Bioassay‐guided Isolation and Antioxidant Activity of Sulfur‐containing Compounds from Clinacanthus nutans

Clinacanthus nutans has been used in traditional herbal medicine for cancer prevention, but the specific bioactive compounds responsible for the observed activities have not been explored. Different polar solvents such as methanol, chloroform, ethyl acetate, and hexane were used for the extraction. The extracts, fractions, and isolated compounds were subjected to DPPH and ferric reducing antioxidant potential (FRAP) assays. Methanol extracts show significant free‐radical scavenging activity of 69.09% in DPPH and 56.49% FRAP. Purification of MeOH extracts afforded the fraction FB28 and two new sulfur‐containing compounds, named clinamide D and E ( 1 , 2 ). Compound ( 1 ) proved to be more active with an IC₅₀ value for DPPH radical scavenging of 118.27 ± 0.01 µg/mL and reduction of Fe³⁺–TPTZ complex of 386.24 ± 0.02, higher than that of the standard ascorbic acid. Sulfur‐containing compounds isolated from C. nutans is a potential natural antioxidant.     

Full–dimensional quantum molecular dynamics calculations of the rovibrationally mediated X → 2 transition of nitrous oxide

A full dimensional time‐dependent quantum wavepacket approach is used to study the photodissociation dynamics of nitrous oxide for the X → 2 bound–bound transition based on new highly accurate potential energy and transition dipole moment surfaces. The computed 2 absorption spectra at room temperature are characterized by sharp vibrational structures that contribute slightly to the diffuse vibrational structures around the maximum peak at 180 nm of the first ultraviolet absorption band (from the contribution of 2 , 1 , and 2 states) of N₂O. Transitions from different initial rovibrational states reveal that the sharp structures arise mainly from N₂? O bending vibrations, whereas, at higher temperatures, the N₂? O and N? NO stretching vibrations are responsible for enhancing the intensity of the structures. At absorption wavelengths 166 nm and 179 nm, vibrational quantum state distributions of N₂ product fragments decrease monotonically with increasing vibrational quantum number v = 0, 1, 2. At 166 nm, rotational quantum state distributions of N₂ at fixed v = 0 and v = 1 display multimodal profiles with maximum peaks at j = 77 and j = 75, respectively, whereas, the distributions at the 179 nm absorption wavelength display bimodal profiles with maximum peaks at j = 73 and j = 71, respectively. Accordingly, the presence of rotationally hot N₂ from previous experimental and theoretical works in the first band strongly implies a significant influence of the 2 state in determining the final dissociation pathway of N₂ + O. © 2016 Wiley Periodicals, Inc.     

Sucrose analogs: an attractive (bio)source for glycodiversification

Covering: up to April 2012Sucrose is a widespread carbohydrate in nature and is involved in many biological processes. Its natural abundance makes it a very appealing renewable raw material for the synthetic production of high-valued molecules. To further diversify the structure and the inherent properties of these molecules, the access to sucrose analogs is of utmost interest and has historically been widely explored through chemical means. Nature also offers a large panel of sucrose-scaffold derivatives, including phosphorylated or highly substituted phenylpropanoid esters amenable to transformation. Additionally, the use of microorganisms or enzymes could provide an alternative ecologically-compatible manner to diversify sucrose-scaffold derivatives to enable the synthesis of oligo- or polysaccharides, glycoconjugates or polymers that could exhibit original properties for biotechnological applications. This review covers the main biological routes to sucrose derivatives or analogs that are prevalent in nature, that can be obtained via enzymatic processes and the potential applications of such sucrose derivatives in sugar bioconversion, in particular through the engineering of substrates, enzymes or microorganisms.     

Protonation Equilibria of Carminic Acid and Stability Constants of Its Complexes with Some Divalent Metal Ions in Aqueous Solution

The dissociation constants of carminic acid (7-D-glucopyronosyl-3,5,6,8-tetra- hydroxy-1-methyl-9,10-dioxo-anthracene-2-carboxylic acid) (CA), together with the stability constants of its Cu(II), Zn(II), Ni(II), Co(II) and Hg(II) complexes, were studied potentiometrically in aqueous medium at 25.0?(1)?°C, and at the ionic background of 0.1?mol?dm^?3 of NaCl, and determined with the SUPERQUAD computer program. It has been observed that carminic acid has five dissociation constants, and for H₅L their values are 3.39?(7), 5.78?(7), 8.35?(7), 10.27?(7), and 11.51?(7). This ligand behaves as a bi-dentate ligand, and the carboxyl and the ortho hydroxy groups of the ligand coordinate to the metal ions. Various metal complexes were produced in solution under the experimental conditions, for each metal ion used, including hydrolyzed species. The species distribution curves of the complexes formed in the solution were calculated and reviewed. The stability of the complexes was found to follow the order: Cu(II) > Zn(II) > Ni(II) > Co(II) > Hg(II).     

