In mammals most of the absorbed 4-toluenesulfonic acid (1) is excreted unchanged due to its high water solubility. A hydroxylation of 4-toluenesulfonic acid (1) (shown as the anion) by cytochrome P450 at the methyl group is also possible and confirmed in bacteria. Bacterial cultures are capable of degrading 4-toluenesulfonic acid (1) to the endproducts propanal (2), pyruvic acid (4) and inorganic sulfate (5). Propanal (2) and pyruvic acid (3) can enter the primary metabolic pathways of cells.