Immunomodulatory activity of Inula viscosa (L.) compounds identified via LC-ESI-MS and their COX-2-targeted anti-inflammatory potential: in vitro, in vivo and in silico analysis.

Inula viscosa is a medicinal plant widely recognized in the Mediterranean area. Endemically, it has been used to manage various inflammatory conditions and alleviate rheumatic discomfort. However, its immunomodulatory mechanisms remain insufficiently characterized. In this study, we investigated the immunosuppressive activity of I. viscosa leaves and flowers methanol extracts, through a combined in vitro, in vivo, phytochemical identification, and in silico approach, using the SRBC-induced humoral immune response model, both extracts at 50 mg/kg significantly (***p < 0.001) reduced hemagglutination titers and (****p < 0.0001) decreased splenic CD138⁺ plasma cell recruitment, restoring white/red pulp architecture, confirming their ability to downregulate antibody-mediated immunity. LC-ESI-MS analysis identified 20 phenolic compounds, including flavonoids and phenolic acids known for antioxidative and immunosuppressive effects. Molecular docking against COX-2 revealed that several phytochemicals, particularly diosmin, silymarin, and quercetin exhibited stronger binding affinities (- 9.7, - 9.1 and - 9.0 kcal/mol, respectively) than diclofenac (- 7.3 kcal/mol), with quercetin showing the most favorable pharmacokinetic profile as ADME evaluations through Lipinski's "rule of five" confirmed that it fulfills the pharmaceutical requirement. These findings align with our previous formaldehyde-induced arthritis study, reinforcing the anti-inflammatory potential of I. viscosa at low doses, through combined antioxidant action, suppression of humoral immune responses, and COX-2 inhibition.