In vitro Antibacterial Activity of Alchornea cordifolia Bark Extract Against Salmonella Species Causing Typhoid Fevers

Abstract

Four extracts of Alchornea cordifolia (Schumach.) Müll. Arg. (Euphorbiaceae) bark, including aqueous, methanol, acetone and hexane extracts, were tested for their antibacterial activities against Salmonella typhi, Salmonella paratyphi A and Salmonella paratyphi B, using both agar diffusion and broth dilution methods. Acute toxicity study and phytochemical screening were also performed using standard methods. The aqueous, methanol and acetone extracts showed considerable activities against S. typhi (zones of inhibition having diameters of 24, 23 and 25 mm, respectively), S. paratyphi A (24, 24 and 25 mm, respectively) and S. paratyphi B (24, 24 and 26 mm, respectively). The hexane extract did not show significant activity on the three bacterial strains. Minimum inhibitory concentrations (MIC) ranged from 1.25 to 2.5 mg/ml dependingon the type of solvent used in the preparation of the extract, whereas minimum bactericidal concentrations (MBC) varied from 5 to 10 mg/ml depending on the bacterial strains and the type of solvent used for theextraction. The ratio MBC/MIC of the various extracts ranged between 4 and 8. Flavonoids, cardiac glycosides, anthraquinones, polyphenols, triterpenes, steroids, saponins and tannins were found to be present, whereas alkaloids, anthocyanins and phlobatannins were not detected. In mice to which the acetone extract was administered, the activity, reaction to noise, reaction to pinch and reactivity were all reduced, suggesting a depressant or sedative effect of the extract on the central nervous system. Losses in body weight were also observed. The LD50 values of this extract were 19.2 g/kg body weight for female mice, and greater than 32 g/kg body weight for the males. The results obtained suggest that A. cordifolia bark extract has in vitro antimicrobial activity against the causative agents of typhoid and paratyphoid fevers, and may have no toxic effects.