MOLECULE

Isocitric acid

Isocitric Acid, also known as isocitrate, belongs to the class of organic compounds known as tricarboxylic acids and derivatives. These are carboxylic acids containing exactly three carboxyl groups. Isocitric acid is a structural isomer of citric acid and is mildly acidic (based on its pKa). Isocitric acid exists in all living species, ranging from bacteria to humans. It is formed from citrate with the help of the enzyme aconitase and is transformed to alpha-ketoglutarate by isocitrate dehydrogenase. Outside of the human body, isocitric acid has been detected, but not quantified in, several different foods, such as red currants, wild celeries, gooseberries, soursops, and apples. This could make isocitric acid a potential biomarker for the consumption of these foods. Salts and esters of isocitric acid are known as isocitrates. In authentic orange juice, for example, the ratio of citric acid to D-isocitric acid is usually less than 130. As a result, isocitric acid is commonly used as a marker to detect the authenticity and quality of fruit products, most often citrus juices.