Several corticosteroids are commonly used for treatment of
conditions associated with inflammatory disorders and as immune
modulators. Specifically in cases of ulcerative colitis and the
related inflammatory bowel syndromes, these therapeutic agents
are administered rectally and are subjected to several intestinal
micro floras. The present study aimed to investigate the effect of
human intestinal bacterial (HIB) aerobic incubation on prednisone
1 as a model for corticosteroids. Within 96 hours, 1 was mostly
transformed by HIB in vitro to various metabolites, which could be
separated by column chromatography into two fractions. The first
eluted fraction A was found to contain the major metabolite
adrenosterone, androst-4-ene-3,11,17-trione m1, whereas fraction
B contains metabolite m2, which was identified by chiral HPLC as
a mixture of androst-1,4-diene-3,11,17-trione enantiomers. The
structures of metabolites m1 and m2 were identified and
characterized by spectroscopic techniques, including 2D-NMR and mass spectrometry. Time course of biotransformation of 1 by HIB
was also studied.