Objective:The therapeutic effect of less polar ginsenosides on rats with rheumatoid arthritis was studied, and the metabolic pathway that produce anti-inflammatory effect of less polar ginsenosides was identified.Methods:Rats were randomly divided into the control group, the model group, methotrexate treatment group, and high dose, medium dose, and low dose less polar ginsenosides groups. After 30 days of oral administration, less polar ginsenosides reduced the disease activity significantly in rats with rheumatoid arthritis. Blood and ankle synovial tissue metabolisms were measured by ultra performance liquid chromatography (UPLC) tandem mass spectrometry (MS) to explore the mechanism of less polar ginsenosides.The resulting data were subjected to principal component analysis and orthogonal partial least squares discriminant analysis(OPLS-DA).Results:Compared with the model group, erythrocyte sedimentation rate and RF decreased significantly in the high dose of less polar ginsenosides ( P<0.01). Metabolomics showed that R2X and R2Y of serum OPLS-DA were 0.626 and 0.904 respectively. The R2X and R2Y of synovial OPLS-DA were 0.429 and 0.689 respectively. Major differential metabolites were identified in the model group of rats, including arachidonic acid, valine, linoleic acid, and guanine nucleoside, etc. The main differential metabolites were identified in rats in the high dose group of less polar ginsenosides, including linoleic acid, betaine, eicosapentaenoic acid, alanine, methionine sulfoxide, isoleucine, etc. Conclusion:The metabolic spectrum has shown that inflammation is associated with linoleic acid metabolism, valine, leucine and isoleucine degradation, arachidonic acid metabolism. Less polar ginsenosides regulatethe linolenic acid metabolism, methionine metabolism and glucose alanine cycle.