Ligia R. Gomes

Ethnopharmacological notes about ancient uses of medicinal plants in Trás-os-Montes (northern of Portugal)

AIM OF THE STUDY In order to preserve the ancestral knowledge, an ethnopharmacological study has been carried out in two councils belonging to Trás-os-Montes region a small area located in the northern of Portugal. In that area, medicinal plants, most of the species wild, are still in use among farmers, shepherds and other people who live far from villages and built-up areas. MATERIALS AND METHODS Among the 46 people that were interviewed (mean age of 66 years old), 88 species belonging to 42 families of vascular plants were identified for treatment of various human ailments. An ethnopharmacological report is made consisting of species names, vernacular names, popular uses of the plants and their pharmacological properties. RESULTS AND CONCLUSION The most dominant family is Lamiaceae (18%) and the most frequently part of the plant used for the treatment of diseases are leaves (37.9%). The largest number of taxa is used to treat gastrointestinal disorders (73.9%).

High-Accuracy Vapor Pressure Data of the Extended [CnC1im][Ntf2] Ionic Liquid Series: Trend Changes and Structural Shifts

For the first time, two distinct trends are clearly evidenced for the enthalpies and entropies of vaporization along the [Cnmim][Ntf2] ILs series. The trend shifts observed for Δ(l)(g)H(m)(o) and Δ(l)(g)S(m)(o), which occur at [C6mim][Ntf2], are related to structural modifications. The thermodynamic results reported in the present article constitute the first quantitative experimental evidence of the structural percolation phenomenon and make a significant contribution to better understanding of the relationship among cohesive energies, volatilities, and liquid structures of ionic liquids. A new Knudsen effusion apparatus, combined with a quartz crystal microbalance, was used for the high-accuracy volatility study of the 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide series ([Cnmim][Ntf2], where n = 2, 3, 4, 5, 6, 7, 8, 10, 12). Vapor pressures in the (450–500) K temperature range were measured, and the molar standard enthalpies, entropies, and Gibbs energies of vaporization were derived. The thermodynamic parameters of vaporization were reported, along with molecular dynamic simulations of the liquid phase structure, allowing the establishment of a link between the thermodynamic properties and the percolation phenomenon in ILs.

Design, synthesis and biological evaluation of (E)-2-(2-arylhydrazinyl)quinoxalines, a promising and potent new class of anticancer agents

A series of forty-seven quinoxaline derivatives, 2-(XYZC6H2CHN-NH)-quinoxalines, 1, have been synthesized and evaluated for their activity against four cancer cell lines: potent cytotoxicities were found (IC50 ranging from 0.316 to 15.749 μM). The structure-activity relationship (SAR) analysis indicated that the number, the positions and the type of substituents attached to the aromatic ring are critical for biological activity. The activities do not depend on the electronic effects of the substituents nor on the lypophilicities of the molecules. A common feature of active compounds is an ortho-hydroxy group in the phenyl ring. A potential role of these ortho-hydroxy derivatives is as N,N,O-tridentate ligands complexing with a vital metal, such as iron, and thereby preventing proliferation of cells. The most active compound was (1: X,Y=2,3-(OH)2, Z=H), which displayed a potent cytotoxicity comparable to that of the reference drug doxorubicin.

Structural and thermodynamic characterization of polyphenylbenzenes

The thermodynamic and structural study of a series of polyphenylbenzenes, from benzene, n(Ph) = 0, to hexaphenylbenzene, n(Ph) = 6, is presented. The available literature data for this group of compounds was extended by the determination of the relevant thermodynamic properties for 1,2,4-triphenylbenzene, 1,2,4,5-tetraphenylbenzene, and hexaphenylbenzene, as well as structural determination by X-ray crystallography for some of the studied compounds. Gas phase energetics in this class of compounds was analyzed from the derived standard molar enthalpies of formation in the gaseous phase. The torsional profiles relative to the phenyl-phenyl hindered rotations in some selected polyphenylbenzenes, as well as the gas phase structures and energetics, were derived from quantum chemical calculations. In the ideal gas phase, a significant enthalpic destabilization was observed in hexaphenylbenzene relative to the other polyphenylbenzenes, due to steric crowding between the six phenyl substituents. A relatively low enthalpy of sublimation was observed for hexaphenylbenzene, in agreement with the decreased surface area able to establish intermolecular interactions. The apparently anomalous low entropy of sublimation observed for hexaphenylbenzene is explained by its high molecular symmetry and the six highly hindered phenyl internal rotations. For the series of polyphenylbenzenes considered, it was shown that the differentiation in the entropy of sublimation can be chiefly ascribed to the torsional freedom of the phenyl substituents in the gas phase and the entropy terms related with molecular symmetry.

