UC San Diego

Tyrosinase, an important oxidase involved in the primary immune response in humans, can sometimes become problematic as it can catalyze undesirable oxidation reactions. Therefore, for decades there has been a strong pharmaceutical interest in the discovery of novel inhibitors of this enzyme. Recent studies have also indicated that tyrosinase inhibitors can potentially be used in the treatment of melanoma cancer. Over the years, a number of new tyrosinase inhibitors have been isolated from various natural sources, although marine natural products (MNPs) have contributed only a small number of promising candidates. In this regard, the exploration of tyrosinase inhibitors from marine cyanobacteria has been especially understudied. This research therefore mainly focused on the discovery of new tyrosinase inhibitors of marine cyanobacterial and algal origins. A colorimetric fungal tyrosinase inhibitory assay was used to screen extracts, fractions, and pure compounds for anti-tyrosinase activity. Scytonemin monomer (ScyM), the monomeric structure of the well-known cyanobacterial sunscreen pigment scytonemin (Scy), was found to have the highest tyrosinase inhibitory score and was more potent than the commercial standard inhibitor kojic acid (KA). Consequently, ScyM has become our top compound and we explored a series of follow-up studies on its structure, inhibitory power, and mode of inhibition.