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Attached Proton Test

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François Xavier Etoa – 1st expert on this subject based on the ideXlab platform

  • Effect of fractioning on antibacterial activity of n-butanol fraction from Enantia chlorantha stem bark methanol extract
    BMC Complementary and Alternative Medicine, 2019
    Co-Authors: Rebeca Madeleine Ebelle Etame, Raymond Simplice Mouokeu, Frank Stève Monthe Poundeu, Igor Kenfack Voukeng, Cedric Laurel Pouaha Cidjeu, Alembert Tchinda Tiabou, Abel Joel Gbaweng Yaya, Rosalie Anne Ngono Ngane, Jules Roger Kuiate, François Xavier Etoa

    Abstract:

    Background Enantia chlorantha is a plant belonging to Annonaceae Family. The Barks and leaves are used traditionally to treat infectious diseases. Earlier studies highlighted the antibacterial activity of stem barks methanol extract. This study is thus aimed at investigating the effect of fractionation on antibacterial activity of its n-butanol fraction. Methods The extract of E. chlorantha stem barks was obtained by maceration in methanol and then subjected to a liquid/liquid partition by successive depletion with solvents of increasing polarity. The n-butanol fraction was fractionated by adsorption chromatography on silica gel. A product was isolated from the dichloromethane/methanol (2%) fraction and the structure was determined on the basis of spectroscopic data; Proton Nuclear Magnetic Resonance (^1H NMR), Carbon -13 Nuclear Magnetic Resonance (^13C NMR), Heteronuclear Multiple Bond Correlation (HMBC), H-correlation spectroscopy (H-COSY), Attached Proton Test (APT), heteronuclear multiple quantum coherence (HSQC). The antibacterial activity was evaluated by broth microdilution method against six reference strains and eight clinical bacterial strains. Results The n-butanol fraction was found to be active with MIC values ranging from 32 to 256 μg/mL. The F_A sub-fraction was more efficient among the eight sub-fractions, the n-butanol fraction and comparable to Chloramphenicol used as reference antibiotic. The product obtained was elucidated as palmitin. The antibacterial activity of the latter was comparable to that of Chloramphenicol on one reference strain and 4 of the 6 clinical strains. Conclusion The F_A sub-fraction had better antibacterial activity than the n-butanol fraction and other sub-fractions, and possibly palmitin was the active substance responsible for the antibacterial activity of E. chlorantha.

  • Effect of fractioning on antibacterial activity of n-butanol fraction from Enantia chlorantha stem bark methanol extract
    BMC Complementary and Alternative Medicine, 2019
    Co-Authors: Rebeca Madeleine Ebelle Etame, Raymond Simplice Mouokeu, Frank Stève Monthe Poundeu, Igor Kenfack Voukeng, Cedric Laurel Pouaha Cidjeu, Alembert Tchinda Tiabou, Abel Joel Gbaweng Yaya, Rosalie Anne Ngono Ngane, Jules Roger Kuiate, François Xavier Etoa

    Abstract:

    Enantia chlorantha is a plant belonging to Annonaceae Family. The Barks and leaves are used traditionally to treat infectious diseases. Earlier studies highlighted the antibacterial activity of stem barks methanol extract. This study is thus aimed at investigating the effect of fractionation on antibacterial activity of its n-butanol fraction. The extract of E. chlorantha stem barks was obtained by maceration in methanol and then subjected to a liquid/liquid partition by successive depletion with solvents of increasing polarity. The n-butanol fraction was fractionated by adsorption chromatography on silica gel. A product was isolated from the dichloromethane/methanol (2%) fraction and the structure was determined on the basis of spectroscopic data; Proton Nuclear Magnetic Resonance (1H NMR), Carbon-13 Nuclear Magnetic Resonance (13C NMR), Heteronuclear Multiple Bond Correlation (HMBC), H-correlation spectroscopy (H-COSY), Attached Proton Test (APT), heteronuclear multiple quantum coherence (HSQC). The antibacterial activity was evaluated by broth microdilution method against six reference strains and eight clinical bacterial strains. The n-butanol fraction was found to be active with MIC values ranging from 32 to 256 μg/mL. The FA sub-fraction was more efficient among the eight sub-fractions, the n-butanol fraction and comparable to Chloramphenicol used as reference antibiotic. The product obtained was elucidated as palmitin. The antibacterial activity of the latter was comparable to that of Chloramphenicol on one reference strain and 4 of the 6 clinical strains. The FA sub-fraction had better antibacterial activity than the n-butanol fraction and other sub-fractions, and possibly palmitin was the active substance responsible for the antibacterial activity of E. chlorantha.

