Anti-melanogenic activity of salacinol by inhibition of tyrosinase oligosaccharide processing

Hyperpigmentation that manifests through melasma and solar lentigo (age spots), although mostly harmless for health, bothers many people. Controlling the rate-limiting activity of tyrosinase is most effective for suppressing excessive melanin formation and accordingly recent research has focused on the maturation of tyrosinase. Salacia, a medicinal plant, has been used to treat diabetes in India and Sri Lanka. Salacia extract reportedly contains components that inhibit the activity of α-glucosidase. Salacinol, the active ingredient in Salacia extract, has unique thiosugar sulphonium sulphate inner salt structure. Here, we observed that the salacinol component of Salacia extract possesses anti-melanogenic activity in comparison to various existing whitening agents. Although the anti-melanogenic mechanism of salacinol is presumably medicated by inhibition of tyrosinase activity, which is often found in existing whitening agents, salacinol did not inhibit tyrosinase activity in vitro. Analysis of the intracellular state of tyrosinase showed a decrease in the mature tyrosinase form due to inhibition of N-linked oligosaccharide processing. Salacinol inhibited the processing glucosidase I/II, which are involved in the initial stage of N-linked glycosylation. Owing to high activity, low cytotoxicity and high hydrophilicity, salacinol is a promising candidate compound in whitening agents aimed for external application on skin.