Evaluation of the Antimicrobial Activity of Erythrina abyssinica Leaf Extract

Natural plant products have been important for the development of new active molecules for drug development since the ancient times. This is particularly due to the presence of secondary metabolites in plants, which are known for their antimicrobial activity. Thus, this study focused on investigating the antimicrobial activity of Erythrina abyssinica against Candida albicans and Staphylococcus aureus. Erythrina abyssinica is a medicinal plant which has been used traditionally for the treatment of various infections, snakebites and some sexually transmitted diseases. However, not much scientific studies have been done to validate the use of Erythrina abyssinica as a medicinal plant. The bark was extracted using solvent-solvent extraction method. The extracts were tested for their antimicrobial activity using the agar disc diffusion assay. Antimicrobial activity was observed in most extracts with the ethyl acetate extract showing the highest zone of inhibition of 25 mm and dichloromethane showing the least zone of inhibition against C. albicans. The minimum inhibitory concentrations (MIC) for all the extracts were determined using the broth dilution assay. The dichloromethane and hexane extracts were the most potent with MICs of 62.5 μg/ml. However, the hexane extract showed the highest zone of inhibition of 23 mm against S. aureus whilst dichloromethane was found to be the most potent with an MIC of 15.6 μg/ml against C. albicans by broth dilution assay. Minimum fungicidal concentrations for all the extracts were 500 μg/ml except for ethyl acetate which was 250 μg/ml. The minimum bactericidal concentration for all the extracts was greater than 500 μg/ml except for hexane showing that extracts inhibited growth of S. aureus but did not kill the cells. Toxicity studies showed that all extracts may not be toxic to human cells. Therefore, these results scientifically validate the use of the Erythrina abyssinica bark for the treatment of various ailments.