Identification of isomer of volatile oils in peppermint leaves and its stalks by gas chromatography-mass spectrometry

The fine composition of volatile oils in a raw peppermint in July were analysed by combined means of programmed temperature capillary gas chromatography/mass spectrometry (GC/MS). 20 compounds were separated and identified. The main constituents were (1 alpha ,2 alpha ,5 beta)-menthol (16.88%), (1 alpha ,2 beta ,5 beta)-menthol (74.98%), cis-menthone(3.84%) and (2R-cis)-menthone (1.25%). In the whole July mint there were 4 groups of isomeric compound, their molecular formula were C10H16(5 components), C10H18O (2 components), C10H18O (2 components) and C15H24(8 components), respectively.