In this study, inhibition profiles of some natural products, which are digoxin, L-Dopa, dopamine, isoliquiritigenin, and 1,1,2,2-tetrakis(p-hydroxyphenyl)ethane (Tetrakis), were investigated against bovine lactoperoxidase (LPO) enzyme. Digoxin, L-Dopa, and dopamine are active ingredients of some drugs, which have important functions in our body, especially in cases of heart failure. Isoliquiritigenin and tetrakis are types of natural phenolic compounds, which play an important role in cancer prevention and treatment. LPO enzyme was purified from bovine milk using sepharose-4B-l-tyrosine sulfonamide affinity column chromatography. LPO is responsible for the nonimmune biological defense system and has antibacterial activity so selection of these active substances is important. The inhibition studies are performed with the ABTS substrate. Bovine LPO enzyme was effectively inhibited by phenolic molecules. K-i values of these natural products were found as 0.20 +/- 0.09, 0.22 +/- 0.17, 0.49 +/- 0.11, 0.49 +/- 0.27, and 1.20 +/- 0.25 M, respectively. Tetrakis and digoxin exhibited noncompetitive inhibition, and other molecules showed competitive inhibition.