Thermal study of chalcones

Journal of Thermal Analysis and Calorimetry - Chalcones α-β-unsaturated ketones are found in large plant species. Synthesis of chalcones and its three analogues hydroxy group at 2′,...     

Chemical,thermal and rheological properties and stability of sapucaia (<Emphasis Type="Italic">Lecythis pisonis</Emphasis>) nut oils

Sapucaia (Lecythis pisonis) is a tree that grows in Colombia, Venezuela and the Guyanas and is widely distributed in Brazil. This work presents a study of sapucaia nut oils (SO) that were obtained by Bligh and Dyer (LP1) and Soxhlet (LP2) methods and were evaluated for their fatty acid composition, rheological and thermal properties, total phenolic compounds (TPC), antioxidant properties and oxidative stability using Rancimat and ATR-FTIR spectroscopy. The analyses showed that the method of extraction impacts the fatty acid profiles of SO. Oil extracts present considerable TPC content and antioxidant properties. Thermal analysis revealed three degradation steps for SO in the air atmosphere, starting at around 130 °C, being thermally stable up to 300 °C (with a ~ 5% mass loss) and reaching total degradation near 620 °C. Thermal analysis under N₂ produced two degradation steps, initiating at around 130 °C and finishing at 500 °C. Rancimat also confirmed the high thermal stability of SO, with induction periods of 13.28 h (LP1) and 7.18 h (LP2). The DSC parameters of SO were similar among each other. Crystallization (? 8.04 to ? 73.93 °C) and melting (? 31.34 to 8.28 °C) phases occurred over a large temperature range. SO presented FTIR spectral features with characteristic bands for vegetable oils. Ostwald–de Waele and Herschel–Bulkley rheological models indicated major pseudoplastic behavior for SO, with a predominant viscous component. These results reinforce that SO are appropriate for human consumption and open up new possibilities for their industrial exploitation, such as for food and the cosmetic, pharmaceutical and biodiesel industries.     

Chemical investigation of metabolites produced by an endophytic fungi Phialemonium curvatum from the leaves of Passiflora edulis

Phialemonium curvatum, an endophytic fungus isolated from the leaves of Passiflora edulis was cultured in potato dextrose broth (PDB) media and chromatographic separation of the EtOAc extract of the broth and mycelium led to the isolation of 4-hydroxybenzoic acid (1), 3-indole acetic acid (2), solaniol (3), uracil (4), uridine (5) and glycerol (6). Compound 2 showed a weak antifungal activity against Cladosporium cladosporioides. This is the first report of the isolation of the endophytic fungus P. curvatum from P. edulis and complete ¹³CNMR assignments of 3.     

Preparation and X-Ray crystal structure of a Novel Nickel(II) complex with dithiocarbimate

The reaction of potassiumN-(methanesulfonyl)-dithiocarbimate, K₂[S₂C=NSO₂CH₃], with nickel(II) chloride hexahydrate, NiCl₂·6H₂O, formed the complex anion bis(N-(methanesulfonyl)-dithiocarbimate)nickelate(II), [Ni(S₂C=NSO₂CH₃)₂]^2}-, which was isolated as its tetra-n-butylammonium salt. The UV-Vis data obtained were consistent with the formation of a nickelsulfur diamagnetic planar complex. The¹H NMR and the¹³C NMR spectra showed the expected signals for then-Bu₄N⁺ cation and the dithiocarbimate moiety. The single-crystal structure analysis showed that tetra-n-butylammonium bis(N-(methanesulfonyl)-dithiocarbimate)nickelate(II), (Bu₄N)₂[Ni(S₂C=NSO₂CH₃)₂], crystallizes in the monoclinic space groupP2_l/c witha=9.3197(5),b=15.0795(8),c=17.5286(9) å,=91.262(3),V=2462.8(3) å³, andZ=2. The nickel atom is coordinated to four sulfur atoms.     

Synthesis, characterization, and structure of a new N-nitrosamine of cyclam (1,4,8,11-tetraazacyclotetradecane)

A novel N-nitrosamine of cyclam has been synthesized. The N-N bond lengths values, as determined from the X-ray crystal structure, fall in the 1.318(2) and 1.320(2) Å range, smaller than the ones expected for the N-N single bond. The N-NO bond angles are in the 115.0(1)° and 114.8(1)° range. The νNO, νNN, and δN-NO vibrational modes were observed in the infrared spectrum at 1454, 1139, and 555 cm⁻¹, respectively. The photolysis of the cyclam(NO)₄ compound gives rise to the nitrosyl release through an heterolytic cleavage of the N-NO bonds, as indicated by the appearance of the νNO⁺ band at 2228 cm⁻¹ at the expense of decreasing the νNO, νNN, and δN-NO bands.     

