Excretion of a Highly Lipophilic Phenolic Antioxidant from Rats

Abstract

Excretion of highly lipophilic (log P = 8.14) 4-methyl-2,6-diisobornylphenol (IBP) from rats was evaluated from renal excretion and elimination through the gastrointestinal tract (GIT) with feces and bile. A total of 81% of the administered dose was detected in feces after a single intragastric administration of IBP at a dose of 20 mg/kg in starch paste. The excretion kinetics through the GIT were represented by two elimination phases, i.e., rapid (within 24 h after IBP administration) accounting for elimination of 70% of the administered dose and slow (24 – 96 g) presumably related to elimination of IBP stored in tissues and organs. The bile IBP concentrations were an order of magnitude less than those in blood plasma. However, the times to reach the maximum concentration differed little. Renal excretion turned out to be minor despite the high kidney concentrations. Total elimination of IBP with urine for 4 d was ~0.01% of the administered dose.