Substance SC (ubichromenol): a naturally-occurring cyclic isomeride of ubiquinone-50

Abstract
A normal minor unsaponifiable lipid, hitherto designated substance SC, and present in kidney and other tissues of many species, has been isolated from normal human kidney, its concentration in this tissue being about 10 mg/kg. Substance SC is a yellow crystalline compound, melting point about 18[degree]. It is isomeric with ubiquinone, C59H90O4, but is not itself a quinone. Substance SC contains a chromene ring system and a large polyisoprenoid side chain. Perhydro-SC can be oxidized by ferric chloride to perhydroubiquinone. Substance SC is therefore a cyclic isomeride of ubiquinone, the cycliza-tion involving the first isoprenoid unit of the side chain and the adjacent oxygen function. The name ubichromenol is suggested for substance SC.