INHIBITION OF POLYPHENOL OXIDASE BY PHENOLIC-COMPOUNDS

Several inhibitors of polyphenol oxidase (PPO) were isolated from a plant extract. The inhibitors were purified and their relative potencies determined using commercially-available mushroom PPO in an in vitro assay system. Structural elucidation of the inhibitors showed them to be novel, plant secondary metabolites closely related to other phenolic compounds known to play important roles in flowering plants. Structure/activity relationships have been studied using synthetic analogs, several of which are potent PPO inhibitors. In addition to the in vitro studies, certain of these compounds inhibit enzymatic browning (melanosis) in foods such as shrimp, potatoes and apples as well as beverages such as grape juice. The inhibitors are water-soluble, stable, effective at low concentration, and have potential as functional alternatives to sulfites for the inhibition of melanosis. The chemical nature of the PPO inhibitors, kinetic studies, safety data, and results obtained on foods are discussed.