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The effluent was directly introduced to the APCI-MS (Agilent 1100 series LC/MSD Trap SL system, USA) for analysis. The APCI-MS analysis was divided into two time segments. The first 4?min were set as waste to avoid the influx of inorganic ions into the mass analyzer; subsequent analysis was carried out under the following optimized conditions: positive ion mode; nebulizer (N2), 60 psi; dry gas (N2), 5?L/min; drying gas temperature, 325?��C; target mass, 500?m/z; trap drive level, Oxacillin 80%, full scan range, 140�C1100?m/z. Two precursor ions were selected for MSn (n=2�C3) experiments in automatic mode with active exclusion. The fragmentation amplitude was 1.20?V. The four major lignans, schisandrin, schisandrol B, schisandrin A and schisandrin B, were well separated (Fig. 1). Simultaneous quantification of these compounds was performed using UV detection at 230?nm. The calibration curves showed good linear correlation (r2��0.9995) between peak area and concentration at the range from 0.5 to 200?��g/mL. Intra- and inter-day precision of the method was within the acceptable limits of R.S.D.EPZ5676 the range of 96.5�C108.9%. Schisandrin was found to be the most abundant lignan, constituting 75.4% (2.96?mg/g) and 46.2% (15.48?mg/g) of total lignans in the aqueous extract and 70% ethanol extract, respectively. The contents of schisandrol B, schisandrin A and schisandrin B in the aqueous extract were 852, 49 and 60?��g/g, respectively, while those in 70% ethanol extract increased to 7.20, 2.31 and 8.53?mg/g, respectively. In order to achieve more information for the identification of absorbable LY2109761 in vivo components of S. chinensis, a lignan standard mixture, containing schisandrin, gomisin D, schisandrol B, angeloylgomisin F, gomisin G and schisantherin A, was separated under the above HPLC condition, and subsequently introduced to APCI source for characterizing their MS behaviors and dissociation patterns. The chemical structures and MS spectra of the six standards acquired by HPLC-MS are shown in Figure 2?and?Figure 3, respectively. The ion patterns in first-stage spectra exhibited notable difference from those reported in ESI-MS analysis 18?and?21. In our study, the protonated molecular ion [M+H]+ was much less intensive and the adduct ions [M+Na]+ or [M+K]+ were hardly observed. Alternatively, if the lignan possesses an ester group in its chemical structure, such as gomisin D and schisantherin A, it likely formed an adduct ion [M+NH4]+ as the base peak; if an �COH substitution group is present in the C-7 position, such as schisandrin and schisandrol B, the fragment ion [M+H?H2O]+ produced from the loss of H2O would be the base peak.