Classical and Advanced Chemical Sciences
Four new mixed ligand transition metal (Co(II), Ni(II), Cu(II) and Zn(II)) complexes of p-coumaric acid and coumarine have been synthesized and the structurally characterized. These complexes contain hydrate water except the Cu(II) complex. Coumaric acid is a monodendate ligand except Cu(II)-complex in which a bidendate coordination mode could be observed. The thermal decomposition starts with dehydration of Co(II), Ni(II) and Zn(II) complexes while in Cu(II) complex decomposition starts with fragmentation of organic ligands at 145 °C. Studies on their biological activity have also been performed. Molecular formulas of the obtained complex are as follows: (I) [Co(C9H7O3)2(C9H6O2)2(H2O)2].4H2O; (II) [Ni(C9H7O3)2(C9H6O2)2(H2O)2].6H2O; (III) [Cu(C9H7O3)2(C9H6O2)2] and (IV) [Zn(C9H7O3)2(C9H6O2)2(H2O)2].3H2O. The ratio of metal: p-coumaric acid: coumarin in complexes are found to be 1:2:2. The complex IV is diamagnetic, and the other complexes are paramagnetic. According to BM data and result of electronic spectra, the geometry for all of the complexes has thought to be octahedral coordination around the metal ions.
Keywords: Biological activity, coumarin, mixed ligand, coumaric acid, metal complexes, spectroscopic methods
New N-[1-(4-amino)pyridinium]-N-methoxyurea chloride, N-[1-(2-amino)pyridinium]-N-methoxyurea chloride and their analogs were synthesized by N-alkoxy-N-chloroureas reaction with the proper pyridines in acetonitrile or ether solution by improved procedure. XRD study of N-[1-(4-amino)pyridinium]-N-methoxyurea and N-[1-(2-amino)pyridinium]-N-methoxyurea revealed the elongation of N-N+ bonds and some shortening of MeO-N bonds, qunonoid deformation of pyridine rings compare to it unsubstituted analog. The substantial pyramidality of central nitrogen atom in O-N-N+ moiety and N-C carbamoyl bonds difference were established too. The structure summary of N-alkoxy-N-(1-pyridinium)ureas salts and other derivatives of 1-(N-alkoxyamino)pyridinium salts has been done.
Keywords: N-alkoxy-N-(1-pyridinium)urea salts, 1-N-alkoxyaminopyridinium salts, N-alkoxy-N-chloroureas, synthesis, structure
2-Chloro-3-formyl-1,8-naphthyridine (1) has been synthesized in a Vilsmeier-Haack type reaction route. Starting from (1) a number of novel 1,8-naphthyridines were also synthesized. The structures of synthesized compounds were confirmed by their spectral and physical data. Some of the newly synthesized compounds exhibited antibacterial activity.
Keywords: Novel heterocycles, 1,8-naphthyridine , 1,3,4-oxadiazole, 1,3,4-thiadiazole, 1,2,4-trazole , Vilsmeier-Haack
Chemical and Biological Aspects of Life
The aim of this study was the identification and quantification of biologically active compounds from three Artemisia species, used as remedies in Romanian traditional medicine. A new LC-MS method was developed for the analysis of methoxylated flavones and also the quantification of caffeic and chlorogenic acids was performed. The antioxidant activity of plant extracts was evaluated by DPPH radical scavenging assay. We report for the first time the presence of eupatorin and hispidulin in A. absinthium and A. vulgaris, of eupatilin in A. annua and casticin in A. vulgaris. Jaceosidin and acacetin were not identified in any sample. Although all extracts showed antiradical scavenging activity, A. vulgaris exhibited the strongest antioxidant effect. Chlorogenic acid was found in high amounts in all species, notably in A. annua and A. vulgaris.
Keywords: Methoxylated flavones, antioxidant, Artemisia annua, Artemisia vulgaris, Artemisia absinthium
The present study focuses on the quantification of caffeine from 11 pharmaceutical and natural products. Pharmaceutical products were purchased from pharmacy and include 4 types of tablets and 1 suppository type product. Natural products were purchased from specialty stores and comprise green tea, black tea and different kinds of coffee. Some of the quality parameters like friability and disintegration time for tablets, melting behavior, deformation temperature and time of deformation for suppositories were determined. The caffeine content was determined using UV spectrophotometric methods by measuring the absorbance at 272 nm, after separating the caffeine from the others active ingredients and excipients. The results showed that caffeine content in pharmaceutical products purchased from pharmacies is in the range recommended by European and Romanian Pharmacopoeia. In the case of natural products, the caffeine content decreases in the following order: bulk coffee beans freshly ground > ground coffee packed > black tea > green tea > decaffeinated coffee.
Keywords: quantification, extraction, UV spectrophotometric methods, tablets, suppositories, green tea, black tea, coffee
Studies on chemical constituents of A. wilkesiana var. golden-yellow (Muell & Arg.) syn. A. wilkesiana var. tropical tempest used in traditional medicine, was carried out with solvent-partitioning of the aqueous extract of the plant with various organic solvents and subjecting the organic phases to silica gel column chromatography. Two compounds could be isolated from the butanol fraction which were assigned as 4-ethoxy-4-oxobutanoic acid (ethyl succinate) and 2-ethoxy-5(hydroxymethyl)-oxalane-3,4-diol (ethyl β-riboside) using the 1H NMR, 13C NMR, MS and IR spectral techniques. Both compounds were inactive against B. subtilis, S. aureus and E. coli. and showed minimal activity against Ps. aeruginosa, S. typhi and V. cholerae, and they had no anticandidal activity. The two isolates would serve as chemotaxonomic markers for this species and variety in particular and the genus, Acalypha in general.
Keywords: ethyl succinate, ethyl β-riboside, A. wilkesiana var. golden-yellow (Muell & Arg.)
Theoretical and Computational Chemistry
The concept of the entropy of spatial-energy interactions is used similarly to the ideas of thermodynamics on the static entropy. In this research we are trying to apply the concept of entropy to assess the degree of spatial-energy interactions using their graphic dependence and a nomogram to assess the entropy of different processes is obtained. The variability of entropy demonstrations is discussed, in biochemical processes, economics and engineering systems as well.
Keywords: Entropy, nomogram, spatial-energy parameter, biophysical processes, business, engineering systems
Correlation between chemical structure and enantioselectivity in baker’s yeast reduction of a set of carbonyl compounds was constructed by means of a multi-layer neural network using the back-propagation algorithm. To evaluate the predictive power of the neural network (NN) model, the cross-validation procedure was used, 88 % of the reactions were correctly predicted.
Keywords: β-ketoacid; reduction; enantioselectivity; prediction; neural networks