Centaurea species

Sesquiterpene Lactones and Allelochemicals from Centaurea Species... 

Other phenolic compounds of commercial importance include the terpenoids, including mono, di, tri, and sesquiterpenes. While most of these are used as essential oils, fragrances, and flavors in various products, they are toxins in certain species. For example the sesquiterpene lactones of the Centaurea species cause an irreversible Parkinson s-like condition in horses called nigro-pallidal encephalomalacia. This is a lethal condition and the prognosis for recovery is grave in most cases, affected horses should be euthanized before reaching the terminal stages. 

Tamura, FI. et al.. Structures of a succinyl anthocyanin and a malonyl flavone, two constituents of the complex blue pigment of cornflower Centaurea cyanus. Tetrahedron Lett., 24, 5749, 1983. Sulyok, G. and Laszlo-Bencsik, A., Cyanidin 3-(6-succinyl glucoside)-5-glucoside from flowers of seven Centaurea species. Phytochemistry, 24, 1121, 1985. 

The lignans are a large group of plant phenolics, biosynthesized from the union of two phenylpropane molecules e.g., both matairesinol (Centaurea species, family Asteraceae) and podophyllotoxin Podophyllum peltatum, family Berberidaceae) are formed from the phenylpropane coniferyl alcohol. Lignans are essentially cinnamoyl alcohol dimers, though further cyclization and other structural modifications result in various structural types, e.g. dibenzylbutyrolactone and epoxy lignan. 

Stevens, K.L., G.B. Merrill. Sesquiterpene lactones and allelochemicals from Centaurea species. In The Chemistry of Allelopathy Biochemical Interactions Among Plants. Thompson, A.C. ed. ACS Symp. Ser. 268. American Chemical Society. Washington, D.C., 1985. 

Centaurea deflexa is a perennial plant belonging to the Asteraceae family. In vitro cytotoxic activity against different pancreatic and colon cancer cell lines has been also reported for several Centaurea species [108]. The major constituents identified in Centaurea L. species, responsible for most of their pharmacological properties, are sesquiterpene lactones which induce apoptosis in cancer cells [109]. 

Koukoulitsa E, Skaltsa H, Karioti A, Demetzos C, Dimas K (2002) Bioactive sesquiterpene lactones from Centaurea species and their cytotoxic/cytostatic activity against human cell... 

In individual plants of Centaurea montana originating from different restricted areas in the French southern Alps, in addition to practically pure (9-glycosidic patterns, these molecules are arranged in many diverse assemblages of simple or complex C-glycoside derivatives — along with (9-glycosides in some. This results in an extraordinary diversity of flavonoid patterns of this species, which comprise from five to more than 20 compounds. 

At the outset of this study we chose to examine Centaurea maculosa L. (spotted knapweed), a species of Immense economic importance in the northwestern United States. This plant threatens forage production of millions of acres of rangeland in this region... 

Naturally Occurring Thiophens.—Re-investigation of the polar fractions of the aerial parts of Centaurea ruthenica gave, amongst twenty new compounds, 5-hydroxymethyl-2-(3-hydroxypropynyl)thiophen. ° The investigation of two further Helichrysum species led to the isolation of three new unusual thiophen derivatives (137)—(139). New acetylenic thiophen derivatives such as (140) have been isolated from Cullumia setosa. ... 

There are many notable examples of species introduced into alien ecosystems where natural predators did not exist. The water hyacinth (Eichhomia crassipes) in Florida, kudzu (Pueraria thunbergiana) in the southeastern United States, the star thistle (Centaurea calcitrapa) in California, and purple loosestrife (Lythrum salicaria) in the northeastern United States are examples of these. In many of these instances, the alien plants spread widely with little to stop them. Native plants with their natural enemies were at a disadvantage compared to the introduced aliens. 

Janackovic, R, V. Tesevic, P.D. Marin, et al. 2008. Brine shrimp lethality bioassay of selected Centaurea L. species (Asteraceae). Arch. Biol. Sci. 60(4) 681-685. 

Allelopathic processes via (-)-catechia (2S,3R-enantiomer) (Fig. 1) have been invoked to partially explain the snccess of Centaurea maculosa (spotted knapweed) in North America [46-48], Throngh bioassays, root exnded (-)-catechin was identified as the pntative allelochemical of spotted knapweed, and mnltiple stndies have examined varions facets of the role of this compound as an allelochemical [46-51 ]. The 2R,3S-(+)-catechin enantiomer is also produced by the plant, but was reported essentially to be nonphytotoxic. This work supported the novel weapons hypothesis, which states that the success of some exotic invasive plant species may be due to the production of allelochemicals that native species have never encountered and, thus, to which they have not evolved defenses [52]. 

In one of the original papers of the Vivanco laboratory [46], the mechanism of action of (-)-catechin was linked to induction of ROS. This is debatable since catechins are well known antioxidants (e.g. [62]). In fact, more than 1500 papers mention catechin as an antioxidant (SciFinder search, as of February 2008). Finally, Qin et al. [63] found no evidence of root exudate-mediated allelopathy with Centaurea solstitialis, but the authors apparently did not determine if this species produces ( )-catechin. If it were to produce similar amounts of ( )-catechin as C. maculosa, it would be strong evidence of the lack of allelo-pathic influence of these compounds. 

Qin, B. et al. (2007) No evidence for root-mediated allelopathy in Centaurea solstitialis, a species in a commonly allelopathic genus. Biolog. Invasions 9, 897-907... 

The entire series was isolated from the same composite species, Centaurea ruthenica Lam. (Bohlmann Postulka, Ruhnke, 1958 (Bohlmann, Sucrow, Jastrow and Koch, 196I). The sequence is highly suggestive of biological epoxi-dation followed by hydration or hydrochlorination of the epoxide. 

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