The Chemical Degradation of a Humic Acid

1973 ◽  
Vol 51 (10) ◽  
pp. 1554-1566 ◽  
Author(s):  
Morris Schnitzer ◽  
Maria Ines Ortiz de Serra
Keyword(s):  
Humic Acid ◽  
Chemical Structure ◽  
Degradation Products ◽  
Cupric Oxide ◽  
Chemical Degradation ◽  
Chromatographic Retention ◽  
Sequential Reaction ◽  
The Core ◽  
Preparative Gas Chromatography ◽  
Complex Core

A humic acid (HA) extracted from the A1 horizon of a Brunizem soil was degraded in the unmethylated and methylated form by sequential reaction with oxidants of increasing strength. The HA was first oxidized with alkaline cupric oxide; the products were then further degraded by oxidation with first alkaline KMnO4 and then with H2O2 in alkaline solution. Unmethylated HA was also degraded by Na-amalgam reduction. The degradation products were extracted into organic solvents, methylated, and separated by preparative gas chromatography into relatively pure components which were analyzed by mass spectrometry and micro-i.r. spectrophotometry. A matching of the mass and i.r. spectra and gas chromatographic retention times of the isolated components with those of authentic specimens led to their identification.The experimental data show that the HA contains a relatively easily degradable portion, which comprises guaiacyl and syringyl units and which may be lignin-derived (about 10% of the total weight). This material is degraded by CuO–NaOH oxidation and Na-amalgam reduction. The bulk of the HA structure, however, consists of a more condensed, chemically complex "core", which degrades on more drastic oxidation into complex phenolic and benzenepolycarboxylic acids. It is likely that the "core" originates in part from condensed lignin and in part from products of microbial synthesis. Of the methods investigated, the CuO–NaOH and the KMnO4 oxidation of methylated HA appear most promising for providing information on the chemical structure of the HA.

CHEMISTRY OF HUMIC SUBSTANCES EXTRACTED FROM AN ARCTIC SOIL

1975 ◽  
Vol 55 (2) ◽  
pp. 93-103 ◽  
Author(s):  
M. SCHNITZER ◽  
E. VENDETTE
Keyword(s):  
Humic Acid ◽  
Structural Information ◽  
Degradation Products ◽  
Cupric Oxide ◽  
Fulvic Acids ◽  
Climatic Conditions ◽  
Optical Measurements ◽  
The Arctic ◽  
Humic And Fulvic Acids ◽  
Near Surface

A humic and a fulvic acid, extracted from the Ahb horizon of an earth hummock occurring on an Alpine Tundra (Brunic Turbic Cryosol) in the northern part of the Mackenzie river in the Northwest Territories, were characterized by elementary and functional group analyses and by optical measurements. To obtain more detailed structural information, the humic acid, the major organic fraction in the soil extract, was degraded by alkaline permanganate and alkaline cupric oxide oxidation. The degradation products were identified on a gas chromatographic–mass spectrometric–computer system. The analytical characteristics of the Arctic humic and fulvic acids were similar to those reported in the literature for humic and fulvic acids from more moderate climates. However, effects of near-surface permafrost and harsh Arctic climatic conditions manifested themselves in the degradation data. Compared to humic acids from warmer climates, the Arctic humic acid appeared to be poorly developed, exhibiting a low degree of condensation and aromaticity, a low resistance to mild chemical oxidants, yielding only very small amounts of benzenepolycarboxylic acids higher than the di-forms, but relatively large quantities of aliphatic carboxylic acids, especially the n-C16 and n-C18 fatty acids.

Phase I Study of the Novel Epothilone Analog Ixabepilone (BMS-247550) in Patients With Advanced Solid Tumors and Lymphomas

2007 ◽  
Vol 25 (9) ◽  
pp. 1082-1088 ◽  
Author(s):  
Carol Aghajanian ◽  
Howard A. Burris ◽  
Suzanne Jones ◽  
David R. Spriggs ◽  
Marvin B. Cohen ◽  
...  
Keyword(s):  
Plasma Concentration ◽  
Solid Tumors ◽  
Dose Escalation ◽  
Mononuclear Cells ◽  
Degradation Products ◽  
Standard Dose ◽  
Chemical Degradation ◽  
Maximum Plasma ◽  
Advanced Solid Tumors ◽  
Phase Ii Studies

Purpose To establish the maximum-tolerated dose (MTD), dose-limiting toxicity (DLT), safety, pharmacokinetics, and pharmacodynamics of ixabepilone when administered as a 1-hour infusion every 3 weeks to patients with advanced solid tumors or relapsed/refractory non-Hodgkin's lymphoma. Dosing schedules of 40 mg/m2 and 50 mg/m2 over 3 hours were also evaluated. Patients and Methods Sixty-one patients were enrolled using an initial accelerated dose-escalation phase followed by a standard dose-escalation phase, with doses of ixabepilone ranging from 7.4 to 65 mg/m2. The pharmacokinetics of ixabepilone and two of its chemical degradation products were evaluated. Plasma pharmacodynamics were evaluated for both 1- and 3-hour infusions using an assay that measures the amount of endogenous tubulin in peripheral-blood mononuclear cells that exists in the polymerized versus the unpolymerized state. Response evaluation was performed every 6 weeks. Results The most common DLTs were neutropenia, stomatitis/pharyngitis, myalgia, and arthralgia. The MTD of ixabepilone as a 1-hour infusion every 3 weeks was established as 50 mg/m2. The maximum plasma concentration and area under the plasma concentration time curve appeared to increase less than proportionally to dose. Durable objective responses were seen in eight patients, including two complete responses. Five of the responders had experienced treatment failure with a taxane. Conclusion The recommended dose of ixabepilone for the initiation of phase II studies on the basis of these results is 50 mg/m2 over 1 hour every 3 weeks. The promising efficacy and tolerability results demonstrated by ixabepilone in this study warrant its continued development.

