Background: Many species of the genus Centaurea have been reported to be used in Anatolian folk medicine. In the present study, methanolic and aqueous extracts of three species of Centaurea L. (C. calcitrapa subsp. calcitrapa, C. ptosimopappa and C. spicata) have been assessed for antioxidant and cytotoxic activities. Materials and Methods: Antioxidant activity was investigated by DPPH and superoxide anion scavenging and anti-lipid peroxidation assays. Cytotoxic effect on HeLa and Vero cells were investigated by MTT assay. Results: Superoxide anion scavenging activities of aqueous extracts were higher than those of methanolic extracts, and the highest activity was detected in the aqueous extracts of C. calcitrapa subsp. calcitrapa with the IC 50 value of 25.91 µg/mL. The methanolic extract of C. ptosimopappa showed the strongest anti-lipid peroxidation activity. Total phenolic contents (mg gallic acid equivalent per gram) were ranged between 17.25 and 120.50 and the highest value was detected in aqueous extract of C. ptosimopappa. The highest cytotoxic activity was observed in the methanolic extract of C. calcitrapa subsp. calcitrapa on both cell lines with the IC 50 values of <100 µg/mL. Conclusions: According to the results of activity tests, the selected Centaurea species, especially C. calcitrapa subsp. calcitrapa can be regarded as a potential source of natural antioxidants in the prevention and treatment of diseases in which oxidants or free radicals are implicated.Key-words: Antioxidant activity; Centaurea; Cytotoxicity; Free radical scavenging.Key Messages: The selected Centaurea species showed an antioxidant activity and very low cytotoxic activity. Thus, Centaurea species might be a good candidate for further studies targeting the development of new antioxidants.

IntroductionThe Brassicaceae is a large family that includes 338 genera and 3700 species. It has major scientific and economic importance . The tribal classification of the Brassicaceae is problematic because the characteristics traditionally used at this rank are few in number, usually only 1 or 2 morphological characteristics. These characteristics are also variable within genera, and they conflict with one another in their distribution patterns among genera and tribes; thus, they may not support natural groups (Khalik et al., 2002).Seed morphology is frequently used for understanding and classifying Brassicaceae at the tribal level (Zohary, 1948;El Naggar, 2005). According to morphological studies, Lepidieae is a natural tribe of about 66 genera, of which 23 are monotypic, with some 680 species distributed throughout the world (Al-Shehbaz, 1986). However, according to molecular research, Lepidieae is not monophyletic (Al-Shehbaz et al., 2006;Beilstein et al., 2006).Seed characteristics are also important at genus level. The genus Lepidium L. is one of the largest genera of the Brassicaceae, consisting of 175 species. It is distributed worldwide, primarily in temperate and subtropical regions. The genus is poorly represented in Arctic climates; in tropical areas, it grows in the mountains (Al-Shehbaz, 1986). In Turkey, 14 taxa are represented in which 1 endemic is placed in 4 sections: Lepia (Desv.

This study examines the exomorphic achene characteristics of 23 taxa belonging to Centaurea, Cyanus, Psephellus and Rhaponticoides in Asteraceae using light microscope and scanning electron microscope (SEM). The exomorphic characteristics studied are shape, size, colour and surface pattern of achene, and hair, length and colour of pappus. The results of the present investigation showed that achene size of the studied taxa is 3-7 × 1-4 mm. Pappus length is 1-14 mm, deciduous for three taxa and inner row is differentiated from the outer, 1-3 mm long, for 10 taxa. SEM studies showed eight different types of achene surface patterns for the studied taxa: Glebulate, glebulate-ruminate, reticulate, ribbed, ruminate, smooth, smooth-glebulate and undulate. Achene characteristics are useful for both intrageneric and intraspecific classification of the studied taxa.

This article investigates the exomorphic characteristics of the achenes which are achene size, color, and surface pattern, and pappus length, and colour. All these characteristics in seven taxa of Asteraceae namely, C. aggregata Fisch. & C.A. Mey. ex DC. subsp. aggregata, C. sivasica Wagenitz, C. polypodiifolia Boiss. var. polypodiifolia, C. polypodiifolia Boiss. var. szowitziana (Boiss.) Wagenitz, C. iberica Trev. ex Spreng, C. urvillei DC. subsp. stepposa Wagenitz, and C. carduiformis DC. subsp. carduiformis var. carduiformis in are described, illustrated and compared. The results of SEM at higher magnification showed three types of achene surface patterns: glebulate-ruminate, smooth, and rugose. In these patterns, there were diagnostic characteristics and differences at the specific level for Centaurea. A key to the taxa has been provided on the basis of these achene characteristics.

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