Tyrosinase Inhibitory Kinetics, LC-QTOF-MS Based Chemical Profiling and Molecular Docking of Phytochemicals from Dillenia indica L. Barks

The present study was aimed to investigate the role of Dillenia indica L. bark extracts and their kinetics of inhibition against the tyrosinase enzyme. The kinetics study of various concentrations of the extracts was executed by spectrophotometric assay. Out of four extracts, only hydro-ethanolic extract of D. indica barks (HEEBDI) showed the maximum radical scavenging capacity (36.73 ± 1.65 μg/ml) compared to ascorbic acid. Additionally, HEEBDI scavenging capacity and tyrosinase inhibitory properties showed a significant correlation. In HEEBDI, fifteen marker compounds were identified by LC-QTOF-MS method. The tyrosinase inhibitory activity of HEEBDI (IC 50 19.32 ± 0.57 μg/ml) showed a significant value compared to kojic acid (IC 50 22.08 ± 0.19 μg/ml). The inhibitory mechanism was confirmed in a mixed manner by enzyme kinetics. With minimal conformational energy, betulinic acid and kaempferol bind to the tyrosinase enzyme (PDB ID: 2y9x) as proved by their respective docking score and binding interaction.