Hydroxylated biphenyls as tyrosinase inhibitor: a spectrophotometric and electrochemical study

Tyrosinase [EC 1.14.18.1] is a copper-containing enzyme involved in melanin biosynthesis, in unfavourable enzymatic browning of plant-derived foods, in pathological melanogenesis and in insects moulting process]. It catalyses the oxidation of both monophenols (monophenolase or cresolase activity) and o-diphenols (diphenolase or catecholase activity) to o-quinones (Fig. 1A). Investigation of tyrosinase inhibitors may lead to development of novel skin whitening agents, medicinal products, antibrowning substances or insect control compounds]. Many natural occurring compounds have been identified for those targets whose structure has inspired the preparation of several collections of synthetic tyrosinase inhibitors. 4,40-Dihydroxy-biphenyl 1, a natural biphenol, was found to be a potent tyrosinase inhibitor, more effective than kojic acid and arbutin. Hydroxylated biphenyls are a class of polyphenols widely present in nature , some of them manifest high biological activity like ellagitannins, vancomicin, biphenomicins. Compared to phenols, hydroxylated biphenyls manifest higher antioxidant activity and generally they are less toxic than the corresponding phenolic monomer .