Polyphenolic Contents and Antioxidant Potential of Stem Bark Extracts from Jatropha curcas (Linn)

We assessed the polyphenolic contents and antioxidant potential of the aqueous, ethanol and methanol stem bark extracts of Jatropha curcas. The total phenol, flavonoids, flavonols and proanthocyanidin contents of the extracts were evaluated to determine their effect on the antioxidant property of this plant, using standard phytochemical methods. The antioxidant and free radical scavenging activity of ethanol, methanol and aqueous extracts of the plant were also assessed against 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), ferric reducing, nitric oxide (NO), superoxide anion, (O(2) (-)) and hydrogen peroxide (H(2)O(2)) using spectroscopic methods and results were compared with that of butylated hydroxyl toluene (BHT) and ascorbic acid as standards. The concentrations of different classes of phenolic compounds were higher in methanol and ethanol extracts compared to aqueous extracts. There was correlation between total phenol, total flavonoids, total flavonol and total proanthocyanidins (r = 0.996, 0.978, 0.908, and 0.985) respectively. There was correlations between the amount of phenolic compounds and percentage inhibition of DPPH radicals scavenging activity of the extract (r = 0.98). Findings from the present study indicated that J. curcas is a potential source of natural antioxidants and may be a good candidate for pharmaceutical plant based products.     

Toward the discovery of novel anti-HIV drugs. Second-generation inhibitors of the cellular ATPase DDX3 with improved anti-HIV activity: synthesis, structure-activity relationship analysis, cytotoxicity studies, and target validation

A hit optimization protocol applied to the first nonnucleoside inhibitor of the ATPase activity of human DEAD-box RNA helicase DDX3 led to the design and synthesis of second-generation rhodanine derivatives with better inhibitory activity toward cellular DDX3 and HIV-1 replication. Additional DDX3 inhibitors were identified among triazine compounds. Biological data were rationalized in terms of structure-activity relationships and docking simulations. Antiviral activity and cytotoxicity of selected DDX3 inhibitors are reported and discussed. A thorough analysis confirmed human DDX3 as a valid anti-HIV target. The compounds described herein represent a significant advance in the pursuit of novel drugs that target HIV-1 host cofactors.     

Rapid and Green Analytical Method for the Determination of Quinoline Alkaloids from Cinchona succirubra Based on Microwave-Integrated Extraction and Leaching (MIEL) Prior to High Performance Liquid Chromatography

Quinas contains several compounds, such as quinoline alkaloids, principally quinine, quinidine, cinchonine and cichonidine. Identified from barks of Cinchona, quinine is still commonly used to treat human malaria. Microwave-Integrated Extraction and Leaching (MIEL) is proposed for the extraction of quinoline alkaloids from bark of Cinchona succirubra. The process is performed in four steps, which ensures complete, rapid and accurate extraction of the samples. Optimal conditions for extraction were obtained using a response surface methodology reached from a central composite design. The MIEL extraction has been compared with a conventional technique soxhlet extraction. The extracts of quinoline alkaloids from C. succirubra obtained by these two different methods were compared by HPLC. The extracts obtained by MIEL in 32 min were quantitatively (yield) and qualitatively (quinine, quinidine, cinchonine, cinchonidine) similar to those obtained by conventional Soxhlet extraction in 3 hours. MIEL is a green technology that serves as a good alternative for the extraction of Cinchona alkaloids.     

Anodic behavior of gold in 1-butyl-3-methylimidazolium methanesulfonate ionic liquid with chloride anion

The anodic behavior of gold has been investigated in presence of chloride and/or water in 1-butyl-3-methylimidazolium methanesulfonate (BMI CH₃SO₃) ionic liquid (IL). The cyclic voltammetry (CVs) in presence of chloride ions shows two waves attributed to the oxidation of the gold electrode which occurs under two steps: the first one is attributed to the electrochemical dissolution of gold into to gold(I), while the second one is attributed to an overlap of the chloride oxidation step as well as the oxidation of Au(I) to Au(III). Furthermore the determination of water and chloride content in IL allowed observing that the passive layer induced by water could be removed under chloride. Thanks to those results we were able to clarify the conditions of gold recovering in this kind of electrolyte.     

A Decade of Oxothiomolybdenum Wheels: Synthesis,Behavior in Solution,and Electrocatalytic Properties

The last decade has see the development of sulfur-containing polyoxometalates (POTMs) as a subclass of the polyoxometalate family. The structural and physico-chemical properties of this emerging class of compounds is dominating by the striking coordination properties of the [Mo₂O₂S₂(OH₂)₆]²⁺ oxothio cation, used as a building block. The cyclic topology of this arrangement corresponds to the main feature of the {Mo₂O₂S₂}-based compounds, able to develop cycle-based chemistry. The control of the linear oligomerization of the {Mo₂O₂S₂} core is achieved by the presence of the anionic component, which acts as a template. Here, we report on recent examples which illustrate how the use of various template ions such as halide, sulfate, polyphosphate, and polycarboxylate anions allows to tune the nuclearity of the inorganic host from {Mo₈} to {Mo₁₈}. A special focus on behavior in solution is given, highlighting the dynamic and fluxional character of these host–guest systems. The Diffusion Ordered Spectroscopy (DOSY) ¹H NMR, carried out on a large series of cycle-based and capsule-like compounds, demonstrates that such a method can be applied for the speciation of POM anions in solution. Finally, electrocatalytic behavior of the {Mo₂O₂S₂}-based compounds is presented. Preliminary results show that the electrocatalytic reduction of protons into hydrogen (HER) could constitute one of the most relevant applications for this class of molecular compounds.     

