Cyclodextrin-based Gas Chromatography and GC/MS methods for determination of chiral pair constituents in mint essential oils

The genus Mentha has been known as culinary source of minty note. Besides, the essential oil imparts value to consumer products like confectionery, cosmetics, and pharmaceutical preparations. A simple and sensitive enantioselective gas chromatographic method is described for the quantitative analysis of terpenoid enantiomers in essential oils using different cyclodextrin coated stationary phases. Limonene, menthone, menthol, and menthyl acetate were identified as pure (-)-enantiomers whereas isomenthone, neomenthol, pulegone, and piperitone as pure (+)-enantiomers in menthol mint, and peppermint oils, respectively. The selectivity of each enantiomer was also demonstrated. A β-cyclodextrin phase with diethyl substitution provides baseline resolution for all target enantiomers with selectivity ranged from 1.004 to 1.050. Moreover, permethylated or diacetylated-β-cyclodextrin showed no selectivity for (+/-)-menthol enantiomers. The current study may facilitate the origin authentication studies of mint oils. Investigation of enantiomers involved in menthol biosynthesis revealed that only (-)-menthol is present in the essential oils of Mentha species.