Studies on steroids. CCXXIX. Separation and characterization of catechol oestrogen glucuronides in urine of pregnant women by high-performance liquid chromatography

Ferrocene-based derivatization in analytical chemistry

Ferrocene-based derivatization has raised considerable interest in many fields of analytical chemistry. This is due to the well-established chemistry of ferrocenes, which allows rapid and easy access to a large number of reagents and derivatives. Furthermore, the electrochemical properties of ferrocenes are attractive with respect to their detection. This paper summarizes the available reagents, the reaction conditions and the different approaches for detection. While electrochemical detection is still most widely used to detect ferrocene derivatives, e.g., in the field of DNA analysis, the emerging combination of analytical separation methods with electrochemistry, mass spectrometry and atomic spectroscopy allows ferrocenes to be applied more universally and in novel applications where strongly improved selectivity and limits of detection are required.

A liquid chromatography-mass spectrometry method for the quantitative analysis of urinary endogenous estrogen metabolites

The ability to measure estrogen metabolites (EMs) quantitatively is important for investigating their individual roles in cancer screening, treatment and prevention, as well as in a host of other hormone-related disorders. In this protocol we describe a method that is capable of quantitating 15 distinct EMs in urine. Endogenous EMs are quantitatively measured using a liquid chromatography-tandem mass spectrometry method in which the spectrometer operates in a selected reaction monitoring mode. This method is capable of quantifying estrone and its 2-, and 4- and 16alpha-hydroxy and its 2-, 4-methoxy derivatives, and 2-hydroxyestrone-3-methyl ether; 17beta-estradiol and its 2-hydroxy, and 2- and 4-methoxy derivates, and estriol, 16-epiestriol, 17-epiestriol, and 16-ketoestradiol. The method requires only 0.5 ml of urine and approximately 60 urine samples can be quantitatively analyzed per week.

Measuring Fifteen Endogenous Estrogens Simultaneously in Human Urine by High-Performance Liquid Chromatography-Mass Spectrometry

A sensitive, specific, accurate, and precise high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry method for measuring the absolute quantities of 15 endogenous estrogens and their metabolites in human urine has been developed and validated. The method requires a single hydrolysis/extraction/derivatization step and only 0.5 mL of urine, yet is capable of simultaneously quantifying estrone and its 2-, 4-methoxy and 2-, 4-, and 16alpha-hydroxy derivatives, and 2-hydroxyestrone-3-methyl ether; estradiol and its 2-, 4-methoxy and 2-, 16alpha-hydroxy derivatives, 16-epiestriol, 17-epiestriol, and 16-ketoestradiol in pre- and postmenopausal women as well as men. Standard curves are linear over a 10(3)-fold concentration range with the standard error of the estimate (SEE) and the relative standard error of the estimate (RSEE) for the linear regression line ranging from 0.0131 to 0.1760 and 1.2 to 7.3%, respectively. The lower limit of quantitation for each estrogen is 0.02 ng/0.5 mL urine sample (2 pg on column), with the percent recovery of a known added amount of compound (accuracy) of 96-107% and an overall precision, including the hydrolysis, extraction, and derivatization steps, of 1-5% relative standard deviation (RSD) for samples prepared concurrently and 1-12% RSD for samples prepared in separate batches. Since individual patterns of estrogen metabolism may influence the risk of breast cancer, accurate, precise, and specific measurement of endogenous estrogen metabolites in biological matrixes will facilitate future research on breast cancer prevention, screening, and treatment.

Measuring Seven Endogenous Ketolic Estrogens Simultaneously in Human Urine by High-Performance Liquid Chromatography−Mass Spectrometry

