Tytti SAARNI, Kimmo NURMI and Kalevi PIHLAJA
Department of Chemistry, University of Turku, FIN-20014 Turku, Finland
In context of our studies on the role of different chemical components in the leaves of mountain birch trees (Betula pubescens ssp. tortuosa) we also decided to determine the composition of essential oils in the leaves. Terpenes and their oxygen derivatives are hydrocarbons present in vegetation which are formed by isoprene (C5H8) units. A special emphasis is given on mono- (C10 - two isoprene units) and sesquiterpenes (C15 - three isoprene units).
In our ongoing investigation the leave material is first crushed in liquid nitrogen and then treated with one of the following methods: (i) solvent hexane/acetone/hexaneEt2O (1:2), mixing in a test tube, and sonification for 30 min. After sentrifugation the solution is concentrated with a Widmer column, purified on a silica gel column and concentrated again with the Widmer column under the flow of nitrogen and then analysed; (ii) steam distillation (for 3 or 6 h), extraction in hexane/Et2O (1:2), evaporation to dryness and analysis; (iii) Soxhlet extraction with pentane/Et2O (1:2) at 318 K (heating with water bath) for 6 h, purification on a Sep-Pak column and concentration with the Widmer column and analysis. The components of the samples so obtained were analyzed on GC and GC-MS. Kóvats' retention indexes were applied on the qualitative analysis. Compound identification with IR-spectrophotometer was also tested.
The leaves of mountain birch trees contain minor amounts of monoterpenes tike tricyclene, a-pinene, camphene, ß-pinene, 3-carene, a-phellantrene, a-terpinene, limonene, y-terpinene and bornyl acetate. Sesquiterpenes like caryophyllene, a and ß-betulenol, and their derivatives were found in higher concentrations-1. Furthermore the leaves of mountain birch trees contain markable concentrations of various longchain alkanes.
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