Amino Aldehydes Research Articles

Effects of dietary N-carbamylglutamate supplementation on milk production performance, nutrient digestibility and blood metabolomics of lactating Holstein cows under heat stress

Heat stress is a serious threat to dairy cow health worldwide. N-carbamylglutamate (NCG), a novel feed additive, has been applied in dairy cow industry. However, the effects and mechanisms of NCG on dairy cows under heat stress are still unknown. A total of 48 Holstein dairy cows with similar days in milk (154 ± 13.6 d), parity (1-3), and body condition score were randomly divided into 4 groups of 12 animals each. Under heat stress, the cows were fed a TMR diet supplemented with 0 (control), 15, 20, 25 g of NCG/d per cow for 60 days. Milk production performance was recorded and serum parameters were examined. Meanwhile, metabolomics study of plasma based on liquid chromatography-mass spectrometry was also applied to investigate metabolites and pathways in response to NCG supplementation. Milk yield was increased but milk urea nitrogen was reduced by the NCG treatment. Addition of 15 g of NCG/d increased the milk protein percentage compared with the control. No effect of NCG was observed on dry matter intake, lactose percentage, milk fat percentage and somatic cell count. Serum glucose concentrations in cows fed with 15, 20, 25 g of NCG/d were 5.34 ± 0.312, 5.78 ± 0.473 and 5.54 ± 0.711 mmol/L, which were greater than those in the control (4.87 ± 0.367 mmol/L, P < 0.05). Meanwhile, the concentrations of blood urea nitrogen and blood ammonia were decreased with the addition of NCG. Results for antioxidant capacity and immune function showed beneficial effects of NCG, such as the increases in total antioxidant capacity, superoxide dismutase, glutathione peroxidase, IgG, IgM and IgA. Clear separations of plasma metabolic profiles between control and NCG groups were observed in the score plots. Sixteen different metabolites involved in metabolisms of amino acids, ketone bodies, butanoate and energy, as well as gut microbiome-derived metabolism were regulated by NCG supplementation. In conclusion, supplementation with NCG has the potential to enhance production performance, antioxidant capacity and immune function, and improved the metabolic profile of dairy cows under heat stress.

Decarboxylative Carbonylation of α-Amino Acids

Key words photoredox catalysis - N-heterocyclic carbene catalysis - amino ketones - decarboxylation - carbonylation

Formal Ring Contraction of Cyclic N‐Sulfonamides via C−N Bond Cleavage and α‐Amination by Oxidation of Halides

AbstractAn oxidative C−N bond cleavage reaction of substituted cyclic sulfonamides that proceeds via oxidation of bromide ion in hydrogen bromide solution was developed to furnish N‐sulfonamide‐protected acyclic amino ketones in high yields. The subsequent α‐amination of the amino ketones via the oxidation of iodide in tetrabutylammonium iodide provided 2‐acyl cyclic sulfonamides in good yields. The combination of these transformations involving the oxidation of halides resulted in a formal ring contraction of substituted cyclic amides.magnified image

Jiangrine-like scaffolds from biorenewable platforms

Dihydrolevoglucosenone (DLGO) and amino aldehydes undergo an aldol reaction mediated by the heterogenous base KF-alumina; exposure of the aldol adducts to hydrogenation followed by silica gel results in the formation of pyrrole-2-carbaldehydes bearing the jiangrine alkaloid scaffold. KF-alumina is also an effective base in the aldol condensation between DLGO and aliphatic/aromatic aldehydes, with no self-aldol reaction apparent.