A rapid, sensitive, and specific high-performance liquid chromatography-electrospray ionization-multistage mass spectrometry (MS) method for measuring endogenous ketolic estrogen metabolites in human urine has been developed. The method requires a single hydrolysis/extraction/derivatization step and only 2.5 mL of urine, yet is able to simultaneously quantify estrone and its 2-methoxy and 2-, 4-, and 16alpha-hydroxy derivatives, 16-ketoestradiol, and 2-hydroxyestrone-3-methyl ether metabolites. The combination of a simple hydrazone derivatization step with multistage MS greatly enhances the sensitivity and specificity of the analysis of endogenous estrogen within human urine. Standard curves are linear over a 100-fold concentration range with linear regression correlation coefficients typically greater than 0.99. The lower limit of quantitation for each ketolic estrogen is 0.2 ng/2.5-mL urine sample (10 pg on column), with an accuracy of 93-103% and an overall precision, including the hydrolysis, extraction, and derivatization steps, of 1-13% relative standard derivation (RSD) for samples prepared concurrently and 8-16% RSD for samples prepared in separate batches. This method also allows for the identification of 2-hydroxyestrone-3-methyl ether in urine obtained from both pre- and postmenopausal women. This potentially protective estrogen metabolite has been previously reported only in the urine of pregnant women. Since individual patterns of estrogen metabolism may influence the risk of breast cancer, accurate and specific measurement of estrogen metabolites in biological matrixes will facilitate future research on breast cancer prevention, screening, and treatment.

Stable isotope dilution high-performance liquid chromatography-electrospray ionization mass spectrometry method for endogenous 2- and 4-hydroxyestrones in human urine

A sensitive, precise and accurate stable isotope dilution high-performance liquid chromatography-electrospray ionization mass spectrometry method has been developed for measuring endogenous 2- and 4-hydroxyestrones, the main catechol estrogens in human urine. Compared to the published methods using gas chromatography-mass spectrometry, this approach simplifies sample preparation and increases the throughput of analysis. The unique part of our method is the use of a simple and rapid derivatization step that forms a hydrazone at the C-17 carbonyl group of catechol estrogens. This derivatization step has greatly enhanced method sensitivity as well as HPLC separability of 2- and 4-hydroxyestrones. Standard curves were linear over a 100-fold calibration range with correlation coefficients for the linear regression curves typically greater than 0.996. The lower limit of quantitation for each catechol estrogen is 1 ng per 10-ml urine sample, with an accuracy of 97-99% and overall precision, including the hydrolysis, extraction and derivatization steps, of 1-3% for samples prepared concurrently and 2-11% for samples prepared in several batches. This method is adequate for measuring the low endogenous levels of catechol estrogens in urine from postmenopausal women.

Isolation and characterization of the monkey UDP-glucuronosyltransferase cDNA clone monUGT1A01 active on bilirubin and estrogens

Although enzymes that catalyze the formation of steroids are well known, less information is available about the enzymes involved in the metabolism of these hormones. Steroid glucuronidation, by UDP-glucuronosyltransferase enzymes, is one mechanism by which steroid hormones can be metabolized and eliminated from a tissue. Previous results suggest that the monkey represents the most appropriate animal model for studying the physiologic relevance of steroid glucuronidating enzymes. The monkey UGT1A01 cDNA clone was isolated by RT-PCR amplification of the liver RNA. The cDNA contains an open reading frame of 1599 bp encoding a protein of 533 residues. The primary structure of monkey UGT1A01 is 95% identical to human UGT1A1. To compare monkey and human UGT1A1 enzymes, both cDNA clones were transfected into HK293 cells and stable cell lines expressing each UGT1A1 protein were established. Western blot analysis of the monUGT1A01-HK293 and hUGT1A1-HK293 cell lines using a anti-UGT1A polyclonal antibody (RC-71) revealed expression of exogenous 55 kDa UGT1 proteins. The transferase activities of monkey and human UGT1A1 proteins were tested with over 60 compounds and were demonstrated to be active on the same compounds. For endogenous compounds only bilirubin and C18 steroids were glucuronidated by these enzymes. Using microsome preparation (from HK293 cell expressing monkey UGT1A01), the apparent K(m) values were 13, 5 and 6 microM for the conjugation of estradiol, 2-hydroxyestradiol and 2-hydroxyestrone, respectively, and were very similar to the values obtained with human UGT1A1. Specific RT-PCR analysis demonstrated the expression of monkey and human UGT1A1 transcripts in several tissues including liver, kidney, intestine, prostate, testis and ovary suggesting a contribution of this isoenzyme to estrogen metabolism in the cynomolgus monkey as in human.

