Degradation Of Dicarboxylic Acids Research Articles

The biochemistry and physiology of long-chain dicarboxylic acid metabolism.

Mitochondrial β-oxidation is the most prominent pathway for fatty acid oxidation but alternative oxidative metabolism exists. Fatty acid ω-oxidation is one of these pathways and forms dicarboxylic acids as products. These dicarboxylic acids are metabolized through peroxisomal β-oxidation representing an alternative pathway, which could potentially limit the toxic effects of fatty acid accumulation. Although dicarboxylic acid metabolism is highly active in liver and kidney, its role in physiology has not been explored in depth. In this review, we summarize the biochemical mechanism of the formation and degradation of dicarboxylic acids through ω- and β-oxidation, respectively. We will discuss the role of dicarboxylic acids in different (patho)physiological states with a particular focus on the role of the intermediates and products generated through peroxisomal β-oxidation. This review is expected to increase the understanding of dicarboxylic acid metabolism and spark future research.

The Mechanism and Kinetics Model of Degradation of Dicarboxylic Acids by Hydroxyl Radicals under Atmospheric Conditions.

The atmospheric degradation mechanism of dicarboxylic acids (DCAs) initiated by hydroxyl radicals has been theoretically investigated at the DLPNO-CCSD(T)/def2-TZVP//BH&HLYP/6-311++G(d,p) level of theory. In the presence of O2, the degradation of DCAs by hydroxyl radicals takes place through a two-step mechanism: the α-H elimination and the degradation of the peroxyl radical intermediate. The latter degradation mechanism is easy to proceed for the exothermic process of radical recombination. Therefore, the degradation rate of DCAs is determined by an α-H elimination step, which is accelerated in the case of long carbon-chain DCAs with a lower energy barrier. Canonical variational transition state theory has been employed to estimate the rate constants of the H-elimination step of the DCA degradation reaction by hydroxyl radicals over the temperature range of 220-1000 K.

Lignin Depolymerization to Dicarboxylic Acids with Sodium Percarbonate

Lignin depolymerization to dicarboxylic acids (DCAs) by the one-step Fenton oxidation process results in poor yield and significant amounts of residual solids. A process based on the use of sodium percarbonate on bagasse lignin depolymerization was conducted at 60–300 °C, for 1–6 h. This approach resulted in significantly higher DCA yields (predominantly oxalic, malonic, and succinic acids), without the formation of char, when compared to the acidic H2O2/chalcopyrite process. This was in part due to the effectiveness of the alkaline reaction medium in suppressing the thermal degradation of DCAs during processing. It was determined that increasing the alkaline content of the reaction mixture further significantly improved DCA yield. When applying this process at 200 °C for 3 h, using 1 M NaOH (in addition to 0.6 M sodium percarbonate) increased DCA yield by 85%. The process developed was applied to the lignin model compounds; guaiacol, vanillic acid, and p-hydroxybenzoic acid. It was demonstrated that the ...

Laboratory photochemical processing of aqueous aerosols: formation and degradation of dicarboxylic acids, oxocarboxylic acids and α-dicarbonyls

Abstract. To better understand the photochemical processing of dicarboxylic acids and related polar compounds, we conducted batch UV irradiation experiments on two types of aerosol samples collected from India, which represent anthropogenic (AA) and biogenic (BA) aerosols, for time periods of 0.5 to 120 h. The irradiated samples were analyzed for molecular compositions of diacids, oxoacids and α-dicarbonyls. The results show that photochemical degradation of oxalic (C2), malonic (C3) and other C8–C12 diacids overwhelmed their production in aqueous aerosols, whereas succinic acid (C4) and C5–C7 diacids showed a significant increase (ca. 10 times) during the course of irradiation experiments. The photochemical formation of oxoacids and α-dicarbonyls overwhelmed their degradation during the early stages of experiment except for ω-oxooctanoic acid (ωC8), which showed a similar pattern to that of C4. We also found a gradual decrease in the relative abundance of C2 to total diacids and an increase in the relative abundance of C4 during prolonged experiment. Based on the changes in concentrations and mass ratios of selected species with the irradiation time, we hypothesize that iron-catalyzed photolysis of C2 and C3 diacids controls their concentrations in Fe-rich atmospheric waters, whereas photochemical formation of C4 diacid (via ωC8) is enhanced with photochemical processing of aqueous aerosols in the atmosphere. This study demonstrates that the ambient aerosols contain abundant precursors that produce diacids, oxoacids and α-dicarbonyls, although some species such as oxalic acid decompose extensively during an early stage of photochemical processing.

