Tyrosinase inhibitor screened from Olea europaea L. leaves: Identification, molecular docking analysis and molecular mechanisms

Olea europaea L. leaves have been reported to possess anti melanogenesis activity; however, the active components and related mechanisms have not been fully elucidated. This study established an integration strategy combining quantitative HPLC fingerprints, anti-tyrosinase activity analysis and LC-MS analysis to screen and identify active components in olive leaves. Oleuropein, luteolin-7-O-β-D-glucoside, apigenin-7-O-β-D-glucoside, and oleuroside were screened as active compounds by Pearson correlation and partial least squares regression analysis (PLSR). Molecular docking further revealed the interaction between the four active polyphenols and human tyrosinase (h-Tyr). Oleuropein was validated to possess the highest inhibitory effect and binding capacity on h-Tyr and to interact with proteins at the active center. The antimelanogenic activity of oleuropein was confirmed by dose-dependent inhibition of melanin production and tyrosinase activity in B16 cells. Western blotting assays further indicated that oleuropein dose-dependently downregulated the expression of the critical melanogenic proteins TRP, TRP1, TRP2, and MIFT. These antimelanogenesis actions of oleuropein might be mediated by both the CREB and MAPK signaling pathways. Further research on the zebrafish model demonstrated successful depigmenting and antimelanin production activity of oleuropein in vivo. These data provide insight into the bioactive components and molecular mechanisms of olive leaves in inhibiting melanogenesis, rationalizing the application of natural compounds in skin health care.