Flow-Injection Analysis with Photometric Detection for the Screening of Tyrosinase Inhibitors

Abstract

A rapid and simple method for the screening of tyrosinase inhibitors based on a flow-injection analysis (FIA) method using a spectrophotometric detector is described. An aqueous solution of L-DOPA (5.0×10^-3mol/L) and a 5.0×10^-2mol/L phosphate buffer solution were pumped into the analytical line at a constant flow rate. An aliquot of the tyrosinase solution containing an inhibitor was injected into the phosphate buffer stream by a loop-valve injector, and then it was fed to the spectrophotometric detector through the reaction coil. The absorbance of reaction products was monitored at 475nm. As a result, the peak height of the flow signal was proportional to the enzyme activity unit, ranging from 1 unit/mL to 10 units/mL (r=0.992). The FIA system could measure a sample within 5min. β-Arbutin, L-ascorbic acid, and caffeic acid showed strong inhibition for tyrosinase activity in the method described here.