On-line surface plasmon resonance-high performance liquid chromatography–tandem mass spectrometry for analysis of human serum albumin binders from Radix Astragali

• Novel SPR-HPLC–MS/MS method for screening of HSA binders was proposed.
• The developed method was simple, effective and high-throughput.
• Twenty bioactive components in Radix Astragali were identified.
• Comprehensive mass fragmentation pathways were established.

Development of sensitive and effective methods that meet the demand of high-throughput, high-fidelity screening of bioactive components from natural products are important to drug discovery. We describe here a novel surface plasmon resonance-high performance liquid chromatography–tandem mass spectrometry (SPR-HPLC–MS/MS) system for rapid, continuous and effective screening and identification of human serum albumin (HSA) binders from Radix Astragali. The HPLC six-port valve was used as interface through which the dissociated HSA binders from SPR was collected and injected automatically to HPLC–MS/MS for analysis. Eleven isofalvonoids and nine astragalosides have been screened and identified as the main HSA binders in ethyl acetate extract of Radix Astragali. Compared with reverse ultrafiltration assay, the developed configuration is more cost effective and reproductive because of the higher reusability and stability of immobilized HSA on SPR chip. Furthermore, the assay minimized the matrix interference in MS because of the elimination of non-binding components before HPLC separation. It is concluded that this novel technology offers new perspectives for screening and identification of active components from complex mixtures.