Solvent–solvent fractionations of Combretum erythrophyllum (Burch.) leave extract : studies of their antibacterial, antifungal, antioxidant and cytotoxicity potentials

Abstract

OBJECTIVE : To evaluate the biological activities of Combretum erythrophyllum (C. erythrophyllum) leaf extracts against infectious diseases' pathogenesis and their cytotoxicity potentials. METHODS : Powdered leaf material (300 g) of C. erythrophyllum was extracted (1:10 w/v) using acetone to obtain the crude extract. Liquid–liquid fractionation was performed on the crude acetone extract (30 g) using solvents of different polarity. The bioautographic method was used to detect the inhibition of bacterial and fungal growth by active compounds present in the crude and fractions. The extracts were then tested on bacterial strains: Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa; fungal strains: Candida albicans (C. albicans), Cryptococcus neoformans, and Aspergillus fumigatus, by microtitre dilution method for MIC determination. RESULTS : The extracts MIC values ranged between 0.08 and 2.50 mg/mL against the tested pathogens. Water fraction had the highest activity against bacteria strains, while the fungal assay revealed crude acetone extract and ethyl acetate fraction to be active against C. albicans (1.25 mg/mL), dichloromethane extract against C. albicans and A. fumigatus (0.16 mg/mL). Extract fractions showed a good antioxidant activity via DPPH, ABTS and hydroxyl radical scavenging assays, in the order: ethyl acetate > water > acetone > dichloromethane > hexane. The toxicity level of crude extract and fractions evaluated in Vero monkey kidney cells ranged from 34 to 223 mg/ mL, while doxorubicin (IC50 = 7.19 mg/mL) served as the positive control. CONCLUSIONS : It can be concluded that the extracts of C. erythrophyllum are safe for medicinal use in folk medicine for treating infectious and stress related diseases.