3,5-Dihydroxybenzoic acid

3,5-Dihydroxybenzoic acid (α-resorcylic acid) is a dihydroxybenzoic acid. It is a colorless solid.
Preparation and occurrence.
It is prepared by disulfonation of benzoic acid followed by hydrolysis of the disulfonate.
It is a metabolite of alkylresorcinols, first identified in human urine and can be quantified in urine and plasma, and may be an alternative, equivalent biomarker of whole grain wheat intake.