I. Reduction and Hydroxylation of Camphor and Related Compounds
Abstract
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.
Footnotes
- Received November 17, 1972.
- Copyright © 1973 by The American Society for Pharmacology and Experimental Therapeutics
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