TY - JOUR T1 - MAMMALIAN METABOLISM OF TERPENOIDS JF - Drug Metabolism and Disposition JO - Drug Metab Dispos SP - 543 LP - 551 VL - 1 IS - 2 AU - KENNETH C. LEIBMAN AU - ELSA ORTIZ Y1 - 1973/03/01 UR - http://dmd.aspetjournals.org/content/1/2/543.abstract N2 - The metabolism of D-(+)-camphor, of some of its oxidation products, and of L-(-)-camphor has been studied in the dog and rabbit in vivo and in liver preparations from rats and rabbits in vitro. In all cases, the major hydroxylation products of D- and L-camphor were 5-endo- and 5-exo-hydroxycamphor, and a compound identical in chromatographic behavior to 3-endo-hydroxycamphor. These reactions were shown to occur in liver microsomes and to be NADPH-dependent. A small amount of 2,5-bornanedione was also formed in liver microsomes. The 5-keto group of (+)-2,5-bornanedione was reduced in liver cytosol, and there was interconversion between the endo- and exo-isomers of 5-hydroxycamphor in the presence of both microsomes and cytosol, but this interconversion could not account for the production of both 5-hydroxy isomers from camphor in liver microsomes. The 3-keto group of (+)-2,3-bornanedione was readily reduced in the presence of either microsomes or cytosol of rat liver. In contrast, the 2-keto group of D-camphor underwent no detectable reduction in rat liver preparations, although L-camphor was reduced to a small extent. Rabbit liver cytosol, however, mediated a vigorous NADPH-dependent, stereospecific endo-reduction of D-camphor to borneol; a very small amount of isoborneol was also formed. Rabbit liver preparations reduced L-camphor to a much smaller extent; here the stereospecificity favored the formation of isoborneol. D-Camphor gives a type I difference spectrum with rat liver microsomes. Copyright © 1973 by The American Society for Pharmacology and Experimental Therapeutics ER -