Phloroglucinol carboxylic acid

Phloroglucinol carboxylic acid, also called ‘Phloroglucinic acid’ or simply ‘PGCA’, is a trihydroxybenzoic acid, a type of phenolic acid. It can be encountered in nature were it is produced by plants or microorganisms. Structurally, the molecule can be perceived as Gallic acid in which the 2 hydroxy groups at positions 3 and 5 respectively on the benzene ring backbone have been moved “up” to positions 2 and 6, closely neighboring the carboxylic acid functional group. Salts and esters of PGCA (e.g. potassium salt or methyl ester) are known as Phloroglucinates.

It is produced by Pseudomonas fluorescens. It is a catechin degradation product excreted by the bacterium Acinetobacter calcoaceticus, a species of bacteria part of the human body normal flora, grown on catechin as sole source of carbon. It is also found in wine.