Muconic

Muconic is an adjective referring to muconic acid, a naturally occurring dicarboxylic acid produced during aerobic degradation of aromatic compounds. The most studied form is trans,trans-muconic acid, a conjugated diene with two carboxyl groups at the ends. The molecular formula is C6H6O4.

Structure and isomerism: The core structure is HOOC-CH=CH-CH=CH-COOH, a six-carbon chain with a conjugated four-carbon diene between terminal carboxyl groups. The compound exists as several geometric isomers, with trans,trans-muconic acid (tt-MA) the most common in nature and in analytical contexts. Other possible forms include cis,trans-, and cis,cis-muconic acids, depending on the orientations around the double bonds.

Biosynthesis and occurrence: In environmental microbiology, muconic acid is an intermediate produced during the microbial breakdown of benzene and related aromatic compounds. Catechol 1,2-dioxygenase converts catechol into muconic semialdehyde, which is further oxidized to muconic acid. This pathway is part of the bacterial strategy to cleave and metabolize aromatic rings.

Uses and significance: Trans,trans-muconic acid is used as a biomarker of benzene exposure, detectable in urine and sometimes in blood. It is used in occupational health surveillance, though its measurement can be influenced by dietary sorbic acid, which can form muconic acid in vivo or during analysis, potentially confounding results.

Safety and references: Muconic acid itself is not highly toxic at typical exposure levels; like many metabolites, it is handled within standard laboratory and environmental contexts. For further details, see benzene metabolism and muconic acid biosynthesis literature.