MPO and inflammatory bowel disease: Of these markers, the following have been in saliva samples of patients with IBD: enzymes, including glutathione peroxidase (GPX), superoxide dismutase (SOD), and myeloperoxidase (MPO); nonenzymatic antioxidants, such as the total antioxidant capacity (TAC), uric acid (UA), and total thiol level (SH); thio-barbituric acid reactive substances (TBARS) and ROS-induced proteins modifications, including advanced oxidation protein products (AOPP); and advanced glycation end products (AGE) (Table 2) [42,43,81,82,83,84].