P112. Role of metabolites in bio-fluids as a prognostic indicator of neurological recovery in acute spinal cord injury (ASCI)

BACKGROUND CONTEXT Acute spinal cord injury (ASCI) is still having substantial morbidity and mortality despite of advanced therapeutics. Major obstacles are paucity of monitoring tools or biomarkers for severity determination, recovery and prognostication. A prospective case control pilot study with serum 1H NMR spectroscopic metabolic profiling was carried out to evaluate metabolites perturbations and its relationship with recovery and to see role of stem cells in facilitating neurological recovery. PURPOSE A pilot study with serum 1H NMR spectroscopic metabolic profiling was carried out to evaluate metabolites perturbations and its relationship with recovery and to see role of stem cells in facilitating neurological recovery. STUDY DESIGN/SETTING A prospective case control pilot study was conducted in the spinal cord injury (SCI) unit of the Department of Orthopaedic Surgery in collaboration with the Department of Neurology, Department of Biochemistry, King George's Medical University (KGMU), Lucknow and Department of CBMR, Sanjay Gandhi Post Graduate Institute of Medical Science (SGPGIMS), Lucknow from December 2012 to July 2018. PATIENT SAMPLE A total of 135 subjects were enrolled in the study. OUTCOME MEASURES NMR data of serum and urine samples were quantified and subjected to multivariate analysis using supervised OSC-PCA followed by OPLS-DA was performed in the full study. This finding was further validated in the VIP scores. METHODS A prospective case control pilot study total of 135 subjects were enrolled in the study; 65ASCI subjects, divided into two groups. Fixation alone (FA, n= 34). Fixation with stem cells therapy (FST, n= 31). Seventy healthy subjects (HCs) were enrolled. Serum and urine samples were collected at admission (baseline), sixth week, third month and after sixth month (follow-up). RESULTS Gender analysis revealed that 103 out of 135 participants were male. The age group of 18 to 30 years was found most prone to SCI. Fall from height and road traffic accidents were the two most common modes of injuries. Most common injured segments of thoraco-lumbar spine were T10-L2 levels. On AIS grading, highly significant improvement was observed in FST group in comparison to FA group. In FST group, 61.29% subjects remained in AIS A and the percentage improvements to AIS B, C and D were 12.90%, 16.13% and 9.68%, respectively, whereas in FA group these values were 67.65%, 17.64%, 11.76% and 2.94%, respectively. At the sixth month follow-up, improvements in sensory and motor scores were observed in both cases groups (FST and FA), but FST group showed better results. In the spectra of urine biofluid, 43 metabolites were identified and assigned and t28 metabolites were identified and assigned in serum biofluid. Predominantly amino acids and ketone bodies played vital role in the differentiation of groups. An OSC-PCA and OPLS-DA model was created for investigating the role of metabolites in differentiation amid all ASCI subjects against healthy control at baseline as well as at final follow-up. Statistical comparison was validated by OSC-PCA as well as OPLS-DA methods and multivariate data analysis resulted in to R2 value of 0.91 and 0.81 and Q2 value of 0.81 and 0.67, respectively. The generated model was robust enough for evaluating the differentiation among the present data set. The 3D OSC-PCA model generated resulted to the total explained variance of 50.21% and 50.67%, respectively. The 3D scattered score plots represented the shifting of more ASCI subjects towards healthy control in the final follow-up, which is suggestive of improved health status and an indicator of better prognosis in ASCI subjects. CONCLUSIONS Serum and urine NMR spectroscopy reveals certain metabolites perturbations having clear correlation with pattern of recovery in treated ASCI subject. Stem cells treatment group had comparatively effective recovery. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

Nitrogen metabolism of branched‐chain alcohols acetates in jujube wine assessed by 13 C‐labeling

