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    Antimicrobial activity of the essential oil of Centaurea aladagensis
    (Elsevier Science Bv, 2007) Kose, Y. Bulent; Iscan, G.; Demirci, B.; Baser, K. H. C.; Celik, S.
    Composition of the water-distilled oil of the aerial parts of Centaurea aladagensis, endemic in Turkey, was analysed by GC-MS. Hexadecanoic acid (39.3%), caryophyllene oxide (6.6%) and hexahydrofamesyl acetone (4.3%) were found as main constituents in the oil. The oil was tested against 7 human pathogenic microorganisms. (C) 2007 Published by Elsevier B.V.
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    Bioactivity of the extracts and isolation of lignans and a sesquiterpene from the aerial parts of Centaurea pamphylica (Asteraceae)
    (Tehran Univ Medical Sciences, 2007) Shoeb, M.; Macmanus, S. M.; Kong-Thoo-Lin, P.; Celik, S.; Jaspars, M.; Nahar, L.; Sarker, S. D.
    Centaurea pamphylica Boiss. & Heldr. (Family: Asteraceae), commonly known as 'pamphylia daisy', is a Turkish endemic species of the genus Centaurea that comprises ca. 500 species, many of which have been used as traditional medicines. The n-hexane, dichloromethane (DCM) and methanol (MeOH) extracts of the aerial parts of C. pamphylica were assessed for antioxidant activity and general toxicity using, respectively, the 2,2-diphenyl-l-picrylhydrazy] (DPPH), and the brine shrimp lethality assays. The reversed-phase preparative HPLC and PTLC were used to isolate compounds from the extracts. The structures of these compounds [1-4] were elucidated by spectroscopic means, and also by direct comparison with the respective published data. Both the DCM and the MeOH extract showed significant levels of antioxidant activities with the RC50 values of 72.6 x 10(-2) and 47.3 x 10-2 mg/mL, respectively. The MeOH extract exhibited low levels of toxicity towards brine shrimps (LD50 = 125.0 x 10(-2) mg/mL). Three major bioactive components of the MeOH extract were matairesinoside [1], arctim [21 and matairesinol [3]. An eudesmane-type sesquiterpene, pterodontriol [4], was also isolated from the DCM extract. Since reactive oxygen species are important contributors to various ailments, the antioxidant properties of the extracts as well as the isolated compounds may be of medicinal significance. This is the first report on the occurrence of 1-4 in C. pamphylica, and 4 in the genus Centaurea.
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    Bioactivity of the extracts and the isolation of lignans from the seeds of Centaurea dealbata
    (Univ Granada, Editorial, 2006) Shoeb, M.; Jaspars, M.; Macmanus, S. M.; Thoo-Lin, P. K.; Celik, S.; Sarker, S. D.
    Centaurea dealbata Willd. (Family: Asteraceae) belongs to the big genus Centaurea that comprises ca. 500 species. The n-hexane, dichloromethane (DCM) and methanol (MeOH) extracts of the seeds of C. dealbata have been assessed for antioxidant activity and general toxicity using, respectively, the DPPH assay, and the brine shrimp lethality assay. Both the DCM and the MeOH extract showed significant levels of antioxidant activities with an RC 50 value 6.8 x 10(-2) and 4.7 x 10(-2) mg/ mL, respectively. None of the extracts exhibited any signifi cant general toxicity (LD50 = > 1000 mg/ mL). Three major bioactive components of the MeOH extract were found to be the lignans, arctigenin, arctiin and matairesinoside. The structures of these lignans were elucidated by comprehensive spectroscopic analyses, and also by direct comparison with the respective published data. This is the first report on the occurrence of arctiin and matairesionl in C. dealbata. The distribution of these lignans within the genus Centaurea has also been presented.
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    Determination of the volatile constituents and total phenolic contents of some endemic Stachys taxa from Turkey
    (Springer, 2006) Ozkan, G.; Gokturk, R. S.; Unal, O.; Celik, S.
