β-Pinene and Limonene Enantiomers

The essential oils from Korean mint (Agastache rugosa (Fisch. et Mey)) and Lemon mint (Mentha piperita var. citrata (Ehrh.) Briq.) have a high content of chiral terpene compounds that reaches 16.1 % and 10.5 % accordingly with the predominance of limonene, while the oils are obtained from preliminary dried plant material. The content of the enantiomers in peppermint (Mentha x piperita L) oil does not exceed 3.8 %. In each of three investigated Lamiacea species, one specific enantiomeric form of α-pinene, β-pinene, and limonene prevails during all vegetation period; the differences in accumulation of these three monoterpene enantiomers in essential oils obtained from the plants on different ontogenetic stages and after different preprocessing history (fresh and dried material) are discussed for the first time. (-)-α-Pinene was found as the dominating form in the essential oils from all investigated species. (-)-β-Pinene and (+)-limonene with a 86- 100 % enantiomeric excess were detected in the oil from Agastashe, while the (+)-enantiomer of β-pinene and the (-)-limonene prevails in both essential oils from the Mentha kind. The analysis of terpene enantiomer composition in the plant essential oil confirms the morphological classification of M. citrata as a variant of M. piperita with a high accumulation of citral B.