Size-fractionated airborne particulate matter characterization of a residential area near Islamabad airport by IBA methods

Size fractionated PM_2.5 and PM_2.5?C10 airborne particulates collected from the airport housing society site in Rawalpindi were characterized using the non destructive ion beam analysis method. Proton induced X-ray emission and Proton induced gamma ray emission were employed to quantify 28 trace elements in fine and coarse filter samples. The average PM_2.5 and PM_2.5?C10 masses were found to be 15.7 and 144???g/m³, respectively which, when combined exceed the Pakistani limit for PM₁₀ of 100???g/m³. The average black carbon (BC) content was found to be 3.49 and 5.95???g/m³ corresponding to 23.8 and 4.30% of the fine and coarse masses, respectively. The reconstructed mass (RCM) was calculated for both particle modes using 5 pseudo sources, namely soil, sulfate, smoke, sea salt and BC. It was found that 5 sources could account for 80.6 and 49.0% of the fine and coarse masses, respectively. The low value of RCM for the coarse mode may imply a much higher organic content. The major sources contributing to the fine mode were soil, sulfate and BC. Similarly for the coarse mass fraction it was found that soil was the major source whereas the sulfate and BC sources did not contribute as much.     

Thermal decomposition of rice husk: a comprehensive artificial intelligence predictive model

Journal of Thermal Analysis and Calorimetry - This study explored the predictive modelling of the pyrolysis of rice husk to determine the thermal degradation mechanism of rice husk. The study can...     

Heat dissipation in two-terminal Benzene junction

We investigate the heat dissipation mechanism in the Benzene molecular junctions. Using the tight-binding model and the generalised Green’s function formalism, heat dissipation in the electrodes is studied numerically. Results reveal a strong dependence of heat dissipation on the transmission characteristics and the bill polarity. For a pure Benzene molecular junctions, regardless the electrodes positions, namely meta, ortho and para configurations, heat dissipates in a symmetric fashion at both electrodes and does not rely on the bias polarity. This feature is a consequence of a symmetric transmission function over the energy spectrum of incoming electrons. Introducing a single impurity on the Benzene molecule, we force the model to lose its particle-hole symmetry and a drastic change occurs in the heat dissipation of the junction.     

Synthesis and characterization of polymeric Pd(II), Pt(IV), and Au(III) complexes of 2,2′-(1,4-phenylenedivinylene)-bis-8-hydroxyquinoline

The complexes of 2,2′-(1,4-Phenylenedivinylene)-bis-8-hydroxyquinoline (LH₂) with K₂PdCl₄, H₂PtCl₆ and HAuCl₄ were synthesized and characterized with ¹H-and ¹³C-NMR, elemental analysis, FT-IR, and molar conductivity. Au(III) and Pt(IV) complexes have characteristic conductance, while the Pd(II) complex has a non-ionic structure according to the molar conductivity and elemental analysis. This text was submitted by authors in English.     

Characterisation of some exotic fruits (Morus nigra, Morus alba, Salvadora persica and Carissa opaca) used as herbal medicines by neutron activation analysis and estimation of their nutritional value

In the under developed countries, the people of far-flung rural areas still depend to a large extent upon herbal medicines. At the foundation of usage of herbal medicine is the experience of thousands of years. The present paper deals with the characterisation of exotic fruits for essential and toxic elements. The samples include Morus nigra, Morus alba, Salvadora persica and Carissa opaca (from low and high altitude). Two standardizations of neutron activation analysis, that is, semi-absolute k ₀-instrumental neutron activation analysis (k ₀-INAA) and epithermal neutron activation analysis (ENAA) were employed for the quantification of elements. The analysis methodologies were validated by analyzing the IAEA-336 (lichen) and NIST-SRM-1572 (citrus leaves). Sixteen elements including Br, Ca, Cl, Co, Cr, Fe, I, K, Mg, Mn, Na, Rb, Sb, Sc Sr, and Zn were determined in all samples. Daily intakes of various elements from the samples were measured and compared with the dietary reference intakes. Additionally, principal component analysis was performed to extract information regarding samples and elements.