Experimental Support for the Role of Dispersion Forces in Aromatic Interactions

Herein a core scaffold of 1-phenylnaphthalenes and 1,8-diphenylnaphthalenes with different substituents on the phenyl rings was used to study substituent effects on parallel-displaced aromatic π⋅⋅⋅π interactions. The energetics of the interaction was evaluated in gas phase based on the standard molar enthalpies of formation, at T=298.15 K, for the compounds studied; these values were derived from the combination of the results obtained by combustion calorimetry and Knudsen/Quartz crystal effusion. A homodesmotic gas-phase reaction scheme was used to quantify and compare the intramolecular interaction enthalpies in various substituted 1,8-diphenylnaphthalenes. The application of this methodology allowed a direct evaluation of aromatic interactions, and showed that substituent effects on the interaction enthalpy cannot be rationalized solely on classical electrostatic grounds, because no correlation with the σ(meta) or σ(para) Hammett constants was observed. Moreover, the results obtained indicate that aromatic π⋅⋅⋅π interactions are significantly enhanced by substitution, in a way that correlates with the ability of the interacting aryl rings to establish dispersive interactions. A combined experimental and computational approach for calculation of the true aromatic π⋅⋅⋅π interaction energies in these systems, free of secondary effects, was employed, and corroborates the rationale derived from the experimental results. These findings clearly emphasize the role of dispersion and dilute the importance of electrostatic forces on this type of interactions.

Nickel(II) complexes with N2OS and N2S2 co-ordination spheres: reduction and spectroscopic study of the corresponding Ni(I) complexes

Nickel(II) complexes with Schiff-bases obtained by condensation of 1,3-propanediamine with salicylaldehyde and thiosalicylaldehyde, which present a N2OS or N2S2 co-ordination sphere, were synthesized and studied. The molecular and crystal structure of the asymmetric complex [2-({3-[(3,5-dichloro-2-hydroxyphenyl)methyleneamino]propyl}iminomethylene)benzenethiolato-O,N,N′,S]nickel(II) [Ni(t-salCl2salpd)] has been determined by X-ray crystallography and shows a tetrahedrally distorted square-planar co-ordination geometry for the nickel center. The complexes were characterized by spectroscopic and electrochemical techniques and the results were used to assess the influence of the donor-atoms on their chemical properties. The results obtained show that the compounds may be reduced, either chemically or electrochemically, to Ni(I) complexes. Reduction potentials were found to be strongly dependent on the tetrahedral distortion of the Ni(II) complexes. EPR parameters for Ni(I) complexes, although not very sensitive to ligand substituents, show a regular dependence on the co-ordination set and the tetrahedral distortion of the complexes.

N′-Benzoyl-N,N-diethyl­thio­urea: a monoclinic polymorph

In the crystal of the title compound, C12H16N2OS, inversion dimers linked by pairs of N—H⋯S hydrogen bonds occur, generating R 2 2(8) loops. The molecules are also linked by weak C—H⋯O hydrogen bonds. The structure is isostructural with that of N′-benzoyl-N,N-diethylselenourea [Bruce et al. (2007 ▶). New J. Chem. 31, 1647–1653].

Synthesis, spectroscopic and electrochemical study of nickel-(II) and -(I) complexes with Schiff-base ligands giving a NN′OS co-ordination sphere

A set of nine new tetradentate ligands were prepared and the corresponding nickel(II) complexes with co-ordination spheres NN′OS synthesized and studied by spectroscopic and electrochemical techniques. The structure of (methyl 2-{[3-(2 hydroxyphenyl)methyleneamino]propylamino}cyclopent-1-ene-1-dithiocarboxylato)nickel(II) has been determined by X-ray crystallography. The complex has a tetrahedrally distorted square-planar geometry, and spectroscopic results indicated that this structure is retained even in strong co-ordinating solvents. Moreover, as the spectroscopic properties of this complex are very similar to those of the other complexes studied, it can be concluded that the introduction of substituents in the ligand does not induce significant structural changes. Electrochemical and EPR data show that the complexes are typically reduced to four-co-ordinate nickel(I) species although, with some of the ligands, formation of six-co-ordinate nickel(I) complexes was observed and an explanation is put forward to account for these different behaviours. Cyclic voltammetry studies showed that these complexes may also be oxidized but chemically and/or electrochemically oxidized solutions did not show any evidence for the formation of nickel(III) species.

Crystal structures of three 6-substituted coumarin-3-carboxamide derivatives

Three coumarin derivatives display intramolecular N—H⋯O and weak C—H⋯O hydrogen bonds, which probably contribute to the approximate planarity of the molecules. The supramolecular structures feature C—H⋯O hydrogen bonds and π–π interactions, as confirmed by Hirshfeld surface analyses.

The crystal structures of four N-(4-halophen­yl)-4-oxo-4H-chromene-3-carboxamides

In four N-(4-halophenyl)-4-oxo-4H-chromene-3-carboxamides, halo = -F, -Cl, -Br and -I, the molecules are essentially planar and exhibit anti conformations with respect to the C—N rotamer of the amide and with cis geometries with respect to the relative positions of the C3arom—C2arom bond of the chromone ring and the carbonyl group of the amide.