| The active ingredients from the local medicinal plants with tyrosinase inhibitory property play an important role as alternative agents for skin care products and the treatment of Parkinson's disease. Objective: To optimize the optimal conditions for extraction of the phenolics from Terminaliachebula Retz. fruits, study the inhibitory kinetics of the plant extract and its chemical markers on tyrosinase, and predict the interaction between the chemical markers and the catalytic site of tyrosinase. Methods: The phenolics were extracted from T. chebula fruits by application of the microwave-assisted extraction (MAE) combined with Box-Behnken Design (BBD). The ratio of liquid to solid (X1), ethanol concentration (X2), microwave power (X3), and irradiation time (X4) were chosen as independent variables, whereas contents of the three biomarkers (gallic acid, corilagin, and ellagic acid) were the responses. The extraction efficiency of the proposed method was compared to other previously reported techniques. Phytochemicals in the resulting plant extract were quantified and identified using HPLC-DAD and LC-ESI/MS, respectively. The obtained extract was further studied for its tyrosinase inhibitory activity, followed by predicting the interaction between the biomarkers and binding pocket of tyrosinase using in-silico docking study. Results:The best condition to obtain the maximum yields of the desired phenolics was X1, X2, X3 and X4 of 10:1 mL/g, 43.50 %v/v, 800 W and 3.9 min, respectively. These conditions gave the extraction yields of gallic acid, corillagin and ellagic acid of 3.97±0.964.47±0.79and6.13±0.73 mg/g plant material. Furthermore, MAE showed higher extraction efficiency compared to other extraction methods. Among the 12 identified substances, gallic acid and ellagic were classified as phenolic compounds and the others were hydrolysable tannins. The plant extract and its biomarkers could inhibit mushroom tyrosinase in a dose-dependent manner. Kinetic analysis revealed that only plant extract and gallic acid were found to be a non-competitive inhibitor, whereas ellagic acid was a mixed type inhibitor of the tyrosinase. The mechanism underlying the tyrosinase inhibitory effect was further predicted by in silico molecular docking technique, gallic acid and ellagic acid strongly interacted with the amino acid residues in the binding site mainly by hydrogen bonds and van der Waals forces, followed by induced rearrangement and conformation changes of the enzyme. Conclusion: This study provided useful information regarding the application of the environmental-friendly MAE-BBD for isolation of the phenolics from T. chebula fruits. The resulting extract and its biomarkers showed strong tyrosinase inhibitory property.
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