Highly potent tyrosinase inhibitor, neorauflavane from Campylotropis hirtella and inhibitory mechanism with molecular docking

Bioorg Med Chem. 2016 Jan 15;24(2):153-9. doi: 10.1016/j.bmc.2015.11.040. Epub 2015 Nov 30.


Tyrosinase inhibition may be a means to alleviate not only skin hyperpigmentation but also neurodegeneration associated with Parkinson's disease. In the course of metabolite analysis from tyrosinase inhibitory methanol extract (80% inhibition at 20 μg/ml) of Campylotropis hirtella, we isolated fourteen phenolic compounds, among which neorauflavane 3 emerged as a lead structure for tyrosinase inhibition. Neorauflavane 3 inhibited tyrosinase monophenolase activity with an IC50 of 30 nM. Thus this compound is 400-fold more active than kojic acid. It also inhibited diphenolase (IC50=500 nM), significantly. Another potent inhibitor 1 (IC50=2.9 μM) was found to be the most abundant metabolite in C. hirtella. In kinetic studies, compounds 3 showed competitive inhibitory behavior against both monophenolase and diphenolase. It manifested simple reversible slow-binding inhibition against monophenolase with the following kinetic parameters: Ki(app)=1.48 nM, k3=0.0033 nM(-1) min(-1) and k4=0.0049 min(-1). Neorauflavane 3 efficiently reduced melanin content in B16 melanoma cells with 12.95 μM of IC50. To develop a pharmacophore model, we explored the binding mode of neuroflavane 3 in the active site of tyrosinase. Docking results show that resorcinol motif of B-ring and methoxy group in A-ring play crucial roles in the binding the enzyme.

Keywords: Campylotropis hirtella; Competitive inhibitor; Molecular docking; Neorauflavane; Tyrosinase.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Proliferation / drug effects
  • Cell Survival / drug effects
  • Dose-Response Relationship, Drug
  • Enzyme Inhibitors / chemistry
  • Enzyme Inhibitors / isolation & purification
  • Enzyme Inhibitors / pharmacology*
  • Fabaceae / chemistry*
  • Isoflavones / chemistry
  • Isoflavones / isolation & purification
  • Isoflavones / pharmacology*
  • Melanins / biosynthesis
  • Mice
  • Molecular Docking Simulation*
  • Molecular Structure
  • Monophenol Monooxygenase / antagonists & inhibitors*
  • Monophenol Monooxygenase / chemistry
  • Monophenol Monooxygenase / metabolism
  • Structure-Activity Relationship
  • Tumor Cells, Cultured


  • Enzyme Inhibitors
  • Isoflavones
  • Melanins
  • neorauflavane
  • Monophenol Monooxygenase