Bisabolone derivatives and sesquiterpene lactones from centaurea species

Centaurea polyacantha and C. maroccana: the chemical composition of the aerial parts essential oils of these Centaurea species (Asteraceae) collected in Morocco

In the present study, the chemical composition of the essential oil from the aerial parts of two Centaurea species not previously investigated, C. polyacantha Willd. (sect. Seridia, Asteraceae) and C. maroccana Ball. (sect. Calcitrapa, Asteraceae), collected in Morocco, was evaluated by GC-MS. The main components of the essential oil of the first one were limonene (18.2%), β-bisabolene (11.5%), (Z)-β-farnesene (8.6%), and spathulenol (8.3%), whereas the C. maroccana essential oil, practically devoid of terpenoids, was shown to be rich in some unusual Centaurea metabolites: 1-hexadecanol (24.9%), docosane (23.7%), and 1-octadecanol (19.5%). Furthermore, a complete literature review on the composition of the essential oils of all the other taxa of Centaurea, belonging to sections Seridia and Calcitrapa, studied so far, was performed.

The introduction of an invasive weed was not followed by the introduction of ethnobotanical knowledge: a review on the ethnobotany of Centaurea solstitialis L. (Asteraceae)

Invasive plants are known for their impacts to ecosystems and societies, but their potential cultural use tend to be unexplored. One important mechanism of plant invasion is the use of "allelochemicals" or "novel weapons": chemical defenses which are new to their invaded habitats and that confer them competitive advantages. However, these chemicals are precisely what confers them ethnobotanical and medicinal properties. We reviewed the literature assessing the biogeography of the cultural uses of the model invasive plant yellow-starthistle (Centaurea solstitialis L.; Asteraceae), and assessed the extent to which the introduction of a weed native to Eurasia into several non-native world regions was paralleled by the spread of cultural uses from its native range. We found that the species was rich in pharmaceutically active compounds and that the species had been traditionally used for medicinal purposes, as raw material, and as food. However, ethnobotanical uses were reported almost exclusively in its native range, with no uses described for the non-native range, apart from honey production in California, Argentina, and Australia. Our study exemplifies how, when plant introductions are not paralleled synchronously by significant human migrations, cultural adoption can be extremely slow, even within the native range of the species. Invasive species can provide real-time insights into the cultural processes by which humans learn to use plants. This case study highlights how biological invasions and cultural expansions can be subjected to different constraints.

Phytotherapy Perspectives for Treating Fungal Infections, Migraine, Sebhorreic Dermatitis and Hyperpigmentations with the Plants of the Centaureinae Subtribe (Asteraceae)

Sesquiterpene lactones, coumarins, phytoecdysones and phenolic compounds are characteristic of the species from the subtribe Centaureinae (Asteraceae). Many of the compounds isolated from plants of the Centaureinae subtribe have strong pharmacological properties. It may be suggested that these compounds' chemical structure might be an indicator of these pharmacological properties. The aim of the study was to describe recent studies in the field of phytotherapy, focusing on compounds isolated from chosen plants of Centaureinae and the possibilities of using them to treat antifungal infections, inhibit serotonin and ease symptoms of seborrhea dermatitis and hyperpigmentation. The results of these biological studies have shown that in the future, extracts from the above-mentioned plant material may be used as active substances in new safe and effective drugs.

Sesquiterpenoids in subtribe Centaureinae (Cass.) Dumort (tribe Cardueae, Asteraceae): distribution, (13)C NMR spectral data and biological properties