Branched-chain alcohols acetates (BCAA) are important aroma components of jujube wine. However, their presence is somewhat difficult to control during fermentation. In this regard, 13C-labeling and Gas Chromatography-Mass Spectrometer (GC-MS) were used to explore the Ehrlich pathway for the formation of BCAA. Initially, branched-chain (BC) amino acids, known to be involved in the production of BCAA, were investigated. BC amino acids, aldehydes, and alcohols were observed to gradually transform, while a small amount of alcohols was esterified to BCAA. Following the addition of 13C-BC amino acids into the jujube pulp, 13C-aldehydes, 13C-alcohols and 13C-BCAA were detected in the wine at 2, 24, and 72 hr, respectively, by mass spectrometric analysis. BC amino acids were observed to be transaminated, decarboxylated to aldehydes and then reduced to alcohols. The alcohols were subsequently esterified with acetyl CoA to form BCAA confirming a potential pathway for flavor regulation and quality improvement of jujube wine. Practical applications Jujube wine, produced by jujube fermentation with Saccharomyces cerevisiae, is a famous alcoholic beverage in Taihang Mountain districts in Hebei with Chinese characteristics. But the development of jujube wine was restricted because its flavor and quality were very unstable. Branched-chain alcohols acetates (BCAA) are the key aroma compounds of jujube wine. Understanding the formation mechanism of BCAA could provide the guide of process optimization and flavor regulation, making it become a unique brandy with Chinese characteristics, recognized, and accepting by the world.

Chiral Phosphoric Acid Catalyzed Enantioselective Synthesis of α-Tertiary Amino Ketones from Sulfonium Ylides.

Herein we disclose a new catalytic asymmetric approach for the synthesis of chiral α-amino ketones, which is particularly useful for the less accessible acyclic α-tertiary cases. By a protonation-amination sequence, our approach represents a rare asymmetric H-heteroatom bond insertion by α-carbonyl sulfonium ylides, an attractive surrogate of diazocarbonyls. The mild intermolecular C-N bond formation was catalyzed by chiral phosphoric acids with excellent efficiency and enantioselectivity. The products are precursors to other important chiral amine derivatives, including drug molecules and chiral ligands. The enantioselectivity was controlled by dynamic kinetic resolution in the amination step, rather than the initial protonation. This process opens up a new platform for the development of other related insertion reactions.

Synthesis of hexahydrophenanthridines via the tandem reaction of benzynes

A tandem insertion-cyclization reaction between carbocyclic β–amino ketones and benzynes has been described, producing hexahydrophenanthridines in moderate to high yields.

Effects Of Exercise Training On Circulating Branched-chain Amino Acid And Ketone Levels In Diabetics

PURPOSE: Elevated levels of circulating branched-chain amino acid (BCAA) and ketone bodies are recognized as biomarkers for cardiovascular disease (CVD) and other pathological conditions in type-2 diabetes mellitus (T2DM). Aerobic exercise interventions have previously shown decreases in levels of these markers, suggesting improved metabolic status and reduced risk of CVD. However, the efficacy of resistance training and concurrent programs in reducing BCAA and ketone body levels has not been well researched. METHODS: The current study was performed as a secondary analysis of the HART-D trial, a 9-month randomized, controlled exercise-training trial of 262 participants with T2DM. Participants were randomized to one of four groups; non-exercise control, aerobic training (AT), resistance training (RT), or a combined aerobic-resistance training (ATRT). The effects of the 9-month intervention on BCAAs (leucine, valine, and isoleucine) and ketone bodies (β-hydroxy-butyrate, BHB; acetoacetate, AcAc; and acetone) were examined across groups using generalized linear models adjusting for age, race, sex, and baseline BMI. We performed per-protocol analyses limited to all control participants (n=33) and only the exercise group participants who met the criteria of at least 70% adherence to their exercise prescription for 6 months (AT, n=62; RT, n=55; ATRR, n=64). RESULTS: AcAc (-17.6 ± 6.4, p=0.006), acetone (-10.6 ± 3.6, p=0.003), and total ketone body (-51.4 ± 20.0, p=0.01) concentrations (shown as mean ± SE in μmol/L) decreased in the RT group compared to the control group. Acetone also decreased in ATRT compared to the control group (-10.2 ± 3.5 μmol/L, p=0.004). CONCLUSIONS: Our results suggest that RT and ATRT programs could improve ketone body metabolism in those with T2DM.

