Seasonal variations in essential oil content and quality of Scots pine and Norway spruce foliage | Ēterisko eļļu satura un kvalitātes izmaiņas priedes un egles zalenī saistībā ar gadalaiku

anglais. The foliage products obtained from the needles and non-lignified shoots and twigs of Latvia’s major conifers species, Scots pine Pinus sylvestris L. and Norway spruce Picea abies (L) H. Karst., contain a variety of biologically active substances that can be used as the raw material for various products in medicine, cosmetics, food and fodder, as well as plant protection. Among these substances are essential oils, well known for their healing effect. In Latvia, the essential oils from pine and spruce foliage are now produced in small quantities only. There have been no studies regarding seasonal changes in the concentration of oils in conifer foliage or variations in their characteristics. The aim of this study was to determine the content of essential oils in pine and spruce foliage throughout the year and to characterize these oils. For this end the samples of pine and spruce foliage were harvested twice a month (at the beginning and in the middle of each month) during one year. The samples were stored at the temperature of +4 °C and the analysis was carried out within 3 days after harvesting. The content of essential oils was determined by hydrodistillation method. Samples of crashed foliage were placed in a laboratory fl ask, filled with water and heated. A mixture of water and essential oil vapours was condensed and the oil fraction was separated from water in special laboratory equipment and the amount recovered was recorded. For all the essential oil samples the density and refractive indices were determined. Density was determined using picnometer method, and refractive index – by using a refractometer (model 2WAJ). For all raw material samples the content of dry matter was determined by desiccating the sample at the temperature of 105 °C till a constant mass appeared, with the essential oil content calculated following the amount of dry matter. The analysis shows the content of essential oils in pine and spruce foliage to vary over different seasons of year. Seasonal variability was also found for the oil density and refractive indices. The amount of essential oils in pine foliage varies over the year from 0.46 % in winter to 0.76 % in spring. The average content over the year is 0.56 %. The refractive index of pine essential oil varies within the year from 1.4760 to 1.4840 with the average annual value 1.4808. The density of pine essential oil varies from 0.864 to 0.888 g cmE-3, with the average per year 0.877 g cmE-3. The results show that the density and refractive index variations in essential oils over the year are proportionally smaller than those of oil content. It means that the oil composition throughout the year remains relatively constant and that slight fluctuations may be explained by variations in the proportion of individual terpenes and their derivatives. Correspondingly, the indices for spruce foliage varied over the year from 0.26 % to 0.55 % (content of dry matter), from 1.4695 to 1.4790 (refractive index), and from 0.892 g cmE-3 to 0.910 g cmE-3 (density). Corresponding average indices for the year are: refractive index 1.4740, density 0.900 g cmE-3 and content 0.37 % from the dry matter. In spruce foliage the content of essential oils is higher at the onset of winter, and the smallest early in summer. As to the pine essential oil, no correlation between the spruce oil content, density and refractive index over the year was found. The results of analysis show that the amount and quality of pine and spruce foliage essential oils available in each season is sufficient for running production in a year-long cycle.

letton. Latvijas galveno skujkoku – priedes un egles – zalenis (skujas un nepārkoksnējušies zariņi) satur daudz bioloģiski aktīvu vielu, kas radušas plašu pielietojumu dažādās tautsaimniecības nozarēs. Viens no vērtīgākajiem produktiem, kam piemīt arī ārstnieciskas īpašības, ir ēteriskās eļļas, kuras līdz šim ieguva nelielos daudzumos. Jāatzīmē, ka Latvijā nav veikti pētījumi par priežu un egļu zaleņa ēterisko eļļu iznākuma sezonālo dinamiku un nav noskaidrotas iegūto eļļu būtiskākās īpašības. Darba mērķis – noteikt priežu un egļu zaleņa ēterisko eļļu daudzuma dinamiku viena gada laikā un raksturot iegūtās eļļas. Pētījumu rezultātā konstatēts, ka priedes zalenim ēterisko eļļu daudzums gada laikā svārstījies robežās no 0,46 % līdz 0,76 %, bet egles zalenim – no 0,26 % līdz 0,55 % no sausnas. Iegūtie dati liecina, ka priežu un egļu zalenī ēterisko eļļu daudzums gada laikā bijis mainīgs. Tomēr būtiskas sakarības eļļu daudzuma izmaiņām zalenī novērojumu periodā netika konstatētas. Arī eļļu blīvumi un refrakcijas koeficienti neuzrādīja savstarpēju korelāciju. Konstatēts, ka priedes zalenī ēterisko eļļu ir vairāk nekā egles zalenī un ka ēterisko eļļu kvalitāte un daudzums priežu un egļu zalenī ir pietiekams, lai nodrošinātu to rūpniecisku ieguvi visa gada garumā, neatkarīgi no sezonas.