Antibacterial, antifungal and in vitro cytotoxic activities of three extracts isolated from mint

A number of reports have been focusing on chemical compositions and functional properties of essential oils isolated from mint. However, there is little data available on the biological activities of non-volatile constituents. In this study, the antibacterial (against 2 gram-positive bacterial strains: Staphylococcus aureus and Bacillus cereus; 2 gram-negative bacterial strains: Escherichia coli and Pseudomonas aeruginosa), antifungal (against Candida albicans, Colletotrichum gloeosporioides and Penicillium polonicum) and cytotoxic (against Human Embryonic Kidney 293 cell line) activities of three non-volatile extracts (Extracts 1 to 3) from the leaves and stems of mint were evaluated. Extract 1 showed significant antibacterial activity against gram-positive pathogens S. aureus and B. cereus, with an inhibition zone of 12.60 and 12.08 mm, respectively. The minimal inhibitory concentration (MIC) of extract 1 against S. aureus was 0.94 mg/ml. On the other hand, it exhibited low cytotoxic activity against normal Human Embryonic Kidney 293 cell line (CI50 nearly 30 mg/ml), which suggested that Extract 1 could be a potential and safe antibacterial agent. Nevertheless, the tested gram-negative bacteria and pathogenic fungi were not susceptible towards Extracts 2 and 3.  Key words: Mint, antibacterial activity, antifungal activity, cytotoxicity.