    The total phenolic contents and the essential oil compositions of the previously unknown Stachys taxa (Labiatae), including Stachys pinardii Boiss, Stachys cretica L subsp. mersinaea (Boiss.) Rech., and Stachys aleurites Boiss. & Heldr., all endemic to Turkey, were studied. Their essential oil compositions were investigated by GC-MS. It was found that the main constituents were alpha-curcumene (34.10%)for S. cretica, cedrandiol (25.26%) and caryophyllene dioxide (22.15%) for S. pinardii, and (Z)-beta-caryophyllene (31.60%) for S. aleurites. The total phenolic contents, by the Folin-Ciocalteu colorimetric method, of the S. pinardii, S. cretica subsp. mersinaea, and S. aleurites methanolic extract were found to be 600.74+/-0.23, 1200.94+/-0.11, and 900.61+/-0.06 mg gallic acid equivalent (GAE)/100 g in dried herb, respectively.
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    Lignans and flavonoids from the seeds of Centaurea bornmuelleri Hausskn. Ex. Bornm. and Centaurea huber-morathii Wagenitz
    (2007) Shoeb, M.; MacManus, S.M.; Jaspars, M.; Nahar, L.; Kong-Thoo-Lin, P.; Celik, S.; Sarker, S.D.
    The reversed-phase preparative HPLC purification of the methanol extracts of the seeds of two Turkish endemic species Centaurea bornmuelleri and Centaurea huber-morathii afforded several dibenzylbutyrolactone-type lignans and flavonoids. The lignans arctiin, matairesinol and matairesinoside, and the flavonoid, afzalin, were found in both species. While arctigenin and astragalin were only present in C. bornmuelleri, kaempferol was isolated from huber-morathii. A plant sterol, stigmast-4-en-3?-ol, was also isolated from the dichloromethane extract of C. bornmuelleri. The structures of the isolated compounds were determined by spectroscopic means. The chemotaxonomic significance of these compounds within the genus Centaurea has been discussed.
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    Lignans and flavonoids from the seeds of Centaurea bornmuelleri Hausskn. ex. Bornm. and Centaurea huber-morathii Wagenitz.
    (Polish Chemical Society, 2007) Shoeb, M.; MacManus, S. M.; Jaspars, M.; Nahar, L.; Kong-Thoo-Lin, P.; Celik, S.; Sarker, S. D.
    The reversed-phase preparative HPLC purification of the methanol extracts of the seeds of two Turkish endemic species Centaurea bornmuelleri and Centaurea huber-morathii afforded several dibenzylbutyrolactone-type lignans and flavonoids. The lignans arctim, matairesinol and matairesinoside, and the flavonoid, aftalin, were found in both species. While arctigenin and astragalin were only present in C. bornmuelleri, kaempferol was isolated from huber-morathii. A plant sterol, stigmast-4-en-3 beta-ol, was also isolated from the dichloromethane extract of C. bornmuelleri. The structures of the isolated compounds were determined by spectroscopic means. The chemotaxonomic significance of these compounds within the genus Centaurea has been discussed.
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    Studies on the germination of an endemic species Centaurea tomentella Hand.-Mazz.
    (Pakistan Botanical Soc, 2006) Uysal, Ismet; Celik, S.; Ozkan, K.
    Centurea tomentella an endemic species of Turkey is facing a threat of extinction due to its overuse for the decorative purposes. The species is under an abiotic stress of salinity in its natural habitats. Studies on the germination of this species were thus started in order to evaluate the possibilities which would enable us to sustain and cultivate the native populations on a large scale. The germination behaviour of this species was investigated under two different light regimes (8 h light-16 h darkness and 16 h light- 8 h darkness) at a constant temperature of 25 degrees C. The results showed that germination was higher (59.50 %) in 16h light- 8 h darkness, but lower in 8 h light-16 h darkness (52.25 %). Different concentrations of NaCl and KNO3 were applied to assess if any improvement in germination could be obtained. Both the rate as well as total germination were higher at 0.25 % KNO3 under 8/16 h light/dark condition as compared to the control. The effect of 0.25 % KNO3 was significant, but light interactions were non significant.