Molecular Docking Simulation of Phenolics towards Tyrosinase, Phenolic Content, and Radical Scavenging Activity of Some Zingiberaceae Plant Extracts

Abstract

In Indonesia, plants have been indigenously used to treat various diseases and as cosmetics. It is always challenging to explore the molecular interactions of phenolic compounds towards the levels of constituents that contribute to the biological activities of plants. This study aimed to select a plant of the Zingiberaceae family with the highest phenolics and flavonoids, the strongest radical scavenging activity, and the best interaction towards tyrosinase in terms of docking score and binding mode. Initially, the total phenolics and radical scavenging capacity of Zingiberaceae plants, namely, Hedychium coronarium, Curcuma zedoaria, Curcuma heyneana, and Alpinia galanga, were determined using the Folin–Ciocâlteu method and the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. The main phytoconstituents of plants with the highest phenolic levels were docked to the binding site of tyrosinase. Three anti-melanogenesis agents commonly used in cosmetics, namely, arbutin, hydroquinone, and kojic acid, were used as the standard. Our study revealed that all the tested plants contain polyphenolic compounds in the range of 17.92 (C. zedoaria rhizome extract) to 252.36 (A. galanga rhizome extract) mg GAE/g and have radical scavenging capacity, with IC50 values in the range of 66.67 (A. galanga rhizome extract) to 320.0 (C. heyneana rhizome extract) μg/mL. A molecular docking simulation demonstrated that four constituents, i.e., kaempferol, galangin, ethyl p-methoxycinnamate, and 6-gingerol, could occupy the binding site of tyrosinase with prominent affinity and interact with essential residues of the enzyme. This study confirms that Alpinia galanga possesses the potential to be further developed as a cosmetic with a radical scavenging and tyrosinase inhibitory activity. However, it may be interesting to carry out further studies of how the plant extract affects the melanogenesis signaling pathway.