Classical chemical sciences
Crystal structure of (1R,2S)-1,2-bis(4-chlorophenyl)-3,8-dimethoxyacenaphthene-1,2-diol, C26H20O4Cl2, is reported and discussed from the viewpoints of characteristics in spatial organization, i.e., single molecular structures of four conformers, tetrameric aggregates, and higher ordered structures, with clarification of a classical and two non-classical hydrogen bonding interactions as the structure determining interactions. The title compound crystallizes with four independent molecules (conformers G, B, R, and Y) in the asymmetric unit. Furthermore, each independent molecule displays a meso configuration, with one 4-chlorophenyl group R and the other S. The four molecules are related by inversion center in the asymmetric unit of P-1 space group, exhibiting the number of molecules is eight, Z = 8. Single molecular structure of each conformer shows that the two benzene rings are bonded with large dihedral angles against the naphthalene plane and the two phenyl rings are oriented in the same direction with respect to the naphthalene ring plane (syn-orientation). The four conformers are classified into two groups according to overlapping feature of phenyl rings, i.e., conformers G and Y have larger slippage of the phenyl rings than conformers B and R. In the molecular packing, four conformers Y, B, R, and G are connected by classical O–H…O(H) hydrogen bonds in head-to-head fashion forming S-shaped tetramer. Tetramers composed of four conformers are stacked into columnar structure along a-axis through non-classical C–H…Cl hydrogen bonds between conformers G. The columns are linked into a sheet structure by non-classical C–H…Cl hydrogen bonds between conformers G and Y along ab-diagonal. The waved sheets are interlocked by two types of non-classical C–H… hydrogen bonds forming the stripe structure along c-axis, i.e., non-classical C–H… hydrogen bonds between conformers R and Y, and those between conformers B and G.
Keywords: S-shaped tetramer composed of four conformers, pseudo-centrosymmetricity, classical hydrogen bonds, non-classical hydrogen bonds
Ozone (O3) is a secondary gaseous pollutant in the urban environment, and its variation correlates well with nitrogen oxides (NOx = NO + NO2). Continuous monitoring has been done in the Campo Grande city urban area, using ozone 49C and NO-NO2-NOx 42CTL gas analyzers. The results show that the maximum concentrations of O3 and oxidant (Ox = O3 + NO2) in Campo Grande often appear in the early afternoon around 15:00 hours. The daily variation of NO concentrations shows a very clear cycle with two peaks, one appearing around 07:00 a.m. and the other at 11:00 p.m. At the lowest level, NO2 is the main component of NOx, while NO dominates the higher mixing ratio. It is also shown that the level of Ox is composed of two factors: the regional and the local contributions. The former is affected by the regional O3 level, while the latter is effectively correlated with the primary pollution level. The daily variation also appears in the concentrations of oxidant components.
Keywords: Ozone; Nitrogen dioxide; NOx; Oxidant; Regional Pollution; Local pollution; Nitrous acid; Network monitoring
A convenient procedure for the synthesis of 3β-acetoxy-3′-chloro-5α-cholest-6-eno[7,6-d]-2′,3′-dihydro-1H-pyrrole (4), 3β,3′-dichloro-5α-cholest-6-eno[7,6-d]-2′,3′-dihydro-1H-pyrrole, (5) and 3′-chloro-5α-cholest-6-eno[7,6-d]-2′,3′-dihydro-1H-pyrrole (6) has been made from steroidal oximes (1-3) under refluxing conditions. The structural assignment of the products was confirmed on the basis of IR, 1H NMR, 13C NMR, MS and analytical data.
Keywords: Steroidal oxime, hydroxylamine, dihydropyrrole, vinyl chloride
Doxycycline is a second-generation semi-synthetic antimicrobial of tetracyclines family. It is a broad spectrum antimicrobial agent used in several countries for the treatment of diseases such as chronic prostatitis, sinusitis, syphilis, chlamydia, pelvic inflammatory disease as well as additives in animal feed to improve its growth. Doxycycline is distributed free of charge through Unified Health System in Brazil, which, according to its acquisition, for subsequent distribution, does not always guarantee the same brand. Five different brands of doxycycline tablets (the reference pharmaceutical of doxycycline, two generic and two similar products) were used for evaluation of the interchangeability of the tablets by determination of average weight, hardness, friability, disintegration, the active principle content, content uniformity and in vitro dissolution. All tablets submitted to the tests of average weight, friability, hardness, and disintegration were according to specification. Tests of content uniformity show drugs out of specification, with contents higher than 105%. In the trial of dissolution, there were no statistical differences in the profiles. Due to the results obtained, all doxycycline tablets analyzed should not be approved by the Quality Control authorities. Sectors of production, analytical development, and quality control should meet to resolve this issue. Thus, the importance of a pharmaceutical equivalence study is important to guarantee a safe interchangeability and consequently the same therapeutic effect.
