LC–MS-Based Qualitative Analysis and Pharmacokinetic Integration Network Pharmacology Strategy Reveals the Mechanism of Phlomis brevidentata H.W.Li Treatment of Pneumonia

[Image: see text] Phlomis brevidentata H.W.Li Radix (PbR) is a rare traditional Tibetan medicine, and it is widely used in the Chinese Tibetan region for the treatment of pharyngitis, pneumonia, and so forth. Nevertheless, there is very little research on its modern pharmacy, and the active ingredients and mechanisms against these diseases remain unknown. In this study, we employed the qualitative analysis and pharmacokinetic based on LC–MS technology and network pharmacology to explore the active ingredients and mechanisms of PbR for treatment of pneumonia. Ultraperformance liquid chromatography coupled with time-of-flight mass spectrometry (UPLC-Q-TOF/MS) methodology was applied to identify the chemical composition of PbR. Meanwhile, a UPLC-MS/MS method was developed to quantify three active constituents (sesamoside, shanzhiside methyl ester, and barlerin) in rat plasma for the pharmacokinetic analysis after oral administration of PbR. Finally, in order to clarify the anti-pneumonia mechanism of this rare Tibetan medicine, a comprehensive network pharmacology strategy was applied. As a result, a total of 23 compounds were identified in PbR, including 14 iridoid glycosides, 7 phenylethanoid glycosides, and 2 other kinds of compounds. Pharmacokinetic studies have shown that the three compounds exhibit extremely similar pharmacokinetic characteristics, possibly due to their highly analogous chemical structure. We speculate that the iridoid glycosides may be the main active component in PbR. Then, the three iridoid glycoside constituents absorbed into blood were subjected to network pharmacology analysis for treatment of pneumonia. Compound-target-disease, gene ontology bioanalysis, KEGG pathway, and other network pharmacology analysis methods were applied to reveal that five main targets of the three iridoid glycosides, namely, GAPDH, ALB, MAPK1, AKT1, and EGFR, were significant in the regulation of the above bioprocesses and pathways. These results provide a basis for elucidating the bioactive compounds and the pharmacological mechanisms of P. brevidentata H.W.Li radix under clinical applications.