Synthetic procedures for the preparation of deuterium-labeled analogs of naturally occurring steroids

Synthesis of stable isotope labelled steroid bis(sulfate) conjugates and their behaviour in collision induced dissociation experiments

Steroid bis(sulfate) metabolites derived from the two-fold sulfation of unconjugated precursors represent an important yet understudied portion of the steroid profile. The investigation of these compounds in fields such as medicine or anti-doping science relies on mass spectrometry (MS) as the principal tool to identify and quantify biomarkers of interest and depends in turn on access to steroid reference materials and their stable isotope labelled (SIL) derivatives. A new [¹⁸O] stable isotope label for sulfate metabolites is reported, which allows for the selective, late-stage and 'one-pot' synthesis of a variety of SIL-steroid conjugates suitable as MS probes and internal standards. The method is applied to more comprehensively study the MS behaviour of steroid bis(sulfate) compounds through collision-induced dissociation (CID) experiments.

A Sulfuryl Group Transfer Strategy to Selectively Prepare Sulfated Steroids and Isotopically Labelled Derivatives

The treatment of common steroids: estrone, estradiol, cortisol, and pregnenolone with tributylsulfoammonium betaine (TBSAB) provides a convenient chemoselective conversion of the steroids alcohol/phenol moiety to the corresponding steroidal organosulfate. An important feature of the disclosed methodology is the millimolar scale of the reaction, and the isolation of the corresponding steroid sulfates as their biologically relevant sodium salts without the need for ion-exchange chromatography. The scope of the method was further explored in the estradiol and pregnanediol steroid systems with the bis-sulfated derivatives. Ultimately, a method to install an isotopic label, deuterium (²H) combined with estrone sulfation is a valuable tool for its mass-spectrometric quantification in biological studies.

Influence of isotopically labeled internal standards on quantification of serum/plasma 17α-hydroxyprogesterone (17OHP) by liquid chromatography mass spectrometry

Objectives Our recent survey of 44 mass spectrometry laboratories across 17 countries identified variation in internal standard (IS) choice for the measurement of serum/plasma 17α-hydroxyprogesterone (17OHP) by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The choice of IS may contribute to inter-method variations. This study evaluated the effect of two common isotopically labeled IS on the quantification of 17OHP by LC-MS/MS. Methods Three collaborating LC-MS/MS laboratories from Asia, Europe and Australia, who routinely measure serum 17OHP, compared two IS, (1) IsoSciences carbon-13 labeled 17OHP-[2,3,4-13C3], and (2) IsoSciences deuterated 17OHP-[2,2,4,6,6,21,21,21-2H]. This was performed as part of their routine patient runs using their respective laboratory standard operating procedure. Results The three laboratories measured 99, 89, 95 independent samples, respectively (up to 100 nmol/L) using the 13C- and 2H-labeled IS. The slopes of the Passing-Bablok regression ranged 0.98-1.00 (all 95% confidence interval [CI] estimates included the line of identity), and intercept of <0.1 nmol/L. Average percentage differences of -0.04% to -5.4% were observed between the two IS materials, which were less than the optimal bias specification of 7% determined by biological variation, indicating no clinically significant difference. The results of 12 Royal College of Pathologists of Australasia Quality Assurance Programs (RCPAQAP) proficiency samples (1-40 nmol/L) measured by the laboratories were all within the RCPAQAP analytical performance specifications for both IS. Conclusions Overall, the comparison between the results of 13C- and 2H-labeled IS for 17OHP showed good agreement, and show no clinically significant bias when incorporated into the LC-MS/MS methods employed in the collaborating laboratories.

