Coenzyme Q10 (CoQ10) is a natural antioxidant synthesized by the body, found in many foods, and available as a supplement. It comes in two forms: ubiquinol, the active antioxidant form, and ubiquinone, the oxidized form, which the body partially converts to ubiquinol. Many multi-ingredient supplements contain both forms of CoQ10. In general, coenzymes support enzymes in their various biochemical functions. CoQ10 is a vital participant in the chain of metabolic chemical reactions that generate energy within cells. It is found in every cell of the body (the name ubiquinone stems from its ubiquity), but is present in higher concentrations in organs with higher energy requirements such as the kidneys, liver, and heart.