Screening the aqueous stem bark extract of Parkia filicoidea (Fabaceae) for anti-nociceptive activity

Abstract

Parkia filicoidea, family: Fabaceae is commonly known as the African Locust bean tree and is held to have numerous ethnoeconomic uses including medicinal uses like easing of rheumatism and toothache in traditional medicine. The stem bark of the plant is prepared via decoction and taken orally by individuals routinely as an analgesic agent. The aim of this study is thus to screen the aqueous stem bark extract of the plant for analgesic activities using different animal models to validate the plant’s folkloric use. The methods used in the study include: Acetic acid-induced writhing test in mouse, Hot plate test, Tail flick test and formalin-induced pain test. In each of these models, albino rats or mice were divided into five groups of five animals each. The plant extract was administered orally at 100, 200 and 400 mg/kg doses, the negative control received distilled water, while the positive controls received aspirin (100 mg/kg) orally and pentazocine (10 mg/kg) intraperitoneally, depending on the model. The results of this study showed a significant (p˂0.05) decrease in the number of the writhes for the acetic acid-induced test when compared with the control (distilled water) as well as a significant increase (p<0.05) in the response latencies or reaction time in the hot plate, tail flick and formalin-induced pain test. The effect of the extract compares well with the standard drugs used. The extract can thus be said to possess analgesic activity comparable to the reference drugs; aspirin and pentazocine, and due to the mechanism of action of these reference drugs, the extract’s effect is therefore believed to be both centrally and peripherally-mediated. The study suggests that the aqueous extract of the stem bark of Parkia filicoidea has an analgesic activity that can be employed for therapeutic advantage as an alternative treatment for pain.