Guiera senegalensis J. F. Gmelin (Combretaceae): Biological activities and chemical investigation

Guiera senegalensis J. F. Gmelin (Combretaceae) leaves are used in African traditional medicine for gastrointestinal disorders, cough and topically for wound healing. This paper regards the evaluation of antiradical, antielastase, antimicrobial, genotoxic and antimutagenic activities of the leaf extracts and the determination of chemical structure of the elastase inhibitors. Antimicrobial activity was tested against Gram positive and negative bacteria, moulds and yeasts. Genotoxic potential was assayed with Bacillus subtilis rec -assay and Salmonella-microsome test. The latter was used also for determining antimutagenic activity. Antiradical properties were evaluated as inhibition of ADP-Fe(2+) induced lipoperoxidation in rat liver microsomes. Porcine pancreatic elastase was used to test enzyme inhibition. The methanolic extract was fractionated with dichloromethane, w-butanol and water and these fractions were tested for the above mentioned activities. The crude extract possessed a mild antimicrobial effect only on Gram positive bacteria (MIC 0.8-1.5 mg/ml) and the effect was associated to dichloromethane and n-butanol fractions. The crude extract and the dichloromethane and n-butanol fractions were weakly genotoxic but showed also a significant antimutagenicity. Inhibition of lipoperoxidation was assignable mainly to the n-butanol fraction. Elastase was inhibited (IC(50) 181 μg/ml) and the inhibition was retained in the water soluble fraction (IC(50) 37μg/ml). The compounds responsible for the enzyme inhibition were a mixture of proanthocyanidins constituted predominantly by (-)-epicatechin and (-)-epigallocatechin units. The mean degree of polymerization was 2-6.