Unstable Compounds Research Articles

Pyrometallurgical processing of deactivated nickel catalysts on Al2O3 carrier

The paper considers the use of deactivated nickel-containing catalysts based on Al2O3 as a significant raw material resource of one of the most important metals. The research highlights the features of this secondary nickel source that determine the acceptable methods of processing such raw materials. The effect of fluxing additives on the properties of the melt containing catalysts prepared beforehand has been studied subject to limitations as to their list (lime, fluorspar) in order to implement a pyrometallurgical method of metal extraction featuring by a relatively small amount of additives themselves. Due to induction heating used in combination with a graphite crucible, adding the total amount of fluorspar and marble additives close in mass made it possible to obtain the melt at a temperature slightly higher than the nickel melting temperature. In this case, the level of metal losses was about 2 %, which indicates the applicability of this method in laboratory conditions to ensure correct incoming analysis. It was proposed to use the pyrometallurgical method on an industrial scale using closed arc heating. To confirm this conclusion, experiments were conducted with a representative (more than 100 kg) amount of catalyst using a tailored arc furnace. Graphite chips were used as a reducing agent. The necessity of electrical matching of the load with the power source resulted in some adjustment of the fluxing additive ratio towards a reduction of calcium oxide content. As a result of a series of experiments, nickel with an up to 5 % iron admixture, similar in composition to the metal formed in the graphite crucible, was obtained. The presence of iron was caused by the fundamentally distinctive capability of the pyrometallurgical technology to reduce unstable compounds. Therefore it was suggested to use this metal for ferronickel production. The use of scarce fluorspar is justified by the fact that the resulting slag can be in demand in the production of fluxes for the electroslag remelting process.

Surface Analysis of Pristine and Cycled NMC/Graphite Lithium-Ion Battery Electrodes: Addressing the Measurement Challenges.

Lithium-ion batteries are the most ubiquitous energy storage devices in our everyday lives. However, their energy storage capacity fades over time due to chemical and structural changes in their components, via different degradation mechanisms. Understanding and mitigating these degradation mechanisms is key to reducing capacity fade, thereby enabling improvement in the performance and lifetime of Li-ion batteries, supporting the energy transition to renewables and electrification. In this endeavor, surface analysis techniques are commonly employed to characterize the chemistry and structure at reactive interfaces, where most changes are observed as batteries age. However, battery electrodes are complex systems containing unstable compounds, with large heterogeneities in material properties. Moreover, different degradation mechanisms can affect multiple material properties and occur simultaneously, meaning that a range of complementary techniques must be utilized to obtain a complete picture of electrode degradation. The combination of these issues and the lack of standard measurement protocols and guidelines for data interpretation can lead to a lack of trust in data. Herein, we discuss measurement challenges that affect several key surface analysis techniques being used for Li-ion battery degradation studies: focused ion beam scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and time-of-flight secondary ion mass spectrometry. We provide recommendations for each technique to improve reproducibility and reduce uncertainty in the analysis of NMC/graphite Li-ion battery electrodes. We also highlight some key measurement issues that should be addressed in future investigations.

Addition of Trans-Resveratrol-Loaded, Highly Concentrated Double Emulsion to Moisturizing Cream: Effect on Physicochemical Properties

Resveratrol is a compound increasingly studied for its many beneficial properties for health. However, it is a highly unstable photosensitive compound, and therefore it is necessary to encapsulate it to protect it if you want to use it in a commercial product. Emulsions are systems that allow the encapsulation of active ingredients, protecting them and allowing their release in a controlled manner. They are highly used systems in the pharmaceutical, cosmetic and food industries. The main objectives of this work are to study the feasibility of encapsulating resveratrol in concentrated water-in-oil-in-water double emulsions and the effect produced by adding the double emulsion with optimal formulation to a commercial cream for cosmetic applications. The effect of the selected optimal double emulsion on a commercial cream was studied, analyzing droplet size distribution, morphology, stability and rheology. The main conclusion of this work is that incorporating 1/3 of concentrated double emulsion W1/O/W2 into a commercial moisturizing cream had a positive physical effect and produced cream with a resveratrol concentration of up to 0.0042 mg/g.

Food preservation by cold plasma from dielectric barrier discharges in agri-food industries.

