxides, and x (g/dl) indicates the total protein. We obtained what we considered to be satisfactory results by the above formula, as it allowed us to observe that lipid peroxides in fresh human serum undergo a change, momentarily.     

Methods for the determination of organochlorine pesticide residues in human serum

The effectiveness of solid-phase extraction with Florisil for the determination of 12 organochlorine pesticide residues from human serum was examined. Recoveries greater than 84% and coefficients of variation better than 19% were obtained. Others methods, such as column partition and matrix solid-phase dispersion, were compared. The better method provides quantification limits ranging from 1.08 microg/l for gamma-HCH and 37.5 microg/l for p,p'-DDT when capillary gas-liquid chromatography with electron-capture detection is used for the final determination.     

Simple and fast chromatographic method for the determination of sotalol in human serum

We developed a method for the determination of sotalol in human plasma. After a simple deproteinization of the sample, we submit the supernatant to high-performance liquid chromatography with fluorescence detection. A few minutes are necessary to complete the analysis.     

Application of derivative spectrophotometry for determination of coenzyme Q10 in pharmaceuticals and plasma

The use of derivative spectrophotometry is proposed in this work for determination of coenzyme Q10 in formulations and in human plasma. The spectrophotometric procedure is simpler and less expensive than chromatographic techniques commonly used for the analysis of coenzyme. The active compound can be determined in the range 0.25-10 ppm for standard solutions and pharmaceuticals and 0.05-1.5 ppm in plasma. The proposed method was applied for coenzyme determination in real samples. The results agree well with declared value and with these obtained by HPLC.     

Direct determination of selenium in human blood serum and plasma by electrothermal atomic absorption spectrometry

A method is described for the direct determination of selenium in serum or plasma by electrothermal atomic absorption spectrometry with deuterium-arc background correction. Samples are diluted (1 + 2) with a modifier containing palladium nitrate and Triton X-100. Samples are atomised from a L'vov platform in a pyrolytically-coated electrographite tube and peak area signals are measured. Direct determination is possible by using selenium standards matched to the physiological concentrations of sodium chloride, calcium and phosphate. The detection limit is 6 micrograms/L in the original sample. Precision at a selenium concentration of 97 micrograms/L was 2.2% RSD within batch and 3.0% RSD between batch. Accuracy is shown by (i) analysis of a Seronorm reference serum (value obtained 97 +/- 3 micrograms/L; recommended value 96 micrograms/L); (ii) recovery of added selenium (93.3 +/- 6.7% and 98.2 +/- 3.3% at additions of 30 and 60 micrograms/L, respectively) and (iii) comparison of results with mean of all laboratories in an external quality assessment scheme.     

Gas-chromatographic determination of dyphylline in serum and saliva

We describe a simple determination of dyphylline in serum and saliva by gas chromatography after solvent extraction. Dyphylline concentrations were found to be about 36% higher in saliva than in the corresponding serum.     

High-performance liquid chromatographic determination of phenylephrine in human serum using column switching with fluorescence detection

A method for the determination of total phenylephrine (free plus conjugated) in human serum was developed using column-switching high-performance liquid chromatography (HPLC) with fluorescence detection. After serum was deproteinized with acetonitrile, the conjugated phenylephrine was hydrolyzed with diluted hydrochloric acid. The solution was evaporated to dryness. The reconstituted residue was analyzed with HPLC using a heart-cut technique. Good recoveries of the analytes from spiked human serum samples were obtained with small coefficients of variation. A good linear response was obtained for the concentration range 5-500 ng/ml. The lower limit of quantitation for phenylephrine in human serum was 5 ng/ml. The method was applied to the determination of phenylephrine in human serum after oral administration of phenylephrine hydrochloride.     

Improved colorimetric determination of serum zinc

We show how zinc may easily be quantified in serum by first using an optimum concentration of guanidine hydrochloride to cause release of zinc from proteins, followed by complexation of released metals with cyanide. The cyanide complex of zinc is preferentially demasked with chloral hydrate, followed by a colorimetric reaction between zinc and 4-(2-pyridylazo)resorcinol. This is a sensitive water-soluble ligand; its complex with zinc has an absorption maximum at 497 nm. Values found by this technique compare favorably with those obtained by atomic absorption spectroscopy.     

