Analysis of lignans in Schisandra chinensis and rat plasma by high-performance liquid chromatography diode-array detection, time-of-flight mass spectrometry and quadrupole ion trap mass spectrometry.

High-performance liquid chromatography/diode-array detection (HPLC/DAD), time-of-flight mass spectrometry (HPLC/TOFMS) and quadrupole ion trap mass spectrometry (HPLC/QIT-MS) were used for separation, identification and structural analysis of lignans in Schisandra chinensis and rat plasma after oral administration of the herbal extract. Six lignans in Schisandra chinensis extract were identified unambiguously by comparing the retention time, their characteristic ultraviolet (UV) absorption and accurate mass measurement. A formula database of known lignans in Schisandra chinensis was established, against which the other 15 lignans were identified effectively based on the accurate extract masses and formulae acquired by HPLC/TOFMS. In order to distinguish the isomers, multi-stage mass spectrometry (ion trap mass spectrometry, MSn) was also used. The fragmentation behavior of the lignans in the ion trap mass spectrometer was studied by the six lignan standards, and their fragmentation rules in MSn spectra were summarized. These deduced fragmentation rules of lignans were successfully implemented in distinguishing the three groups of isomers in Schisandra chinensis by HPLC/QIT-MS. By using the three different analytical techniques, 21 lignans in Schisandra chinensis were identified within 30 min. After oral administration of the extract, 11 lignans in rat plasma were detected and identified by comparing their retention time, characteristic UV absorption and accurate mass measurement of peaks in HPLC/TOFMS chromatograms of the herbal extract. Finally, HPLC/TOFMS fingerprints of Schisandra chinensis in vitro and rat plasma in vivo were established. It is concluded that a rapid and effective method based on three analytical techniques for identification of chemical components was established, which is useful for rapid identification of multiple components in Schisandra chinensis in vitro and in vivo. In addition, it can provide help for further pharmacology and action mechanism study of lignans in Schisandra chinensis.