Abstract

Leaves from Combretum imberbe traditionally used to treat symptoms of malaria in most parts of Southern Africa were studied for interaction of its crude methanolic, ethyl acetate and hexane extracts with hemin a product of hemoglobin degradation in 40% water-dimethylsulphoxide at pH 9, 7.4 and 5 using a spectrophotometric method. It has been established that hemin is the target of antimalaria quinolines thus, interaction of extracts with hemin may represent a crucial initial screening test to define efficacy. Observations were compared to results of interaction of hemin with quinine and artemisia as standards. The present results indicate that hemin complexed more strongly with methanolic extracts than with ethyl acetate and hexane extracts. The binding constants were pH-dependent. The present results are interesting because the crude extracts share a similar mode of action with quinine and artemisia with an isosbetic point at 352 nm. Methanolic extract showed better affinity for hemin than artemisia with complexation constants (K) of 1.011 × 10⁴ and   0.612 × 10⁴ M, respectively. However, quinine showed better affinity than methanolic extract with K of 1.101 × 10⁴ M.

Key words: Ferriprotoporphyrin IX, Combretum imberbe, crude extracts, hemin.