Variability in the Essential-Oil Composition of Sideritis scardica Griseb. from Native Bulgarian Populations

a The essential-oil composition of six native populations of Sideritis scardica from Bulgaria was studied by GC-FID and GC/MS analyses. Altogether, 37 components, representing 73.1 to 79.2% of the total oil content were identified. Among them, a-pinene (4.4 - 25.1%), b-pinene (2.8 - 18.0%), oct-1-en-3-ol (2.3 - 8.0%), phenylacetaldehyde (0.5 - 9.5%), b-bisabolene (1.3 - 11.0%), benzyl benzoate (1.1 - 14.3%), and m-camphorene (1; 0.3 - 12.4%) were the main compounds. All samples were characterized by low contents of oxygenated mono- and sesquiterpenes ( � 1.6 and 2.3%, resp.). Principal component analysis (PCA) and cluster analysis (CA) showed a significant variability in the chemical composition of the studied samples as well as a correlation between the oil profiles and the ecological conditions of the natural habitats of S. scardica. Introduction. - Sideritis scardica Griseb. (Lamiaceae; mountain tea) is a Balkan endemic plant encountered in Southwest Albania, Macedonia, Bulgaria, and Greece (1) as well as in Turkey (cf. (2) and refs. cit. therein). The species is distributed in the mountainous regions of Southern Bulgaria from 1000 up to 2200 m.a.s.l. (Slavyanka, Pirin, and Rhodope Mts). The plant is used in traditional medicine as herbal tea for the treatment of bronchitis, lung emphysema, etc. (3), and for this reason it is intensively collected from the natural habitats for years. Nowadays, the distribution of S. scardica is quite limited, and the species has been included in the Red Book of Bulgaria as an endangered plant (4). It is under governmental protection, and its collection from the native habitats is prohibited. A literature survey revealed few reports on the S. scardica essential-oil composition from native Bulgarian, Macedonian, Greek, and Turkish populations. Kokkalou (5) reported that monoterpene hydrocarbons ( > 80%) were the principal components in the essential oil of Greek origin with a-pinene (52%) as the major compound. b-Pinene (17.9%), carvacrol (14.8%), and a-pinene (7.3%) were found as main constituents in a sample of Turkish origin (2). In contrast, Macedonian and Bulgarian S. scardica essential oils (6) were reported to be poor in monoterpenes ( 21%) and octadecenol ( > 20%) (6). Sesquiterpenoids as b-