CD spectrometric methods for the simultaneous determination of ethisterone and its Δ~5-isomer

摘要

Quick and accurate direct and indirect circular dichroism (CD) spectrometric methods were developed for the simultaneous determination of ethisterone (17α-ethinyl-17-hydroxy-4-androstene-3-one) and its Δ~5-isomer (Δ~5-ethisterone). The direct method is based on the selective negative Cotton effect of the Δ~4-3-oxo group in ethisterone (negative maximum at 348 nm in dioxan) and measurement of the ellipticity at 296 nm (positive maximum of Δ~5-ethisterone), where the measured ellipticity is the sum of those of the two isomers. In the indirect procedure Δ~5-ethisterone is transformed to ethisterone by base-catalysed isomerization and the ellipticities are measured at 339 nm in ethanol before and after isomerization. Preliminary experiments show the usefulness of CD detector in the HPLC determination of the mixture of the isomers. A major advantage of the direct CD spectrometric and the HPLC/CD methods is the Δ~5-isomer with extremely low UV activity can also be directly measured with high sensitivity.