Cold plasma (CP) can be defined as partially or wholly ionized gas carrying myriads of highly reactive products, such as electrons, negative ions, positive ions, free radicals, excited or non-excited atoms, and photons at ambient temperature. It is generated at 30-60°C under atmospheric or reduced pressure (vacuum). In contrast to thermal plasma, it requires less power, exhibits electron temperatures much higher than the corresponding gas (macroscopic temperature), and does not present a local thermodynamic equilibrium. Dielectric barrier discharges (DBD) are one of the most convenient and efficient methods to produce CP. Cold plasma technology has the potential to replace traditional agri-food processing purification methods because of its low energy requirements and flexible system design. CP technology works by reducing bacteria levels and removing pests and mycotoxins from your produce at harvest. It can also catalyze physiological and biochemical reactions and modify materials. It can meet microbial food safety standards, improve the physical, nutritional, and sensory characteristics of the products, preserve unstable bioactive compounds, and modulate enzyme activities. This manuscript also discusses the quality characteristics of food components before/after CP treatment. In the past decade, CP treatments of food products have experienced increased popularity due to their potential contributions to non-thermal food processing. There is no doubt that CP treatment is a flexible approach with demonstrated efficacy for controlling many risks across food and agricultural sustainability sectors. In addition, CP technologies also can be applied in food-related areas, including modification of chemical structures and desensitization treatments. There is a need to fully assess the benefits and risks of stand-alone CP unit processes or their integration as a processing chain as soon as the economic, ecological, and consumer benefits and acceptability are considered.

In Silico Identification of Multi-Target Ligands as Promising Hit Compounds for Neurodegenerative Diseases Drug Development.

The conventional treatment of neurodegenerative diseases (NDDs) is based on the "one molecule-one target" paradigm. To combat the multifactorial nature of NDDs, the focus is now shifted toward the development of small-molecule-based compounds that can modulate more than one protein target, known as "multi-target-directed ligands" (MTDLs), while having low affinity for proteins that are irrelevant for the therapy. The in silico approaches have demonstrated a potential to be a suitable tool for the identification of MTDLs as promising drug candidates with reduction in cost and time for research and development. In this study more than 650,000 compounds were screened by a series of in silico approaches to identify drug-like compounds with predicted activity simultaneously towards three important proteins in the NDDs symptomatic treatment: acetylcholinesterase (AChE), histone deacetylase 2 (HDAC2), and monoamine oxidase B (MAO-B). The compounds with affinities below 5.0 µM for all studied targets were additionally filtered to remove known non-specifically binding or unstable compounds. The selected four hits underwent subsequent refinement through in silico blood-brain barrier penetration estimation, safety evaluation, and molecular dynamics simulations resulting in two hit compounds that constitute a rational basis for further development of multi-target active compounds against NDDs.

Possible molecular mechanism for acute encephalopathy by angel-wing mushroom ingestion – Involvement of three constituents in onset –

In Japan in 2004, 59 people who had consumed angel-wing mushroom, Pleurocybella porrigens, experienced acute encephalopathy, and of these 17 died. We purified a lethal protein to mice, pleurocybelline (PC), from P. porrigens. Although PC caused no damage to the brain, PC formed a complex with a lectin (PPL) and showed exo-protease activity, degrading substrates from both N- and C-termini. In addition, the presence of an unstable toxic compound, pleurocybellaziridine (PA), in the mushroom was demonstrated. We hypothesized that the complex and PA are involved in disease development and verified that apoptotic cells in the hippocampus were significantly increased by injection of the mixture of PC, PPL, and PA, indicating that these substances might be involved in acute encephalopathy.

Measurement of the critical temperatures, pressures, heat capacities, and thermal diffusivities of four furanic compounds involved in the production of second-generation biofuels

The critical temperatures, critical pressures, heat capacities, and thermal diffusivities have been measured for furfural, furfuryl alcohol, furfuryl acetate, and tetrahydrofurfuryl alcohol, the compounds of industrial importance because they are involved in the production of biofuels. The critical properties have been measured using the pulse-heating method applicable to thermally unstable compounds. The relative combined expanded uncertainties with the 0.95 level of confidence are 0.01 and 0.03 for the critical temperature and pressure of furfural and furfuryl acetate and 0.015 and 0.04 for furfuryl alcohol and tetrahydrofurfuryl alcohol. The acentric factors of the compounds have been calculated based on the experimental data. The critical properties of the compounds have also been calculated by the group contribution methods of Wilson and Jasperson, Nannoolal et al. Marrero and Gani, Hukkerikar et al. in two variants. The Wilson and Jasperson and Nannoolal et al. techniques provide the best estimation of the critical temperature; for the critical pressure, the Nannoolal et al. method gives the best results. The heat capacities in the liquid phase have been measured at atmospheric pressure in the temperature range from 298.15 to 451.15 K by DSC technique with relative combined expanded uncertainty 0.03. The data obtained have been approximated by third-order polynomials. The experimental heat capacities have been compared with those calculated by the group-contribution method of Kolska et al. The thermal diffusivities have been measured by laser flash method at atmospheric pressure in the temperature range from 313.15 to 373.15 K with relative combined expanded uncertainty 0.05. The experimental data have been approximated by first-order polynomials. The thermal conductivities have been calculated using the experimental data obtained.

