Investigation of anti-inflammatory and anti-arthritic potentials of Terminalia catappa bark using in vitro assays and carrageenan-induced inflammation, complete Freund's adjuvant induced arthritis model in rats

Terminalia catappa Linn (T. catappa) belongs to the family Combretaceae, locally known as Bengal Almond. The plant is known to have many phytochemicals such as carbohydrates, phytosterols, tannins, polyphenols, flavonoids, and saponins. It is widely used in the treatment of various diseases such as dermatitis, leprosy, and scabies and internally for colic, headache and hepatitis and also, the plant possesses anticancer, antioxidant, antidiabetic, hepatoprotective and extracts have been shown to modify reproductive behavior in rats. The main objective of this study is to assess the pharmacological potentials of T. catappa bark in the therapeutic areas of inflammation and arthritis. T. catappa bark alcoholic extract (TCE) and water extract (TCW) were prepared and evaluated for its possible anti-inflammatory activity by in vitro protein denaturation assays and membrane stabilization assay. Further, the anti-inflammatory and anti-arthritic activity of bark extracts were evaluated by in vivo models such as carrageenan-induced paw edema, air-pouch model and Complete Freund's adjuvant (CFA) induced arthritis model in rats. Total phenolic content (TPC) was found to be 287 and 175 mg/g for TCE and TCW. Total flavonoid content (TFC) was found to be 10.2 and 61.7 mg/Kg for TCE and TCW. The concentration required for the 50 % inhibition of the protein denaturation (IC50) was found to be lower for TCE (36.2 mu g/mL) in egg albumin denaturation assay, whereas in the membrane stabilization assay method TCW exhibited a lower IC50 value in comparison with diclofenac. Both the extracts showed activity in the in vitro models of inflammation and were also found to be effective in reducing the paw edema in the carrageenan-induced inflammation model and inhibition of cellular infiltration and Myeloperoxidase activity in air pouch fluid, suggesting its anti-inflammatory activity. In CFA-induced arthritis model, the extracts exhibited anti-arthritic potential by improving the altered blood parameters, arthritic scores, radiographical, and histopathological changes. The results of the study suggested that the bark of T. catappa possessed anti-inflammatory and anti-arthritic activities. (C) 2021 SAAB. Published by Elsevier B.V. All rights reserved.