The Instability of the Lipid-Soluble Antioxidant Ubiquinol: Part 1-Lab Studies

Coenzyme Q10 (CoQ10) is a popular nutritional supplement that is available in both the oxidized and reduced form. The marketing of CoQ10 to physicians often asserts that one form is superior to the other. This study was designed to compare and contrast the stability, absorption and claims made for the reduced form of CoQ10 (ubiquinol) compared with the oxidized form (ubiquinone). There is a need for studies that examine the contents of commercially available ubiquinol products microscopically at room, body and 50°C temperatures. There is also a need for studies of the state of the ubiquinol contents when exposed to a 2.2 pH solution that simulates stomach acidity and an 8.2 pH solution that simulates acidity in the duodenum.

An investigation of the instability of ubiquinol supplements was conducted via an in vitro study of 13 ubiquinol products marketed in the United States that measured the extent of the conversion of the ubiquinol content to ubiquinone, when the ubiquinol was squeezed out of the capsule at room temperature and when the ubiquinol contents were exposed to a 2.2 pH solution and an 8.2 pH solution.

In the in vitro study, the percentage of ubiquinol converted to ubiquinone at body temperature was greatest in the 8.2 pH simulated small intestinal juice: 76%. The percentage of ubiquinol converted to ubiquinone at body temperature in the 2.2 pH gastric juice that simulated conditions in the stomach was 54%.

Ubiquinol in commercial nutritional supplements is fairly stable inside the gelatin capsule but unstable in gastric and small intestine digestive fluids. Based on the data from the lab studies, most of the ubiquinol from the capsule will be converted to ubiquinone prior to reaching the absorption cells in the small intestines. Animal studies are needed to test this hypothesis.