Zinc benzoate, a contaminating environmental compound derived from polystyrene resin inhibits A-type monoamine oxidase

Abstract The contaminants in deionized and distilled water (DDI water) boiled with polystyrene resin inhibited A-type monoamine oxidase (MAO, MAO-A preferentially deaminates serotonin and norepinephrine and regulates these amines concentration) activity in monkey brain mitochondria. To identify these contaminants, we attempted measurements by HPLC, FT–IR and NMR. The compound inhibiting MAO-A activity was zinc benzoate. Although it potently inhibited MAO-A activity, zinc benzoate did not effect MAO-B in monkey brain mitochondria. It also reversibly and competitively inhibited MAO-A activity in a dose-dependent manner. Zinc benzoate, however, did not inhibit either MAO-A or -B activities in rat brain mitochondria. These results indicate that zinc benzoate, which inhibits MAO-A activity, is easily incorporated in DDI water by boiling polystyrene and also may be a contaminating environmental chemical compound that alters the levels of serotonin and norepinephrine in the central nervous system.