Metabolism of camphors and related compounds

Abstract

1. The metabolism of (±)-norcamphor, (+)-camphor, (−)-camphor, (+)-epicamphor, (±)-camphorquinone, (±)-camphane-2,5-dione and camphane was investigated in rabbits. All the compounds except camphane-2,5-dione increased the content of glucuronide in the urine. 2. (±)-Norcamphor was reduced to endo-norborneol; (+)-camphor, contrary to expectation, was reduced to (+)-borneol, as well as being hydroxylated to (+)-5-endo-hydroxycamphor and (+)-3-endo-hydroxycamphor, 5-endo-hydroxycamphor being the predominant product. (+)-Epicamphor was reduced mainly to (+)-epiborneol; (±)-camphorquinone gave 3-endo-hydroxycamphor and 2-endo-hydroxyepicamphor, the former being the major metabolite. (±)-Camphane-2,5-dione was reduced to 5-endo-hydroxycamphor. Camphane was hydroxylated to borneol and epiborneol, the latter predominating. 3. An explanation of these findings is given in terms of steric hindrance and thermodynamic stability. 4. The possibility was investigated that NADH was involved in the reductions.