Stephen B Kahl – 2nd expert on this subject based on the ideXlab platform

  • a useful modification of the Attached Proton Test 13c nmr experiment unambiguous peak assignments for carbons with large 1j ch values
    Tetrahedron Letters, 1996
    Co-Authors: Peggy A Radel, Stephen B Kahl

    Abstract:

    We have developed an extension of the APT 13C NMR experiment which differentiates tetracoordinate methine carbons and hexacoordinate 2-carboranyl carbons in complex organic molecules bearing o-carboranyl functionalities, as well as discriminating between pairs of carbons such as methylenes and terminal alkynes. The differences in the 1J(CH) of each carbon results in modified intensities in APT experiments using a 7.5 msec and a 10 msec delay. Comparing the spectra from these two experiments definitively assigns the peaks to the appropriate carbon, yielding information often only obtainable from 2D experiments.

Matej Krajnc – 3rd expert on this subject based on the ideXlab platform

  • Kinetic modeling of the peroxide cross-linking of polymers: From a theoretical model framework to its application for a complex polymer system
    Chemical Engineering and Processing, 2011
    Co-Authors: Blaž Likozar, Matej Krajnc

    Abstract:

    Peroxides react with polymers in a variety of ways. The fundamental comprehension and prediction of pertinent kinetics of reactions is consequently indispensable. Based on the mechanisms of reactions of cross-linking process, a new theoretical kinetic model framework was developed. The kinetic model was then applied to the reactions of cross-linking process of various peroxides and a chosen complex polymer compound, namely partially hydrogenated poly(acrylonitrile-co-1,3-butadiene). Whereas the initial macromolecular backbone structure was determined utilizing Attached Proton Test carbon nuclear magnetic resonance, the evolution of overall concentration of cross-links was monitored through viscoelastic characteristics of the system. The model demonstrated good agreement with experimentally measured data and, moreover; the evolution of concentrations of various crucial species inherent to the cross-linking process were predicted. The most significant advantage of the developed kinetic model is that it may be readily applied to an assortment of polymer/peroxide systems.

  • Kinetic modeling of the peroxide cross-linking of polymers: From a theoretical model framework to its application for a complex polymer system
    Chemical Engineering and Processing: Process Intensification, 2011
    Co-Authors: Blaž Likozar, Matej Krajnc

    Abstract:

    Peroxides react with polymers in a variety of ways. The fundamental comprehension and prediction of pertinent kinetics of reactions is consequently indispensable. Based on the mechanisms of reactions of cross-linking process, a new theoretical kinetic model framework was developed. The kinetic model was then applied to the reactions of cross-linking process of various peroxides and a chosen complex polymer compound, namely partially hydrogenated poly(acrylonitrile-co-1,3-butadiene). Whereas the initial macromolecular backbone structure was determined utilizing Attached Proton Test carbon nuclear magnetic resonance, the evolution of overall concentration of cross-links was monitored through viscoelastic characteristics of the system. The model demonstrated good agreement with experimentally measured data and, moreover; the evolution of concentrations of various crucial species inherent to the cross-linking process were predicted. The most significant advantage of the developed kinetic model is that it may be readily applied to an assortment of polymer/peroxide systems. © 2011 Elsevier B.V.