The synthesis of mercapturic acids from diethyl sulphate and di-n-propyl sulphate in the rat

Mercapturic acids as metabolites of aromatic aldehydes and alcohols

After administration of substituted (CH3, OH, OCH3, F, CL, Br, NO2) benzaldehyde or benzyl alcohols in the rat an enhanced urinary thioether excretion was found in some cases. With p-substituted benzaldehyde only occasionally a slight increase could be shown, but with o-substituted aldehydes and alcohols thioether excretions amounted up to 13% of the dose. Mercapturic acids were isolated and identified by synthesis, mass-, and n.m.r.-spectrometry as the arylmethyl thioethers of N-acetylcysteine. Steric hindrance by o-substituents must be the main cause of a relative decrease in oxidation to the carboxylic acid and an increase of the importance of both the reduction of the aldehydes and the reaction of the alcohols, presumably to sulphuric acid esters, as intermediates for the alkylation of glutathione. Consequently, previous administration of pyrazole, an inhibitor of alcohol dehydrogenase, caused an even larger thioether excretion after injection of o-chlorobenzyl alcohol.

Isolation and identification of mercapturic acids of cinnamic aldehyde and cinnamyl alcohol from urine of female rats

Rats dosed with cinnamic aldehyde (I) excreted two mercapturic acids in the urine. The major one was identified as N-acetyl-S-(1-phenyl-3-hydroxypropyl)cysteine (V). The minor one was identified as N-acetyl-S-(1-phenyl-2-carboxy ethyl)cysteine (VI). The ratio appeared to be V : VI = 4 : 1. The hydroxy mercapturic acid (V) was also isolated from urine of rats dosed with cinnamyl alcohol (II). The total mercapturic acid excretion as percentage of the dose was 14.8 +/- 1.9% for cinnamic aldehyde (250 mg/kg) (n = 4) and 8.8 +/- 1.7% for cinnamyl alcohol (n = 4) (125 mg/kg). Inhibition of the alcohol dehydrogenase by pyrazole (206 mg/kg) diminished the thioether excretion of cinnamyl alcohol to 3.3 +/- 1.4% of the dose (n = 8). Cinnamic aldehyde has been proposed to be an intermediate in the mercapturic acid formation of cinnamyl alcohol.