Capsicum annuum L. oleoresin attenuates complete Freund's adjuvant-induced arthritis through modulation of COX-2-associated inflammation and oxidative stress.

Abstract

Rheumatoid arthritis is a chronic autoimmune disorder involving inflammatory cytokine dysregulation, oxidative stress and progressive joint damage. This study evaluated the anti-arthritic activity of Capsicum annuum L. oleoresin using in vitro, in vivo and in silico approaches. Oleoresins were prepared by Soxhlet and maceration extraction with solvents of different polarities and characterized by FTIR and GC-MS. Ethanolic Soxhlet extraction produced the highest yield (29.68%) and strongest antioxidant activity, showing 76.22 ± 0.58% DPPH, 63.77 ± 0.29% H₂O₂, 74.09 ± 0.21% ABTS and 65.49 ± 0.10% FRAP activity. GC-MS tentatively identified 28 compounds, including capsaicinoids, fatty acids, vitamin E and phytosterols. The selected oleoresin showed low hemolytic activity and concentration-dependent protein denaturation inhibition. In complete Freund's adjuvant-induced arthritic rats, oral oleoresin treatment at 100, 200 and 250 mg/kg reduced paw edema and arthritic score, with the 250 mg/kg dose lowering edema to 0.01-0.02 mm by day 28. It also reduced rheumatoid factor from 34.42 to 18.32 IU/L and C-reactive protein from 22.57 to 12.10 mg/dL. TNF-α and IL-6 levels decreased to 25.82 and 8.42 pg/mg protein, respectively, along with marked COX-2 suppression and improved oxidative stress markers. Histopathology examination showed reduced tissue alterations. Docking and molecular dynamics simulation predicted homocapsaicin as a stable COX-2-interacting constituent. These findings suggest that C. annuum oleoresin attenuates experimental arthritis by modulating inflammatory and oxidative stress markers, while further target specific studies are required to confirm the underlying mechanisms.