Bioactivation and irreversible binding of the cognition activator tacrine using human and rat liver microsomal preparations. Species difference

Tacrine's [1,2,3,4-tetrahydro-9-acridinamine monohydrochloride monohydrate, (THA)] metabolic fate was examined using human and rat liver microsomal preparations. Following 1-hr incubations with human microsomes, [14C]THA (0.4 microM) was extensively metabolized to 1-hydroxyTHA with trace amounts of 2-, 4-, and 7-hydroxyTHA also produced. Poor recovery of radioactivity in the postreaction incubates suggested association of THA-derived radioactivity with precipitated microsomal protein. After exhaustive extraction, 0.034, 0.145, 0.126, and 0.012 nmol eq bound/mg protein/60 min of THA-derived radioactivity was bound to human liver preparations H109, H111, H116, and H118, respectively. Preparations H109 and H118 were lower in P4501A2 content and catalytic activity as compared with preparations H111 and H116. Incubations of equimolar [14C]1-hydroxyTHA with human liver microsomes also resulted in binding to protein, although to a lesser extent than observed with THA. [14C]THA (0.4 microM) was incubated for 1 hr with rat liver microsomes (1 microM P-450) prepared from noninduced (N), phenobarbital (PB), isoniazid (I), and 3-methylcholanthrene (3-MC)-pretreated animals. In all incubations, 1-hydroxyTHA was the major biotransformation product detected. After exhaustive extraction, 0.048, 0.054, 0.049, and 0.153 nmol eq/mg protein/60 min of THA-derived radioactivity was bound to microsomal protein from N, PB, I, and 3-MC pretreated rats. Increased binding with 3-MC induced rat liver preparations suggests the involvement of the P-450 1A subfamily in THA bioactivation. Glutathione (5 mM) coincubation inhibited the irreversible binding of THA-derived radioactivity in both human and 3-MC-induced rat liver preparations, whereas human epoxide hydrase (100 micrograms/incubate) had a relative minor effect. A mechanism is proposed involving a putative quinone methide(s) intermediate in the bioactivation and irreversible binding of THA. A species difference in THA-derived irreversible binding exists between human and noninduced rat liver microsomes, suggesting that the rat is a poor model for studying the underlying mechanism(s) of THA-induced elevations in liver marker enzymes found in clinical investigations.     

Elucidation of mitochondrial effects by tetrahydroaminoacridine (tacrine) in rat, dog, monkey and human hepatic parenchymal cells

Tetrahydroaminoacridine (tacrine) causes morphological and functional changes in the endoplasmic reticulum, ribosomes, and mitochondria in the liver of humans and animals. In order to investigate species differences as well as to understand the morphological changes, we examined the effects of tacrine on respiration and electron transport in mitochondria isolated from rat, dog, monkey, and human liver. Tacrine produced significantly decreased respiratory control ratios (RCR) in all species at concentrations ranging from 5 to 25 microg/ml. Human mitochondria were more sensitive to tacrine effects with RCR decreased 24% at 5 microg/ml while other species were unaffected at this concentration. The tacrine effects were characterized by increased hepatic mitochondrial State 4 respiration in rats and decreased State 3 respiration in humans. Mitochondria from aged rats were more sensitive to the effects of tacrine than mitochondria from young animals, with significantly decreased RCR at 10 microg/ml in aged rats while mitochondria from young rats were unaffected at this concentration. Concomitant with the respiratory changes, mitochondrial DNA synthesis was impaired. Since tacrine undergoes extensive biotransformation, we also explored the possibility that metabolites could exert detrimental effects. The ranking order of potency for decreasing RCR caused by monohydroxylated metabolites was: tacrine > 4-OH and 7-OH > 2-OH, 1-OH, and velnacrine with the latter group of metabolites having no effect on mitochondrial respiration at concentrations up to 50 microg/ml. In vivo administration of 20 mg/kg tacrine to rats for up to 20 days caused a paradoxical increase in RCR and P/O on Day 1 and decreased RCR on Days 9 and 20, the later findings being consistent with in vitro data. From these data we propose that tacrine does not necessarily have to be metabolized to exert effects on mitochondria at different sites in the electron transport chain that differ among species. These effects are exacerbated in mitochondria from older animals and humans appear to be more sensitive than the laboratory animals studied.