Studies on pathways of ring opening of benzene in a Fenton system

Ring-opened products of benzene metabolism have been postulated to play a role in hematotoxicity and leukemogenesis. The reaction of benzene in the Fenton system was reexamined to determine the presence of compounds which might serve as intermediates in the formation of trans, trans-muconaldehyde (MUC), a microsomal hematotoxic metabolite of benzene. Benzene dihydrodiol (DHD) was found in this system based on coelution with authentic standard, ultraviolet (UV) absorption characteristics, and molecular weight. Incubation of DHD in the Fenton system resulted in the formation of phenol (PH), catechol (CAT), and products which reacted with thiobarbituric acid to form chromogens absorbing at 495 nm and 532 nm, consistent with products containing an alpha, beta-unsaturated aldehyde group. However, muconaldehyde was not detected in the Fenton system incubated with DHD, indicating that MUC is not formed via ring opening of DHD. When benzene was incubated in the Fenton system, MUC, cis,trans-muconaldehyde, PH, hydroquinone (HQ), and CAT were identified. Identification of cis,trans-muconaldehyde, an isomer which can quickly rearrange to MUC, suggests that cis,cis-muconaldehyde is originally formed from benzene and converted to cis,trans- and then trans,trans-muconaldehyde.