Chemiluminescence detection of nine corticosteroids in liver

Electrocatalytic oxidation and determination of dexamethasone at an Fe3O4/PANI–CuII microsphere modified carbon ionic liquid electrode

A novel, simple, sensitive and selective electrochemical sensor based on an Fe₃O₄/PANI–Cu^II microsphere modified carbon ionic liquid electrode is constructed and utilized for the determination of dexamethasone.

Micro determination of cortisol and cortisone in umbilical cord blood by chemiluminescent high-performance liquid chromatography

A simple, sensitive and specific chemiluminescent high-performance liquid chromatography method, based on the luminol reaction, for determination of serum cortisol and cortisone, was established. In infants, placental 11beta-hydroxysteroid dehydrogenase type 2 enzyme (11beta-HSD2) activity may affect adrenal function early after birth. The cortisol-cortisone ratio of serum concentrations in umbilical cord blood is an indicator of placental 11beta-HSD2 activity. The optimum conditions for the luminol reaction were determined to be 1.5 mM luminol, 0.6 M sodium hydroxide, 0.15 mm potassium hexacyanoferrate(III) and 200 mM potassium hexacyanoferrate (II). The calibration curves for cortisol and cortisone exhibited good linearity. The correlation coefficients of the calibration curves were 0.996. The intra- and inter-day precisions were in the ranges: cortisol 7.0-12.2 and 4.4-9.2%, cortisone 5.3-7.0 and 6.2-9.9%. The recoveries of these steroids were in the ranges: cortisol 97-105%, cortisone 94-102%. The limits of detection were as follows: cortisol, 0.17 microg/dl; cortisone 0.15 microg/dl. This assay could be successfully applied to determination of the cortisol-cortiosone ratio of serum concentrations in umbilical cord bloods.

Methionine restriction effects on 11 -HSD1 activity and lipogenic/lipolytic balance in F344 rat adipose tissue

Methionine restriction (MR) limits age-related adiposity in Fischer 344 (F344) rats. To assess the mechanism of adiposity resistance, the effect of MR on adipose tissue (AT) 11beta-hydroxysteroid dehydrogenase-1 (11beta-HSD1) was examined. MR induced 11beta-HSD1 activity in all ATs, correlating with increased tissue corticosterone. However, an inverse relationship between 11beta-HSD1 activity and adipocyte size was observed. Because dietary restriction controls lipogenic and lipolytic rates, MR's effects on lipogenic and lipolytic enzymes were evaluated. MR increased adipose triglyceride lipase and acetyl-coenzyme A carboxylase (ACC) protein levels but induced ACC phosphorylation at serine residues that render the enzyme inactive, suggesting alterations of basal lipolysis and lipogenesis. In contrast, no changes in basal or phosphorylated hormone-sensitive lipase levels were observed. ACC-phosphorylated sites were specific for AMP-activated protein kinase (AMPK); therefore, AMPK activation was evaluated. Significant differences in AMPKalpha protein, phosphorylation, and activity levels were observed only in retroperitoneal fat from MR rats. No differences in protein kinase A phosphorylation and intracellular cAMP levels were detected. In vitro studies revealed increased lipid degradation and a trend toward increased lipid synthesis, suggesting the presence of a futile cycle. In conclusion, MR disrupts the lipogenic/lipolytic balance, contributing importantly to adiposity resistance in F344 rats.

Detection of glucocorticoid residues in pig liver by high-performance liquid chromatography with on-line electrogenerated [Cu(HIO6)2]5−—luminol chemiluminescence detection

