Screening and identifying antioxidants from Oplopanax elatus using 2,2ʹ-diphenyl-1-picrylhydrazyl with off-line two-dimensional HPLC coupled with diode array detection and tandem time-of-flight mass spectrometry

The root of Oplopanax elatus (Nakai) Nakai has a well‐known history of use for the treatment of diseases such as neurasthenia, cardiovascular disorders, and cancer by the native people in northeast China. It is important to screen and identify the bioactive molecules from its root rapidly. Hereby, an off‐line two‐dimensional high performance liquid chromatography coupled with diode array detection and tandem time‐of‐flight mass spectrometry together with 2,2ʹ‐diphenyl‐1‐picrylhydrazyl was established to screen antioxidants from the root of O. elatus. A Waters cyanogen column (150 × 3.9 mm, id, 4 μm) was used for the first dimensional liquid chromatography, while a Hypersil BDS‐C18 column (250 × 4.6 mm, id, 5 μm) was installed for the second dimension liquid chromatographic analysis. Twenty‐eight compounds had been tentatively identified from the methanol extract of the air‐dried root of O. elatus including six polyynes and eight phenolic derivatives were screened with antioxidant activity. The developed method could be expedient for screening and identifying antioxidants from O. elatus.