Effects of abiotic environmental conditions on amount and enantiomeric composition of α-pinene in Juniperus communis L.

Abstract

Effects of some abiotic environmental conditions on amounts of essential oil and α-pinene therewith and enantiomeric composition of α-pinene in Juniperus communis L. were studied. The leaf and unripe cone samples of total 110 cone-bearing J. communis individuals were sampled from 11 natural habitats, differing mainly by illumination intensity and soil chemical characteristics, across Lithuania. The analysis of α-pinene in essential oils of leaves and unripe cones was carried out by GC-FID, and the enantiomeric analysis of α-pinene – by chiral-phase capillary GC. The study confirmed that the unripe cones accumulate more essential oils than leaves (1.3 ± SD 0.63% and 0.4 ± SD 0.14%, respectively), and the amount of essential oils in leaves negatively significantly correlated with illumination (r = −0.69, p < 0.05) and soil acidity (r = −0.83, p < 0.05) of habitats. The α-pinene was the main essential oil compound in 97% and 98% of all analysed leaf and unripe cone samples, respectively. Leaves and unripe cones contained very similar amounts of this monoterpene (54.1 ± SD 13.9% and 58.0 ± SD 14.62%, respectively). Significant positive correlations between the percentage of α-pinene and the ratio of (1R)-(+)-α-pinene/(1S)-(−)-α-pinene in essential oils of cones and leaves implies that the synthesis of this monoterpene and its enantiomers both in leaves and cones is interdependent. It was established that the (1R)-(+)-α-pinene is more prevalent than (1S)-(−)-α-pinene both in leaves and unripe cones of J. communis growing wild in Lithuania, and that purity of (−) enantiomer varied more than purity of (+) enantiomer. Our study showed that the amount of α-pinene and its enantiomeric composition did not correlate significantly with the illumination and soil characteristics of habitats neither in leaves nor in unripe cones.