Glycosidic vs. Aglycol Form of Natural Products as Putative Tyrosinase Inhibitors

Numerous natural products and designed molecules have been evaluated as tyrosinase inhibitors that impede enzymes' oxidation activity. In the present study, new potent natural inhibitors were retrieved from the ZINC database by the similarity-screening of 37 previously reported tyrosinase inhibitors. The screening resulted in 42 candidate inhibitory molecules that were categorized into five groups. Molecular-docking analysis for these compounds, as well as for three others known for their inhibition activity (caffeic acid, naringenin, and gallic acid), was carried out against the tyrosinase structure from Agaricus bisporus (AbTYR). The top-scoring compounds were used for further comparative analysis with their corresponding naturally occurring glycosides. The results suggested that the glycosylated inhibitors could interact better with the enzyme than their aglycon forms. In order to further examine the role of the sugar side group of potent tyrosinase inhibitors, the dynamic behavior of two such pairs of glycosidic/aglycol forms (naringin-naringenin and icariin-icaritin) in their complexes with the enzyme were studied by means of 20-ns MD simulations. The increased number of intermolecular hydrogen bonds and their augmented lifetime between AbTYR and the glycosidic analogues showed that the naringin and icariin molecules form more stable complexes than naringenin and icaritin with tyrosinase, and thus are more potent inhibitors.