High efficient vanadium extraction from vanadium slag using an enhanced acid leaching-coprecipitation process

Vanadium slag (VS) is a by-product of vanadium titanium magnetite BOF steelmaking process and becomes an important material for vanadium products preparation. Sodium roasting-water leaching is a mainstream process for industrial production, but the water leaching residue (WLR) usually remains 1.0 wt% to 3.0 wt% V2O5, which still has value for recycling extraction of vanadium. In this research, a two-stage leaching process was proposed for high efficient vanadium extraction. The first stage leaching was sodium roasting-water leaching for vS and the second stage leaching was sulfuric acid leaching for WLR. As a result, the total leaching efficiency of vanadium can reach as high as 98.52%, which was 7.72% higher than that of conventional water leaching efficiency of vanadium (90.80%). The mechanism analysis indicates that the CaNaFe2Si4O12 and NaFeSi2O6 water-insoluble phases formed and covered on (Mn,Fe)(V,Cr)2O4 spinel surface during roasting, hindering vanadium oxidation and dissolution. The structures of wrapping phases and spinel can be effectively destroyed by acid leaching, releasing vanadium in WLR. By using hydrolytic precipitation of iron ions in acid leachate, 99.78% of vanadium can be recovered as V-Fe precipitation slag, which contains 6.83 wt% V2O5 and can be cycled back to sodium roasting process. The V-Fe slag belongs to amorphous precipitation, illustrating that residual vanadium in WLR can be changed to unstable compound by acid leaching and hydrolysis precipitation, which makes vanadium easier to extract during sodium roasting-water leaching process. This research has the advantages of enhanced reuse of V resource in the WLR, achieving a high V recovery. The short process has a strong adaptability and can provide technical support for efficient V extraction from vS.

Experimental and theoretical study on the transformation of typical organic sulfur during hydrothermal carbonization of sludge

This study reports the migration and transformation of sulfur during the hydrothermal carbonization of sludge and two thermal unstable organic-S model compounds (aliphatic-S and aromatic-S) at 150 to 240 °C, focusing on the pathways based on the molecular level. The theoretical calculation indicates that the sulfur atom is the initial attacked position by nucleophile in the organic-S molecule, caused by its maximum contribution (i.e., 73.54 % for aliphatic-S) to the highest occupied molecular orbital (HOMO) and the minimum point of electrostatic potential (ESP, i.e., −103.68 kJ/mol for aliphatic-S). This leads to the nucleophilic addition reaction of aliphatic-S and aromatic-S, especially at 210 °C, along with the generation of sulfoxide-S and sulfone-S. Compared with aromatic-S, the aliphatic-S is more inclined to oxidation because of its higher HOMO contribution and lower ESP. Due to the low bond dissociation energy of CS of formed sulfoxide-S and sulfone-S, large of them (i.e., 47.51 % at 210 °C) transform to SO32- and SO42- ions via desulfurization and oxidation reactions, resulting in a low sulfur content in hydrochar. Also, the sulfoxide-S derived from aliphatic-S is more likely to decompose than other intermediates, together with the aliphatic-S, released as sulfur-containing odorants (especially for H2S, CH3SH and SO2). These findings indicate that fixing the aliphatic-S is an effectively method to control the emission of odorants.

Effect of Spray Drying Encapsulation on Nettle Leaf Extract Powder Properties, Polyphenols and Their Bioavailability.

