In vitro growth-inhibitory activity of Calophyllum inophyllum ethanol leaf extract against diarrhoea-causing bacteria

Purpose: To investigate the in vitro growth-inhibitory effect of Calophyllum inophyllum, a medicinal plant traditionally used to cure gastrointestinal disorders caused by diarrhoea-causing bacteria.Methods: The minimum inhibitory concentration (MIC) of C. inophyllum ethanol leaf extract was determined against six diarrhoea-causing bacteria, namely, Clostridium difficile infant, Clostridium perfringens, Enterococcus faecalis, Escherichia coli, Listeria monocytogenes, and Salmonella enterica. The effect of the plant extract on bacterial growth kinetics was further evaluated by slightly modified broth microdilution method.Results: The plant extract showed significant inhibitory activity against C. perfringens and L. monocytogenes (MIC = 128 μg/mL) followed by C. difficile (MIC = 512 μg/mL). Monitored growth curves also showed that the plant extract at ½ MIC inhibits bacterial growth by distinct extension of the lag phase or suppression of the whole growth rate in C. difficile and L. monocytogenes, respectively.Conclusion: These results demonstrate the significant anti-clostridial and anti-listerial activities of C. inophyllum ethanol leaf extract. Thus, the extract seems to be a promising material for the development of new antibacterial agents.Keywords: Calophyllum inophyllum, Alexandrian laurel, Intestinal infections, Antibacterial activity, Anticlostridial, Anti-listeria