p-Cresol

p-Cresol is a small organic compound also called 4-methylphenol. Its structure contains a benzene ring with a hydroxy group, made of oxygen and hydrogen, and a methyl group, made of carbon and hydrogen. The “p” stands for “para” and identifies the positions of those two groups on opposite sides of the ring. Its chemical formula is C7H8O .¹

In the intestine, certain bacteria can produce p-cresol while breaking down the amino acid tyrosine and related intermediate compounds. Different bacteria have different capacities to carry out these reactions, so p-cresol production is not a property shared equally by all gut microbes .²

After absorption, p-cresol is extensively modified in the intestinal lining and liver. Most is converted to p-cresyl sulfate, with a smaller fraction converted to p-cresyl glucuronide. These products can enter the circulation and are normally eliminated through the kidneys. They are chemically distinct from unmodified p-cresol, an important distinction when interpreting measurements or biological effects attributed to the parent compound .³