Gentisic acid, also known as gentisate or 2,5-dioxybenzoate, belongs to the class of organic compounds known as hydroxybenzoic acid derivatives. Hydroxybenzoic acid derivatives are compounds containing a hydroxybenzoic acid (or a derivative), which is a benzene ring bearing a carboxyl and a hydroxyl groups. Gentisic acid is an extremely weak basic (essentially neutral) compound (based on its pKa). Gentisic acid exists in all living organisms, ranging from bacteria to humans. Outside of the human body, Gentisic acid is found, on average, in the highest concentration within a few different foods, such as tarragons, common thymes, and common sages and in a lower concentration in grape wines, rosemaries, and sweet marjorams. Gentisic acid has also been detected, but not quantified in, several different foods, such as common grapes, fennels, german camomiles, evening primroses, and guava. This could make gentisic acid a potential biomarker for the consumption of these foods. Gentisic acid is also a byproduct of tyrosine and benzoate metabolism. There is an increasing amount of evidence indicating that gentisic acid has a broad spectrum of biological activity, such as anti-inflammatory, antirheumatic and antioxidant properties. Gentisic acid is an active metabolite of salicylic acid degradation. It is a crystalline powder that forms monoclinic prism in water solution. It is a fungal metabolite as well (ChEBI). Gentisic acid is a dihydroxybenzoic acid.