Itaconic acid is a fatty acid containing five carbons , two of which are in carboxyl groups and two others which are double bonded together . . At the strongly acidic pH levels below 2, itaconic acid is electrically neutral because both of its carboxy residues are bound to hydrogen ; at the basic pH levels above 7, it is double negatively charged because both of its carboxy residues are not bound to H, i.e., CO2

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; and at acidic pH's between 2 and 7, it exists as a mixture with none, one, or both of its carboxy residues bound to hydrogen. In the cells and most fluids of living animals, which generally have pH levels above 7, itaconic acid exists almost exclusively in its double negatively charged form; this form of itaconic acid is termed itaconate. Itaconic acid and itaconate exist as cis and trans isomers . Cis-itaconic acid and cis-itaconate isomers have two H's bound to one carbon and two residues bound to the other carbon in the double bound whereas trans-itaconic acid and trans-itaconate have one H and one R residue bound to each carbon of the double bound. The adjacent figure shows the cis form of itaconic acid. Cis-aconitic acid spontaneously converts to its thermodynamically more stable isomer, trans-aconitic acid, at pH levels below 7. The medical literature commonly uses the terms itaconic acid and itaconate without identifying them as their cis isomers. This practice is used here, i.e., itaconic acid and itaconate refer to their cis isomers while the trans isomer of itaconate is here termed trans-itaconate .