Immunoprecipitation coupled with HPLC–MS/MS to discover the aromatase ligands from Glycyrrhiza uralensis

Affinity chromatography, applied to discover the enzyme inhibitors, needs special column with target protein and its carrier. Selection of stationary phase and mobile phase needs careful considerations due to the characteristics of proteins. In this study, a method immunoprecipitation (IP) coupled with HPLC-DAD–MS was developed to discover the aromatase ligands from Glycyrrhiza uralensis. An SB-C18 column was employed to separate target compounds without special consideration in mobile phase. Twenty-one compounds, including isolated compounds 4, 7, 8, 10, 11, 13, 15, 18–20, 23 and non-isolated compounds A-J, were found to have good affinity to aromatase by LC–MS. Seven of them (7, 15, 18, 19, 23, D, E) were detected to bind with aromatase in MCF-7 cells by IP coupled with HPLC–MS/MS. Bioassays disclosed aromatase inhibitory activities of the isolated compounds mentioned above, verifying the efficiency of IP coupled with HPLC–MS/MS as a method to screen aromatase ligands.