Degradation of steroids in the human gut

Introduction Systematic and trivial names Enzyme and steroid nomenclature Classes of steroid in the human gut T h e enterohepatic circulation Cholesterol Bile acids Neutral, phenolic, and synthetic steroids Experimental approaches in studying the degradation of steroids by human intestinal bacteria Administration of labeled steroids Analysis of steroids in bile, urine, and feces Cholesterol Bile acids Steroid hormones Animal models Metabolism of steroids by mixed fecal flora Studies with crude and purified enzyme and pure cultures in vitro systems in vitro Metabolism of cholesterol Reduction of cholesterol to coprostanol Coprostanone from cholesterol Side chain cleavage of cholesterol Hydrolysis of conjugated bile acids Oxidation of 3a-, 7a-, and 12a-hydroxyl 7-Dehydroxylation Epimerization of the 3a-and 7a-hydroxyl Formation of 5a-(allo) bile acids Other bile acid transformations Metabolism of bile acids groups to ketones groups Formation of C-24 ethyl esters