Analysis of tyrosinase binders from Glycyrrhiza uralensis root: evaluation and comparison of tyrosinase immobilized magnetic fishing-HPLC and reverse ultrafiltration-HPLC.

Tyrosinase inhibitors play an important role in cosmetic products, food supplements and medicinal industries. In this study, a new facile method based on tyrosinase immobilized magnetic fishing (IMF) coupled with high performance liquid chromatography-diode array detector-tandem mass spectrometry (HPLC-DAD-MS/MS) was developed to screen and identify tyrosinase binders from Glycyrrhiza uralensis root. Experiments were carried out to select optimal immobilization and incubation conditions. The activity of immobilized tyrosinase retained 76.3% after ten consecutive cycles, and remained over 95% when stored at 4°C for about two months. Eleven tyrosinase binders, including original compounds and transformation products were successfully screened and characterized from G. uralensis root, while dihydrodaidzein and pratensein were reported for the first time. Compared with ultrafiltration-HPLC assay, IMF-HPLC displayed many attractive advantages, including convenient solid-liquid separation ability, good stability, high reusability and activity, which indicated that IMF-HPLC had a broad applicability. The results indicated that IMF-HPLC method is a facile, effective and reproductive way to screen and identify active components from complex mixtures.