Evaluating Anti-Inflammatory activity of aqueous root extract of Strophanthus hispidus DC. (Apocynaceae)

Summary: The present study explored the anti-inflammatory potential of aqueous root extract of Strophanthus hispidus (SPH) DC (Apocynaceae) in rodents, using standard laboratory models. Doses of 50, 100, 500 and 1000 mg/kg of aqueous SPH were administered orally in carrageenan-induced rat hind paw oedema, xylene-induced ear oedema in mice, and formalin-induced mice hind paw oedema (sub-acute 6 days), using indomethacin (10 mg/kg), dexamethasone 1 mg/kg and acetylsalicylic acid (Aspirin), 100 mg/kg) respectively as standard drugs. The study further explored the effect of the herbal drug on some inflammatory mediators-histamine, serotonin and prostaglandin, using only the highest dose of SPH. Results obtained showed that the extract exerted a dose-dependent and significant (p<0.05) anti-inflammatory activity, which compared favourably with the positive control. Significant inhibitions of mediators were also recorded; however, the least inhibition (42.8 %) was produced in the serotonin model. Phytochemical analysis indicated the presence of flavonoids, cardiac glycosides, tannins, and anthraquinones. It is also noteworthy that zinc, copper, manganese, lead, and chromium were the elemental constituents in the aqueous extract of SPH, some of which have been reported to possess anti-inflammatory property. While 2 g/kg of SPH administered orally did not produce any mortality, the median lethal dose by i.p route was 39.81 mg/kg, and it is thought that the lead contribute to the toxicity recorded. The pH of the herbal drug was 6.7. Our findings substantiate the local use of SPH in the treatment of acute and sub-acute inflammatory conditions, while it also suggests some possible pathways for its anti-inflammatory activity. Lastly, since the herbal drug is liable to producing toxic effects, it must be used with caution. Industrial relevance: Herbal remedies continue to serve as an important source of conventional therapies for diverse disease conditions, including inflammatory reactions. These reported benefits are attributed to the phytoconstituents in the natural medicaments. The present study will aid the industry to produce new anti-inflammatory drugs, which apart from lacking the adverse effects often recorded with the orthodox therapies, are more affordable and accessible to users.