An iboga alkaloid chemotaxonomic marker from endemic Tabernaemontana ternifolia with antitubercular activity

Abstract

Coronaridine (1) was isolated from the CH₂Cl₂ root extract of Tabernaemontana ternifolia. The structure of 1 was established from 1D- and 2D-NMR and HR-ESIMS experiments, and by comparison with reported spectroscopic data. To date, this is the first report of compound 1 from T. ternifolia, introduced as new Tabernaemontana species from Philippines in 2005 on the basis of morphological characters. Coronaridine, an iboga-type indole alkaloid, has been isolated from over 50 Tabernaemontana species and can thus be inferred as a chemotaxonomic marker of the genus. T. ternifolia has a distinct arrangement of leaves not known in the genus, but is variable in other genera. Its isolation from endemic T. ternifolia establishes its position in the genus and supports the claim that coronaridine is a chemical marker of the genus Tabernaemontana. Interestingly, coronaridine exhibited relatively weak activity against Mycobacterium tuberculosis H₃₇Rv (MIC 82.64?μg/mL) (Rifampicin MIC 0.05?μg/mL).     

Synthesis and characterization of uranium (IV) complexes with various amino acids

Complexes of uranium in its IV oxidation state, using cysteine, glycine, serine and aspartic acid as ligands, have been synthesized. Semi-microanalysis of the complexes indicate 1:1 metal to ligand ratio for all the synthesized complexes. Infrared spectra of solid complexes have been employed to establish the groups, coordinated to the metal ion. Effective magnetic moment of the complexes were also estimated.     

Comparative study of spectroscopic techniques for the estimation of iron in apple and vegetables

Iron has been determined in apple and vegetables spectrophotometrically, by complexing it with xylenol orange. 1:1 complex formed in a highly acidic medium is measured for its absorbance at its λ_max of 585 nm. The results have been compared by employing atomic absorption technique. Apples and vegetable samples were collected from local markets of Pakistan. Statistical manipulations, t-test and F-test, were performed and it was found that the results from the two techniques have an excellent agreement.     

A bis-bithiophene from Tridax procumbens L. (Asteraceae)

The ethyl acetate soluble part of hexane extract of Tridax procumbens yielded a new bis-bithiophene named tridbisbithiophene along with four known terpenoids: taraxasteryl acetate, beta-amyrenone, lupeol and oleanolic acid, which have never been reported so far from Tridax procumbens. The structures of all the isolated constituents were elucidated with the aid of 1D-NMR spectroscopy whereas, the structure of new constituent tridbisbithiophene was confirmed via COSY and HMBC interactions.     

Inelastic deformations of stainless steel leaf springs-experiment and nonlinear analysis

A stainless steel leaf spring is designed and constructed followed by its performance evaluation by experiment and non-linear analysis so that an insight into the optimum use of material can be made. Cantilever beams of uniform strength, popularly termed as leaf springs, undergo much larger deflections in comparison to a beam of constant cross-section; that needs inclusions of geometric non-linearity for rigorous analysis. This study deals with such a cantilever beam, but takes into account the material non-linearity as well. Experiments were conducted for such a cantilever beam, with highly non-linear stress-strain curves. In addition to the experiment, a computer code in ‘C’ has been developed using the Runge-Kutta technique for the purpose of simulation. Effective modulus-curvature relations are obtained from the non-linear stress-strain relations for different sections of the beam and used for the analysis. It is seen that non-linear stress-strain curve governs the bending of the beam. Importantly, non-linear analysis shows the stresses are not so high as predicted by the linear theory without end-shortening. Moreover, the tensile and compressive stresses are different in magnitude and both decrease along the span. Experimental load-deflection curves are found to be initially concave upward but, non-linear and convex upward at a high load. Comparison of the numerical results with the available experimental results from another research group and theory shows excellent agreement verifying the soundness of the entire numerical simulation scheme.     

Biogenic Synthesis of Gold Nanoparticles on a Green Support as a Reusable Catalyst for the Hydrogenation of Nitroarene and Quinoline

Direct attachment of gold nanoparticles to a green support without the use of an external reducing agent and using it for removing toxic pollutants from wastewater, i. e., reduction of nitroarene to amine, are described. A novel approach involving the reduction of gold by the jute plant (Corchorus genus) stem-based (JPS) support itself to form nanoparticles (AuNPs) to be used as a catalytic system (‘dip-catalyst’) and its catalytic activity for the hydrogenation of series of nitroarenes in aqueous media are presented. AuNPs/JPS catalyst was characterized using SEM, UV-Vis, FTIR, TEM, XPS, and ICP-OES. Confined area elemental mapping exhibits uniform and homogeneous distribution of AuNPs on the support surface. TEM shows multi-faceted AuNPs in the range of 20–30 nm. The reactivity of AuNPs/JPS for the transfer hydrogenation of nitroarene as well as hydrogenation of quinoline under molecular H₂ pressure was evaluated. Sodium borohydride, when used as the hydrogen source, demonstrates a high catalytic efficiency in the transfer hydrogenation reduction of 4-nitrophenol (4-NP). Quinoline is quantitatively and chemoselectively hydrogenated to 1,2,3,4-tetrahydroquinoline (py-THQ) using molecular hydrogen. Reusability studies show that AuNPs are stable on the support surface and their selectivity is not affected.     

Experimental investigation and optimization of loop heat pipe performance with nanofluids

Journal of Thermal Analysis and Calorimetry - High heat generation from electronic devices needs to cool down properly to prevent overheating. Loop heat pipe (LHP) is one of the excellent cooling...     

Computational study on the effects of variable viscosity of micropolar liquids on heat transfer in a channel

Journal of Thermal Analysis and Calorimetry - A numerical model is developed to study the effects of temperature-dependent viscosity on heat transfer in magnetohydrodynamic flow of micropolar fluid...     

On model for Darcy–Forchheimer 3D nanofluid flow subject to heat flux boundary condition

Journal of Thermal Analysis and Calorimetry - This paper provides a theoretical study of 3D nanofluid flow with zero nanoparticles mass and constant heat fluxes conditions. An incompressible...