3a, 7a-dihydroxycholanic acid

The most important end products in mammalian cholesterol metabolism are the bile acids. The parent C24-acid is cholanic acid with a ring structure identical to that of coprostanol (A/B cis). The bile acids are hydroxylated cholanic acids, all hydroxyl-groups have a-orientation. Consequently, they do not form digi-tonides. The principal acids are cholic acid (3a, 7a, 12a-trihydroxy-cholanic acid), chenodeoxycholic acid (3a, 7a-dihydroxycholanic acid) and deoxy-cholic acid (3a, 12a-dihydroxycholanic acid). Lithocholic acid (3a-hydroxycholanic acid) also occurs in human bile, but only in small amounts. 

The chief bile acids are the taurine and glycine derivates of dwlic add (3a, 7a, 12a-trihydroxycholanic acid), of deoxycholic add (3a, 12a-dihydroxycholanic acid), and of the isomeric chenodeoxycholic add (3a,7a-dihydroxycholanic acid). The bile acids are one of the end products of the metabolism of cholesterol however, over 90% of the amount secreted (20-30 gm per day) is reabsorbed in the intestine and thus stays in the enterohepatic circulation. 

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