The ethanolic extract of Eysenhardtia polystachya (Ort.) Sarg. Bark and its fractions delay the progression of rheumatoid arthritis and show antinociceptive activity in murine models

Eysenhardtia polystachya is widely used in folk medicine as an anti-rheumatic and analgesic agent, but no systematic study of its effects on several markers associated with rheumatoid arthritis and its ethnomedical use as analgesic agent has been performed. We evaluated the anti-arthritic and antinociceptive properties of an ethanolic extract of E. polystachya (EE) bark and its rich-flavonoids fractions in murine models. The EE was administered orally at doses of 25, 50, 100, and 200 mg/kg/day, and its fractions at 25 mg/kg/day in all animal models. Anti-arthritic activity was evaluated using a complete Freund´s adjuvant (CFA)-induced rheumatoid arthritis model in rats. The severity of arthritis was evaluated by changes in paw oedema, body weight, arthritic index, radiological scores, histological assessment of synovial joints, erythrocyte sedimentation rate, haematocrit, haemoglobin, serum rheumatoid factor, serum C-reactive protein and serum levels of the pro-inflammatory cytokines IL-1β, IL-6, TNF-α, IL-18, IFN-γ, GM-CSF, and anti-inflammatory cytokines IL-4, IL-10, IL-13. Antinociceptive activity was evaluated using an acetic acid-induced abdominal contraction test and a hot-plate test in mice. EE and its rich-flavonoids fractions inhibited secondary inflammatory reactions, diminished the specific histopathological alterations in the joint capsule and reduced the serum concentrations of the pro-inflammatory cytokines IL-6, TNF-α, and GM-CSF in arthritic rats. EE also reduced the number of writhes produced by acetic acid and increased the response time on the hot plate for mice. Our findings support the use of Eysenhardtia polystachya bark for the treatment of rheumatoid arthritis and pain management.