Stepwise tracking strategy to screen ingredient from Galla Chinensis based on the “mass spectrometry guided preparative chromatography coupled with systems pharmacology”

Galla chinensis, a traditional Chinese herbal medicine, was widely used to treat ulcerative colitis (UC) in folk prescriptions, however, its active ingredients and mechanism of action in the treatment of UC remain unclear.The aim of our study was to discover the lead compounds and anti-inflammatory active ingredients of Galla chinensis and clarify their molecular mechanism for UC treatment.The ingredients of Galla chinensis were prepared by column and mass spectrometry guided preparative chromatography. Besides, the relationship among the ingredients of Galla chinensis and targets was predicted by systems pharmacology. Additionally, Lipopolysaccharide (LPS)-induced RAW264.7 macrophages were used as in vitro model. The cell viability, the level of the pro-inflammatory factors, the generation of reactive oxygen species (ROS), and trans epithelial electric resistance (TEER) values were detected to screen out the active ingredients of Galla chinensis. Moreover, 4% dextran sodium sulfate (DSS)-induced ulcerative colitis mice were used as the UC animal model. The disease activity index (DAI), pathological degree of colon tissue, activities of antioxidant-related enzymes and expression level of pro-inflammatory cytokines were performed to assess the anti-UC effects of the active ingredients. Meanwhile, the mRNA expression level of inflammatory factors and antioxidant related genes were analyzed by real-time quantitative polymerase chain reaction (Q-PCR). And the expression of nuclear factor erythroid-2 related factor 2 (Nrf2) pathway related proteins, intestinal mucosal proteins and nuclear factor kappa-B (NF-κB) pathway related proteins in colon tissues were analyzed by Western Blotting.Herein, a stepwise tracking strategy was adopted to screen out the anti-inflammatory active ingredients of Galla Chinensis based on "preparative chromatography pharmacology combined with mass spectrometry guidance and system". 11 categories of ingredients of Galla chinensis were prepared and ethyl gallate (EG) was screened out the lead compound and anti-inflammatory active ingredient of Galla Chinensis through in silico, in vitro and in vivo studies. In addition, EG had a significant therapeutic effect on ameliorating DSS-induced UC mice and protected intestinal mucosal integrity through Nrf2 and NF-κB signaling pathway.Ethyl gallate was the lead compound and anti-inflammatory active ingredient in Galla chinensis. And it was discovered for the first time that EG could treat mice with ulcerative colitis. This research not only found the lead compound of Galla Chinensis for UC treatment and determined the possible mechanism, but also provided valuable references for finding lead compounds from natural products by systems pharmacology coupled with equivalent components group technology.