Asteraceae Bercht. & J. Presl is one of the biggest and most economically important plant families. The taxonomy and phylogeny of Asteraceae is rather complex and according to the latest and most reliable taxonomic classification of Panero & Funk, based on the analysis of nine chloroplast regions, the family is divided into 12 subfamilies and 35 tribes. One of the largest tribes of Asteraceae is Cardueae Cass. with four subtribes (Carlininae, Echinopinae, Carduinae and Centaureinae) and more than 2500 species. Susanna & Garcia-Jacas have organized the genera of Centaureinae (about 800 species) into seven informal groups, which recent molecular studies have confirmed: 1. Basal genera; 2. Volutaria group; 3. Rhaponticum group; 4. Serratula group; 5. Carthamus group; 6. Crocodylium group; 7. Centaurea group. This review summarizes reports on sesquiterpenoids from the Centaureinae subtribe of the Asteraceae family, as well as the (13)C NMR spectral data described in the literature. It further reviews studies concerning the biological activities of these metabolites. For this work, literature data on sesquiterpenes from the Centaureinae subtribe were retrieved with the help of the SciFinder database and other similar data banks. All entries from 1958 until the end of 2011 were considered. This review is addressed to scientists working in the metabolomics field such as chemists, botanists, etc., the spectroscopic data reported make this work a good tool for structural elucidation, the biological section gives useful information to those who wish to study the structure activity relationships.

Secondary metabolites from the aerial parts of Centaurea pannonica (Heuff.) Simonk. from Serbia and their chemotaxonomic importance

The non polar extract of Centaurea pannonica (Heuff.) Simonk., growing wild in Serbia, was studied and twenty-five compounds including 14 sesquiterpene lactones, 7 flavonoids, 3 lignans and 1 phenylpropanoid glycoside were isolated. All compounds were isolated for the first time from this species. Among them, one germacranolide 2α-hydroxy, 8-dehydroxy 15-O-methacrylate salonitenolide (1) and two guaianolides 2α,8α-dihydroxy-dehydrocostus lactone (2) and pannonin (3) are new natural compounds. The structures of the compounds were established on the basis of spectroscopic analyses (UV, IR, HREIMS and 1D & 2D NMR). The chemical profile of C. pannonica, which belongs to the "Centaurea jacea" group, was compared to previously studied taxa of the same group and used to assess the phylogenetic relationships in the group.

Flavonoids in subtribe Centaureinae (Cass.) Dumort. (tribe Cardueae, Asteraceae): distribution and (13)C-NMR spectral data

This review reports the occurrence of flavonoids in subtribe Centaureinae of Asteraceae family. It extensively covers the literature up to 2010 and collects all available (13)C-NMR data.

Bioactivity-guided isolation of antiproliferative compounds from Centaurea jacea L

Bioassay-guided fractionation of the chloroform extract of Centaurea jacea L. afforded the isolation of cirsiliol, apigenin, hispidulin, eupatorin, isokaempferide, axillarin, centaureidin, 6-methoxykaempferol 3-methyl ether, trachelogenin, cnicin, 4'-acetylcnicin and three aliphatic glucose diesters, including the new natural product 1β-isobutanoyl-2-angeloyl-glucose. The structures of the compounds were established on the basis of spectroscopic analyses (UV, MS and NMR). All compounds were isolated for the first time from this species. The compounds were evaluated for their tumour cell growth inhibitory activities on HeLa, MCF-7 and A431 cells. Different types of secondary metabolites (flavonoids, sesquiterpenes) were found to be responsible for the antitumour effects of the extracts; the highest activity was exerted by centaureidin, in addition to moderately active compounds (cirsiliol, isokaempferide, apigenin, hispidulin, cnicin and 4'-acetylcnicin).

Phytotoxic polyacetylenes from roots of Russian knapweed (Acroptilon repens (L.) DC.)

