Formation of multiple trimethylsilyl derivatives in the derivatization of 17alpha-ethinylestradiol with BSTFA or MSTFA followed by gas chromatography-mass spectrometry determination.
ABSTRACT N,O-bis(trimethylsily)trifluoroacetamide (BSTFA) and N-methyl-N(trimethylsily) trifluoroacetamide (MSTFA) are common derivatization reagents used in the GC-MS analysis of estrogen steroids such as estrone (El) and 17alpha-ethinylestradiol (EE2). In this study, three trimethylsilyl (TMS) steroid derivatives, mono- and di-trimethylsilyl EE2 and mono-trimethylsilyl E1, were observed during the derivatization of EE2 with BSTFA or MSTFA and/or GC separation. Factors influencing the production of multiple TMS derivatives and their relative abundance were examined. It was found that both methanol and bisphenol A competed with estrogenic esteroids when reacting with silylation reagents, and thus affected the formation of TMS derivatives and their relative abundance in the derivatization products. Methanol was found to be more reactive than bisphenol A with the BSTFA reagent. None of the three solvents tested in this study could prevent the generation of multiple TMS derivatives during the derivatization of EE2 with BSTFA, followed by GC analysis. A similar result was observed using MSTFA as the derivative reagent followed by GC analysis. Thus, the suitability of BSTFA or MSTFA as the derivatization reagent for the determination of E1 and EE2 by GC-MS, under the conditions reported here, is questionable. This problem can be solved by adding trimethylsilylimidaz (TMSI) in the BSTFA reagent as recommended, and the performance of the method has been proved in this study.
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ABSTRACT: The cortex and leaves of Eucommia ulmoides Oliv. from the family Eucommiaceae are traditional Chinese medicines (TCM). Roasted Eucommiae cortex is utilized to reinforce the muscles and lungs, lower blood pressure and improve the tone of the liver and kidneys, while E. ulmoides leaves (EUL) are traditionally used as folk remedies to treat diabetes. EUL extract, obtained by ethanol (40%), was loaded onto an AB-8 macroporous resin column, and washed thoroughly with 0, 20, 40, 60, and 80% (v/v) ethanol for purification. The ethanol eluents of EUL were first determined to inhibit α-glucosidase in vitro, and then the inhibition of the most potent eluent, i.e., the 20% ethanol eluent of EUL (EEUL), against carbohydrate-degrading enzymes and glucose transport in Caco-2 cells was demonstrated. And computational modeling was also employed to evaluate the binding modes of compounds identified in EEUL by GC-MS analysis. EEUL significantly inhibited α-glucosidase (43.08 ± 0.55%) competitively in vitro and concentration-dependently suppressed sucrase (IC50, 0.07mg/mL) and maltase (IC50, 0.53mg/mL) in Caco-2 cells. The inhibitory activity of EEUL (0.02mg/mL) on sucrase and maltase was identical to that of acarbose (0.02mg/mL). Moreover, 1.0mg/mL EEUL decreased glucose transport in cells by 26.25 ± 0.86%. GC-MS revealed that EEUL was rich in monosaccharides, polyphenols and esters, which comprised 47.16% of the total extract. Computational modeling showed that catechin, α-D-glucopyranose and D-mannono-1,4-lactone docked tightly into the sucrose active site with low binding energies. These results indicated that EEUL exerted marked anti-hyperglycemic effects by suppressing disaccharidases and glucose transporters. Therefore, EUL is a beneficial source of inhibitors of carbohydrate-utilizing enzymes, glucose transporters, and potentially hyperglycemia. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.Journal of Ethnopharmacology 01/2015; 163. DOI:10.1016/j.jep.2015.01.015 · 2.94 Impact Factor
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ABSTRACT: Comprehensive two-dimensional gas chromatography (GC × GC) hyphenated with rapid quadrupole mass spectrometry was successfully used to develop a novel method for the determination of trace level estrogens in influent and effluent wastewater. Five estrogens used for the study were 17β-estradiol (βE2), 17α-estradiol (αE2), estrone (E1), 17α-ethynylestradiol (EE2) and estriol (E3). Two orthogonal columns and thermal modulation result in enhanced separation, while the rapid scanning quadrupole mass spectrometer gives high resolution peaks. Samples were extracted with Hydrophilic–Lipophilic Balance (HLB) cartridges and derivatized with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) prior to analysis. The method uses a single extraction step and ng L−1 method detection limits were achieved using a relatively low sample volume of 500 mL. Elimination of additional cleanup steps make the method time effective. Furthermore, the method has less initial cost as the instrument is far less expensive than a tandem mass spectrometer. A parallel conventional gas chromatographic-mass spectrometric (GC/MS) study was carried out to compare the results. Detection limits were 2 to 4 times improved with the GC × GC over the GC/MS.Analytical methods 07/2014; 6(15). DOI:10.1039/C4AY00960F · 1.94 Impact Factor
ChemInform 07/2014; 45(28). DOI:10.1002/chin.201428279