Lahtinen Maria, Lempa Kyösti, Salminen Juha-Pekka, Pihlaja Kalevi
Laboratory of Organic Chemistry and Chemical Biology. Department of Chemistry, University of Turku, FI-20014 Turku, Finland.
Phytochem Anal. 2006 May-Jun;17(3):197-203. doi: 10.1002/pca.906.
Flavonoid aglycones found on the surfaces of birch (Betula spp.) leaves may constitute up to 10% of the dry weight of the leaf. A facile extraction and HPLC procedure has been developed that can be used for the preliminary classification of birch species according to the patterns of their leaf surface flavonoids. The procedure involves no complex sample preparation steps, and is able to provide HPLC chromatograms from fresh leaves in less than 30 min. If necessary, leaves do not even need to be removed from the tree. Since the genus Betula is taxonomically complex and separation of different birch species can be problematic, the developed method was applied to 15 Betula species and four sub-species of Betula pendula Seven of the studied species were classified as B. pubescens and eight as B. pendula-type birches. The remaining four species did not belong to either of these two classes on account of their unique pattern of external flavonoids. The difference between the leaf surface flavonoid composition of B. pubescens and B. pendula type birch species was unambiguously clear, and the developed method could reliably distinguish between the two species. Whilst leaf surface flavonoids can be valuable chemotaxonomic markers, they classify birch species differently from morphological markers. Birch species with diploid chromosome sets did not contain any of the flavanones that were present in the leaves of other species. The close relationship between the occurrence of some flavonoid aglycones and the ploidy level of Betula species suggests that these chemotaxonomic markers may be useful both in taxonomic and phylogenetic analyses.
在桦树（桦木属物种）叶片表面发现的类黄酮苷元可能占叶片干重的10%。已开发出一种简便的提取和高效液相色谱法，可用于根据桦树叶片表面类黄酮的模式对桦树种类进行初步分类。该方法无需复杂的样品制备步骤，能够在不到30分钟的时间内从新鲜叶片中获得高效液相色谱图。如有必要，甚至无需从树上摘下叶片。由于桦木属在分类学上较为复杂，区分不同的桦树种类可能存在问题，因此将所开发的方法应用于15个桦木种类以及垂枝桦的4个亚种。在所研究的种类中，7种被归类为毛桦，8种被归类为垂枝桦类型的桦树。其余4个种类因其独特的外部类黄酮模式，不属于这两类中的任何一类。毛桦和垂枝桦类型桦树种类的叶片表面类黄酮组成差异清晰明确，所开发的方法能够可靠地区分这两个种类。虽然叶片表面类黄酮可能是有价值的化学分类学标记，但它们对桦树种类的分类与形态学标记不同。具有二倍体染色体组的桦树种类不含其他种类叶片中存在的任何黄烷酮。一些类黄酮苷元的出现与桦木属物种的倍性水平之间的密切关系表明，这些化学分类学标记可能在分类学和系统发育分析中都有用。
