The kidney-shaped, red-colord fruit from the plant, Schisandra chinensis (Turcz.) Baill, which belongs to the Schisandraceae family, is among the most popular remedies used in traditional Chinese medicine. The English name of the plant is “Chinese magnolia vine”. It has been used in Asia since ancient times to treat a variety of ailments, including chronic cough and dyspnea, frequent urination, diarrhea, and diabetes. This is because of the wide range of bioactive constituents, such as lignans, essential oils, triterpenoids, organic acids, polysaccharides, and sterols. In some cases, these constituents affects the pharmacological efficacy of the plant. Lignans with a dibenzocyclooctadiene-type skeleton are considered to be the major constituents and main bioactive ingredients of Schisandra chinensis. However, because of the complex composition of Schisandra chinensis, the extraction yields of lignans are low. Thus, it is particularly important to study pretreatment methods used during sample preparation for the quality control of traditional Chinese medicine. Matrix solid-phase dispersion extraction (MSPD) is a comprehensive process involving destruction, extraction, fractionation, and purification. The MSPD method is simple, it requires only a small number of samples and solvents, it does not require any special experimental equipments or instruments, and it can be used to prepare liquid, viscous, semi-solid, solid samples.
In this study, a method combining matrix solid-phase dispersion extraction with high performance liquid chromatography (MSPD-HPLC) was established for the simultaneous determination of five lignans (schisandrol A, schisandrol B, deoxyschizandrin, schizandrin B, and schizandrin C) in Schisandra chinensis. The target compounds were separated on a C18 column with a gradient elution of 0.1% (v/v) formic acid aqueous solution and acetonitrile as the mobile phases, and detection was performed at a wavelength of 250 nm. First, the effects of 12 adsorbents, including silica gel, acidic alumina, neutral alumina, alkaline alumina, Florisil, Diol, XAmide, Xion, and the inverse adsorbents, C18, C18-ME, C18-G1, and C18-HC, on the extraction yields of lignans were investigated. Second, effects of the mass of the adsorbent, the type of eluent, and volume of eluent on the extraction yields of lignans were investigated. Xion was chosen as an adsorbent for MSPD-HPLC analysis of lignans from Schisandra chinensis. Optimization of the extraction parameters showed that the MSPD method had a high lignan extraction yield with Schisandra chinensis powder (0.25 g) as a fixed value, Xion as the adsorbent (0.75 g), and methanol as the elution solvent (15 mL). Analytical methods were developed for five lignans from Schisandra chinensis and these methods showed good linearity (correlation coefficients (R2)≥ 0.9999) for each target analyte. The limits of detection and quantification ranged from 0.0089 to 0.0294 μg/mL and 0.0267 to 0.0882 μg/mL, respectively. Lignans were tested at low, medium, and high levels. The average recovery rates were 92.2% to 111.2%, and the relative standard deviations were 0.23% to 3.54%. Both intra-day and inter-day precisions were less than 3.6%. Compared with hot reflux extraction and ultrasonic extraction methods, MSPD has the advantages of combined extraction and purification, being less time-consuming, and requiring lower solvent volumes. Finally, the optimized method was successfully applied to analyze five lignans from Schisandra chinensis samples from 17 cultivation areas.