Evaluation of two medicinal plants used for arthritis in northern Nigeria with focus on Terminalia avicennioides Guill. & Perr. and its mechanism of action

Abstract

Chronic inflammation underlying non-communicable diseases continues to impose serious economic and public health burden globally. Exploring medicinal plants presents a valid approach to sourcing new anti-inflammatory therapies. This study was performed to evaluate Cassia sieberiana root and Terminalia avicennioides stem bark extracts in pain and inflammation, in order to identify an active extract and its mechanism of action. Aqueous and 70% v/v ethanol extracts of C. sieberiana root (CSA and CSE) and T. avicennioides stem bark extracts (TAA and TAE) were prepared. Acute toxicity, phenolic content and antioxidant activity of the extracts were determined. Graded doses of each extract were tested against acetic acid-induced nociception and acute formalin-induced paw inflammation. T. avicennioides stem bark ethanol extract was further tested in chronic paw inflammation and its effects on edematous response and nitric oxide in inflammed tissue were measured. All the extracts were acutely safe following oral administration of doses up to 2000 mg/kg. Comparatively, T. avicennioides aqueous extract (TAA) showed the highest phenolic content and displayed the highest antioxidant potency among the extracts. T. avicennioides and C. sieberiana ethanol extracts produced comparable inhibition of acetic acid-induced pain. Only T. avicennioides ethanol extract significantly (p < 0.001) ameliorated acute formalin-induced nociception in phase 1 of the test compared with other extracts. It was also the most effective in inhibiting edema formation during the inflammatory phase. In chronic paw inflammation, 300 and 900 mg/kg TAE significantly (p < 0.01) lowered post-treatment edema and reduced the relative paw index of the inflammed paw. At these doses, nitric oxide levels were also reduced compared to the control group. T. avicennioides and C. sieberiana extracts possess beneficial effects against pain, but T. avicennioides has a comparatively higher acute anti-inflammatory effect, concentrated in its ethanol extract. Inhibition of nitric oxide and prostaglandin activity may contribute to the anti-inflammatory effect of T. avicennioides ethanol extract in chronic inflammation.