Comparative metabolism of 3,5-di-tert-butyl-4-hydroxytoluene (BHT) in mice and rats.

In male and female DDY/Slc mice given single oral doses (20 or 500 mg/kg body weight) of 3,5-di-tert-butyl-4-hydroxytoluene (BHT) labelled with 14C at the p-methyl group, 14C was distributed mainly in the stomach, intestines, liver and kidney, and then excreted in the urine, faeces and expired air. During the 7 days after treatment, 41-65, 26-50 and 6-9% of the 14C dose was excreted in faeces, urine and expired air, respectively, and the total recovery was 96-98%. Levels of 14C in 21 male and 22 female tissues 7 days after treatment were less than 1 microgram BHT equivalents/g tissue (ppm) in mice given 20 mg/kg and less than 11 ppm in mice given 500 mg/kg. When [14C]BHT was given orally to male mice at 20 mg/kg/day for 10 days, 14C was rapidly excreted and did not exhibit any tendency to accumulate in any tissues. Thin-layer chromatography and high-performance liquid chromatography analyses showed that more than 43 metabolites were present in the urine and faeces of both species, and all of these were identified to determine metabolic pathways for BHT in mice and rats. Major metabolic reactions of [14C]BHT in mice were the oxidation of the p-methyl group attached to the benzene ring and of the tert-butyl groups. The products from the latter reaction were cyclized to some extent by reacting with the adjacent phenolic OH group to give hemiacetals or lactones. The carboxyl derivatives from the p-methyl oxidation were conjugated with glucuronic acid. When single oral doses of 20 or 500 mg [14C]BHT/kg were given to male Sprague-Dawley rats, metabolites similar to those in mice were found. However, the major biotransformation was oxidation of the p-methyl group, and oxidation of the tert-butyl groups was a minor reaction in rats.

Urinary metabolites of 3,5-di-(1-[13C]methyl-1-methylethyl)4-hydroxytoluene (BHT-13C) in man.

Butylated hydroxytoluene (BHT) containing the stable isotope 13C was synthesized from 2-[13C]methylpropan-2-ol. A minor constituent of urine following ingestion of BHT-13C by a human volunteer was identified as 3,5-di-(1-[13C]methyl-1-methylethyl)-4-hydroxybenzoic acid, The major metabolite detected was 13C-labeled 5-carboxy-7-(1-carboxy-1-methylethyl)-3,3-dimethyl-2-hydroxy-2,3-dihydrobenzofuran. Detailed spectral analysis provided the basis for structural assignment. No evidence was found for intermediate metabolites leading from BHT-13C to the above compounds. Analysis of one fraction indicated the presence of traces of S-(3,5-di-(1-[13C]methyl-1-methylethyl-4-hydroxy-benzyl)-N-acetylcysteine. Analysis of serum samples by gas chromatography detected only trace quantities of unchanged BHT. No evidence was found for the presence of other nonpolar or unconjugated metabolites.

Methods of extraction and high-performance liquid chromatographic analysis of butylated hydroxytoluene from the tissues and serum of rats.

Butylated hydroxytoluene (BHT) is a phenolic antioxidant which is widely used in foods and has been shown to inhibit chemical carcinogenesis in the mammary gland induced by 7,12-dimethylbenz(a)anthracene. However, its mechanism of action as a tumor inhibitor is unclear. The purpose of this work was first to develop a method for extracting and quantitating BHT and then to determine the amounts that accumulate in the tissues and serum of rats as a starting point for looking at mechanistic possibilities in the inhibition of mammary carcinogenesis. Methodology of extracting BHT from rat tissues and serum was developed using a modified lipid extraction procedure. The sensitive nature of reverse-phase high-performance liquid chromatography proved useful in detecting and quantifying BHT after its extraction from biological tissues. All tissues were taken from animals consuming semipurified diets with and without 0.3% BHT for various periods of time (weeks). BHT was found in much higher levels in mammary tissue than in the liver and serum of rats. The lipid content in mammary tissue appears to be predictive of the amount of BHT found in this tissue, presumably because of the lipophilic character of the antioxidant.

Probability model of dibunol pharmakinetics.

A mathematical description of the inflow of dibunol from the site of administration and its distribution by organs and tissues in experimental animals and man are examined. Parameters quantitatively characterizing the behavior of the preparation in the organism were obtained. The mechanism of the accumulation of dibunol in the tissues and its subsequent transfer to the blood are described within the framework of the proposed model. The model of the pharmakinetics of dibunol makes possible a calculation of the concentration of the preparation in the tissues depending on the method of administration and special features of the medicinal form. In clinical practice when administered per os microcapsules, which provided maximum absorbability, proved to be the best medicinal form. Satisfactory agreement of the concentrations of the preparation actually observed in a human tumor with those calculated theoretically on the basis of the proposed model was observed.