Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.15.1 (ACE)
 18,300 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Two modes of stepwise gradient elution of capillary electrochromatography were developed for the analysis of environmental samples on both a laboratory-made and a commercial CE instrument. Using the laboratory-made apparatus, another mobile phase was dropped directly into the inlet vial with a pipet. By this means, nine 2,4-dinitrophenylhydrazine (DNPH)-derivatized ketones and aldehydes were separated with high resolution. Not only was analysis time shortened by more than one half, but the detection limit was greatly improved compared to that in isocratic elution. The latter was achieved using the P/ACE 5510 system (Beckman Instruments, Fullerton, CA, U.S.A.), which moved the mobile phase vials automatically. The stop-flow technique was utilized during transfer. It had no effect on solute retention. With this method, the concentration and type of organic modifier in the mobile phase could be changed. A mixture of 13 aromatic hydrocarbons was separated completely in 14 min by changing the mobile phase from 80% methanol to 80% acetonitrile and 90% acetonitrile in a sequential step mode. The RSD of the retention time of each component in six consecutive injections was below 0.374%. All of these results demonstrate that stepwise gradient elution of capillary electrochromatography may be useful in the analysis of complex environmental samples.
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PMID:Stepwise gradient elution of capillary electrochromatography in the analysis of environmental samples. 1032 76

In clinical practice, the measurement of urinary free cortisol (UFC) provides the most sensitive and specific diagnostic information for excess adrenal production of cortisol. The existing methodologies (RIA and HPLC) are time consuming, costly, involve tedious extractions, derivatizations and problems with non-specific interactions with cortisol metabolites in urine. In the present study, we describe the development of an SPE-CE method for the rapid analysis of UFC. UFC was concentrated using SPE C18 cartridges (3M Empore) under a vacuum and eluted with acetonitrile-SDS. The use of 10% acetone to wash cartridges before final elution with acetonitrile-SDS showed significant improvements in the free cortisol recovery. The complete extraction was accomplished in 10-15 min with a recovery of 89-94%. CE analysis was done on a Beckman P/ACE 5010 with detection at 254 nm using a neutral capillary. Detection limits of free cortisol in urine was improved to 10 microg/l with SPE compared to 500 microg/l without SPE. No interferences either from BSA or other urinary cortisol metabolites affected the free cortisol determinations. The results showed the feasibility of a rapid UFC detection with improved sample handling capacity.
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PMID:Development of a urinary free cortisol assay using solid-phase extraction-capillary electrophoresis. 1043 79

A novel capillary zone electrophoresis method is described for the determination of taurine in plasma. The method is rapidly executed and is highly selective for taurine as separation is based on the difference in ionisation of this amino acid from that of other amino acids. Following addition of homotaurine as internal standard, plasma proteins were precipitated with acetonitrile and the supernatant was derivatised with fluorescamine in the presence of a borate buffer. Capillary electrophoresis (CE) separations were carried out in reverse polarity mode at 27.5 kV on a Beckman P/ACE MDQ CE instrument, equipped with a diode array detector (DAD) set at 266 nm. The sample tray was cooled to 5 degrees C and separations were carried out at 20 degrees C. The fused-silica capillary was 50.2 cm in length (40.2 cm to detector) with an internal diameter of 75 microm. A capillary conditioning solution was applied daily in order to suppress the residual electroosmotic flow (EOF). The method, which was validated using feline plasma as the blank matrix, was shown to be linear and reproducible over the concentration range 2.5-100 microg/mL. The coefficients of variation (CVs) of replicate analyses were less than 4.5% at 1 microg/mL taurine in feline plasma and less than 3% for 2.5 microg/mL in human plasma. Recovery was estimated at 99.2% with a CV of 4.85%. It has been demonstrated that quantitation in aqueous solution yields similar results to those obtained by interpolation on a plasma calibration curve provided that subtraction for the taurine peak in unspiked plasma is carried out and that a suitable internal standard is employed.
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PMID:Determination of taurine in plasma by capillary zone electrophoresis following derivatisation with fluorescamine. 1073 9