scholarly journals Demystifying and Unravelling the Factual Molecular Structure of the Biopolymer Sporopollenin

2019 ◽  
Author(s):  
Abanoub Mikhael ◽  
Kristina Jurcic ◽  
Celine Schneider ◽  
David carr ◽  
Gregory L. Fisher ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Nuclear Magnetic Resonance ◽  
Chemical Structure ◽  
Pollen Grains ◽  
Outer Wall ◽  
Mass Spectrometric ◽  
Chemical Degradation ◽  
Ionization Mass ◽  
Soft Ionization ◽  
Biochemical Pathways

<p></p><p>Sporopollenin is a natural, highly cross-linked biopolymer composed of carbon, hydrogen, and oxygen, which forms the outer wall of pollen grains. Sporopollenin is resilient to chemical degradation.<sup> </sup>Because of this stability, its exact chemical structure and the biochemical pathways involved in its biosynthesis remains a mystery and unresolved.<sup> </sup></p> <p>We have identified and characterized the molecular structure of the clean, intact sporopollenin using soft ionization mass spectrometric and nuclear magnetic resonance techniques. These analyses showed that sporopollenin contained a poly(hydroxyacid) dendrimer-like network, which accounted for the sporopollenin empirical formula. In addition, the identified hydroxy acid monomers contained a beta diketone moiety, which most probably accounts for the known antioxidant activity of sporopollenin. Moreover, our elucidation studies allowed us to identify a unique circular polyhydroxylated tetraketide polymer. This polymer acted as the rigid backbone on which the poly(hydroxyacid) network can be built, forming the scaffold of the spherical sporopollenin exine.</p><br><p></p>

Identification of new aqueous chemical degradation products of isophosphoramide mustard

2001 ◽  
Vol 25 (3-4) ◽  
pp. 669-678 ◽  
Author(s):  
Stéphane Breil ◽  
Robert Martino ◽  
Véronique Gilard ◽  
Myriam Malet-Martino ◽  
Ulf Niemeyer
Keyword(s):  
Degradation Products ◽  
Chemical Degradation ◽  
Isophosphoramide Mustard

scholarly journals Effect of Chemical Structure and Degree of Branching on the Stability of Proton Exchange Membranes Based on Sulfonated Polynaphthylimides

Polymers ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 652
Author(s):  
Chunmei Gao ◽  
Jiale Chen ◽  
Boping Zhang ◽  
Lei Wang
Keyword(s):  
Oxidative Stability ◽  
Chemical Structure ◽  
Hydrolytic Stability ◽  
Oxidation Stability ◽  
Proton Exchange Membranes ◽  
Proton Exchange ◽  
Ether Linkage ◽  
Degree Of Branching ◽  
The Core ◽  
The Stability

Hydrolytic stability and oxidative stability are the core properties of sulfonated polynaphthylimides (SPIs) as proton exchange membranes. The chemical structure of SPIs directly influences the performance. Herein, three different series of branched SPIs were designed and prepared using 1,3,5-tris (2-trifluoromethyl-4-aminophenoxy) benzene as a trifunctional monomer and three non-sulfonated diamine monomers, such as 4,4′-oxydianiline (ODA), 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (6FODA), and 4,4′-(9-fluorenylidene)dianiline (BFDA). The effect of the chemical structure and degree of branching on SPIs properties is discussed. The results showed that by controlling the chemical structure and degree of branching, the chemical stability of SPIs changed significantly. SPI-6FODA with two ether linkages and a hydrophobic CF3 group has higher hydrolytic stability than SPI-ODA with only one ether linkage. In addition, with the increase of the introduced B3 monomer, the oxidation stability of SPI-6FODA has been greatly improved. We successfully synthesized SPIs with a high hydrolytic stability and oxidative stability.

scholarly journals A dynamic plant chamber system with downstream reaction chamber to study the effects of pollution on biogenic emissions

2013 ◽  
Vol 6 (5) ◽  
pp. 9005-9036
Author(s):  
J. Timkovsky ◽  
P. Gankema ◽  
R. Pierik ◽  
R. Holzinger
Keyword(s):  
Degradation Products ◽  
Proton Transfer Reaction ◽  
Reaction Chamber ◽  
Oxidation Products ◽  
Chemical Degradation ◽  
Biogenic Emissions ◽  
Dynamic Plant ◽  
Cryogenic Trapping ◽  
Plant Emissions ◽  
Set Up

Abstract. A system of two dynamic plant chambers and a downstream reaction chamber has been set up to investigate the emission of biogenic volatile organic compounds (BVOC) and possible effects from pollutants such as ozone. The system can be used to compare BVOC emissions from two sets of differently treated plants, or to study the photochemistry of real plant emissions under polluted conditions without exposing the plants to pollutants. The main analytical tool is a proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF-MS) which allows online monitoring of biogenic emissions and chemical degradation products. The identification of BVOCs and their oxidation products is aided by cryogenic trapping and subsequent in situ gas chromatographic analysis. The data presented in the paper demonstrates the good performance of the setup.

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