Chemical profiling and anti-inflammatory effect of phenolic extract of Gentiana rigescens Franch

Ethnopharmacological relevance: Gentiana rigescens Franch. (G. rigescens), known as "Dian Long Dan" in Southern Yunnan Herbal, has a long history in traditional Chinese medicine for treating hepatitis, allergies, postherpetic neuralgia, cholecystitis and rheumatism.

Aim of the study: This study aims to comprehensively analyze the phenolic composition of G. rigescens, evaluate its potential anti-inflammatory effects, elucidate underlying mechanisms, and identify its in vivo bioactive phenolic constituents.

Materials and methods: The extraction of G. rigescens phenolic compounds (GRP) was optimized using the Box-Behnken response surface method, with four phenolic compounds (mangiferin, esculetin, ferulic acid and kaempferol) used as quality index markers. GRP's phytochemical composition was subsequently profiled via UPLC-Q-TOF-MS/MS analysis. Anti-inflammatory activity and mechanisms were assessed in LPS-stimulated RAW264.7 cells and murine models, utilizing NO production assays, ELISA, qRT-PCR, Western blotting and histopathological analysis. Bioactive phenolic compounds in blood were identified post-oral administration for in vivo activity prediction.

Results: The optimal extraction conditions for GRP were determined as follows: Soxhlet extraction using acetone with hydrochloric acid 0.06 mol/L, at a liquid-to-solid ratio of 132: l. for 6.6 h. Seventy-one of phenolic compounds were identified in GRP using UPLC-Q-TOF-MS/MS. GRP significantly inhibited LPS-induced NO production in RAW 264.7 macrophages and reduced pro-inflammatory cytokines IL-6, IL-1β, and TNF-α while increasing anti-inflammatory IL-10. In the carrageenan-induced inflammatory model, GRP exhibited a 69.81% inhibition rate of toe swelling at high doses (1 g/kg), along with protective effects against joint injury, as observed in histological assessments. Mechanistically, GRP downregulated mRNA levels of inflammatory cytokines and reduced the expression of inflammatory proteins iNOS, COX-2, p65, p-p65 and P-IκB as shown by Western blotting. Twenty-five of phenolic compounds, including mangiferin, swertianolin, acacetin, umbelliferone and caffeic acid, were identified in vivo in the blood, indicating potential bioactive roles.

Conclusions: This study provides the first comprehensive profile of the phenolic composition of G. rigescen, alongside a detailed investigation of its anti-inflammatory activity, mechanisms, and in vivo bioactive components. These findings highlight the therapeutic potential of Dian Long Dan's phenolic constituents and support further research on G. rigescens.