There are several factors thought to assist invasive weeds in colonization of ecosystems. One of these factors is allelopathy, the negative effect of chemicals produced by one plant on neighboring plants, frequently mediated through root exudates and other plant leachates. Acroptilon repens (Asteraceae) is one of the most invasive and ecologically threatening weed species in western North America. A bioassay-guided fractionation of the root extracts of this plant led to the isolation of five polyacetylenic compounds, of which one [5'-methoxy-1'-(5-prop-1-yn-1-yl-2-thienyl)-hexa-2',4'-diyin-6'-yl acetate] was hitherto unknown. The structures of these compounds were elucidated on the basis of spectroscopic analysis (IR, ESIMS, (1)H, (13)C NMR and 2D NMR). All of the compounds obtained, except 1-chloro-4-(5-penta-1,3-diyn-1-yl-2-thienyl)but-3-yn-2-ol, showed phytotoxic activity against Arabidopsis thaliana seedlings. The presence of 4'-chloro-1'-(5-penta-1,3-diyn-1-yl-2-thienyl)-but-2'-yn-3'-ol was detected in the root exudates of aeroponically grown A. repens plants. None of the polyacetylenes isolated in this study were found in Colorado soils collected between September 2006 and July 2007 in an A. repens colonized site. However, polyacetylene 5 in A. repens infested soil from Washington was found in June, 2007. Contrary to our previous report, the compound 7,8-benzoflavone (6) was not detected in root exudates, nor was it encountered in extracts of roots, aerial parts or infested soil. Since we could not repeat this work, the original report has been retracted [Stermitz, F.R., Bais, H.P., Foderaro, T.A., Vivanco, J.M., 2003. 7,8-Benzoflavone: a phytotoxin from root exudates of invasive Russian knapweed [A retraction]. Phytochemistry 64, 493-497.].

Quantitative analysis of sesquiterpene lactone cnicin in seven Centaurea species wild-growing in Serbia and Montenegro using 1H-NMR spectroscopy

1H-NMR spectroscopy was applied for the quantitative analysis of cnicin, a bioactive germacranolide type sesquiterpene lactone, in the aerial parts of seven wild-growing Centaurea species collected in Serbia and Montenegro. The analysis was performed by comparison of the integral of the one-proton signal of cnicin (H-13, ? 5.75) with that of the two-proton singlet ( ? 6.98) of 2,6-bis(1,1-dimethylethyl)-4-methylphenol (BHT), used as the internal standard. Cnicin, within the concentration range 1.06-6.12 mg/g, calculated per weight of the fresh plant material was detected in six species, the exception being C. salonitana. This method allows the rapid and simple quantification of cnicin without any pre-purification step.

Sesquiterpene lactones from Centaurea thessala and Centaurea attica. Antifungal activity

The aerial parts of Centaurea thessala ssp. drakiensis and C. attica ssp. attica afforded, in addition to several known sesquiterpene lactones, two new eudesmanolides, 4-epi-sonchucarpolide and its 8-(3-hydroxy-4-acetoxy-2-methylene-butanoyloxy) derivative and one new eudesmane derivative, named atticin. The in vitro antifungal activity of most compounds was tested against nine fungal species, using the micro-dilution method. All the compounds tested showed great antifungal activity.

Search for chlorinated sesquiterpene lactones in the neurotoxic thistle Centaurea solstitialis by liquid chromatography-mass spectrometry, and model studies on their possible artifactual formation

An HPLC method has been developed for the analysis of sesquiterpene lactones of the neurotoxic plant Centaurea solstitialis (Asteraceae). The presence of sesquiterpene lactone chlorohydrins in extracts was investigated by means of liquid chromatography-thermospray mass spectrometry. In contrast to earlier reports of a series of mono- and dichlorohydrins from this plant, traces only of two monochlorohydrins could be detected in lipophilic extracts. Model studies carried out with extracts and with the genuine sesquiterpene diepoxide repin and its epimer subluteolide showed that (i) monochlorohydrins can be formed in CHCl3 under usual laboratory conditions; (ii) the epoxide moiety at C-4 of the sesquiterpenes is extremely labile, reacting immediately and quantitatively with traces of HCl to the corresponding monohydrins; (iii) epoxide ring opening at the acyl side chain occurs only at higher HCl concentrations. Confirmation of the peak identity was obtained by the isotope ratio of chlorinated compounds and comparison with authentic samples. The structures of the mono- and dichlorohydrins were established by NMR spectroscopy.