RT Journal Article
SR Electronic
T1 The metabolism of the abortifacient terpene, (R)-(+)-pulegone, to a proximate toxin, menthofuran.
JF Drug Metabolism and Disposition
JO Drug Metab Dispos
FD American Society for Pharmacology and Experimental Therapeutics
SP 589
OP 594
VO 15
IS 5
A1 Gordon, W P
A1 Huitric, A C
A1 Seth, C L
A1 McClanahan, R H
A1 Nelson, S D
YR 1987
UL http://dmd.aspetjournals.org/content/15/5/589.abstract
AB (R)-(+)-Pulegone, the major monoterpene component of the abortifacient mint oil, pennyroyal oil, is metabolized by hepatic microsomal monooxygenases of the mouse to a hepatotoxin. The formation of a toxic metabolite is apparently mediated by cytochromes P-450 of the phenobarbital class inasmuch as phenobarbital pretreatment of mice increases, whereas beta-naphthoflavone pretreatment decreases, the extent of hepatic necrosis caused by pulegone. Furthermore, two inhibitors of cytochromes P-450, cobaltous chloride and piperonyl butoxide, block toxicity. An analog of (R)-(+)-pulegone that was labeled with deuterium in the allylic methyl groups was found to be significantly less hepatotoxic than the parent compound. The results indicate that oxidation of an allylic methyl group is required for generation of a hepatotoxic metabolite. Menthofuran was identified as a proximate toxic metabolite of (R)-(+)-pulegone, and investigations with (R)-(+)-pulegone-d6 and 18O2 strongly indicate that menthofuran is formed by a sequence of reactions that involve: 1) oxidation of an allylic methyl group, 2) intramolecular cyclization to form a hemiketal, and 3) dehydration to form the furan.