Rapid screening of natural-origin tyrosinase regulators from Vernonia anthelmintica (L.) Willd. by offline two-dimensional liquid chromatography coupled with mass spectrometry.

Finding and developing safe and effective tyrosinase (TYR) regulators is of great significance for the prevention and treatment of melanin-related skin diseases in the medical and cosmetic industries. In the current research, an approach based on offline two-dimensional liquid chromatography coupled with mass spectrometry (offline 2D LC-MS) was established to screen TYR modulators from Vernonia anthelmintica (L.) Willd. (VA) extract. Firstly, the reliability of the proposed method was evaluated by using kojic acid (inhibitor), psoralen (activator) and ranitidine as positive and negative control, respectively. Some significant parameters including incubation time, TYR concentrations, and reaction temperature were investigated. Then, the developed new method was successfully applied to rapidly discover the active compounds from VA extract. Seven TYR ligands were successfully screened by comparing the chromatographic profiles of VA extract incubated with active and denatured TYR, respectively. To verify the activity of the screened compounds, in vitro bioassay was carried out and the result showed two of them, isorhamnetin and luteolin, had good TYR inhibitory activity with IC value of 0.86 and 1.00 mg/mL, respectively, while the other five compounds including eriodictyol, butochalcone, chlorogenic acid, isochlorogenic acid B, and isochlorogenic acid C showed strong activation against TYR. Furthermore, molecular docking displayed that these compounds could bind to the amino acid residues in TYR catalytic pocket. The results demonstrate that the established technique can be efficiently used for rapid screening of TYR-active compounds from plant extracts.