The evolution of methods for urinary steroid metabolomics in clinical investigations particularly in childhood

The metabolites of cortisol, and the intermediates in the pathways from cholesterol to cortisol and the adrenal sex steroids can be analysed in a single separation of steroids by gas chromatography (GC) coupled to MS to give a urinary steroid profile (USP). Steroids individually and in profile are now commonly measured in plasma by liquid chromatography (LC) coupled with MS/MS. The steroid conjugates in urine can be determined after hydrolysis and derivative formation and for the first time without hydrolysis using GC-MS, GC-MS/MS and liquid chromatography with mass spectrometry (LC-MS/MS). The evolution of the technology, practicalities and clinical applications are examined in this review. The patterns and quantities of steroids changes through childhood. Information can be obtained on production rates, from which children with steroid excess and deficiency states can be recognised when presenting with obesity, adrenarche, adrenal suppression, hypertension, adrenal tumours, intersex condition and early puberty, as examples. Genetic defects in steroid production and action can be detected by abnormalities from the GC-MS of steroids in urine. New mechanisms of steroid synthesis and metabolism have been recognised through steroid profiling. GC with tandem mass spectrometry (GC-MS/MS) has been used for the tentative identification of unknown steroids in urine from newborn infants with congenital adrenal hyperplasia. Suggestions are made as to areas for future research and for future applications of steroid profiling. As routine hospital laboratories become more familiar with the problems of chromatographic and MS analysis they can consider steroid profiling in their test repertoire although with LC-MS/MS of urinary steroids this is unlikely to become a routine test because of the availability, cost and purity of the internal standards and the complexity of data interpretation. Steroid profiling with quantitative analysis by mass spectrometry (MS) after chromatography now provides the most versatile of tests of adrenal function in childhood.

The art of measuring steroids: Principles and practice of current hormonal steroid analysis

Steroids are small and highly important structural or signalling molecules in living organisms and their metabolism is complex. Due to the multiplicity of enzymes involved there are many different steroid related disorders. E.g., an individual enzyme defect is rather rare but can share various clinical symptoms and can thus be hardly diagnosed clinically. Therefore, reliable hormonal determination still presents the most reasonable initial diagnostic approach and helps to avoid uncritical and expensive attempts at molecular diagnostic testing. It also presents a backbone of monitoring these complex patients. In science, reliable hormone measurement is indispensable for the elucidation of new mechanisms of steroid hormone actions. Steroid analytics is highly challenging and should never be considered trivial. Most common methods for steroid determination comprise traditionally immunoassay, or more recently, mass spectrometry based methods. It is absolutely necessary that clinicians and scientists know the methods they are applying by heart. With the introduction of automated direct assays, a loss of quality could be observed over the last two decades in the field of steroid immunoassays. This review wants to meet the need for profound information and orientation in the field of steroid analysis. The pros and cons of the most important methods, such as immunoassays and mass spectrometry based methods will be discussed. The focus of the latter will lie on gas chromatography-mass spectrometry (GC-MS) as well as liquid chromatography-mass spectrometry (LC-MS). Selected analytical applications from our Deutsche Forschungsgemeinschaft Research Group FOR 1369 "Sulfated Steroids in Reproduction" will illustrate the contents. In brief, immunoassays have for long presented the traditional technique for steroid analysis. They are easy to set up. Only one analyte can be measured per immunoassay. Specificity problems can arise and caution has to be exerted especially regarding direct assays lacking purification steps. Mass spectrometry based methods provide structural information on the analyte and thus higher specificity. In combination with chromatographic techniques, they permit the simultaneous determination of a multitude of analytes. Highest specificity can be obtained using GC-MS, a sophisticated but most powerful tool for characterizing steroid metabolomes. LC-MS is a true high throughput technique and highly suited for detecting complex steroids. GC-MS and LC-MS are not competing but complementary techniques. Since reliable steroid determination requires extremely high expertise in the field of analytics as well as steroid biochemistry, it is recommended that collaborations and networking with highly specialized centers of expertise are developed.

