In Vitro Anti-Inflammatory and In Vivo Antiarthritic Activities of Aqueous and Ethanolic Extracts of Dissotis thollonii Cogn. (Melastomataceae) in Rats

Dissotis thollonii Cogn. (Melastomataceae) is a tropical plant widely used in traditional Cameroonian medicine to relieve and treat many pathologies. It is widespread in the western region where it is used to treat typhoid fever, gastrointestinal disorders, and inflammatory diseases. The purpose of this study is to scientifically demonstrate the anti-inflammatory and antiarthritic properties of the aqueous and ethanolic extracts of the leaves of Dissotis thollonii. The anti-inflammatory properties were evaluated in vitro by inhibition tests for cyclooxygenase, 5-lipoxygenase, protein denaturation, extracellular ROS production, and cell proliferation; while antiarthritic properties were evaluated in vivo in rats using the zymosan A-induced monoarthritis test and the CFA-induced polyarthritis model. This study shows that aqueous and ethanolic extracts at a concentration of 1000 μg/ml inhibit the activity of cyclooxygenase (47.07% and 63.36%) and 5-lipoxygenase (66.79% and 77.7%) and protein denaturation (42.51% and 44.44%). Similarly, both extracts inhibited extracellular ROS production (IC(50) = 5.74 μg/ml and 2.96 μg/ml for polymorphonuclear leukocytes, 7.47 μg/ml and 3.28 μg ml for peritoneal macrophages of mouse) and cell proliferation (IC(50) = 16.89 μg/ml and 3.29 μg/ml). At a dose of 500 mg/kg, aqueous and ethanolic extracts significantly reduce edema induced by zymosan A (69.30% and 81.80%) and CFA (71.85% and 79.03%). At the same dose, both extracts decreased sensitivity to mechanical hyperalgesia with 69.00% and 70.35% inhibition, respectively. Systemic and histological analyzes show that both extracts maintain the studied parameters very close to normal and greatly restored the normal architecture of the joint in animals. Dissotis thollonii would therefore be a very promising source for the treatment of inflammatory diseases.