In 1950, a small amount of CoQ was isolated from the lining of a horses gut, a compound initially called substance SA, but later deemed to be quinone found in many animal tissues. In 1957, the same compound was isolated from mitochondrial membranes of beef heart, with research showing that it transported electrons within mitochondria. It was called Q-275 as a quinone. The Q-275/substance SA was later renamed ubiquinone as it was a ubiquitous quinone found in all animal tissues. In 1958, its full chemical structure was reported. Ubiquinone was later called either mitoquinone or coenzyme Q' due to its participation to the mitochondrial electron transport chain. In 1966, a study reported that reduced CoQ was an effective antioxidant in cells.