Simultaneous ligand fishing and identification of human serum albumin binders from Eucommia ulmoides bark using surface plasmon resonance-high performance liquid chromatography–tandem mass spectrometry

Eucommia ulmoides bark has long been known as tonic herb, however, the systematic biochemical fingerprint analysis and corresponding structural identification are inadequate so far. Here we describe on-line surface plasmon resonance-high performance liquid chromatography–tandem mass spectrometry (SPR-HPLC–MS/MS) to fish out and identify human serum albumin (HSA) binders from E. ulmoides bark. A total of 22 HSA binders, including 4 iridoids, 11 lignans, 3 flavonoids and 4 phenolic acids, were identified or tentatively characterized based on their retention times, UV spectra and MS/MS spectrum with references or literature data, among which, geniposidic acid, geniposide and chlorogenic acid were the predominant HSA binders. In addition, the major characteristic fragmentation pathways of iridoids and lignans were investigated. The higher reusability and stability of the immobilized HSA allow the method cost-effective and high-throughput. Compared with conventional HPLC–MS/MS for chemical fingerprint analysis, SPR-HPLC–MS/MS is simple and easy to provide biochemical fingerprint, moreover, it is easy to identify low-content HSA binders because of the sample clean-up/concentration procedure.