Nettle (Urtica dioica L.) is a plant rich in a health-promoting compounds such as polyphenols, which are sensitive and unstable compounds with low bioavailability, that need to be stabilized and protected from external influences. Therefore, the aim of this study was to examine how the temperature, type of carrier and sample to carrier ratio influence the physicochemical properties and encapsulation and loading capacity of the nettle leaf extract powder and examine the effect of encapsulation on the antioxidant capacity and bioavailability of polyphenols. The process yield ranged from 64.63–87.23%, moisture content from 1.4–7.29%, solubility from 94.76–98.53% and hygroscopicity from 13.35–32.92 g 100 g−1. The highest encapsulation (98.67%) and loading (20.28%) capacities were achieved at 160 °C, β-CD:GA (3:1) and sample:carrier ratio of 1:3. Extracts encapsulated at selected conditions showed high antioxidant capacity and distinct polyphenolic profile comprised of 40 different compounds among which cinnamic acids were the most abundant. Moreover, the encapsulation increased the bioavailability of nettle leaf polyphenols, with the highest amount released in the intestinal phase. Thus, the obtained encapsulated extract represents a valuable source of polyphenols and may therefore be an excellent material for application in value-added and health-promoting products.

Characterization of key odor-active compounds in pure chicken powder and the effect of yeast extract, using instrumental and sensory techniques

Pure chicken powder (PCP) is a reliable source of mellow chicken soup flavor in seasoning, but it has some unstable compounds and is prone to lipid oxidation, which leads to unpleasant odor. Adding yeast extract (YE) can reduce the off-odor intensity of PCP. Based on the results of gas chromatography–olfactometry–mass spectrometry (GC–O-MS), two-dimensional comprehensive gas chromatography–olfactometry–mass spectrometry (GC×GC–O–MS) and combined aroma extract dilution analysis (AEDA), 14 key odor-active compounds were identified. Internal standard curve method was used for quantitative analysis, and the odor activity value (OAV) was calculated. Octanal, 1-octen-3-ol and hexanal were found to be the most vital odor-active compounds in PCP. The odor-active compounds of YE were studied by the same method, and dimethyl trisulfide was identified as the most important odor-active compound of YE. Additionally, recombination and omission experiments were carried out with PCP. Finally, it was found that a low concentration of dimethyl trisulfide had masking effect on the odor of PCP.

Chitosan-based matrix solid-phase dispersion extraction assisted cell membrane magnetic bead ligand-affinity assay for screening active compounds from Fructus Cnidii.

Cell membrane ligand-affinity assay is a useful tool for screening the active compounds from natural products. However, in traditional cell membrane ligand-affinity assays, natural products need to be refluxed, before being analyzed. This process consumes considerable time and energy and cannot be used for screening natural products that contain thermally unstable compounds. Therefore, an efficient analytical method is required. In this study, chitosan-based matrix solid-phase dispersion extraction was combined with cell membrane magnetic bead ligand-affinity assay to form a novel method for identifying the active compounds in Fructus Cnidii such as osthole and imperatorin. When compared with traditional cell membrane ligand-affinity assays, this assay requires less energy, extraction time (7min), solvent volume (1.2mL), and fewer natural products (40mg). This indicates that the chitosan-based matrix solid-phase dispersion extraction assisted cell membrane magnetic beads ligand-affinity assay is an alternative analytical method for studying natural products.

Carbene reactivity from alkyl and aryl aldehydes.

Carbenes are highly enabling reactive intermediates that facilitate a diverse range of otherwise inaccessible chemistry, including small-ring formation and insertion into strong σ bonds. To access such valuable reactivity, reagents with high entropic or enthalpic driving forces are often used, including explosive (diazo) or unstable (gem-dihalo) compounds. Here, we report that common aldehydes are readily converted (via stable α-acyloxy halide intermediates) to electronically diverse (donor or neutral) carbenes to facilitate >10 reaction classes. This strategy enables safe reactivity of nonstabilized carbenes from alkyl, aryl, and formyl aldehydes via zinc carbenoids. Earth-abundant metal salts [iron(II) chloride (FeCl2), cobalt(II) chloride (CoCl2), copper(I) chloride (CuCl)] are effective catalysts for these chemoselective carbene additions to σ and π bonds.