The fate of 2,4-dichlorophenoxyacetic acid (2,4-D), a mixture of [phenyl(U)-(14)C]-2,4-D and unlabeled 2,4-D, in bluegill sunfish was investigated after exposure to approximately 11 ppm under static conditions for 4 days. Total radioactive residues (TRR) in whole fish increased from 0.41 ppm on day 1 to 0.60 ppm on day 3. TRR levels in fillet (edible) and viscera (nonedible) of treated fish on day 4 were 0.41 and 1.9 ppm, respectively. Most residues in both matrices were acetonitrile soluble; small amounts were hexane soluble or unextractable with solvents. Acid and base hydrolyses with ethyl acetate partitioning were used to release the fillet unextractable residues. The identification of 2,4-D and 2,4-dichlorophenol (2,4-DCP) in the fillet was conclusively confirmed by GC-MS analysis. On the basis of the experimental data from this study, a metabolic pathway for 2,4-D in bluegill sunfish in which the 2,4-D is metabolized to 2,4-DCP and conjugates of 2,4-D and 2,4-DCP is proposed.
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PMID:Uniformly (14)C-ring-labeled 2,4-dichlorophenoxyacetic acid: a metabolism study in bluegill sunfish, Lepomis macrochirus. 1140 78

Captopril, a well-known angiotensin converting enzyme (ACE) inhibitor, is widely used for treatment of arterial hypertension. Recent studies suggest that it may also act as a scavenger of free radicals because of its thiol group. Therefore, the present study describes a rapid, sensitive and relatively simple method for the detection of captopril in biological tissues with reverse-phase HPLC. Captopril was first derivatized with ThioGlo 3 [3H-Naphto[2,1-b]pyran,9-acetoxy-2-(4-(2,5-dihydro-2,5-dioxo-1H-pyrrol-1-yl)phenyl-3-oxo-)]. It was then detected by fluorescence-HPLC using an Astec C(18) column as the stationary phase and a water:acetonitrile:acetic acid:phosphoric acid mixture (50:50; 1 mL/L acids) as the mobile phase (excitation wavelength, 365 nm; emission wavelength, 445 nm). The calibration curve for captopril was linear over a range of 10-2500 nM and the coefficient of variation acquired for the within- and between-run precision for captopril was 0.5 and 3.8%, respectively. The detection limit of captopril with this method was found to be 200 fmol/20 microL injection volume. Its relative recovery from biological samples was determined to the range from 93.3 to 105.3%. Based on these results, we believe that our method is advantageous for captopril determination.
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PMID:Determination of captopril in biological samples by high-performance liquid chromatography with ThioGlo 3 derivatization. 1174 37

Silk fibroin peptides could be obtained from soluble silk fibroin by enzymatic hydrolysis. Its hydrolyzates produced with Alcalase showed significant inhibitory activity against the angiotensin I-converting enzyme (ACE). One inhibitory peptide from the hydrolyzate at a degree of hydrolysis of 20% (sample A20) was purified and identified. Sample A20 was first isolated by size exclusion chromatography(SEC), eluted with 0.01 mol/L hydrochloric acid solution on a Sephadex G-15 column (1.6 cm i.d. x 100 cm). The peak of No. 5 on the SEC chromatography was further purified by reversed-phase HPLC (mu Bondapak C18 P/N 84176 column, 7.8 mm i.d. x 300 mm), eluted with a linear gradient elution with acetonitrile from 0% to 15% at temperature (30 +/- 2) degrees C. Then the pure peptide with ACE inhibitory activity was obtained, the amino acid sequence of which was identified as Gly-Tyr by mass spectrometry.
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PMID:[Separation, purification and identification of angiotensin converting enzyme inhibitory silk fibroin peptide]. 1254 1

Non-steroidal anti-inflammatory drugs (NSAIDs) such as piroxicam and mefenamic acid are commonly prescribed to treat inflammation, pain and fever. Similarly acetylsalicylic acid is used to prevent strokes and heart attacks. A rapid and selective method was developed for the simultaneous assay of three NSAIDs and salicylic acid via HPLC with fluorescence detection. The separation was performed using a "dual-mode" gradient (acetonitrile-0.1% aqueous orthophosphoric acid) and the analysis was completed within 7 min using an ACE column C18, 5 microm, 150 mm x 4.6 mm. Naproxen was used as internal standard. The proposed method is simple, selective as well as with a good sensitivity reaching LOD lower than 2 pmol (0.05 microM) and was applied for quantitative analysis in pharmaceuticals and in human serum samples. The mean recovery was more than 95% and the within-day and between-days precisions were found to be satisfactory having RSD within the acceptable limits (<10%).
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PMID:Determination of non-steroidal anti-inflammatory drugs in pharmaceuticals and human serum by dual-mode gradient HPLC and fluorescence detection. 1764 36

