Planta Med 2013; 79 - PN85
DOI: 10.1055/s-0033-1352427

Seasonal variation of the content and composition of essential oils in Betula spp. leaves naturally growing in Estonia

A Raal 1, A Orav 2, E Arak 1
  • 1Department of Pharmacy, University of Tartu, Tartu (50411), Estonia
  • 2Institute of Chemistry, Tallinn University of Technology, Tallinn (12618), Estonia

The specific terpenoids as potential chemosystematic markers for some birch species (Betula spp., Betulaceae) were found in our previous investigation.

The aim of the current study was to compare the content and composition of essential oils in four Betula species naturally growing in Estonia.

The leaves of B. pendula, B. pubescens, B. humilis and B. nana were collected in the middle of June, August and October from Tallinn, Risti bog and Viru bog in Estonia. The yields of essential oils were analysed by hydrodistillation and their chemical compositions were studied using GC and GC-MS.

The yield of essential oil was the highest (0.11 – 0.27%) in the leaves of B. humilis, and not detectable in the leaves of B. nana. The leaves of the other birch species studied had low concentrations of oil: 0.11% in the B. pendula and 0.05% in the B. pubescens leaves collected in spring, the amounts of oils were not detectable in their leaves in August and October.

a-betulenol (0.9 – 33.1%), a-betulenol acetate (2.9 – 31.9%), b-betulenal (2.5 – 7.6%) and b-betulenol (0.3 – 2.0 – 5.8%) were identified as the main constituents of leaves' oil of B. pendula, B. pubescens and B. humilis, respectively. The composition of the essential oil of B. pubescens resembled more to oil distilled from B. humilis than the oil from B. pendula.

The variation of the main terpenoids in B. nana essential oil was rather different than in the other Betula species studied. A strong negative correlation (r =-0.903; p < 0.01) between the total content of aliphatic compounds and bicyclic sesquiterpenoids was found. The total amounts of bicyclic sesquiterpenoids (birkenal, δ-cadinene, τ-cadinol, a-betulenol, b-betulenol, b-betulenal, a-cadinol, 6-hydroxy-b-caryophyllene acetate, a-betulenol acetate) showed the tendency of decreasing, and aliphatic compounds (n-heptadecane, n-hexadecanal, n-nonadecane, palmitic acid, n-eicosane, n-octadecanal, n-heneicosane, n-tricosane, and n-pentacosane) increased from spring to autumn.