Abstract
A new method based on the difference in the contents of menthofuran and cineol has been developed for the discrimination of the species of peppermint oils by thin-layer chromatography. Thin-layer chromatography was performed with a commercially available silica gel plate (spot film, Easteman Kodak Co.). The solvent system used was a benzene-methyl acetate mixture (95 : 5 v/v). An intense color appeared by spraying 5% solution of vanillin in concentrated sulfuric acid. The location of menthofuran and cineol was easily identified on the plate not only by their Rf values but also by their colors. The detection limit of menthofuran and cineol visualized on the plate was to be 0.3μg and 5μg. Since the contents of menthofuran and cineol were (110)% and (610)% inM. piperita, when 0.5 to 1.0 mg of peppermint oils was subjected to analysis, menthofuran and cineol can be detected as visual spots on the plate, but these species in M. arvensis oil were not detectable. The amount of menthofuran in M.piperita oil decreases gradually during the storage at a room temperature. However, the amount of cineol is not affected. It was found that the method based on the quantity of menthofuran and cineol can be used for the identification of species of peppermint oils.