Storage and heat processing affect flavors of cucumber juice enriched with plant extracts

ABSTRACT Volatile compounds are responsible for juice flavor and aroma characteristics. How volatile components in cucumber juice are affected by heating, storage, and mix with aromatic herbs needs clarification. Aroma compounds were identified in cucumber (Cucumis sativus L.) juices enriched with cinnamon (Cinnamomum verum L.), clove [Syzygium aromaticum (L.) Merr. & L.M. Perry], mint (Mentha spicata L.), and ginger (Zingiber officinale L.) extracts (as a flavor-enhancer), after 6 months of storage under 75 MPa at room temperature. The aroma compounds identified directly after juice processing were hydrocarbons, alcohols, phenol derivatives, esters, aldehydes, ketones, sulfur compounds, fatty acids, and silicone compounds. Tributyl (E)-prop-1-ene-1,2,3-tricarboxylate, tributyl 2-acetyloxypropane-1,2,3-tricarboxylate, (E)-3,7,11,15-tetramethyl hexadec-2-en-1-ol, and (3E,6Z)-nona-3,6-dien-1-ol were identified in control juice. The 4-thio ethyl 5-acetyl-1-phenyl-6-methyl-1-H pyrimidin2one was the main compound (63.5%), followed by 3-hexen-1-ol, and (E)-3,7,11,15-tetramethyl hexadec-2-en-1-ol (4.5% and 6.54%) in cucumber-clove juice. The 1,2,3,4-tetrahydro1,1,4,4,5-pentamethyl 6-phenylanthracene, sulfur compounds, trans [2-(benzenesulfinylmethyl)-3-phenylcyclopropyl] benzene were detected in ginger-enriched juice. The antibacterial ketone anti 5(1hydroxyundecyl) 3(3methylbutyl) oxazolidin2one was the main compound followed by C6 oxygenated p-menthane monoterpene in cucumber-mint juice. Cyclodecasiloxane eicosamethyl was the main compound followed by cinnamaldehyde in cucumber-cinnamon juice. After 6-month storage, numbers of furans, sulfur amino compounds, phenols, and ketone derivatives increased, while aldehydes compounds decreased. The results could be used to establish quality criteria for commercial production of high-quality cucumber juice.

354-OR: Cotadutide (medi0382), a Dual Receptor Agonist with Glucagon-Like Peptide-1 and Glucagon Activity, Modulates Hepatic Glycogen and Fat Content

Background and Aims: Cotadutide, a dual receptor agonist with glucagon-like peptide-1 (GLP-1) and glucagon activity, is being researched for the potential treatment of nonalcoholic steatohepatitis. Given the known effects of glucagon on hepatic glycogen and lipid metabolism, the aim of this phase 2a study was to investigate the effect of cotadutide on hepatic glycogen. Methods: In this double-blind, placebo-controlled study, 21 overweight or obese adults with type 2 diabetes mellitus (HbA1c ≤ 8%) were randomized to receive once-daily subcutaneous cotadutide (n = 12) or placebo (n = 9) for 28 days. Following 48 hours of standardized meals, serial magnetic resonance spectroscopy scans relying on signals from naturally abundant 13C were performed to measure glycogen, and liver fat was also estimated. Fasting amino acid and ketone levels were also assessed. Results: Significant reductions from baseline in postprandial hepatic glycogen content were observed with cotadutide (-100.2 mmol/L; 90% CI: -150.2, -50.1) vs. placebo (+5.5 mmol/L; 90% CI: -47.2, 58.3; P = 0.023). Statistically significant reductions in hepatic glycogen content were observed across serial measures and after a 14-hour fast (P &amp;lt; 0.05), with an overall change in glycogen AUC24h of -27.3% (P = 0.003) vs. placebo. In addition, a relative reduction in liver fat of 33.2% vs. placebo was reported (P = 0.006), and significant reductions in fasting alanine, glutamate, glycine, lysine, and threonine levels were also observed with cotadutide vs. placebo (all P ≤ 0.05). Beta-hydroxybutyrate and acetoacetate levels were not significantly different between the two arms. Conclusions: Cotadutide promoted a generalized reduction in hepatic glycogen and selected amino acid levels. Substantial reductions in liver fat were also observed with cotadutide, suggesting glucagon receptor engagement. Disclosure D. Robertson: Employee; Self; AstraZeneca. Stock/Shareholder; Self; AstraZeneca. L. Hansen: Employee; Self; AstraZeneca. P. Ambery: Employee; Self; AstraZeneca. R.L. Esterline: Employee; Self; AstraZeneca. L. Jermutus: Employee; Self; AstraZeneca. Stock/Shareholder; Self; AstraZeneca. Y. Chang: None. M. Petrone: Employee; Self; AstraZeneca. E. Johansson: None. L. Johansson: Employee; Self; Antaros Medical AB. Stock/Shareholder; Self; Antaros Medical AB. F.B. Sjöberg: None. V. Parker: None. Funding AstraZeneca