Derivatization for electrospray ionization mass spectrometry. 3. Electrochemically ionizable derivatives

In this paper, the use of ferrocene-based "electrochemically ionizable" derivatives to enhance ES-MS analysis of simple alcohols, sterols, and phenols is discussed. These derivatives are designed to take advantage of the electrolysis process inherent to operation of the ES ion source for selective ionization. Derivatization procedures, electrochemical character of the derivatives, and the ES-MS operational parameters necessary to maximize electrochemical ionization and to enhance gas-phase detection are presented with reference to ferrocenecarbamate ester derivatives of a variety of alcohol standards, as well as the ferroceneboronate derivative of the diol, pinacol. Tandem mass spectrometric analysis of the derivatives (precursor and product ion spectra) is shown to provide derivative confirmation, enhanced detection, and additional analyte structure information. The utility of this derivatization approach for the selective detection of alcohols in complicated mixtures is demonstrated using a saw palmetto (Serenoa repens) fruit extract known to contain a variety of alcohols at low levels.

Enzyme histochemistry of the regressing rat decidua and metrial gland

In order to understand more about participation of the basal placental zones in processes of regression and degradation as well as separation on the cellular level, the cell metabolism of the rat decidua and metrial gland was investigated enzyme histochemically in cryosections for activities of oxyradical-forming enzymes and hydrolyzing enzymes. Additionally, plastic sections were studied to facilitate the recognition of cell types. Decidual stromal cells and fibroblasts formed the vast majority amongst many cell types in the decidua and metrial gland. High activities of enzymes involved in purine degradation and oxyradical generation were demonstrated in decidual stromal cells and fibroblasts. Microsomal alanyl aminopeptidase and various acid hydrolases were shown to be extremely active in decidual stromal cells. The abundance of these enzyme activities in the decidua and metrial gland in contrast to other placental areas suggests, that these enzymes may have specialized functions in connection with regression and degradation processes finally contributing to placental separation.

Separation and characterization of the metabolic products of lappaconitine in rat urine by high-performance liquid chromatography

The separation and characterization of the metabolic products of lappaconitine in rat urine by high-performance liquid chromatography with electrochemical and ultraviolet detection are described. Urine samples from rats intravenously administered lappaconitine hydrobromide were extracted with chloroform and then purified on a Sep-Pak C18 cartridge. The subsequent resolution into individual compounds was achieved by high-performance liquid chromatography. Identification of these compounds was based on comparisons of the chromatographic behaviour and the detector response with those of authentic samples. Changes in the ratio of lappaconitine to its metabolites in rat urine with time after dosing led to a proposal for one of the probable metabolic pathways of lappaconitine in the rat.

Studies on the metabolism of lappaconitine in humans. Identification of the metabolites of lappaconitine in human urine by high performance liquid chromatography

The metabolites of lappaconitine in the urine of humans having been previously administered intramuscularly with lappaconitine hydrobromide were studied using high performance liquid chromatography with electrochemical and ultraviolet detection. The urine was extracted by means of liquid- and solid-phase extractions. Each of the metabolites of lappaconitine was purified by high performance liquid chromatography on a reversed phase column and identified on the basis of the chromatographic behaviour and the detector response. It was proved that lappaconitine, N-deacetyl-16-O-demethyllappaconitine and N-deacetyllappaconitine were excreted in urine from humans receiving lappaconitine.

Immobilized enzyme reactors for detection systems in high-performance liquid chromatography

The applications of immobilized-enzyme reactors (IMERs) to detection systems in high-performance liquid chromatography (HPLC) have been reviewed. A substrate unresponsive to the detector is enzymatically converted to a highly responsive product. The main analytes detected by this system are various steroids, conjugates of various compounds, acetycholine, choline and amino acids. The repetitive use of a single batch of expensive enzyme has economic advantages. On the other hand, the organic modifier in the mobile phase exerts a considerable influence on the activity and stability of the IMER. Usually the activities of the IMER decrease after two or three months of ordinary use. These problems need to be overcome in the future. HPLC-IMER systems are being used in the field of clinical chemistry, and further applications to other fields are expected to be developed.

Sensitive ferrocene reagents for derivatization of amines for high-performance liquid chromatography with electrochemical detection

Six reagents possessing ferrocene as an electrophore were prepared and evaluated for pre-column derivatization of amino compounds for their determination by high-performance liquid chromatography with electrochemical detection. The utility of these reagents was investigated employing phenethylamine as a model compound. Among these six, N-succinimidyl 3-ferrocenylpropionate was the best with respect to reactivity, stability and electrochemical properties. The developed method was applied to the determination of putrescine formed from ornithine by ornithine decarboxylase.