Antibacterial Activity of Selected Medicinal Plants and Therapeutic Potential of Bridelia micrantha on Excision Wound Infected with Pseudomonas aeruginosa in Rat

Bridelia micrantha (Hochst.) Baill (Euphorbiaceae) and Smilax krausiana Meisn. (Smilaceae) are traditionally used in tropical Africa to treat various diseases including infectious diseases, stomach pains, skin diseases and wounds. The study aimed to evaluate the antibacterial activity of Bridelia micrantha (Hochst.) Baill (Euphorbiaceae) and Smilax krausiana Meisn. (Smilaceae) extracts and the healing potential of the most active extract in a rat excision wound model infected by Pseudomanas aeruginosa. The crude extracts were prepared by maceration in ethanol. Phytochemical analysis was performed using standard methods. Antibacterial activities of extracts alone and the combinations of extracts with amoxicillin as well as the effect of osmotic stress on their activities were determined by the broth microdilution method against Pseudomonas aeruginosa, Escherichia coli and Staphylococcus aureus. The therapeutic effect of the B. micrantha extract ointment was evaluated in a rat excision wound model infected by P. aeruginosa. Skin and eye toxicity tests were performed using the Draize method. The ethanol extract of B. micrantha (MIC = 512 - 1024 µg/ml) displayed the largest antibacterial activity compared with that of S. krausiana (MIC = 512 - 2048 µg/ml). The antibacterial activities of plant extracts and amoxicillin increased under osmotic stress conditions ((2.5% and 5% NaCl). B. micrantha extract showed indifference and antagonism effects with amoxicillin against the tested bacteria. The B. micrantha extract ointment yielded the shortest epithelization times, highest wound contraction rates and lowest numbers of colony forming units of P. aeruginosa at the infection site as compared with the standard drug (Baneocin) and blank (palm kernel oil). The antibacterial and wound healing effects observed may be attributed to the presence of polyphenols, flavonoids, anthocyanins, alkaloids, triterpenes, saponines and tannins found in the test plants. The results of this study clearly demonstrate the antibacterial activity of B. micrantha and S. krausiana as well as the wound healing potential of B. micrantha.