Formation of Strecker Aldehydes in Casein Digestion

Abstract Objectives This study investigated the occurrence of Strecker degradation during in vitro digestion. Methods Casein was first incubated with artificial gastric fluid containing porcine pepsin and HCl (pH = 2) for 60 min. After adjusting pH to 7 with sodium hydroxide, casein gastric digesta was then incubated with artificial intestinal fluid containing porcine pancreatin (pH = 7) for 120 min. Digesta samples were collected at 0, 10, 20, 30, and 60 min of gastric digestion, and then 10, 20, 30, 60, and 120 min of intestinal digestion. Free amino acids and aldehydes in digesta samples were analyzed by the liquid chromatography-mass spectrometry analysis. Results Multiple aldehydes were detected in gastric digestion samples, and their concentrations were further increased by intestinal digestion. Among them, isovaleraldehyde, isobutyraldehyde, phenylacetaldehyde, and acetaldehyde, are the Strecker degradation products of leucine, valine, phenylalanine, and alanine, respectively. Without digestive enzymes, casein incubation did not produce Strecker aldehydes. Conclusions In vitro digestion of proteins can produce Strecker aldehydes. Funding Sources This research was partially supported by the Agricultural Experiment Station project MIN-18-125 (C. C.) from the United States Department of Agriculture (USDA).

Synergism between SLC6A14 blockade and gemcitabine in pancreactic cancer: a 1H-NMR-based metabolomic study in pancreatic cancer cells.

Gemcitabine is the first-line chemotherapy for pancreatic cancer. To overcome the often-acquired gemcitabine resistance, other drugs are used in combination with gemcitabine. It is well-known that cancer cells reprogram cellular metabolism, coupled with the up-regulation of selective nutrient transporters to feed into the altered metabolic pathways. Our previous studies have demonstrated that the amino acid transporter SLC6A14 is markedly up-regulated in pancreatic cancer and that it is a viable therapeutic target. α-Methyltryptophan (α-MT) is a blocker of SLC6A14 and is effective against pancreatic cancer in vitro and in vivo. In the present study, we tested the hypothesis that α-MT could synergize with gemcitabine in the treatment of pancreatic cancer. We investigated the effects of combination of α-MT and gemcitabine on proliferation, migration, and apoptosis in a human pancreatic cancer cell line, and examined the underlying mechanisms using 1H-NMR-based metabolomic analysis. These studies examined the intracellular metabolite profile and the extracellular metabolite profile separately. Combination of α-MT with gemcitabine elicited marked changes in a wide variety of metabolic pathways, particularly amino acid metabolism with notable alterations in pathways involving tryptophan, branched-chain amino acids, ketone bodies, and membrane phospholipids. The metabolomic profiles of untreated control cells and cells treated with gemcitabine or α-MT were distinctly separable, and the combination regimen showed a certain extent of overlap with the individual α-MT and gemcitabine groups. This represents the first study detailing the metabolomic basis of the anticancer efficacy of gemcitabine, α-MT and their combination.

