Eriocitrin is a flavonoid originally isolated from lemon peel that has antioxidant and enzyme inhibitory activity. Eriocitrin inhibits lipid peroxidation in a cell-free assay when used at a concentration of 10 μM and enhances the effect of α-tocopherol on lipid peroxidation. It also decreases thiobarbituric acid reactive substances (TBARS) in rat plasma when administered at a dose of 75 μmol/kg, indicating a reduction in lipid peroxidation. Eriocitrin prevents acute exercise-induced increases in TBARS, Nε-(hexanoyl)lysine (HEL), o,o-dityrosine (DT), and nitrotyrosine (NT; ) in rat liver when administered at a dose of 600 mg/kg prior to exercise. It is also an inhibitor of monoamine oxidase A (MAO-A) and MAO-B (IC50s = 86.5 and 164 μM, respectively, for human recombinant receptors).