Ergosteroids VII: perchloric acid-induced transformations of 7-oxygenated steroids and their bio-analytical applications—a liquid chromatographic-mass spectrometric study

Sulfate esters of 7-oxo-Δ5-steroids can be selectively and quantitatively hydrolyzed to the corresponding free steroids in the presence of carboxylic acid esters by solvolysis with perchloric acid in ethyl acetate at room temperature. Sulfates as well as carboxylic acid esters, methyl ethers, and ketals can be quantitatively converted to the corresponding 3,5-diene-7-one derivatives by heating with perchloric acid in methanol at 65 °C. The dienes have a strong UV absorption with maximum centered around 284 nm. These reactions have been used for the characterization and structural elucidation of 7-oxygenated-Δ5-steroids that are present in complex biomatrices and can also be used for the quantitative estimation of total 7-oxo-Δ5-steroids (free as well as conjugated) in biological matrices.