Selective COX-2 inhibitors from natural sources: Insights from the analysis of components absorbed into blood from Isatidis Radix Lignans

Ethnopharmacological relevance Isatis tinctoria L. (Isatidis Radix) is a type of Chinese medicine used to treat various inflammations. Lignans are the main active ingredients of Isatidis Radix, which exhibit potent anti-inflammatory properties. However, the targets underlying the anti-inflammatory effects of Isatidis Radix remain unclear. Aim of the study The objective of this research was to investigate the active constituents of Isatidis Radix and the molecular mechanisms behind its anti-inflammatory properties. Materials and methods Firstly, Liquid Chromatography-Mass Spectrometry (LC-MS), network pharmacology, and molecular docking were employed to identify the active ingredients and key targets of Isatidis Radix lignans and predict their underlying anti-inflammatory mechanisms. Secondly, the enzyme-linked immunosorbent assay (ELISA) and the LPS-induced cell model were employed to verify the selective inhibitory effect of the active ingredients on the key target COX-2. Finally, the analgesic and anti-inflammatory effects were evaluated using the hot-plate test, acetic acid-induced writhing, complete Freund’s adjuvant-induced paw edema, and xylene-induced ear edema assays. Results A total of 24 compounds were found to be absorbed into the bloodstream, including 15 prototype components and 9 metabolites, as determined by LC-MS analysis. Furthermore, Network pharmacology analysis revealed that COX-2 served as the central target in the anti-inflammatory mechanism of Isatidis Radix lignans. Lariciresinol, a class of lignans derived from Isatidis Radix, selectively inhibited COX-2 and reduced inflammatory marker production in vitro and in vivo . It significantly increased the incubation period of heat pain, reduced writhing frequency, and decreased the severity of ear and foot swelling. Moreover, lariciresinol had no obvious gastrointestinal side effects and was not toxic to cardiomyocytes. Conclusion Our study indicates that Isatidis Radix lignans exert their anti-inflammatory effect by selectively inhibiting the COX-2 enzyme and confirms lariciresinol as a natural selective COX-2 inhibitor.