Oxidative metabolism of butylated hydroxytoluene by hepatic and pulmonary microsomes from rats and mice.

Metabolism of the antioxidant butylated hydroxytoluene (BHT; 2,6-di-tert-butyl-4-methylphenol) has been studied with liver and lung microsomes from rats and mice. The structures of several previously reported metabolites were confirmed, the identities of four new metabolites were determined, pathways of oxidation were investigated, and quantitative data were obtained for several of the products. Two main metabolic processes occur, hydroxylation of alkyl substituents and oxidation of the aromatic pi electron system. The former leads to the 4-hydroxymethyl product (BHT-BzOH) and a primary alcohol resulting from hydroxylation of a t-butyl group (BHT-tBuOH). Additional metabolites were produced by oxidation of BHT-BzOH to the corresponding benzaldehyde and benzoic acid derivatives. Hydroxylation of BHT-tBuOH occurs at the benzylic methyl position, and the resulting diol is oxidized further to the hydroxybenzaldehyde derivative. Oxidation of the pi system leads to the quinol, 2,6-di-t-butyl-4-hydroxy-4-methyl-2,5-cyclohexadienone, the quinone, 2,6-di-t-butyl-4-benzoquinone, and the quinone methide, 2,6-di-t-butyl-4-methylene-2,5-cyclohexadienone. Derivatives of the quinol and quinone with a hydroxylated t-butyl group were also formed. Quantitative data demonstrate that BHT-BzOH is the principal metabolite in rat liver and lung microsomes. On the other hand, mice produce large amounts of both BHT-BzOH and BHT-tBuOH in these tissues. The metabolite profile was similar in rat liver and lung. Mouse lung, however, produced more quinone relative to other metabolites than mouse liver.(ABSTRACT TRUNCATED AT 250 WORDS)