Description | Cis-cis-muconic acid is a presumptive metabolite of benzene. Muconic acid was first isolated from the urine of rabbits and dogs in 1909 ( M. Jaffe, Z Physiol Chem 62:58-67). It was originally thought that if muconic acid were formed by opening of the benzene ring in vivo then the cis-cis isomer should be the initial (and primary) product. However subsequent studies conducted in the 1950's proved that trans-trans-muconic acid is a true metabolite of benzene in mammals (Parke DV, Williams RT. Biochem J 51:339-348 (1952)). Furthermore, dosing rabbits with phenol or catechol also resulted in the urinary excretion of trans-trans-muconic acid. The oxidative ring opening of benzene first gives rise to cis-cis-muconaldehyde, which then isomerizes to cis-trans- and trans-trans-muconaldehyde; the latter is oxidized in vivo to trans-trans-muconic acid. Isomerization of the trans-trans form may take place in vivo to yield small amounts if the cis-cis and cis-trans form of muconic acid. Cis-cis muconic acid may also be generated from microbial fermentation of benzoic acid. Certain strains of arthobacter are particularly efficient at this process. |