NOPR Community:

NMR studies of some 4-hydroxy-2-methylacetophenone thiosemicarbazones in solutions

2015-12-01T00:00:00Z

Title: NMR studies of some 4-hydroxy-2-methylacetophenone thiosemicarbazones in solutions Authors: Mamedov, I G; Bayramov, M R; Salamova, A E; Maharramov, A M Abstract: Molecular dynamics of (E)-4-hydroxy-2-methylacetophenone thiosemicarbazone and (E,E)-3-(5-bromo-2-hydroxyphenyl)-1-(4-hydroxy-2-methylphenyl)prop-2-en-1-one thiosemicarbazone have been investigated in solution using NMR. The results confirm the presence of conformational transitions in the investigated molecules. The rotational barrier energy for the conformational transitions has been calculated. Page(s): 1518-1527

The hindered internal rotations in isomerism forms of a particular phosphorane involving 2-chloro-phenothiazine: Dynamic ¹H NMR study

2015-12-01T00:00:00Z

Title: The hindered internal rotations in isomerism forms of a particular phosphorane involving 2-chloro-phenothiazine: Dynamic ¹H NMR study Authors: Mofarrah, Eideh; Habibi-Khorassani, Sayyed Mostafa; Maghsoodlou, Malek Taher; Shahraki, Mehdi Abstract: The hindered internal rotations around the partial carbon-carbon double bond, nitrogen-carbon and carbon-carbon single bonds within the 2-(2-chloro-phenothiazine-l-yl)-3-(triphenylphosphoranylidene) butandioate has been experimentally studied by the dynamic ¹H NMR spectroscopic in variable temperatures. The activation (∆H^‡, ∆S^‡, ∆G^‡) and kinetic (k_c, E_a) parameters have been calculated in a series of separate dynamic ¹H NMR spectra. The energy of activation parameters obtained from classic, Eyring and Arrhenius methods have also been compared for carbon-carbon double bond in this compound. The results from Eyring and Arrhenius plots are in good agreement, but are different from the classical method. For nitrogen-carbon bond and carbon-carbon single bond, activation parameters have been calculated based on the coalescence temperature (classic method). In this study, due to spatial form of the compound, the value of N ∆H^‡ of the restricted rotation around the partial carbon-carbon double bond and nitrogen-carbon are in close agreement. Page(s): 1528-1534

Inhibition of photosynthetic electron transport by 6-hydroxynaphthalene-2-carboxanilides

2015-12-01T00:00:00Z

Title: Inhibition of photosynthetic electron transport by 6-hydroxynaphthalene-2-carboxanilides Authors: Pesko, Matus; Kos, Jiri; Kralova, Katarina; Jampilek, Josef Abstract: Inhibition of photosynthetic electron transport (PET) in spinach chloroplasts by 6-hydroxynaphthalene-2-carboxanilides has been investigated. The PET inhibiting activity of the studied compounds depends on compound lipophilicity, on the position of substituents on the anilide moiety as well as on electron-accepting and electron-donating properties of these substituents. The most active PET inhibitors are m-substituted derivatives; the lowest activity is shown by the o-substituted ones. The most potent PET inhibitor is 6-hydroxy-N-(3-trifluoromethylphenyl)naphthalene-2-carboxamide (IC₅₀ = 10.8 μmol/L). Study of chlorophyll a fluorescence in the suspension of spinach chloroplasts in the presence of studied compounds confirms their site of action in PS II, and it can be assumed that the inhibitory site of action of the studied compounds is situated on the acceptor side of PS II at Q_B site. Page(s): 1511-1517

Isolation and quantification of six cardiac glycosides from the seeds of Thevetia peruviana provide a basis for toxological survey

2015-12-01T00:00:00Z

Title: Isolation and quantification of six cardiac glycosides from the seeds of Thevetia peruviana provide a basis for toxological survey Authors: Kohls, Sarah; Scholz-Böttcher, Barbara M; Teske, Jörg; Rullkötter, Jürgen Abstract: In order to support toxicological assessment of poisoning from the ingestion of plant material containing thevetia cardiac glycosides, a new isolation method has been developed for thevetia glycosides from the seeds of the Yellow Oleander [Thevetia peruviana (Pers.) K. Shum, Apocynaceae] with yellow and orange flowers, respectively, using accelerated solvent extraction. The relative proportions of four cardiac-active thevetia glycosides (thevetin A and B, acetylthevetin A and B) and two additional, cardiac-inactive thevetia glycosides (thevetin C and acetylthevetin C) in the extract were determined using an LC-ESI⁺-MS/MS technique. Absolute quantification of thevetin B was achieved using a pure standard of this compound isolated by preparative high performance liquid chromatography. Page(s): 1502-1510

NOPR Community:

NMR studies of some 4-hydroxy-2-methylacetophenone thiosemicarbazones in solutions

The hindered internal rotations in isomerism forms of a particular phosphorane involving 2-chloro-phenothiazine: Dynamic 1H NMR study

Inhibition of photosynthetic electron transport by 6-hydroxynaphthalene-2-carboxanilides

Isolation and quantification of six cardiac glycosides from the seeds of Thevetia peruviana provide a basis for toxological survey

The hindered internal rotations in isomerism forms of a particular phosphorane involving 2-chloro-phenothiazine: Dynamic ¹H NMR study