With a different approach it is possible to develop commercially useful antimicrobial products from plants

Many compounds from plants play a major role as pharmaceutical products in several therapeutic applications in human and animal health. Despite thousands of publications in the field there has been a remarkable absence of therapeutic products from plants to combat microbial infections. Data will be presented to show that the following factors play a role in this absence: the extractant used, the bioassay used, the unexpectedly low activity of isolated antimicrobial compounds, the presence of synergism in crude extracts and focussing on plants traditionally used. The antibacterial activity of acetone leaf extracts of more than 700 South African tree species on four important nosocomial pathogens Staphylococcus aureus, Enterococcus faecalis, Escherichia coli and Pseudomonas aeruginosa were determined. A high proportion of these extracts had antibacterial activities with MICs lower than 0.08mg/ml. Unfortunately in many cases the extracts are toxic to mammalian cells. Many of these species have a good potential to be used as crude extracts to treat topical infections in humans. Examples will be demonstrated where these extracts have been as effective as commercial products in controlling microbial infections in animals and plants. The limitations associated with commercializing plant extracts as antimicrobials such as quality control, availability of material and potentising the extracts to yield patentable products will also be discussed. It appears that if the focus is on using extracts rather than isolated pure compounds there is a considerable opportunity to use the compounds present in plants to combat microbial infections.

Keywords: antibacterial activity, synergism, extractant, MIC, plant extract, nosocomial bacteria, commercial product

Acknowledgement: The National Research Foundation provided financial support