Insights into tyrosinase inhibition by compounds isolated from Greyia radlkoferi Szyszyl using biological activity, molecular docking and gene expression analysis

Greyia radlkoferi ethanol extract and its five compounds were tested for their inhibitory activity against the mushroom Tyrosinase enzyme and melanin production on melanocytes. The crude extract showed significant Tyrosinase inhibition with IC₅₀ of 17.96μg/ml. This is the first report of the isolation of these 5 compounds from Greyia radlkoferi. 2',4',6'-Trihydroxydihydrochalcone showed the highest Tyrosinase inhibition at 17.70μg/ml (68.48μM), with low toxicity when compared with crude extract. This compound is therefore, a key component in the crude extract, which is responsible for Tyrosinase inhibitory activity. The RT-qPCR indicated that the mechanism of action is most likely post transcriptional. Further, the molecular docking study showed that Tyrosinase inhibitory activity depends on interaction of the compound with Cu²⁺ ions at the active site. This is the first report of the Tyrosinase inhibitory activity of the G. radlkoferi extract and molecular insights on interaction of its compounds with Cu²⁺ ions as the driving factor for Tyrosinase inhibition. These results suggest that the extract of G. radlkoferi and the compound 2',4',6'-trihydroxydihydrochalcone have great potential to be further developed as pharmaceutical or cosmetic agents for use against dermatological disorders associated with melanin.

Gene expression; Greyia radlkoferi; Hyper-pigmentation; Melanin inhibition; Molecular docking; Tyrosinase.