Screening and identification of BSA bound ligands from Puerariae lobata flower by BSA functionalized Fe3O4 magnetic nanoparticles coupled with HPLC–MS/MS

Puerariae lobata flower (Willdenow) has a long history used to treat alcoholic intoxication in China, which contains a series of isoflavones as its chief pharmacologically active constituents. In this study, bovine serum albumin (BSA) functionalized iron oxide magnetic nanoparticles (Fe3O4 MNPs) coupled with high performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS) were used to screen and identify active compounds from ethanolic extract of P. lobata flower. Thirteen active isoflavones were screened and identified as glycitin (1), tectoridin (2), daidzin (3), 3′-methoxy daidzin (4), ononin (5), 3′-hydroxyl daidzein (6), tectorigenin (7), biochanin A (8), prunetin (9), genistein (10), 3′-methoxy daidzein (11), irisolidone (12) and 5,7-dihydroxy-3′,4′-methylenedioxyisoflavone (13), while compounds 4, 6, 9, 11 and 13 were identified from this plant for the first time. Furthermore, the activity of each bound ligand was evaluated on-line. The results indicated that the binding affinities of compounds with BSA were highly dependent on chemical structures and the methoxylation and hydroxylation on B-ring could improve the activity. The effective method could be widely applied for rapid screening and identification of active compounds from complex mixtures.