In vitro inhibition of advanced glycation end product formation by ethanol extract of milk thistle (Silybum marianum L.) seed

Glycation of proteins by reducing sugars produces toxic and immunogenic compounds called advanced glycation end products (AGEs). AGEs plays important role in the progression of typical diabetes complications. Silybum marianum L. contains powerful antioxidants that quench free radicals, which are unstable and reactive compounds that damage DNA and cellular structures. This study aimed to evaluate the antioxidant activities and the inhibitory effects of ethanol:water (1:1) extract of the Silybum marianum seed (SlyE) and silymarin (Sly) on fructose mediated protein glycation and AGE formation. The total amount of silymarin in SlyE was found to be 2.59 mg/gDW by HPLC. The composition of phenolic in the extract was found to be 262.70 µg gallic acid (GAE)/mg extract. The composition of flavonoids in the extract was found to be 10.50 µg quercetin (QUE)/mg extract. The seed exhibited ABTS radical cation decolourization inhibition with 70.4% at 300 mg concentration. Ferric reducing power of the extract was also evaluated. The SlyE and Sly also demonstrated strong inhibitory effects on the production AGEs in bovine serum albumin (BSA)/fructose model. SlyE and Sly has a significant effect in preventing oxidative protein damage, including the effect on the formation of fructosamines, α-dicarbonyls and protein carbonyl content (PCC). SlyE and Sly were able to prevent the glycoxidative damage of BSA. It can be concluded that the SlyE has antiglycating potential as well as antioxidant properties.

Reaction of α-Diazopyrroles with Enamines: Synthesis of Pyrrolo[2,1-c][1,2,4]triazines and α-(1,2,5-Triazapenta-1,3-dienyl)pyrroles.

α-Diazopyrroles selectively react with enamines at room temperature to give either (4+2)-cycloaddition-dehydroamination cascade products, pyrrolo[2,1-c][1,2,4]triazines, or azo coupling products. The reaction was used for the synthesis of functionalized ortho-fused heterocycles with new tetrahydrobenzo[e]pyrrolo[2,1-c][1,2,4]triazine and tetrahydro-6H-cyclohepta[e]pyrrolo[2,1-c][1,2,4]triazine frameworks. Unstable azo compounds, 2-[(2-aminovinyl)diazenyl]pyrroles, were obtained from enamines of tetralone or acyclic ketones. According to the density functional theory calculations, (4+2)-cycloaddition of α-diazopyrroles with enamines proceeds in a nonconcerted manner via the zwitterionic intermediate, which undergoes cyclization to pyrrolotriazine or a competitive 1,5-prototropic shift leading to the formation of azo coupling product.

Delivery of silybin using a zein-pullulan nanocomplex: Fabrication, characterization, in vitro release properties and antioxidant capacity

Silybin (Sil) is a natural flavonoid that is mostly used clinically in the treatment of cirrhosis. However, its low water solubility and chemical instability hinder its practical application. In this study, zein-pullulan nanoparticles loaded with Sil (Sil@Pl-zeinNPs) were prepared by an anti-solvent precipitation method for the delivery of Sil, thereby improving its low water solubility and chemical instability with a view to expanding its clinical applications. By optimizing the preparation process of Sil@Pl-zeinNPs, it was found that when the zein-to-Sil ratio of 10:1 (w/w), Pl (0.5 mg/mL), the Sil@Pl-zeinNPs were uniformly distributed and showed smooth spherical shape with an average particle size of about 115 nm. In addition, Sil@Pl-zeinNPs exhibited high encapsulation efficiency (96.93%), remained stable under extreme environments such as strong acids, high temperatures and high salinity, and did not precipitate or aggregate after many days of storage, probably due to zein being encapsulated by pullulan (Pl) to enhance the stability of the drug delivery system. Finally, in vitro experiments have shown that Sil@Pl-zeinNPs could achieve sustained release of Sil while further enhancing antioxidant capacity. Overall, the present study provides a novel and effective delivery system for chemically unstable hydrophobic compounds such as Sil.

Isolation and identification of unstable components from Caesalpinia sappan by high-speed counter-current chromatography combined with preparative high-performance liquid chromatography

Abstract Caesalpinia sappan L. (C. sappan L.), a traditional Chinese medicine, has been widely used to treat bruises and dysmenorrhea, performing pharmacological activities such as anti-inflammatory and anti-tumor. C. sappan L. has been reported to contain compounds such as protosappanins, brazilins, and homoisoflavones. In the pre-experiments, we discovered that there were many unstable components in the characteristic chromatogram of C. sappan L. Here, silica-gel column chromatography, high-speed counter-current chromatography, and preparative high-performance liquid chromatography were combined and applied to isolate the unstable components from alcohol extract of C. sappan L. The results showed that four unstable compounds were collected with the purity higher than 95.0%, characterized as episapponal, brazilin, sapponal, and 4-O-methylsapponal by hydrogen-1 and carbon-13 nuclear magnetic resonance. Based on the above results, the characteristic chromatogram of C. sappan L. was established, and the characteristic peaks were identified. These results provided a theoretical basis for the quality assessment of C. sappan L.

