Antibacterial and Wound Healing Properties of Selected Cameroonian Medicinal Plants

Emilia coccinea (Sims.) G. Don. (Asteraceae), Erigeron floribundus (Kunth) Sch. Bip. (Asteraceae) and Hibiscus asper Hook.f. (Malvaceae) are used ethnomedicinally in tropical region of Africa to treat various diseases including infectious diseases, abscesses, skin diseases and wounds. The study aimed to evaluate the antibacterial activity of E. coccinea, H. asper and E. floribundus extracts and the healing efficiency of the most active extract in a rat excision wound model infected by Staphylococcus aureus. The plant extracts were prepared by maceration in ethanol. Secondary metabolites were detected in the extracts by 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 against Pseudomonas aeruginosa, Escherichia coli and Staphylococcus aureus by using broth micro dilution method. The therapeutic effect of the E. coccinea extract was evaluated in a rat excision wound model infected by S. aureus. E. coccinea extract (MIC = 256 - 512 µg/ml) displayed the largest antibacterial activities followed in decreasing order by the extracts of E. floribundus flowers and leaves (MIC = 256 - 1024 µg/ml), E. floribundus roots (MIC = 512 - 1024 µg/ml) and H. asper (MIC = 1024 µg/ml). The antibacterial activities of plant extracts and amoxicillin increased under osmotic stress conditions. E. coccinea extract showed additive effect with amoxicillin against pathogenic bacteria among which multidrug resistant strains. E. coccinea extract ointment yielded the shortest epithelization times, highest wound contraction rates and lowest numbers of colony forming units of S. aureus at the infection site as compared with the standard drug (Baneocin). Interestingly, this extract ointment is non-irritating to the skin and eyes. The observed biological activities may be attributed to the presence of groups of phytochemical compounds found in the test plants. The results of the present study demonstrate the antibacterial activity of the test plants as well as the healing efficiency of the E. coccinea extract ointment. E. coccinea can be used for the development of phytomedicines to treat wounds and infectious diseases particularly those caused by the tested bacteria. So, further studies are warranted.