Determination of dehydroepiandrosterone and its biologically active oxygenated metabolites in human plasma evinces a hormonal imbalance during HIV-TB coinfection

An estimated one third of the world's population is affected by latent tuberculosis (TB), which once active represents a leading cause of death among infectious diseases. Human immunodeficiency virus (HIV) infection is a main predisposing factor to TB reactivation. Individuals HIV-TB co-infected develop a chronic state of inflammation associated with hypothalamic-pituitary-adrenal (HPA) axis dysregulation. This results in a hormonal imbalance, disturbing the physiological levels of cortisol and dehydroepiandrosterone (DHEA). DHEA and its oxygenated metabolites androstenediol (AED), androstenetriol (AET) and 7-oxo-DHEA are immunomodulatory compounds that may regulate physiopathology in HIV-TB co-infection. In order to study possible changes in plasma levels of these hormones, we developed an approach based on high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). To our knowledge, this represents the first report of their simultaneous measurement in HIV-TB individuals and the comparison with healthy donors, obtaining statistically higher plasma levels of DHEA, AET and 7-oxo-DHEA in patients. Moreover, we found that concentrations of 7-oxo-DHEA positively correlated with absolute CD4+ T cell counts, nadir CD4+ T cell values and with individuals who presented TB restricted to the lungs. This research contributes to understanding the role of these hormones in HIV-TB and emphasizes the importance of deepening their study in this context.

Synthesis of 3α-deuterated 7α-hydroxy-DHEA and 7-oxo-DHEA and application in LC-MS/MS plasma analysis

7-Oxygenated metabolites of dehydroepiandrosterone (DHEA) are known for their neuroprotective and immunomodulatory properties. These neuroactive steroids are currently predominately analysed by mass spectrometry, for which the use of internal deuterated standards is necessary. The aim of this study was to synthesize the deuterated derivatives of 7α-hydroxy-DHEA and 7-oxo-DHEA and test them in liquid chromatography-tandem mass spectrometry (LC-MS/MS) in order to enhance the performance characteristics of this method. Here we report the synthesis of 3α deuterium-labelled 7α-hydroxy-DHEA and 7-oxo-DHEA. Deuterium was introduced into the 3α position by reduction of the corresponding 3-ketone with a protected 17-carbonyl group using NaBD4. Our new procedure allows the easier synthesis of deuterated steroid labelled compounds. The use of these deuterated steroids enabled us to improve the human plasma LC-MS/MS analysis of 7α-hydroxy-DHEA and 7-oxo-DHEA in terms of sensitivity, precision and recovery.

Introduction to gas chromatography-mass spectrometry

Gas chromatography-mass spectrometry (GC-MS) is a technique of pivotal importance for the analysis of hormones in biological fluids. In consequence, it has gained relevance in clinical and endocrinological laboratories, providing reference analytical methods. This chapter offers a general description of its principles, and a real example for GC-MS profiling of plasma steroids.

Profiling oestrogens and testosterone in human urine by stable isotope dilution/benchtop gas chromatography-mass spectrometry