Solvent Cage Concept for the Homolytic Fragmentation of the Peroxynitrite-CO2 Adduct, ONOOCO2.

The toxicity of peroxynitrite, ONOO-, is directed by carbon dioxide via the formation of the corresponding adduct, ONOOCO2-. Entity ONOOCO2- is believed to be a highly unstable compound that primarily decomposes to nitrate and carbon dioxide, but it also undergoes fractional homolysis to generate carbonate radical anion, CO3•-, and nitrogen dioxide, NO2•, in a so-called solvent (radical) cage reaction. Recently, Koppenol et al. reviewed their proposal that ONOOCO2- is a relatively long-lived intermediate, arguing that "the solvent cage as proposed is physically not realistic". To further address whether ONOOCO2- could be a long-lived species, bond dissociation enthalpies (BDE) were calculated by the composite reference method (SMD)W1BD. Anion ONOOCO2- can exist in two conformers, s-cis-gauche and s-trans-gauche with predicted gas-phase O-O BDEs of about 10.8 and 9.5 kcal mol-1, respectively. Therefore, both conformers should have very short lifetimes. The (SMD)W1BD method was also used to evaluate the thermodynamic parameters of interest, revealing that the homolytic decomposition of ONOOCO2- is the most reasonable pathway. Moreover, previously reported experimental chemically induced dynamic nuclear polarization data also support the intermediacy of the radical cage and the formation of products CO2 and NO3- at a total yield of about 70%. Because the solvent radical cage concept for the decay of ONOO- in the presence of CO2 is supported by a variety of spectrometric methods as well as by quantum chemical calculations at high levels of theory, it provides strong evidence against the "out-of-cage" construct. For clarification of the nature of the transient UV/vis absorption(s) between 600 and 700 nm, as observed by Koppenol et al., several experimental approaches are suggested.

Hydrogen-bond acidity of silanols: A combined experimental and theoretical study

The hydrogen-bond (H-bond) donating ability of a series of silanol derivatives has been determined by FTIR spectrometry and complemented by quantum chemistry calculations at the DFT (MPWB1K/6-31+G(d,p)) level. The equilibrium constants of complexation with N-methylpyrrolidinone have been measured in CCl4 solutions. These data expand the pKAHY scale previously covering the field of aliphatic alcohols, phenols and fluorohydrins. Compared to the corresponding alcohol derivatives, the silanol chemical function is found to be a stronger H-bond donor, although the observed frequency shifts, ΔνOH, suggest much greater differences in donor strength than is actually observed. The electrostatic potential descriptor, Vα(r), is successfully used to complete the pKAHY vs. Vα(r) relationship, a helpful methodology to validate the experimental data and to estimate the H-bond acidity of unavailable, unstable, or immiscible compounds.

Molecular composition and structure of organic matter in density fractions of soils amended with corn straw for five years

Corn straw is an important source of carbon (C), and when applied to soil, it alters the accumulation and distribution of organic C. However, the mechanistic pathways by which newly added C is stored and stabilized in soil remain a subject of interest and debate among scholars. In this study, we investigated the chemistry of organic matter in different soil density fractions of Haplic Cambisol (sandy clay loam) separated from no-till (NTS), minimum tilled (MTS), and conventional tilled (CTS) fields amended with 8900 kg ha−1 year−1 of corn straw. After five years of corn (Zea mays L.) monocropping, soils were collected from the 0–20 and 20–40 cm depths, and processed to obtain their light fraction, occluded particulate, and heavy fraction organic matter(LFOM, oPOM, and HFOM, respectively). The results showed that compared with CT (conventional tillage without corn straw return), corn straw-amended soils (i.e., NTS, MTS, and CTS) increased soil organic C content by 11.55–16.58%. Thermogravimetric and Fourier transform infrared analyses demonstrated that the HFOM was characterized by a greater proportion of easily biodegradable substances, which may be due to the deposition of microbially processed materials on the surface of soil minerals. The LFOM and oPOM fractions were distinguished by their greater phenolic, aromatic C, and thermally stable compounds. Compared with CT, the NTS and MTS fields showed higher abundances of hydrophobic, aliphatic, and thermally unstable organic compounds, which increased soil C content and stability in the HFOM. Therefore, NTS and MTS may be ideal practices to increase soil organic C content in Haplic Cambisol.