Ubiquinol is an electron-rich form of coenzyme Q10. The natural ubiquinol form of coenzyme Q10 is 2,3-dimethoxy-5-methyl-6-poly prenyl-1,4-benzoquinol, where the polyprenylated side-chain is 9-10 units long in mammals. Coenzyme Q10 exists in three redox states, fully oxidized, partially reduced, and fully reduced. The redox functions of ubiquinol in cellular energy production and antioxidant protection are based on the ability to exchange two electrons in a redox cycle between ubiquinol and the ubiquinone form.