Midlife Chronological and Endocrinological Transitions in Brain Metabolism: System Biology Basis for Increased Alzheimer\u2019s Risk in Female Brain

Decline in brain glucose metabolism is a hallmark of late-onset Alzheimer’s disease (LOAD). Comprehensive understanding of the dynamic metabolic aging process in brain can provide insights into windows of opportunities to promote healthy brain aging. Chronological and endocrinological aging are associated with brain glucose hypometabolism and mitochondrial adaptations in female brain. Using a rat model recapitulating fundamental features of the human menopausal transition, results of transcriptomic analysis revealed stage-specific shifts in bioenergetic systems of biology that were paralleled by bioenergetic dysregulation in midlife aging female brain. Transcriptomic profiles were predictive of outcomes from unbiased, discovery-based metabolomic and lipidomic analyses, which revealed a dynamic adaptation of the aging female brain from glucose centric to utilization of auxiliary fuel sources that included amino acids, fatty acids, lipids, and ketone bodies. Coupling between brain and peripheral metabolic systems was dynamic and shifted from uncoupled to coupled under metabolic stress. Collectively, these data provide a detailed profile across transcriptomic and metabolomic systems underlying bioenergetic function in brain and its relationship to peripheral metabolic responses. Mechanistically, these data provide insights into the complex dynamics of chronological and endocrinological bioenergetic aging in female brain. Translationally, these findings are predictive of initiation of the prodromal / preclinical phase of LOAD for women in midlife and highlight therapeutic windows of opportunity to reduce the risk of late-onset Alzheimer’s disease.

Half-Sandwich Ruthenium Complexes for One-Pot Synthesis of Quinolines and Tetrahydroquinolines: Diverse Catalytic Activity in the Coupled Cyclization and Hydrogenation Process.

Four types of half-sandwich ruthenium complexes with an N,O-coordinate mode based on hydroxyindanone-imine ligands have been prepared in good yields. These stable ruthenium complexes exhibited high activity in the catalytic synthesis of quinolines from the reactions of amino alcohols with different types of ketones or secondary alcohols under very mild conditions. Moreover, the methodology for the direct one-pot synthesis of tetrahydroquinoline derivatives from amino alcohols and ketones has been also developed on the basis of the continuous catalytic activity of this ruthenium catalyst in the selective hydrogenation of the obtained quinoline derivatives with a low catalyst loading. The corresponding products, quinolines and tetrahydroquinoline derivatives, were afforded in good to excellent yields. The efficient and diverse catalytic activity of these ruthenium complexes suggested their potential large-scale application. All of the ruthenium complexes were characterized by various spectroscopies to confirm their structures.

Metabolic Modulation of Cardiac Health: The Role of Glucose and Amino Acids

The heart has high metabolic flexibility in utilizing a variety of substrates for energy production. Reprogramming of cardiac metabolism is recognized as integral to the development of heart failure. In hypertrophied and failing hearts, fatty acid oxidation is reduced and glucose utilization is increased. Recent studies have also identified changes in the catabolism of amino acids and ketone bodies in the failing hearts. Thus, elucidating the functional consequence of the metabolic remodeling could provide mechanistic insights of pathogenesis and therapy of heart failure. While the switch from fatty acids to glucose has been shown ultimately maladaptive for energy supply, the impact of increased glucose reliance on cardiac hypertrophy and remodeling is incompletely understood. Emerging results suggest that changes in glucose and branched chain amino acid metabolism, apart from their contribution to energy production, serve multiple roles in controlling the hypertrophic growth of the heart. A number of studies have evaluated the impact of substrate switch on energy production in the heart by comparing and contrasting the contribution of multiple substrates using bioengineered mouse models. Emerging studies focus on the role of substrate metabolism in signal transduction and biosynthetic function of the cardiomyocytes undergoing hypertrophic growth.

