Lipoxygenase inhibitory activity of 6-pentadecanylsalicylic acid without prooxidant effect

6-Pentadecanylsalicylic acid, referred to as anacardic acid (C _15:0), was found to inhibit the linoleic acid peroxidation competitively catalyzed by soybean lipoxygenase-1 (EC 1.13.11.12, Type 1) with an IC₅₀ of 14.3 μM (4.88 μg/mL). This inhibition is a reversible reaction without pro-oxidant effects. The inhibition kinetics analyzed by Dixon plots indicates that anacardic acid (C_15:0) is a competitive inhibitor and the inhibition constant, KI, was established as 6.4 μM. The hydrophilic head (salicylic acid) portion first chelates the iron in the active site and then the hydrophobic tail portion begins reversibly interacting with the C-terminal domain where the iron is located. The inhibition of anacardic acid (C_15:0) can be explained by a combination of iron ion-chelation and hydrophobic interaction abilities because of its specific structural feature.