Sample preparation for the chromatographic determination of ecdysteroids using solid-phase extraction methods

Evaluation of ecdysteroid antisera for a competitive enzyme immunoassay and extraction procedures for the measurement of mosquito ecdysteroids

Ecdysteroid hormones regulate several aspects of insect development and reproduction. The predominant ecdysteroids produced by insects including mosquitoes are ecdysone (E) and 20-hydroxyecdysone (20E). The ability to measure E and 20E titers is essential for many studies, but few sensitive, low cost options are currently available for doing so. To address this deficiency, we developed a new enzyme-linked immunoassay (EIA). In the first part of the study, we compared the affinity of two new antisera named EAB25 and EAB27 to other available ecdysteroid antisera. EAB25 had a 27-fold higher affinity for 20E than E, while EAB27 had a four-fold higher affinity for 20E. In the second part of the study, EIA protocols were developed for analyzing E and 20E produced by the mosquito Aedes aegypti. Results indicated that pelts from fourth instar larvae and ovaries from blood-fed, adult females produced E and 20E. Methanol extraction in the presence of magnesium from whole body samples altered antibody recognition of E and 20E by EIA. However, extraction with 1-butanol and two organic/water phase separations eliminated this problem and improved assay performance. We conclude the new antisera used in the EIA provide a low-cost, flexible, and sensitive method for measuring E and 20E in insects.

Detection of 20-hydroxyecdysone in calf urine by comparative liquid chromatography/high-resolution mass spectrometry and liquid chromatography/tandem mass spectrometry measurements: application to the control of the potential misuse of ecdysteroids in cattle

Ecdysteroids, which are steroid hormones in invertebrates, but which are also present in plants, could potentially be used as anabolic agents in food-producing animals. The control of ecdysteroid misuse in cattle relies on the development of an efficient method for their detection in biological matrices at trace levels (microg L(-1)). In order to propose an analytical procedure dedicated to the identification of excreted 20-hydroxyecdysone (20E) in urine and faecal samples of breeding animals, a comparative study of the spectrometric behaviour of these compounds was carried out both by LC/(ESI-)/HRMS(n) (hybrid linear ion trap - orbital trap) and by LC/(ESI+)/MS/MS (triple quadrupole). This study revealed the formation of a large number of product ions both in positive and negative ion mode, corresponding to losses of water molecules and specific cleavages on the side chain. The sample preparation consisted of sequential purification on two solid-phase extraction cartridges (SPE octadecylsilyl and SPE silica). The detection limits were around 0.5 microg L(-1) in the selected reaction monitoring (SRM) mode and recoveries above 60% were obtained. The method was successfully applied to the analysis of real samples collected from calves treated with 60 mg 20E over 4 days. Analysis of the samples allowed the investigation of the kinetics of elimination of 20E in calf urine and determination of the time-frame for the control of potential abuse.

Chromatographic procedures for the isolation of plant steroids

In this review, we consider the general principles and specific methods for the purification of different classes of phytosteroids which have been isolated from plant sources: brassinosteroids, bufadienolides, cardenolides, cucurbitacins, ecdysteroids, steroidal saponins, steroidal alkaloids, vertebrate-type steroids and withanolides. For each class we give a brief summary of the characteristic structural features, their distribution in the plant world and their biological effects and applications. Most classes are associated with one or a few plant families, e.g., the withanolides with the Solanaceae, but others, e.g., the saponins, are very widespread. Where a compound class has been extensively studied, a large number of analogues are present across a range of species. We discuss the general principles for the isolation of plant steroids. The predominant methods for isolation are solvent extraction/partition followed by column chromatography and thin-layer chromatography/HPLC.

Determination of r-7,t-8,9,c-10-tetrahydroxy-7,8,9, 10-tetrahydrobenzo[a]pyrene in human urine by gas chromatography/negative ion chemical ionization/mass spectrometry

r-7,t-8,9,c-10-Tetrahydroxy-7,8,9,10-tetrahydrobenzo[a]pyrene (trans-anti-BaP-tetraol) is the major hydrolysis product of r-7, t-8-dihydroxy-t-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (anti-BPDE), the principal ultimate carcinogen of the environmental pollutant benzo[a]pyrene (BaP). As part of a program to establish activation/detoxification profiles of urinary metabolites of BaP in humans, we developed a method for quantifying trans-anti-BaP-tetraol. Urine was collected from three groups of individuals exposed to BaP: psoriasis patients treated with a coal tar-containing ointment, steel workers, and smokers. [(2)H(12)]-trans-anti-BaP-tetraol was added to the urine as an internal standard. The urine was treated with beta-glucuronidase and sulfatase, and then the BaP-tetraols were enriched by reverse-phase and phenylboronic acid solid-phase extraction. The resulting fraction was treated with sodium hydride and methylmethane sulfonate to convert BaP-tetraols to the corresponding tetramethyl ethers (BaP-TME). The mixture was purified by normal-phase HPLC and analyzed by gas chromatography/negative ion chemical ionization/mass spectrometry with selected ion monitoring. [(13)CH(3)](4)-trans-anti-BaP-TME was used as an external standard. Ions at m/z 376, 380, and 388 were monitored for quantitation of trans-anti-BaP-TME, [(13)CH(3)](4)-trans-anti-BaP-TME, and [(2)H(12)]-trans-anti-BaP-TME, respectively. The instrumental detection limit was approximately 1 fmol of trans-anti-BaP-TME. trans-anti-BaP-tetraol (as trans-anti-BaP-TME) was detected in 20 of 20 individuals receiving coal tar therapy (mean, 16 fmol/mL of urine), 13 of 13 exposed steel workers (mean, 4.1 fmol/mL of urine), and nine of 21 cigarette smokers (mean, 0.5 fmol/mL of urine). The means in these groups were significantly different (P < 0.0001). The urine of steel workers was also analyzed for cis-anti-BaP-tetraol and cys-syn-BaP-tetraol, but neither was found. The results of this study provide a quantitative method for determination of parts per trillion levels of trans-anti-BaP-tetraol in human urine. Ultimately, this method can be employed as part of a phenotyping approach for assessing BaP metabolites in human urine.

Immobilized phenylboronic acids for the selective extraction of beta-blocking drugs from aqueous solution and plasma

The use of phenylboronic acid (PBA) solid-phase extraction cartridges for the extraction of a range of beta-blockers from aqueous buffer and plasma has been investigated and compared with other phases commonly used for solid-phase extraction. PBA was found to provide an efficient means for the extraction of this class of compound from simple aqueous buffer systems. Extraction from buffers was pH-dependent and gave optimum results at approximately pH 8. Extraction from plasma was less efficient for some of the test compounds; this matrix effect was probably due to protein binding. Chromatography showed that plasma extracts were free of major sources of interference.