Ameliorative effect of morin, a plant flavonoid against Freund's complete adjuvant-induced polyarthritis in rats

Background: Rheumatoid arthritis is a chronic relapsing autoimmune disorder with multifactorial etiology and prognosis. Morin [2-(2,4-dihydroxyphenyl)-3,5,7-trihydroxy-4H-1-benzopyran-4-one], a plant flavonoid reported having antioxidant and anti-inflammatory potential. Objective: The aim is to study the anti-arthritic activity of the morin against adjuvant-induced polyarthritis in rats. Materials and Methods: Polyarthritis was induced in female Wistar rats (150–180 g) using Freund's complete adjuvant (FCA) in the tail. Leflunomide (10 mg/kg, as a standard) and morin (10, 30 and 100 mg/kg) were administered orally daily for 28 days. Results: Treatment with morin (30 and 100 mg/kg) showed statistically significant inhibition (P < 0.05) in FCA-induced decrease in thermal hyperalgesia and mechanical hyperalgesia. It also showed significant attenuation (P < 0.05) in FCA-induced alterations in hematological parameters, aspartate aminotransferase, alanine transaminase, alkaline phosphatase, serum turbidity, albumin, C-reactive protein, blood sugar levels, and erythrocyte sedimentation rate. Altered levels of serum and liver lipid profile were significantly attenuated (P < 0.05) by morin (30 and 100 mg/kg). Morin treatment significantly decreased (P < 0.05) serum oxido-nitrosative stress, tumor necrosis factor-alpha (TNF-α), and interleukin-1β (IL-1β) levels. Morin (30 and 100 mg/kg) also significantly (P < 0.05) inhibited FCA-induced up-regulated liver TNF-α, IL-1β, IL-6, heme oxygenase-1, transforming growth factor-beta and down-regulated nuclear factor erythroid 2-related factor-2 messenger RNA expression. Histopathology alteration-induced by FCA was also reduced by morin treatment. Conclusion: Morin showed promising curative properties against FCA-induced polyarthritis in rats via modulation of endogenous biomarkers. Thus, morin can be considered as an alternative treatment regimen for the management of arthritis.