Piperitone from Mentha longifolia var. chorodictya Rech F. reduces the nitrofurantoin resistance of strains of enterobacteriaceae

The diluted essential oil of Mentha longifolia (L.) var. chlorodictya Rech F. foliage enhanced the bactericidal activity of nitrofurantoin decreasing the minimum inhibitory concentration (MIC) of nitrofurantoin for nitrofurantoin‐resistant strains of Enterobacteriaceae. Thin‐layer chromatography (TLC) analysis of the essential oil detected a fraction (Rf = 0.35, UV λmax of 232.5), which was the most effective in enhancement of nitrofurantoin activity. Using gas liquid chromatography and known standards, the active fraction was identified as piperitone. 1 µl of the piperitone fraction decreased the MIC of nitrofurantoin 3–20 fold for the different strains of Enterobacteriaceae tested. Copyright © 2004 John Wiley & Sons, Ltd.