Secondary metabolites from Centaurea grisebachii ssp. grisebachii

The aerial parts of Centaurea grisebachii ssp. grisebachii, a Greek endemic species belonging to section Acrolophus (Cass.) DC., were investigated for the occurrence of sesquiterpene lactones. The eudesmanolide, 4-epi-malacitenolide was the major compound. In addition to the sesquiterpene lactones, five flavonoid aglycons, two lignans, one nor-isoprenoid and one sterol were found.     

Guaianolides from Centaurea canariensis

The aerial parts of Centaurea canariensis afforded four new guaianolides, all closely related to dehydrocostus lactone, and a derivative of costic acid. The structures were elucidated by spectroscopic methods.     

Guaianolides and lignans from Centaurea solstitialis subs Schouwii

Aerial parts of Centaurea solstitialis subs schouwii afforded the guaianolides cynaropicrin and aguerin B and the lignans arctigenin and matairesinol. The structure of a third guaianolide previously found also in Centaurea behen was revised.     

Essential oil composition of two endemic Centaurea species from Turkey, Centaurea mucronifera and Centaurea chrysantha, collected in the same habitat

The essential oils of two endemic Centaurea species from Turkey, C. mucronifera and C. chrysantha, collected in the same habitat, have been studied. The main compounds of the former were germacrene D (29.3%), β-eudesmol (17.4%) and β-caryophyllene (7.3%), while in the latter germacrene D (27.4%), caryophyllene oxide (9.5%) and bicyclogermacrene (5.4%) were detected among its major constituents. The two species produced many similar compounds in their essential oils that could be justified by the similar ecological conditions of their habitat, but also many differences were found that could confirm their taxonomic separation.     

Chemical constituents from Nuxia congesta and their chemotaxonomic significance

A phytochemical investigation of the aerial parts of Nuxia congesta led to the isolation and identification of fifteen compounds, including a new flavonoid, nuxiacin (5-hydroxy-3,8-dimethoxy flavone-7-O-β-D-glycopyranoside) (1). The structure of the new compound was determined using various spectroscopic data including 1D and 2D NMR and mass spectroscopy. All compounds were isolated from N. congesta for the first time. The chemotaxonomic significance of the isolated compounds in the family Stilbaceae and order Lamiales are discussed herein.     

Essential oils from the aerial parts of Centaurea cuneifolia Sibth. & Sm. and C. euxina Velen., two species growing wild in Bulgaria

The volatile constituents of the aerial parts of Centaurea cuneifolia Sibth. & Sm. and Centaurea euxina Velen. from Bulgaria were extracted by hydrodistillation and were analyzed. The main components in C. cuneifolia were β-eudesmol (26.5%) and hexadecanoic acid (17.6%). The main components in C. euxina were hexadecanoic acid (20.3%), spathulenol (10.8%) and caryophyllene oxide (6.2%). The chemotaxonomic significances with respect to other previously studied species of the same sections (Achrolopus and Phalolepis, respectively) are discussed.     

Secondary metabolites from Centaurea ensiformis P.H. Davis

Centaurea ensiformis P.H. Davis was evaluated for its secondary metabolites. 20 different compounds have been isolated and identified; four phenolic compounds, one aminoacid, two acetophenone glycosides, three phenylpropanoide glycosides, one coumarin glucoside, four flavon glycosides, two neolignan glycosides, two megastigmane glycosides and schikimic acid methyl ester.     

Evaluation of the presence of aspartic proteases from Centaurea calcitrapa during seed germination

Aspartic proteinases are present in a variety of organisms including plants. Common features of aspartic proteases include an active site cleft that contains two catalytic aspartic residues, acid pH optima for enzymatic activity, inhibition by pepstatin A. Plant aspartic proteinases occur in seeds and may be involved in the processing of storage proteins. Many of them have been purified and characterized. The presence of aspartic proteases in seeds of Centaurea calcitrapa during germination was investigated by measuring the activity on enzyme extracts. The aspartic proteases are present mainly in the beginning of seed germination suggesting that they could initiate the degradation of protein reserves in germinating seeds.

These proteases were purified by salt precipitation followed by anion-exchange chromatography. Purified aspartic proteases have an optimal pH between 3.5 and 4.5, using FTC-hemoglobin as substrate and an optimal temperature at 52 °C. The ability of seed extracts for milk clotting was tested and the clotting time that was achieved is in the same range found for flower extracts appropriated for special cheeses in which weak clotting agents are required.     

Antinociceptive activity and chemical composition of constituents from Caragana microphylla seeds

This investigation was undertaken to ascertain the antinociceptive activity of Caragana microphylla Lam. seeds and isolate and characterize the constituents. Antinociceptive activity was screened using acetic acid-induced abdominal constriction in ICR mice. The 75% ethanol extract and some fractions showed analgesic activity, but the antinociceptive activity of chloroform fraction was the strongest and was more productive than other fractions. Seven compounds were isolated from it and identified as: (1) machaeric acid, (2) beta-sitosterol, (3) stigmasterol, (4) pratol, (5) dehydrocavidine, (6) formononetin and (7) sucrose. Caragana microphylla Lam. seeds showed analgesic activity, with the chloroform fraction showing the strongest analgesic activity among the fractions.     

Chemical constituents from Aristolochia tagala and their chemotaxonomic significance

Fifteen compounds were obtained from the extract of the whole herbs of Aristolochia tagala, which were divided into eight aristolactam-type alkaloids (1–6, 14 and 15) and seven aristolochic acid derivatives (7–13). Their structures were identified as aristolactam BII, aristolactam II, sauristolactam, aristolactam I, 7-methoxyaristolactam IV, aristolactam AII, 3-hydroxy-4-methoxy-10-nitrophenanthrene-1-carboxylic acid methyl ester, ariskanin A, ariskanin D, ariskanin E, aristolochic acid C, ariskanin C, ariskanin B, aristolactam-N-β-D-glucoside and cepharanone A N-β-D-glucoside by comparison of their spectral data with those reported previously in the literature. The chemotaxonomic relationships between A. tagala and other species of genus Aristolochia were also discussed. As a result, the isolated compounds closely matched the ones obtained in other species of the genus.     

Chemical constituents of flowers from Geoffroea spinosa Jacq. (Leguminosae), a plant species visited by bees

Phytochemical investigation of flowers from Geoffroea spinosa via ultra-performance liquid chromatography coupled with diode array and quadrupole time-of-flight mass spectrometry (UPLC-DAD-TOF-MS/MS) resulted in the characterization of fourteen compounds: six flavonoids, three hydroxycinnamic acid derivatives, and five hydroxycinnamic acid amide derivatives. This is the first report on the identification of hydroxycinnamic acid amide derivatives from the genus Geoffroea. The chemotaxonomic significance of the identified compounds is discussed.