Investigating the Anti-Inflammatory Activity of Saponin-Rich Extracts from Selected Medicinal Plants

This study was undertaken to investigate the anti-inflammatory activity of the crude saponins extracts of the various parts of the above-mentioned medicinal plants. Saponins have been found to possess several pharmaceutical activities such as haemolytic, molluscicidal, anti-inflammatory, antifungal, antibacterial, antiparasitic, antitumor and antiviral. Five medicinal plants used in the treatment of inflammatory diseases like rheumatoid arthritis, gout and haemorrhoids were screened for anti-inflammatory activity using their saponin-rich extracts. These plants were the whole plant materials of Schwenkia americana Linn (WSA), the rhizomes of Asparagus africanus Lam (RAA), the leaves of Dichrostachys cinerea Linn (LDC), the stem bark of Ficus iteophylla Miq (BFI) and the leaves of Indigofera pulchra Willd (LIP). A modified traditional method of saponin-rich extraction was used to give the following percentage yields: WSA-2.74%, RAA-3.59%, LDC-1.62%, BFI-0.81% and LIP-1.57%. Thin-layer chromatography was used to identify the type of saponins present in the extracts. The acute toxicity study of the crude saponin extracts in mice gave the following intraperitoneal LD50 results: WSA-471.2 mg/kg, RAA- 1264.9 mg/kg, LDC-1264.9 mg/kg, BFI-118.3 mg/kg and LIP-1264.9 mg/kg respectively. It has been suggested that the numerous biological activities of saponins were linked to their amphiphilic nature which helps in the accomplishment of these biological activities through their ability to intercalate into the plasma membrane resulting in changes in membrane fluidity that in turn affect membrane function thus eliciting a cellular response. The anti-inflammatory study of the saponin-rich extracts using carrageenan-induced rat paw-oedema showed statistically significant (P<0.05) decreases in the rat paw-oedema as compared to the control. The percentage inhibitions of the extracts on the rat paw-oedema after four hours were as follows: WSA-61%, RAA-55%, LDC-72%, BFI-66% and LIP-40% respectively. These values were found to be comparable to that of ketoprofen 63%. The study showed that the anti-inflammatory properties attributable to these plants may be due to their saponin contents. We suggest the need to further subject these saponin-rich extracts to more studies such as isolation and structural elucidation of the specific saponin responsible for this activity.