A novel method was developed for the simultaneous determination of glucocorticoid residues such as triamcinolone (TR), prednisolone (PR), hydrocortisone (HC), cortisone (CO), methylprednisolone (MP), dexamethasone (DE) and triamcinolone acetonide (TA) by high-performance liquid chromatography (HPLC) coupled with chemiluminescence (CL) detection. The procedure was based on the enhancement effect of glucocorticoids on the chemiluminescence reaction between luminol and the complex of trivalent copper and periodate ([Cu(HIO6)2]5-), which was on-line electrogenerated by constant current electrolysis. The HPLC separation used a Nucleosil RP-C18 column (250 mmx4.6 mm i.d., 5 microm, pore size, 100 A) with a mobile phase consisting of acetonitrile and 1.0 mmol L(-1) ammonium acetate (pH 6.8, 40:60,v/v) at a flow rate of 0.8 mL min(-1). The effects of several parameters on the HPLC resolution and CL emission were studied systematically. Liver samples were hydrolyzed with Helix pomatia juice followed by a solid-phase extraction procedure. Under optimum conditions, the limits of detection (LOD) at a signal-to-noise of 3 ranged from 0.08 to 1.0 ng g(-1) and the limits of quantification (LOQ) at a signal-to-noise of 10 ranged from 0.27 to 3.33 ng g(-1) for seven glucocorticoids. The relative standard deviations (RSD) of intra- and inter-day precision were below 6.8%. The average recoveries for glucocorticoids (spiked at the levels of 5-50 ng g(-1)) in pig liver ranged from 88 to 106%, and the relative standard deviations of the quantitative results were from 2.0 to 6.9%. The proposed method had been successfully applied to the determination of glucocorticoid residues in pig liver.

Development of a chemiluminescent ELISA for determining chloramphenicol in chicken muscle

An indirect competitive enzyme-linked immunosorbent assay (ELISA) with chemiluminescent (CL) detection for chloramphenicol (CAP) in chicken muscle was developed. CAP-specific polyclonal antibody was raised in rabbit with a CAP-succinate derivative conjugated with bovine serum albumin. Luminol solution was used as the substrate of horseradish peroxidase. The detection limit was 6 ng/L. The CL-ELISA was 10 times more sensitive compared to the colorimetric-ELISA. When CAP was spiked in chicken muscle at levels of 0.05-5 microg/kg, recoveries ranged from 97 to 118% with coefficients of variation of 6-22%. In an actual residue study, the results obtained by CL-ELISA correlated well with those obtained by gas chromatography with microcell electron capture detector. The residue levels of CAP in treated chicken decreased with time and dropped rapidly after the first 6 h from around 50 to 10 microg/kg. After 3 days, CAP was not detected in chicken muscle. The developed method is therefore suitable for screening of CAP in chicken muscle samples.

Detection of synthetic corticosteroids in bovine urine by chemiluminescence high-performance liquid chromatography

The development of a black market of chemical cocktails for illegal growth promotion in food-producing animals includes substances that are potentially dangerous for human health, such as synthetic corticosteroids. The potential presence of these residues in food makes it necessary to develop rapid and sensitive analytical methodologies to detect such substances, preferably in live animals before they arrive at the market. A chemiluminescence (CL) detection method for the determination of four synthetic corticosteroids (prednisolone, betamethasone, dexamethasone and flumethasone) in bovine urine has been developed. The proposed system, which does not need any derivatization procedure, offers an easy method well suited for routine research. Urine samples were homogenized with methanol:water (50:50, v/v) and centrifuged. The upper layer was collected and Strata X cartridges were used for cleaning up. The purified residues were evaporated to dryness and then redissolved in the mobile phase. Analysis of the extracts was performed using high-performance liquid chromatography with chemiluminescence detection, employing luminol as the CL reagent. The recovery curves, obtained at four spiking levels (different for each corticosteroid), showed that recoveries of at least 70% could be obtained for urine. The chemiluminescence detection procedure afforded satisfactory results with respect to sensitivity and the LOD and LOQ, taken as the first point of the regression curve, ranged from 4 ppb to 65 ppb. The maximum mean RSD was below 13% and below 15% for intra- and inter-day assay, respectively, in all cases.

Development of a solid phase extraction method for simultaneous determination of corticoids and tranquilizers in serum samples

A simple and fast solid phase extraction (SPE) method allowing the preconcentration, clean-up, and subsequent separate elution of phenothiazines (chlorpromazine hydrochloride, acetopromazine, and propionylpromazine hydrochloride) and glucocorticoids (dexamethasone, betamethasone acetate, and phenylbutazone) from serum samples has been developed. Both fractions were separately collected and analyzed without any additional treatment by high performance liquid chromatography with UV-Vis. The performance of the complete procedure was satisfactory irrespective of the spiking level with recoveries in the range 64-85% for all analytes investigated but for phenylbutazone (20%). Repeatability, evaluated as the relative standard deviation, was globally better than 12%. LC-MS was used for final confirmation of the results.

Separation and detection of neuroactive steroids from biological matrices

This review is based on a selection of research papers published mainly in the last decade and it describes various analytical aspects of separation and detection of neuroactive steroids in biological matrices.