Seasonal Changes in the Composition of Scots Pine (Pinus Syvestris L.) Oleoresin Measured by the NMR Method

Abstract

Analysis of seasonal changes in the composition of Scots pine oleoresin by 1H and 13C NMR spectroscopy was carried out. Due to favorable weather conditions (positive temperatures on the days of sampling throughout the year) samples for each of the 12 months were obtained and studied. Chloroform (CDCl3) solutions of oleoresin were studied. Eight resin acids were identified and quantified: abietic, dehydroabietic, isopimaric, levopimaric, neoabietic, palustric, pimaric and sandaracopymaric, and also 6 monoterpenes: camphene, limonene, myrcene, α-pinene, β-pinene and terpinolene. It was found that the amount of oleoresin and α-pinene contained in it decreased at low temperatures. At the same time other monoterpenes were not detected within the measurement error. It was supposed that monoterpenes formed in smaller amounts during the period of pests' anabiosis, play the main role in the control of coniferous insect pests. It was found that the content of dehydroabietic, isopimaric, neoabietic, pimaric, and sandaracopymaric acids varied insignificantly during the year. The relationship between the amounts of abietic, levopimaric and palustric acids in the composition of oleoresin was found. It was supposed that the observed relationship was caused by low-temperature catalytic reactions of levopimaric acid isomerization with formation of abietic acid mainly. It was suggested that these processes should be taken into account to exclude errors in determining the content of the above acids in oleoresin even in case of statistical analysis.