Oestrogens, such as oestrone (E(1)), 17β-oestradiol (E(2)), oestriol (E(3)) and their biologically active metabolites 2-methoxyoestrone (2-MeOE(1)), 2-hydroxyoestradiol (2-OHE(2)) 16-ketooestradiol (16-OE(2)), 16-epioestriol (16-epiE(3)), as well as testosterone (T) play an important role in physiological and pathological developmental processes during human development. We therefore aimed at developing an isotope dilution/bench top gas chromatography-mass spectrometry (ID/GC-MS) method, based on benchtop GC-MS, for the simultaneous determination ('profiling') of the above analytes in children. The method consisted of equilibration of urine (5 ml) with a cocktail containing stable isotope-labelled analogues of the analytes as internal standards ([2,4-(2)H(2)]E(1), [2,4,16,16-(2)H(4)]E(2), [2,4,17-(2)H(3)]E(3), [16,16,17-(2)H(3)]T, [1,4,16,16-(2)H(4)]2-MeOE(1), [1,4,16,16,17-(2)H(5)]2-OHE(2), [2,4,15,15,17-(2)H(5)]16-OE(2) and [2,4-(2)H(2)]16-epiE(3)). Then, solid-phase extraction (C(18) cartridges), enzymatic hydrolysis (sulphatase from Helix pomatia (type H-1)), re-extraction, purification by anion exchange chromatography and derivatisation to trimethylsilyl ethers followed. The samples were analysed by GC-MS (Agilent GC 6890N/5975MSD; fused silica capillary column 25 m × 0.2 mm i.d., film 0.10 μm). Calibration plots were linear and showed excellent reproducibility with coefficients of determination (r(2)) between 0.999 and 1.000. Intra- and inter-assay coefficients of variation (CV) were <2.21% for all quantified metabolites. Sensitivity was highest for 2-OHE(2) (0.25 pg per absolute injection: signal-to-noise ratio (S/N)=3) and lowest for 16-epiE(3) (2 pg per absolute injection: S/N=2.6), translating into corresponding urine sample analyte concentrations of 0.025 ng ml(-1) and 0.2 ng ml(-1), respectively. Accuracy - determined in a two-level spike experiment - showed relative errors ranging between 0.15% for 16-OE(2) and 11.63% for 2-OHE(2). Chromatography showed clear peak shapes for the components analysed. In summary, we describe a practical, sensitive and specific ID/GC-MS assay capable of profiling the above-mentioned steroids in human urine from childhood onwards.

Mass spectrometric analysis of androstan-17beta-ol-3-one and androstadiene-17beta-ol-3-one isomers

Mass spectrometric identification and characterization of steroids using electrospray ionization and tandem mass spectrometry has advantages in drug testing and doping control analysis attributable to limitations of gas chromatography followed by electron ionization mass spectrometry. Steroids with an androstadiene-17beta-ol-3-one nucleus and double bonds located either at C-1 and C-4, C-4 and C-9, or C-4 and C-6 were used to determine characteristic fragmentation pathways. Diagnostic dissociation routes are proposed using deuterium labeling, MS3 experiments, and analyses of structurally closely related compounds. Steroids such as boldenone (androst-1,4-diene-17beta-ol-3-one) produced characteristic product ions at m/z 121, 135, and 147. Compounds with double bonds at C-4 and C-9 generated abundant product ions at m/z 145 and 147. Conjugated double bonds at C-4 and C-6 gave rise to an intense and characteristic signal at m/z 133. Stereochemical differentiation between 5alpha- and 5beta-isomers of androstan-17beta-ol-3-ones was possible because of significant differences in relative abundance of product ions generated by elimination of acetone from alpha,beta-saturated 3-keto steroids.

N-methyl-N-trimethylsilyltrifluoroacetamide-promoted synthesis and mass spectrometric characterization of deuterated ephedrines

Synthesis and mass spectrometric characterization of drugs or metabolites labeled by stable isotopes has been of great interest in fields of clinical, forensic and doping control analysis. Deuterated ephedrine and p-hydroxypseudoephedrine were prepared from corresponding amines by a novel procedure utilizing N- methyl-N-trimethylsilyltrifluoroacetamide and deuterated iodomethane. The mechanism of methylation was studied by mass spectrometry using phenylethylamine as a model compound, and a rearrangement based on an intermediate six-membered ring structure with a trimethylsilyl-enol-ether is proposed giving rise to a leaving group of trimethyliodosilane and the desired monomethylated product. Deuterated analogues to frequently quantitated ephedrines were readily synthesized with purities >90%, and mass spectra recorded under different ionization and dissociation conditions presented distinct fragmentation processes including eliminations of water and methylamine as well as the generation of a benzyl cation.

