Ubiquinol/Ubiquinone Ratio as a Marker of Oxidative Stress

Oxidative stress is defined as a disturbance in the prooxidant-antioxidant balance in favor of the former (1 ) and has been suggested be a causative factor in aging and degenerative diseases such as heart attack, diabetes, and cancer. The ubiquinol/ubiquinone ratio should therefore be a good marker of oxidative stress because ubiquinol is very labile in the oxidation of low-density lipoprotein (LDL) or plasma. In fact, a decrease in ubiquinol/ubiquinone ratio has been reported in patients with adult respiratory distress syndrome (2 ) and in patients with hepatitis, cirrhosis, and hepatoma (3 ). Interestingly, newborn babies are under oxidative stress as judged by plasma ubiquinol/ubiquinone ratio (4 ). Here we describe a simple and reproducible high-performance liquid chromatography (HPLC) method for the detection of ubiquinol and ubiquinone using an on-line reduction column and an electrochemical detector (ECD), and its application to human plasma (5 ).