Identification of active cytoprotective ingredients from Swertia medicinal plants based on gray relational analysis combined with molecular docking

Swertia species are medicinal plants with unique Tibetan medicine characteristics. They are widely distributed in the Tibet, Sichuan and Qinghai provinces of China and have been used for the treatment of hepatitis, cholecystitis and Chiba disease for hundreds of years. The aim of this study was to compare the protective effects of three Swertia water extracts on the L02 hepatocyte injury model induced by CCl4 and identify their active components and potential mechanisms. The main iridoid glycosides in three Swertia species, Swertia bimaculata (Sieb. et Zucc.) Hook. f. et Thoms. ex C. B. Clark (SBH), Swertia mussotii Franch (SMF) and Swertia pseudochinensis Hara (SPH), were determined by HPLC. The L02 hepatocyte injury model induced by CCl4 was used to evaluate the pharmacodynamic equivalence and differences among the three Swertia water extracts. The molecular targets of action were further assessed by real-time RT–PCR and gray relational analysis (GRA) combined with molecular docking analysis. Three iridoid glycosides, sweroside (SD), swertiamarin (SM) and gentiopicroside (GP), were extracted from Swertia plants. The results indicated that SMF contained the highest amount of iridoid glycoside components, especially SM. The three Swertia extracts all possessed cytoprotective effects to some extent. The EC50 values of SBH, SMF and SPH were 0.3099, 0.1029 and 0.4531, respectively. SMF showed the best cytoprotective effect on cell damage and reduced enzyme activity. Moreover, the three Swertia extracts attenuated L02 hepatocyte injury by regulating the TGF-β/Smad signaling pathway, and SBH showed the best activity. GRA and molecular docking analysis suggested that SM may be the most effective component for the cytoprotective activity of Swertia plants. In summary, SMF showed the best comprehensive quality among the three Swertia species, and SM is the main substance that allows Swertia plants to exert their efficacy. This study provided an effective strategy for effective substance identification and quality evaluation of Swertia herbal medicine.