Essential oil in Betula spp. leaves naturally growing in Estonia

The essential oils of the leaves of Betula pendula Roth., Betula pubescens Ehrh., Betula humilis Schrank and Betula nana L. (Betulaceae), and B. pendula buds were obtained using hydrodistillation and their chemical compositions were analyzed using gas chromatography and gas chromatography – mass spectrometry. The yield of essential oil was the highest (0.27%) in leaves of. B. humilis and the lowest in the leaves of B. pendula (0.11%), B. pubescens (0.05%) and B. nana (traces). Overall, 35–60 compounds were identified representing more than 92% of the total volume of the oils investigated. The bicyclical sesquiterpenoids found in the essential oils extracted from the leaves of B. pendula, B. pubescens and B. humilis and from the buds of B. pendula where α-betulenol (20.4–33.1%), α-betulenol acetate (5,6–28.9%), β-betulenal (5.5–6.2%) and β-betulenol (2.0–5.8%). The buds of B. pendula contained more birkenal, (E)-β-caryophyllene, δ-cadinene and caryophyllene oxide, but less α-betulenol acetate, β-betulenal and aliphatic compounds than the oils extracted from the leaves investigated. The oil composition of B. humilis and B. nana leaves was studied for the first time. The content of essential oil of B. nana leaves was much more varied: the oil contained less bicyclical sesquiterpenoids and more aliphatic compounds than the other Betula species investigated. The findings of our study could be used in chemosystematics of birch species, especially for B. nana. [Display omitted] ► We investigated the essential oils of leaves of Betula pendula, Betula pubescens, Betula humilis and Betula nana. ► The essential oil composition of B. humilis and B. nana leaves was analysed for the first time. ► The bicyclic sesquiterpenoids were found in all birch species as the main group of compounds. ► B. nana contained less bicyclic sesquiterpenoids and more aliphatic compounds than other birches. ► We conclude that the findings could be used in chemosystematics of birch species.