Antimicrobial evaluation of crude methanolic extracts and fractions of Prosopis africana stem bark

Prosopis africana is used traditionally as aphrodisiac, in wound healing and as sterility agent [1,2]. The antimicrobial effect of the crude methanolic extracts and fractions was evaluated in vitro. The pulverized plant material was extracted in methanol by cold maceration. The crude extract (CME) was adsorbed on silica gel and eluted in succession with hexane, chloroform, ethyl acetate, acetone and methanol to yield hexane (A), chloroform (B), ethyl acetate (C), acetone (D) and methanol (E) fractions. The crude extract and all the fractions were screened for anti microbial activity against some clinical strains of bacteria and fungi. The crude methanolic extract and fractions C, D, and E showed promising antimicrobial activity while fractions A and B did not show any activity against the tested microorganisms. C showed a very high activity against Staphylococcus aureus (MIC=440µg/ml) but moderate activity against Escherichia coli, Pseudomonas aerigunosa and Klebsiella pneumoniae with MIC values of 2140, 2290 and 3150µg/ml respectively. D showed moderate activity against Bacillus subtillis (MIC=2660µg/ml) and Candica albicans (MIC=6630µg/ml). Phytochemical investigation of the crude extract and fractions showed the presence of tannins, saponins, terpenoids, steroids, flavonoids, glycosides, carbohydrates, reducing sugars, resins and fats and oils. In conclusion, the antimicrobial activity of Prosopis africana stem bark may be due the tannins and saponins found in preponderance in the most active fractions, C and D. The observed antimicrobial property may justify the ethnomedicinal use of the plant in wound healing.

Acknowledgement: Mr Ogbosor, Pharmaceutical Microbiology, University of Nigeria, Nsukka, Nigeria.

References: 1. Burkart, A., Arnold, J., (1976) African J Biotec. 5: 755–760.

2. Daziel, J.M. (1955)J Agric Food Chem. 5: 6120.