Selective reactions in the analytical characterisation of steroids by gas chromatography—Mass spectrometry

摘要: Gas chromatography-mass spectrometry (GC-MS) is a technique especially suitable for the analysis and characterization of steroids, its power has been extensively demonstrated. The efficacy GC-MS limited, nevertheless, by fact that steroid mixtures—whether natural origin only, or augmented synthetic analogs—often contain similar components are poorly distinguished. fortuitous overlap gas chromatographic peaks from disparate compounds also impairs definition retention data. Controlled modification sample means selective reactions therefore valuable adjunct to application GC-MS. Two examples discussed: (a) enzyme cholesterol oxidase, isolated various microorganisms, catalyzes oxidation many 3β-hydroxy-5-enes (with concomitant isomerization) 4-en-3-ones; 3β-hydroxy-5α-steroids oxidized corresponding 3-ones, but other steroids (3α-hydroxy- 5β-isomers, etc.) unaffected. mild conditions required (pH 7, 30 C) advantageous sensitive index increments, as well mass spectra ketones, characteristic. accepts substrates wide range 3β-hydroxysteroids, tolerating oxygenation in ring B even catalyzing 2-oxacholesterol expected lactone; (b) possessing 1,2-diol 1,3-diol groupings include estriols, 2-hydroxyestrone, 20,22-dihydroxycholesterols, ecdysones, brassinolide corticosteroids. formation cyclic derivatives can provide several analytically useful features, such convenient times, moderate increments (24 amu methaneboronate), distinctive usually abundant molecular ions. These exemplified 5-pregnene-3β-20,21-triols 20,22-dihydroxycholesterol enzymic product.