The ontogenetic variability of chemical composition of the essential oils of Erigeron canadensis L., Daucus carota L. ssp. carota and Anethum graveolens L. was studied. A distinct dependence between the ontogenetic stage and the contents as well as the chemical composition of essential oils was observed. The results obtained are of significance for determining the most favourable time limit for picking plant raw material.

The essential oils from needles, twigs, bark, wood, and cones of Pinus cembra were analyzed by GC-FID, GC/MS, and H-NMR spectroscopy. More than 130 compounds were identified. The oils differed in the quantitative composition. The principal components of the oil from twigs with needles were α-pinene (36.3%), limonene (22.7%) and β-phellandrene (12.0%). The needle oil was dominated by α-pinene (48.4%), whereas in the oil from bark and in the oil from twigs without needles there were limonene (36.2% and 33.6%, resp.) and β-phellandrene (18.8% and 17.1%, resp.). The main constituents of the wood oil as well as cone oil were α-pinene (35.2% and 39.0%, resp.) and β-pinene (10.4% and 18.9%, resp.). The wood oil and the cone oil contained large amounts of oxygenated diterpenes in comparison with needle, twig, and bark oils.

The essential oils from different parts of Thuja plicata and its cultivar varieties "Fastigiata", "Kornik," and "Zebrina" were analyzed by gas chromatography (GC) and GC/mass spectrometry. More than 80 compounds were identified. The oils from leaves, twigs with leaves, and twigs without leaves contained mainly α-thujone (52.1%-59.2%), fenchone (10.0%-11.3%), and beyerene (3.7%-9.5%), whereas in the cone oil there were α-thujone (35.6%), sabinene (24.0%), and α-pinene (8.3%). The main constituents of the oils from twigs with leaves of "Fastigiata," "Zebrina," and "Kornik" cultivars were α-thujone (76.2%, 72.5%, and 67.4%, respectively) and β-thujone (7.6%, 6.2%, and 4.9%, respectively). The oils from cultivars contained more thujones and less fenchone and diterpenes in comparison with T. plicata oil.

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