Bioactivity guided isolation of analgesic and anti-inflammatory constituents of Cnestis ferruginea Vahl ex DC (Connaraceae) root.

Cnestis ferruginea (CF) Vahl ex DC (Connaraceae) is a shrub widely used in Traditional African Medicine (TAM) for the treatment of various painful and inflammatory conditions. To isolate the active pharmacological constituents responsible for the anti-inflammatory and antinociceptive properties of the methanolic root extract of C. ferruginea. The crude methanolic root extract of CF was sequentially fractionated into four sub extracts (chloroform, ethylacetate, n-butanol and the remaining aqueous fraction). The aqueous-butanol fractions, having showed significant inhibition of inflammation and pain, were subjected to fractionation through successive column chromatography on silica gel 60-120 mesh, eluted with a gradient of CHCl(3)-MeOH. Sixty five fractions were collected; fractions with similar TLC profiles were grouped into seven major fractions (1-7). Fraction 4 being the most active in bioassay was rechromatographed to obtain CF-2. Analgesic activity was evaluated using the acetic acid-induced writhing and hot plate tests in mice while carrageenan induced paw oedema test was used to investigate the anti-inflammatory actions of the fractions obtained. Amentoflavone (CF-2) was isolated from the aqueous/n-butanol fraction. CF-2 (12.5, 25 and 100 mg/kg; p.o) produced significant (P<0.05) dose dependent inhibition of pain response elicited by acetic acid and increased nociceptive reaction latency in hot plate test. In addition it produced significant (P<0.05) dose-dependent inhibition of oedema in the carrageenan-induced inflammation. This study showed that amentoflavone is responsible for the analgesic and anti-inflammatory activity of Cnestis ferruginea.