Development and Characterization of Continuous SiC Fiber‐Reinforced HfB2‐Based UHTC Matrix Composites Using Polymer Impregnation and Slurry Infiltration Techniques

This paper discusses the development of continuous SiC fiber‐reinforced HfB₂‐SiC composite laminates. A range of techniques, based on resin‐based precursors and slurries, for infiltrating porous SiC preforms with HfB₂ powder were developed. While resin‐based precursors proved to be ineffective due to low HfB₂ yield and poor adhesion, the slurry infiltration techniques were effective to varying degrees. The greatest pore filling and composite densities were achieved using pressure and vibration‐assisted pressure infiltration techniques. SiC_f/HfB₂‐SiC laminates were subsequently developed via lamination, cure and pyrolysis of fabrics using a HfB₂‐loaded polymeric SiC precursor, followed by HfB₂ slurry infiltration and preceramic polymer infiltration and pyrolysis (PIP). Repeated PIP processing, for 6–10 cycles, resulted in density increases, from the 3.03–3.22 g/cm³ range after HfB₂ slurry infiltration, to 3.97–4.03 g/cm³ after PIP processing. Correspondingly, there was a decrease in open porosity from approximately 52% to less than 11%. The matrix consisted of discreet, lightly sintered HfB₂ particles dispersed in SiC. The PIP SiC matrix was primarily nanocrystalline after 1300°C pyrolysis, but experienced grain growth with further heat treatment at 1600°C.     

Impact of oxygen transport properties on the kinetic modeling of polypropylene thermal oxidation. II. Effect of oxygen diffusivity

The kinetic model, established in a previous article (François‐Heude et al., J. Appl. Polym. Sci., in press) to predict the homogeneous oxidation in iPP films typically thinner than 100 µm, is now extended to simulate the oxidation profiles in thicker plates by coupling the oxygen diffusion and its consumption by the chemical reactions. In this perspective, oxygen transport properties (namely oxygen solubility, diffusivity, and permeability) are measured by permeametry on a reference iPP. These values are compared with an exhaustive compilation of literature data to evaluate their variability among the whole iPP family, which one has been reasonably ascribed to initial differences in polymer morphology, but also to evaluate their consistency, especially their temperature dependence between 20 and 140°C. Failing to simulate oxidation profiles, the kinetic model is then used as an inverse resolution method for estimating more satisfactory values of oxygen transport properties. It is thus evidenced that the crystallinity changes induced by thermal oxidation largely explains the dramatic decrease in oxygen penetration toward the sample core just after the induction period. A strategy aimed for introducing the relationship between the polymer crystalline morphology and oxygen transport properties into the kinetic model is given in the graphical abstract, although the effect of polymer polarity remains to be established prior to this implementation. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41562.     

Field-scale analysis of water and nutrient use efficiency for vegetable production in a West African urban agricultural system

Urban agriculture increasingly supplies food and non-food services to the rapidly growing West African cities. However, with its typically heavy use of fertilizers and uncontrolled use of water, it bears severe risks of soil and groundwater pollution. This study was carried out in Bobo Dioulasso (Burkina Faso, West Africa) at two commercial gardening sites. It aimed at performing a detailed characterization of farmer’s water and nutrient management strategies. Four vegetable crops were monitored (tomato, cabbage, carrot and lettuce). Water inputs (rainfall and irrigation), nutrient inputs (organic and mineral fertilizers and nutrients in irrigation water) and crop uptake were monitored over a 1–2-year period. In addition, pan lysimeters allowed monitoring drainage. Depending on the site, 3–8% of the input water was lost by drainage, i.e., as much as 293 mm/year at one of the sites. During the dry season, when the farmer has full control over the water supply, water application exceeded plant requirements by as much as 40%, which reveals inefficient water use. Up to 800 kg N ha⁻¹, 140 kg P ha⁻¹ and 500 kg K ha⁻¹ were applied for a single crop cycle. With few exceptions, crops tended to be strongly over-fertilized, except for K at one of the two sites. Nutrient supply exceeded crop requirements by 109 to 2,012 kg N, 66 to 450 kg P and 0 to 393 kg K per year. These results, in combination with the large observed rates of drainage, are indicative of a high risk of nutrient leaching and groundwater contamination. The partial factor productivity of nutrients tended to be low. These results therefore suggested that there is scope to substantially reduce nutrient application rates in these systems without adverse effects on yields, which would be beneficial for groundwater resources and improve the economic returns.