Antifungal and antibacterial activity of seven traditionally used South African plant species active against Candida albicans

Abstract

Leaf extracts of seven South African plant species with minimal inhibitory concentrations of 0.1 mg/ml and below against Candida albicans based on a preliminary screening were evaluated for antibacterial and antifungal activities using microplate dilution method and bioautography. Aspergillus fumigatus, Micrococcus canis, C. albicans, Sporothrix schenckii and Cryptococcus neoformans were the fungal test organisms, while the bacterial species used were Staphylococcus aureus, Escherichia coli, Enterococcus faecalis and Pseudomonas aeruginosa. The plant species investigated were Cussonia zuluensis, Vepris reflexa, Curtisia dentata, Trichilia emetica, Terminalia phanerophlebia, Terminalia sambesiaca and Kigelia africana. Plant material was extracted with n-hexane, dichloromethane and acetone. The acetone and dichloromethane extracts of all plant leaves were active against some or all of the tested microorganisms. Extracts of C. dentata, T. sambesiaca and T. phanerophlebia had the highest activities against both bacterial and fungal test organisms with minimal inhibitory concentration (MIC) values as low as 0.02 mg/ml. C. zuluensis was the least active with relatively high MIC values and only one band on TLC plates active against C. albicans. The highest number (5) of active bands against C. albicans on bioautograms was observed in the acetone extracts of C. dentata. C. dentata extracts also had five compounds active against other tested fungal and bacterial species. Compounds with similar R f values in this extract were active against both bacterial and fungal test organisms, suggesting that the microbial growth inhibitory activity of C. dentata extracts was non-selective. C. dentata was selected to isolate compounds active against C. albicans.