Decarboxylation and demethylation of some phenolic benzoic acid derivatives by rat caecal contents

Rat caecal contents decarboxylate phenolic benzoic acid derivatives when a free hydroxyl group is in the para position but the presence of substituents adjacent to this group or the carboxyl group reduce or abolish the reaction. Compounds containing a hydroxyl group in the ortho or meta position but lacking one in the para position are not decarboxylated. Some methoxy-derivatives are demethylated. The possible relationship between these findings and urinary phenols is discussed.