Taxonomic implications of volatile secondary metabolites emitted from birch (Betula L.) buds

The volatile secondary metabolites emitted from the buds of 22 different species and two varieties of birch were analyzed using headspace solid-phase microextraction and gas chromatography-mass spectrometry (HS-SPME/GC-MS) methods. The volatile compositions of 21 birch buds are reported for the first time, to our knowledge. Both the mass spectral data and the calculated retention indices were used to identify the compounds. 273 different components were found and the structures of 200 compounds were precisely identified. An additional 46 compounds were classified according to their group. The terpenes were the biggest group of volatile compounds secreted by birch buds, including 13 monoterpenes, 10 C13 norterpenes, 12 norsesquiterpenes and 108 sesquiterpenes. Among the volatiles of the birch buds, 79 aliphatic compounds, 13 aromatics and six furan derivatives were also detected. Based on our chemical analyses, three different groups of birches were separated. Specific features of the first group included the presence of C13 norterpenes and norsesquiterpenes. Meanwhile, buds of the second group of birches were relatively abundant in sesquiterpenes while they did not emit C13 norterpenes or norsesquiterpenes. Buds from the third group of birches were rich in methyl and ethyl salicylates. Some characteristic features were also found for the eight other birch species that were not classified into either of the three groups. The study of the volatile secondary metabolites emitted by birch buds provided information useful for Betula genus chemotaxonomy.