PHOTON EMISSION BY BACTERIA CHALLENGED WITH PHENYLACETALDEHYDE. A POSSIBLE DISTINCTION BETWEEN GRAM-POSITIVE and GRAM-NEGATIVE BACTERIA

With all bacteria tested, addition of phenylacetaldehyde leads to light emission. The latter is markedly stronger with gram-negative bacteria, presumably because they possess a thinner wall and an extra external lipophilic membrane. Consistent with this explanation, the bactericidal effect of phenylacetaldehyde is also stronger with gram-negative bacteria. The spectrum of the emitted light shows maximal emission in the 500 nm region and is very similar to that observed when a protein (bovine serum albumin), free amino acids or isopropylamine reacts with phenylacetaldehyde.     

Cosmological models with variable gravitational and cosmological “constants”

We consider the Einstein field equations with perfect fluid source and variable andG for the Robertson-Walker metric. When conservation of energy momentum is postulated and the deceleration parameter is assumed constant, we find perfect gas equation of state models in the Euclidean and non-Euclidean cases. The resulting models offer an alternative to the inflationary scenario; they also explain the huge value of the cosmological term in the early universe.     

Molecular Association and Solvent Effects in the Electronic and NMR Spectra of the Tricyanoterpyridineruthenate(II) Complex

Solvent effects on the electronic structure and NMR spectra of the[Ru(terpy)(CN)₃] complex(terpy = 2,2,6,2-terpyridine) have beeninvestigated and interpreted using quantum mechanical semiempirical methods.A systematic splitting of the electronic bands in the visible is observed, in addition to theirbathochromic shifts depending on the acceptor number of the solvent. The solvent-inducedsplittings are rationalized in terms of the involvement of several charge—transfertransitions exhibiting distinct participation of the ruthenium (II), terpy, and CN^–orbitals. Direct evidence of solvent interaction at the cyanide ligands is observedin the [¹³C]NMR spectra. The most enhanced solvent effects are at the middle¹³C-4 and ¹H-4 atoms of terpy, in complete agreement with the theoreticalcalculations. In D₂O, stacking interactions involving the terpy ligands are detectedfrom the [¹H]NMR spectra, leading to a bimolecular association constant of90 mol^–1-dm³. In acetone—D₂O mixed solvents, the spectroscopic changes areindicative of preferential solvation departing from the ideal linear behavior.     

The electrical double layer for a fully asymmetric electrolyte around a spherical colloid: an integral equation study

The hypernetted chain/mean spherical approximation (HNC/MSA) integral equation for a totally asymmetric primitive model electrolyte around a spherical macroparticle is obtained and solved numerically in the case of size-asymmetric systems. The ensuing radial distribution functions show a very good agreement when compared to our Monte Carlo and molecular-dynamics simulations for spherical geometry and with respect to previous anisotropic reference HNC calculations in the planar limit. We report an analysis of the potential versus charge relationship, radial distribution functions, mean electrostatic potential, and cumulative reduced charge for representative examples of 1:1 and 2:2 salts with a size-asymmetry ratio of 2. Our results are collated with those of the modified Gouy-Chapman (MGC) and unequal radius modified Gouy-Chapman (URMGC) theories and with those of HNC/MSA in the restricted primitive model (RPM) to assess the importance of size-asymmetry effects. One of the most striking characteristics found is that, contrary to the general belief, away from the point of zero charge the properties of an asymmetric electrical double layer (EDL) are not those corresponding to a symmetric electrolyte with the size and charge of the counterion, i.e., counterions do not always dominate. This behavior suggests the existence of a new phenomenology in the EDL that genuinely belongs to a more realistic size-asymmetric model where steric correlations are taken into account consistently. Such novel features cannot be described by traditional mean-field theories such as MGC, URMGC, or even by enhanced formalisms, such as HNC/MSA, if they are based on the RPM.     

Isolation and structure determination of bioactive isoflavones from callus culture of Dipteryx odorata

Crude extracts of callus and roots of Dipteryx odorata were analyzed by HPLC to detect and quantify isoflavone contents. Based on spectroscopic and X-ray crystallography data the structures of two isoflavones were elucidated as 7-hydroxy-4',6-dimethoxyisoflavone and 3',7-dihydroxy-4',6-dimethoxyisoflavone. The production of dry biomass of 7-hydroxy-4',6-dimethoxyisoflavone in cultured callus was 4.12 mg/g, approximately eleven fold higher than the amount accumulated in roots of D. odorata wild-growing plants. The 7-hydroxy-4',6-dimethoxyisoflavone was effective against glyceraldehyde-3-phosphate dehydrogenase from Trypanosoma cruzi. This is the first report on those bioactive isoflavones accumulated in callus of D. odorata.