Abstract
A hitherto-unidentified steroid produced in the reaction mixture of 11-deoxycortisol with bovine cytochrome P450(11β) reconstitution system was purified by repeated HPLCs, and subjected to 1H-NMR analysis. The result suggested that the new metabolite was 19-oxo-11-deoxycortisol. This was further confirmed by a new analytical technique using LC/MS equipped with atmospheric pressure chemical ion (APCI)-analyzer.