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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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    Öğe
    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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    Öğe
    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.