Search results for " nuclear magnetic resonance spectroscopy"
showing 10 items of 173 documents
Cytotoxic geranylflavonoids from Bonannia graeca
2011
The analysis of the aerial parts of Bonannia graeca led to the isolation and characterization of two new polar geranylated flavonoids (6 and 7). The structure elucidation was performed by extensive spectroscopic methods (1D and 2D NMR) and comparison with literature data. All natural flavonoids isolated from B. graeca (1–7) and some synthetic derivatives (8–11) were tested for cytotoxic activity against four human tumor cell lines. Preliminary structure-activity relationship correlations are discussed.
Cytotoxic neo-clerodane diterpenes from Stachys aegyptiaca
2018
Abstract Two new E/Z neo-clerodane diterpene isomers, trivially named stachaegyptin D (1) and E (2), together with known compounds, stachysolon monoacetate (3) and stachysolon diacetate (4), were isolated from an organic-solvent extract of the medicinal herb Stachys aegyptiaca. Structures were elucidated by a combination of spectroscopic methods, including HREIMS, 1H, 13C, DEPT, and 2D NMR analysis, as well as, first time X-ray analysis for stachysolone (3). All isolated metabolites showed some activity against the human hepatocellular cell line, HepG2. Compound 4 was the most active with an IC50 of 59.5 μM.
Antileukemic ancistrobenomine B and related 5,1′-coupled naphthylisoquinoline alkaloids from the Chinese liana Ancistrocladus tectorius
2017
A striking feature of the metabolite pattern of the Southeast Asian liana Ancistrocladus tectorius (Ancistrocladaceae) is the predominance of 5,1′-coupled naphthylisoquinoline alkaloids. About 20 alkaloids of this coupling type have so far been discovered in this plant species. Here, we report on the isolation of four new 5,1′-linked naphthylisoquinolines from the twigs and stems of A. tectorius. Two of them, the ancistrobenomines B (5) and C (6), belong to the very rare group of alkaloids with a fully dehydrogenated isoquinoline portion. Likewise unusual for naphthylisoquinoline alkaloids is the presence of a hydroxymethylene group at C-3. Within the large class of meanwhile ca. 180 such n…
Antiproliferative activity against leukemia cells of sesquiterpene lactones from the Turkish endemic plant Centaurea drabifolia subsp. detonsa
2017
The apolar organic extract obtained from aerial parts of Centaurea drabifolia Sibth. & Sm. subsp. detonsa (Bornm.) Wagenitz, growing wild in Turkey, was investigated for the first time for its secondary metabolite composition. Seven sesquiterpene lactones belonging to the guaiane class (1-7), including the new compound 4, along with a fatty acid lactone derivative (8), were isolated. The structures of these compounds were established by spectroscopic analysis, including 2D NMR spectroscopic techniques, with the stereostructure of the new guaiane 4 determined with the help of MTPA derivatization. Cytotoxic activities of compounds 1-7 were evaluated against two cancer cell lines, namely acute…
Cytotoxic glycosides from the roots of Weigela x “Bristol Ruby”
2019
International audience; Seven oleanane-type glycosides were extracted and isolated by various chromatographic methods from the roots of Weigela x "Bristol Ruby" (1-7), six previously undescribed (1-6) and a known one (7). Their structures were assigned by spectroscopic analysis mainly 2D NMR and mass spectrometry (ESIMS). Selected triterpenoid glycosides (1-3, 6, 7) displayed a good cytotoxic activity against a mouse colon cancer cell line CT26.
Secondary metabolites of the lichen-associated fungus Apiospora montagnei
2017
Abstract The endolichenic fungus Apiospora montagnei isolated from the lichen Cladonia sp. was cultured on solid rice medium, yielding the new diterpenoid libertellenone L (1), the new pyridine alkaloid, 23-O-acetyl-N-hydroxyapiosporamide (2) and the new xanthone derivative 8-hydroxy-3-hydroxymethyl-9-oxo-9H-xanthene-1-carboxylic acid methyl ether (3) together with 19 known compounds (4–22). The structures of the new compounds were elucidated by 1D and 2D NMR spectra as well as by HRESIMS data. The absolute configuration of the new 6,7-seco-libertellenone derivative 1 was determined by single-crystal X-ray diffraction. Four additional known compounds 23–26 were isolated when NaCl or NH4Cl w…
Cytotoxic eudesmane sesquiterpenes from Crepis sancta
2019
Abstract Chemical exploration of Crepis sancta (L.) Bornm. (Asteraceae) aerial parts afforded two new eudesmane sesquiterpenes (1 and 2) together with three known congeners (3-5) and two known methylated flavonoids (6 and 7). Structure elucidation of the new compounds was unambiguously performed based on HRESIMS, 1D and 2D NMR spectroscopic analyses. All isolated compounds were subjected to an in vitro cytotoxicity assay against mouse lymphoma (L5178Y) cells, revealing moderate activities with IC50 ranging from 7.9 to 21.0 μM.
1H 2D-NMR characterization of Ni(II)-substituted azurin fromPseudomonas aeruginosa
1993
1 H two-dimemional NMR experiments on nickel(II)-substituted azurin have been succesfully applied. Despite the short relaxation time of the hyperfine-shifted resonances, the combined use of NOESY and COSY spectra allowed the alignment of 15 resonances belonging to the metal-coordinated residues Gly-45, His-46, His-117 and Met-121. Even in the case of the two broad and furthest downfield resonances, the NOESY spectra were successful in assigning these signals to the β-CH 2 protons of Cys-112. The protons of the non-coordinated residues Met-13, Phe-15 and Trp-48 were also assigned via NOESY, COSY and TOCSY experiments
Three New Medicagenic Acid Saponins from Polygala micranthaGuill. & Perr.
2011
Three new medicagenic acid saponins, micranthosides A–C (1–3), were isolated from the roots of Polygala micranthaGuill. & Perr., along with six known presenegenin saponins. Their structures were elucidated on the basis of extensive 1D- and 2D-NMR experiments (1H, 13C, DEPT, COSY, TOCSY, NOESY, HSQC, and HMBC) and mass spectrometry as 3-O-β-D-glucopyranosylmedicagenic acid 28-[O-β-D-galactopyranosyl-(14)-O-β-D-xylopyranosyl-(14)-O-α-L-rhamnopyranosyl-(12)-β-D-fucopyranosyl] ester (1), 3-O-β-D-glucopyranosylmedicagenic acid 28-[O-6-O-acetyl-β-D-galactopyranosyl-(14)-O-β-D-xylopyranosyl-(14)-O-α-L-rhamnopyranosyl-(12)-β-D-fucopyranosyl] ester (2), and 3-O-{O-β-D-glucopyranosyl-(13)-O-[β-D-gluc…
Hydroquinone derivatives from the marine-derived fungus Gliomastix sp.
2017
Eight new hydroquinone derivatives, gliomastins A–D (1–4), 9-O-methylgliomastin C (5), acremonin A 1-O-β-D-glucopyranoside (6), gliomastin E 1-O-β-D-glucopyranoside (7), and 6′-O-acetyl-isohomoarbutin (8), together with seven known analogues were isolated from the marine-derived fungus Gliomastix sp. Their structures were elucidated by extensive spectroscopic analysis including 1D and 2D NMR measurements aided by DFT NMR calculations as well as MS data. TDDFT-ECD and OR calculations were performed to determine the absolute configurations of 1 and the aglycones of 6 and 7. Compound 1 features a novel skeleton, biogenetically derived from a Diels–Alder reaction between derivatives of 11 and 1…