Abstract

Esther O. Agbaje and Oluwole A. Ajidahun

Despite the progress made in medical research in the past decades, the treatment of many diseases including inflammatory diseases is still problematic. Conventional drugs used to ameliorate these conditions are either too expensive or toxic, there is therefore an urgent need to search for newer, cheaper and safer medications. Strophanthus sarmentosus (SMS) is an indigenous plant used in traditional medicine in West Africa for the treatment of inflammatory diseases among other uses. The present study was designed to explore its therapeutic benefits in inflammation, nociception and pyrexia. Analgesic effect of the ethanolic extract of dried SMS root (50, 100 and 200 mg kg-1 ) was evaluated in mice using acetic acid-induced writhing and hot plate models, while the efficacy of the herbal drug was compared with 150 mg kg-1 acetylsalicylic acid, 0.5 mg kg-1 piroxicam and 5 mg kg-1 morphine respectively. Anti-inflammatory activity of SMS was also investigated using groups of oedema-induced rats separately treated with 1 % w/v carrageenan in normal saline and xylene. The effects of 10 mg kg-1 indomethacin and 1 mg kg-1 dexamethasone were also evaluated as respective standard drugs for the two models. The antipyretic effect of SMS was lastly studied using d-amphetamine and Klebsiella-induced pyretic tests with 150 mg kg -1 acetaminophen serving as the comparative agent. Acute toxicity test was conducted on the herbal decoction via both oral and intraperitoneal routes to obtain its LD50. The extract dose-dependently and significantly (p<0.05) inhibited writhing in the acetic acid test group. The effect produced by 200 mg kg-1 extract (72.8 % inhibition), compared well with acetylsalicylic acid (66.6 %), but was much less than piroxicam (90.9 %). A prolongation in reaction time in the hot plate model produced by SMS recorded 68.9 % inhibition with the highest dose and 98.4 % with morphine. The extract produced dose-dependent and significant inhibition (p<0.05) of oedema, which was comparable to indomethacin in the caraageenan-induced paw oedema model. Similarly, SMS demonstrated a significant effect (p<0.05), compared to dexamethasone on the xylene-induced mouse ear oedema test. The extract significantly decreased the hyperthermic temperature in both d-amphetamine and Klebsiella-induced pyrexia as indicated by the percentage reduction in fever recorded. Findings from the present study showed SMS to possess central and peripheral analgesic activity, anti-inflammatory property similar to steroidal and non-steroidal agents as well as antipyretic effect. The presence of diverse secondary metabolites including flavonoids, glycosides, tannins, alkaloids and saponins could account for the wide therapeutic spectrum of SMS. LD50 for oral and intraperitoneal routes were interpolated as 2187.8 and 549.5 mg kg-1 respectively.