Keywords: Doxycycline, generic, quality control, interchangeability, tablets
A simple reversed-phase high-performance liquid chromatographic (RP-HPLC) technique for the simultaneous determination of ascorbic acid (ASC), methionine (MET), paracetamol (PAR) and caffeine (CAF) has been developed and validated. The cited components are separated completely using Brownlee Bio C18 column (250 x 4.6 mm, 5 μm) by isocratic elution of water-acetonitrile (85:15) (v/v) mobile phase flowing at 1.0 mL min-1 at ambient temperature. The spectrophotometric detection is carried out sequentially at 260 nm for ASC (2 min), 200 nm for MET (1 min), 240 nm for PAR (1.5 min) and 270 nm for CAF (1.5 min). Total chromatographic analysis time per sample was approximately 6 min. The linear range of determination for ASC, MET, PAR and CAF are 40-160 μg mL-1, 40-200 μg mL-1, 20-400 μg mL-1 and 40-160 μg mL-1, respectively. Thus, proposed method can be successfully applicable to analysis the pharmaceutical preparation containing the above mentioned drugs without any interference of excipients. Recovery ranges and relative standard deviation are in turn 96.46 to 102.70 %, 2.65 % for ASC, 96.33 to 103.43 %, 2.93 % for MET, 98.31 to 102.73 %, 2.09 % for PAR and 95.82 to 102.13 %, 2.68% for CAF.
Keywords: use the Keywords style for the list of keywords, separating with a comma each items
Chemical and biological aspects of life
Bryophyllum pinnatum (Lam.) Oken is a plant used in treatment/management of ear-ache, cough, gastro-intestinal disorders and inflammation. Prior to this study, reports of the isolation of cardiac glycosides from the ethyl-acetate fraction of the plant abound. However, very scanty or no literature exists on other organic fractions from where chemical constituents could also be obtained. Hence, the chemical and biological properties of the butanol fraction of the plant were studied. The silica gel column chromatography of the fraction led to a steroidal terpene whose identity has been revealed to be 3-hydroxy-(3β, 17β)-spiro(androst-5-ene-17,1ʹ-cyclobutan)-2ʹ-one using the MS and IR spectral techniques. This compound was strongly bacteriostatic against Staphylococcus aureus and Candida albican sbut recorded no activity against Escherichia coli.
Keywords: Butanol, chromatography, terpene, bacteriostatic, Bryophyllum pinnatum
Plants of the genus Malva (Malvaceae) have been used by humans for millennia. In addition to being an important nutritional source, they are used for many medicinal purposes. Modern research not only supports the ethnomedicinal uses of these plants but has discovered many others. Many review articles were published about the traditional uses of Malva, and some reviews were published about modern research findings of the medicinal and other properties of M. sylvestris. However, none of the review articles discussed both traditional and modern scientific knowledge about all plants of this genus. In the present article an attempt has been made to discuss both the aspects comprehensively. Conclusions have been drawn and future research possibilities suggested.
Keywords: Malva, M. sylvestris, antioxidant activity, ethnomedicine, flavonoids, medicinal uses
Theoretical and computational chemistry
This paper reports the density of states (DOS) of chiral (4,1), armchair (4,4), and zigzag ((4,0) single-walled carbon nanotubes (SWCNTs) by using ab-initio Density Functional Theory (DFT). Our simulation results show the distinguishable features of three types of CNTs in terms of density of states (DOS), so that they can be fully exploited in nano-devices. The results are helpful for studying the working principles of the CNT-based electronic devices and designing new ones.
Keywords: Density of states, DFT, Comparative study, ATK