Apocynin is a compound isolated from the traditional medicinal plant P. kurroa and structurally related to vanillin that acts as an inhibitor of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity. Upon oxidation by myeloperoxidase, apocynin inhibits the assembly of a functional NADPH-oxidase complex that is responsible for reactive oxygen species production. At 300 μM it is effective in preventing the production of superoxide in human white blood cells or neutrophilic granulocytes, but does not however obstruct the phagocytic or other defense roles of granulocytes. Due to the selectivity of its inhibition, apocynin can be widely used as an inhibitor of NADPH oxidase without interfering in other aspects of the immune system. It has been used in the treatment of arthritis, bowel disease, asthma, atherosclerosis, and familial amyotrophic lateral sclerosis.