Investigations into the biosynthetic pathways for classical and ring B-unsaturated oestrogens in equine placental preparations and allantochorionic tissues

In on-going studies of 'classical' and ring B-unsaturated oestrogens in equine pregnancy, the products of metabolism of [2,2,4,6,6-2H(5)]-testosterone and [16,16,17-2H(3)]-5,7-androstadiene-3 beta,17 beta-diol with equine placental subcellular preparations and allantochorionic villi have been identified. Using mixtures of unlabelled and [2H]-labelled steroid substrates has allowed the unequivocal identification of metabolites by twin-ion monitoring in gas chromatography-mass spectrometry (GC-MS). Two types of incubation were used: (i) static in vitro and (ii) dynamic in vitro. The latter involved the use of the Oxycell cartridge (Integra Bioscience Systems, St Albans, UK) whereby the tissue preparation was continuously supplied with supporting medium plus appropriate cofactors in the presence of uniform oxygenation. [2H(5)]-Testosterone was converted into [2H(4)]-oestradiol-17 beta, [2H(4)]-oestrone and [2H(3)]-6-dehydro-oestradiol-17 alpha in both placental and chorionic villi preparations, but to a greater extent in the latter, confirming the importance of the chorionic villi in oestrogen production in the horse. On the basis of GC-MS characteristics (M(+) m/z 477/482 (as O-methyl oxime-trimethyl silyl ether), evidence for 19-hydroxylation of testosterone was found in static incubations, while the presence of a 6-hydroxy-oestradiol-17 alpha was recorded in dynamic incubations (twin peaks in the mass spectrum at m/z 504/507, the molecular ion M(+)). It was not possible to determine the configuration at C-6. The formation of small, but significant, quantities of [2H(4)]-17 beta-dihydroequilin was also shown, and a biosynthetic pathway is proposed. In static incubations of placental microsomal fractions, the 17 beta-dihydro forms of both equilin and equilenin were shown to be major metabolites of [2H(3)]-5,7-androstadiene-3,17-diol. Using static incubations of chorionic villi, the deuterated substrate was converted into the 17 beta-dihydro forms of both equilin and equilenin, together with an unidentified metabolite (base peak, m/z 504/506). The isomeric 17-dihydroequilins were also obtained using the dynamic in vitro incubation of equine chorionic villi, together with the 17 beta-isomer of dihydroequilenin. Confirmation of the identity of 17 beta-dihydroequilin and 17 beta-dihydroequilenin was obtained by co-injection of the authentic unlabelled steroids with the phenolic fraction obtained from various incubations. Increases in the peak areas for the non-deuterated steroids (ions at m/z 414 (17 beta-dihydroequilin) and 412 (17 beta-dihydroequilenin) (both as bis-trimethyl silyl ether derivatives) were observed. Biosynthetic pathways for formation of the ring B-unsaturated oestrogens from 5,7-androstadiene-3 beta,17 beta-diol are proposed.

Synthesis of multi-labeled cortisols and cortisones with (2)H and (13)C for study of cortisol metabolism in humans

A method is described for the preparation of multi-labeled cortisol and cortisone with (13)C and (2)H via the indan synthon method, starting from chiral 11-oxoindanylpropionic acid. [1, 3-(13)C(2)]Acetone was used for the syntheses of [1,2,4, 19-(13)C(4)]cortisol (cortisol-(13)C(4)) and [1,2,4, 19-(13)C(4)]cortisone (cortisone-(13)C(4)), and [1,3-(13)C(2),1,1,1, 3,3,3-(2)H(6)]acetone was for [1,2,4,19-(13)C(4),1,1,19,19, 19-(2)H(5)]cortisol (cortisol-(13)C(4),(2)H(5)) and [1,2,4, 19-(13)C(4),1,1,19,19,19-(2)H(5)]cortisone (cortisone-(13)C(4), (2)H(5)). The chemical shifts for the (13)C and (1)H NMR spectra of cortisol and cortisone were fully assigned.

