Composition of the essential oils of two Sideritis species from Turkey and antimicrobial activity (original) (raw)

2008, Chemistry of Natural Compounds

The genus Sideritis (Lamiaceae) is represented in Turkey by 46 species and altogether 55 taxa, 42 taxa being endemic [1-3]. Some species of Sideritis are used as medicinal and aromatic plants. S. perfoliata L. is known as "adacayi, dagcayi, and Kandil cayi" in different regions of Turkey and are widely used as diuretic and in the treatment of coughs and gastrointestinal disorders [4]. S. trojana Bornm. is an endemic species for Turkey and is known as "kazdagi cayi" [4, 5]. The essential oil compositions of some Sideritis species have been subjected to previous studies. Previous phytochemical investigations of S. perfolita and S. trojana have revealed the presence of diterpenes [6, 7], fatty acids [8], and essential oils [9, 10]. The composition of the essential oil of S. perfoliata was investigated and limonene was identified as the major constituent [9]. In our previous work, 8α-13-hydroxy-14-en-epilabdane (26-29%), limonene (19-24%), viridiflorol (14%), sabinene (11%), and β-caryophyllene (10%) were reported as the main constituents in the oil of S. perfoliata [10]. The essential oil composition of S. trojana has also been investigated. β-Pinene (12-17%) and α-pinene (8-14%) were identified as the major components [10]. In another work, the fatty acid composition was investigated in seed oils of S. perfoliata. Linoleic, oleic, 6-octadecynoic, palmitic, and linolenic acids were identified as the main fatty acid components of the seed oil [8]. To the best of our knowledge, this is the first report on the antimicrobial activity of S. perfoliata and S. trojana essential oils. In this present work, the hydrodistilled essential oils from aerial parts of Sideritis perfoliata and S. trojana were analyzed by gas chromatography and gas chromatography-mass spectrometry. The compounds characterized are given in Table 1 with their relative percentage amounts. In the oil of S. perfoliata (0.36%), 60 compounds were identified, representing 98.6% of the oil, with monoterpene hydrocarbons (76.2%) dominating, together with oxygenated monoterpenes (1.3%), sesquiterpene hydrocarbons (6.2%), oxygenated sesquiterpenes (1.9%), diterpenes (12.8%), and other compounds (0.2%). The main constituents were found to be limonene (37.7%) and sabinene (18.8%). S. trojana oil (0.04%) was rich in β-pinene (18.4%) and α-pinene (13.2%). Sixty-two compounds were characterized, representing 87.9% of the oil. The monoterpene hydrocarbon (46.7%) content of this oil was rather low compared to S. perfoliata. The antibacterial and anticandidal activities of the oils are presented in Table 2. The results of the antimicrobial assays indicated that E. coli, methicillin-resistant S. aureus (MRSA), E. aerogenes, B. cereus, and C. albicans were inhibited by the oil of Sideritis trojana moderately with MIC values of 125 to 250 µg/mL, which were lower than that of the standard antimicrobial agent. The oil showed strong inhibitory effect against S. epidermidis with a MIC value of 62.5 µg/mL. S. perfoliata oil, on the other hand, was less active (125 to 500 µg/mL) against the test microorganisms except for C. albicans. The occurrence of a higher content of oxygenated derivatives of mono and sesquiterpenes (20%) in the oil of S. trojana may be responsible for the better antimicrobial activity. Plant Material and Isolation of the Essential Oils. Dried aerial parts of the plant materials were hydrodistilled for 3 h using a Clevenger apparatus to obtain essential oils in dry weight yield.