Analgesic and anti-inflammatory effects of the methanol root extracts of some selected Nigerian medicinal plants

Context: The roots of Alafia barteri Oliver (Apocynaceae), Combretum mucronatum Schumach (Combretaceae) and Capparis thonningii Schum (Capparaceae) are used in Traditional African Medicine to alleviate painful and inflammatory conditions. Objective: This study investigated the analgesic and anti-inflammatory effects of the methanol root extracts of Alafia barteri (MeAB), C. mucronatum (MeCM), and Capparis thonningii (MeCT). Materials and methods: Analgesic activity of the extracts (50, 100, and 200 mg/kg, p.o. 1 h) was evaluated using acetic acid-, formalin-and hot plate-induced pain while anti-inflammatory actions (100 or 200 mg/kg) were investigated using the carrageenan-and xylene-induced edema tests. Results: MeAB, MeCM, and MeCT (200 mg/kg) inhibited acetic acid-induced abdominal constriction by 55.07, 46.67, and 47.25%, respectively. In the formalin test, the index of pain inhibition of early and late phases was, respectively, 47.83 and 81.98% for MeAB, 56.10 and 63.81% for MeCM, and 42.84 and 63.29% for MeCT (200 mg/kg). MeAB and MeCT pretreatments significantly increased the reaction time by 46.67 and 25.53%, respectively, 120 min posttreatment in the hot-plate test. Naloxone (5 mg/kg, s.c.) pretreatment 15 min before extract administration, significantly (p<0.05) reversed the analgesic effect of MeAB and MeCT in the formalin test. MeAB, MeCM, and MeCT showed significant anti-inflammatory activity with 60.44 and 30.39%, 63.74 and 58.08%, and 50.55 and 77.84% (200 mg/kg, 4 h), respectively, inhibition of paw and ear edema. Discussion and conclusion: The analgesic and anti-inflammatory effects of MeAB and MeCT involve an interaction with opioid pathway and/or inhibition of chemical mediators of pain and inflammation.