Simultaneous determination of endogenous and 13C-labelled cortisols and cortisones in human plasma by stable isotope dilution mass spectrometry

This study describes a capillary GC-MS method for the simultaneous determination of endogenous cortisol and cortisone and their 13C-labelled analogues, [1,2,4,19-13C4]cortisol (cortisol-13C4) and [1,2,4,19-13C4]cortisone (cortisone-13C4), in human plasma. [1,2,4,19-13C4,1,1,19,19,19-2H5]Cortisol (cortisol-13C4,2H5) and [1,2,4,19-13C4,1,1,19,19,19-2H5]cortisone (cortisone-13C4,2H5) were used as analytical internal standards. A double derivatization (bismethylenedioxy-pentafluoropropionate, BMD-PFP) with good GC behavior was employed for the GC-MS analysis of cortisol and cortisone. Quantitation was carried out by selected-ion monitoring of the molecular ions ([M]+*) of the BMD-PFP derivatives of cortisol and cortisone. The sensitivity limit of the present GC-MS-SIM method was found to be 150 pg per injection for cortisol (s/n=5.0) and 50 pg for cortisone (s/n=8.1). The within-day reproducibility in which the amounts of unlabelled and labelled cortisols and cortisones determined were in good agreement with the actual amounts added, the relative errors being less than 3.07%. The inter-assay coefficients of variation (C.V.) were less than 1.80% for unlabelled and labelled cortisols and cortisones.

Profiling steroid hormones in amniotic fluid of midpregnancy by routine stable isotope dilution/gas chromatography-mass spectrometry: reference values and concentrations in fetuses at risk for 21-hydroxylase deficiency

Using routine stable isotope dilution/gas chromatography-mass spectrometry, 17-hydroxyprogesterone, androstenedione, testosterone, dehydroepiandrosterone, androstanediol, and 5alpha-dihydrotestosterone have been profiled in amniotic fluid of midgestation in 77 normal fetuses and 38 untreated or dexamethasone-treated fetuses at risk for 21-hydroxylase deficiency. Dexamethasone was suspended 5-7 days before amniocentesis. In normal fetuses, amniotic fluid concentrations (median, range; nanograms per mL) of 17-hydroxyprogesterone did not reveal a sex difference (1.48, 0.21-4.96), whereas those of androstenedione were lower in females (0.53, 0.00-2.71) than in males (0.93, 0.29-1.98). Testosterone levels were higher in males (0.24, 0.00-0.50) than in females (0.00, 0.00-0.27). No sex difference was found for dehydroepiandrosterone (0.47, 0.19-1.77). Levels of androstanediol and 5alpha-dihydrotestosterone were below the detection limit of our method in most cases. Regarding prenatal diagnosis of 21-hydroxylase deficiency, 17-hydroxyprogesterone and androstenedione presented the diagnostically most valuable steroids and were of equal diagnostic potential. They permitted successful diagnosis in 36 of 37 fetuses at risk: 12 were untreated and unaffected, 13 were treated and unaffected, 4 were untreated and affected (3 salt wasters and 1 simple virilizer), and 8 were treated and affected (5 salt wasters and 3 simple virilizers). In the latter group, one simple virilizer revealed normal steroid concentrations. Isotope dilution/gas chromatography-mass spectrometry, providing the highest specificity in steroid analysis, is proposed for routine use in clinical steroid analysis whenever maximal reliability is requested. Our study provides the first mass spectrometric reference data on amniotic fluid steroid concentrations and underscores the high accuracy of prenatal hormonal diagnosis of 21-hydroxylase deficiency.

Androgen metabolism assessment by routine gas chromatography/mass spectrometry profiling of plasma steroids: Part 1, Unconjugated steroids

Using gas chromatography/mass spectrometry we have developed a method for the simultaneous determination of six plasma steroids: testosterone, 4-androstenedione, 17 alpha-hydroxyprogesterone, 5 alpha-androstane-3 alpha,17 beta-diol, 5 alpha-dihydrotestosterone, and dehydroepiandrosterone. For each analyte, a deuterium-labeled internal standard was used for quantification. Due to the high isotopic purity of our standards, no complex corrections for isotope contributions were necessary. The procedure provides a sensitive and specific technique with good accuracy and precision.