[Determination of ubiquinones in biological material by high performance liquid chromatography]

Quantitative high performance liquid chromatographic (HPLC) methods are described for the determination of reduced, oxidized, and total ubiquinone (UQred, UQox, and total UQ, respectively) in biological material. UQ was extracted into n-hexane from an aqueous homogenate after precipitation of protein by addition of alcohol. The n-hexane extract was evaporated to dryness under a N2 atmosphere at 30 degrees C. In order to determine the total UQ, UQred was converted into the corresponding oxidized form (UQox) with ferric chloride. UQox was separated on a reversed-phase column and detected by its ultraviolet absorption (UV275n m). For the simultaneous assay of UQred and UQox, the n-hexane extract was injected onto a HPLC having a UV detector and an electrochemical detector (ECD) coupled in series. UQox was detected by its UV275n m, and UQred by ECD. The HPLC methods described here were applied satisfactorily to the determination of UQred, UQox, and total UQ in human and animal tissues.