Alpha-lipoic acid is an antioxidant used both in the prevention and treatment of various oxidative stress related diseases. It is an important constituent of some dietary supplements and can also be found in plant and animal sources. A rapid method for the determination of alpha-lipoic acid in dietary supplements based on high performance liquid chromatography coupled with a coulometric electrode array detector (CEAD) and an electrospray ionization mass spectrometer (ESI-MS) was developed. First, alpha-lipoic acid was extracted with methanol by sonication, chromatographic separation was then achieved by isocratic elution [acetonitrile/methanol/50mM potassium dihydrogen phosphate (pH 3, adjusted with phosphoric acid): 350/65/585, v/v/v] using an ACE 3-C-18 column at a flow rate of 0.45 ml/min. alpha-Lipoic acid was detected by means of a CEAD at +300, +400, +450, +500, +550, +600, +650, and +700 mV against palladium reference electrodes. For ESI-MS detection (negative mode), the composition of the mobile phase was changed to 0.1% acetic acid in water/acetonitrile 55:45, v/v applying a flow rate of 0.2 ml/min. The presented methods were utilized to determine the alpha-lipoic acid content in six dietary supplements. The results of both detection modes were in good correlation.
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PMID:alpha-Lipoic acid in dietary supplements: development and comparison of HPLC-CEAD and HPLC-ESI-MS methods. 1788 Nov 79

Adequate separation is essential for the quantitation of trace amounts of dexamethasone that are typically found in betamethasone active pharmaceutical ingredients and vice versa. In this paper, we describe three simple and efficient high-performance liquid chromatography methods from which true baseline separations between betamethasone and dexamethasone are achieved even when the concentration ratios between these two epimers are larger than 2000:1. One method is developed on a 5 cm ACE C8 column that uses water and acetonitrile as the mobile phase and 20 mM beta-cyclodextrin as the mobile phase additive. The resolution factor between betamethasone and dexamethasone is 3.3. The second method is developed on a 10 cm ACE C8 column that uses water and acetonitrile as the mobile phase, in which the resolution factor between the epimers is 2.7. The third method is developed on a 10 cm ACE C8 column using water and tetrahydrofuran as the mobile phase, in which the resolution factor between the epimers is 3.1. Preliminary validation studies are carried out for the second and third methods.
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PMID:Quantitation of trace betamethasone or dexamethasone in dexamethasone or betamethasone active pharmaceutical ingredients by reversed-phase high-performance liquid chromatography. 1821 83

Column high-performance liquid chromatographic (LC) and UV spectrophotometric methods for the quantitative determination of citalopram, a potent and selective serotonin reuptake inhibitor, in tablets were developed. The parameters linearity, precision, accuracy, specificity, robustness, limit of detection, and limit of quantitation were studied according to International Conference on Harmonization guidelines. Chromatography was carried out by the reversed-phase technique on an ACE C18 column with a mobile phase composed of 0.30% triethylamine solution-acetonitrile (55 + 45, v/v) adjusted to pH 6.6 with 10% ortho-phosphoric acid at a flow rate of 1.0 mL/min and 25 degrees C. The UV spectrophotometric method was performed at 239 nm. The linearity of the LC method was in the range of 10.00-70.00 microg/mL, and 2.50-17.50 microg/mL for the UV spectrophotometric method. The interday and intraday assay precision was < 1.5% (relative standard deviation) for the LC and UV spectrophotometric methods. The recoveries were in the range 100.70-101.35% for the LC method and 98.48-98.65% for the UV spectrophotometric method. Statistical analysis by Student's t-test showed no significant difference between the results obtained by the 2 methods. The proposed methods are highly sensitive, precise, and accurate and can be used for the reliable quantitation of citalopram in tablets.
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PMID:Development and validation of column high-performance liquid chromatographic and ultraviolet spectrophotometric methods for citalopram in tablets. 1837 85


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