Secondary metabolites of benzo[a]pyrene: 3-hydroxy-trans-7,8-dihydro-7,8-dihydroxybenzo[a]pyrene, a biliary metabolite of 3-hydroxybenzo[a]pyrene in the rat.

Rats administered 3-hydroxybenzo[a]pyrene (50 mg/kg, i.p.), excrete via the bile metabolites which, after treatment with beta-glucuronidase and aryl sulphatase, yield, in addition to 3-hydroxybenzo[a]pyrene, 3-hydroxy-trans-7,8-dihydro-7,8-dihydroxybenzo[a]pyrene (3-OH-BP-7,8-diol) and a minor, highly labile, metabolite tentatively identified as 3,5-dihydroxybenzo[a]pyrene. These novel metabolites are readily isolated in a pure state via preparative layer chromatography. The structure of the 3-OH-BP-7,8-diol was revealed by its u.v., proton magnetic resonance and mass spectral properties. Its hydroxyl functions are in a predominantly quasi-diequatorial conformation.