One-Pot Sequential Cross-Aldol Condensation/Aza-Michael Addition on Graphene Oxide

Key words graphene oxide catalysis - cross-aldol coupling - aza-Michael addition - amino ketones

Electrophilic Amination with Anthranils through Thioamide-Assisted Cobalt(III)-Catalyzed C(sp3)–H Activation

Cobalt(III)-catalyzed electrophilic amination of inert C(sp3)–H bonds of weakly coordinating thioamides with readily accessible anthranil derivatives was accomplished under mild conditions, with good functional group tolerance, thus providing various amino aldehydes and amino ketones. Moreover, our protocol with the versatile [Cp*Co(MeCN)3][SbF6]2 features excellent atom-economy and oxidant-free conditions, and allows facile late-stage functionalization.

Stereoselective Allylic Alkylations of Amino Ketones and Their Application in the Synthesis of Highly Functionalized Piperidines.

Chelated ketone enolates are excellent nucleophiles for allylic alkylations. Electron-withdrawing groups on the allyl moiety allow subsequent intramolecular Michael additions giving rise to piperidines with up to five stereogenic centers.

High-pH and anoxic conditions during soil organic matter extraction increases its electron-exchange capacity and ability to stimulate microbial Fe(III) reduction by electron shuttling

Abstract. Soil organic matter (SOM) is redox-active, can be microbially reduced, and transfers electrons in an abiotic reaction to Fe(III) minerals, thus serving as an electron shuttle. The standard procedure to isolate organic matter (OM) from soil involves the use of alkaline and acidic solutions and the separation of humic acids (HAs) and fulvic acids (FAs). This process potentially leads to unwanted changes in SOM chemical and redox properties. To determine the effects of extraction conditions on the redox and electron-shuttling properties of SOM extracts, we prepared HA, FA, and water-extractable organic matter (OM) extracts, applying either a combination of 0.1 M NaOH and 6 M HCl or ultrapure water (pH 7), from soil samples collected from the subsoil (0–15 cm, A horizon, pH 6.5–6.8) in Schönbuch forest, Baden-Württemberg, Germany. Both chemical extractions (NaOH∕HCl) and water extractions were done in separate experiments under either oxic or anoxic conditions. Furthermore, we applied the NaOH∕HCl treatment to a subsample of the water-extractable OM to separate HA and FA from the water-extractable OM. When comparing the amount of carbon extracted from soil by different extraction methods, we found that FA and HA chemically extracted from the soil can make up to 34 %–40 % of the soil organic carbon pool while the water-extractable OM only represents 0.41 %–2.74 % of the total soil organic carbon. The higher extraction efficiency of the chemical extraction is probably due to the deprotonation of carboxyl and phenol functional groups under high pH. Anoxic extraction conditions also led to more extracted carbon. For water-extractable OM, 7 times more C was extracted under anoxic conditions compared to oxic conditions. This difference was probably due to the occurrence of microbial reduction and dissolution of Fe(III) minerals in the soil during the anoxic water extraction and thus the concomitant release of Fe(III) mineral-bound organic matter. To compare the redox activity of different SOM extracts, the electron-exchange capacity (EEC) of all extracted HA, FA, and water-extractable OM was analyzed and our results showed that, under anoxic extraction conditions, the HA chemically isolated from the water-extractable OM had 2 times higher EEC values compare to the water-extractable OM itself, suggesting the potential formation of redox-active aromatic functional groups during the extraction with NaOH under anoxic conditions by condensation reactions between amino acids, aldehydes, and hydroxyl- and catechol-containing molecules. We also performed a microbial Fe(III) reduction experiment with all extracts and found that higher EEC of extracts in turn resulted in a higher stimulation of microbial Fe(III) mineral reduction by electron shuttling, i.e., faster initial Fe(III) reduction rates, and in most cases also in higher reduction extents. Our findings suggest that OM extracted with water at neutral pH should be used to better reflect environmental SOM redox processes in lab experiments and that potential artefacts of the chemical extraction method and anoxic extraction condition need to be considered when evaluating and comparing abiotic and microbial SOM redox processes.