Molecular distributions of dicarboxylic acids, ketocarboxylic acids and α-dicarbonyls in biomass burning aerosols: implications for photochemical production and degradation in smoke layers

Abstract. Aerosols in the size class <2.5 μm (6 daytime and 9 nighttime samples) were collected at a pasture site in Rondônia, Brazil, during the intensive biomass burning period of 16–26 September 2002 as part of the Large-Scale Biosphere-Atmosphere Experiment in Amazonia – Smoke, Aerosols, Clouds, Rainfall and Climate (LBA-SMOCC). Homologous series of dicarboxylic acids (C2–C11) and related compounds (ketocarboxylic acids and α-dicarbonyls) were identified using gas chromatography (GC) and GC/mass spectrometry (GC/MS). Among the species detected, oxalic acid was found to be the most abundant, followed by succinic, malonic and glyoxylic acids. Average concentrations of total dicarboxylic acids, ketocarboxylic acids and α-dicarbonyls in the aerosol samples were 2180, 167 and 56 ng m−3, respectively. These are 2–8, 3–11 and 2–16 times higher, respectively, than those reported in urban aerosols, such as in 14 Chinese megacities. Higher ratios of dicarboxylic acids and related compounds to biomass burning tracers (levoglucosan and K+) were found in the daytime than in the nighttime, suggesting the importance of photochemical production. On the other hand, higher ratios of oxalic acid to other dicarboxylic acids and related compounds normalized to biomass burning tracers (levoglucosan and K+) in the daytime provide evidence for the possible degradation of dicarboxylic acids (≥C3) in this smoke-polluted environment. Assuming that these and related compounds are photo-chemically oxidized to oxalic acid in the daytime, and given their linear relationship, they could account for, on average, 77% of the formation of oxalic acid. The remaining portion of oxalic acid may have been directly emitted from biomass burning as suggested by a good correlation with the biomass burning tracers (K+, CO and ECa) and organic carbon (OC). However, photochemical production from other precursors could not be excluded.

The kinetics of photocatalytic degradation of aliphatic carboxylic acids in an UV/TiO2 suspension system

Kinetic studies on the photocatalytic degradation of aliphatic carboxylic acids were carried out in a slurry photoreactor with in‐situ monitoring, employing artificial UV light as the source of energy and nano‐TiO2 powder as the catalyst. The influences on the photocatalytic degradation such as the initial concentration of reactant (C0 ), catalyst dosage (CTiO2 ), UV intensity (Ia ) and pH value have been investigated. Good agreement has been obtained between the value calculated by Langmuir–Freundlich–Hinshelwood (L–F–H) model and experimental data, with coefficient of multiple determination (R 2) varying from 0.880 to 0.999. The L–F–H model has been proven to be feasible in describing the kinetic characteristic of the photocatalytic degradation of aliphatic carboxylic acids. Moreover, the apparent reaction rate constant (k) of the photocatalytic degradation of dicarboxylic acids is higher than that of monocarboxylic acids with the same carbon atoms. This shows that the photocatalytic degradation rate is favoured by different chemical structure.

Stable carbon isotopic composition of low‐molecular‐weight dicarboxylic acids and ketoacids in remote marine aerosols

We determined stable carbon isotopic composition (δ13C) of C2 to C9 dicarboxylic acids (DCAs) and some ketoacids in the marine aerosols from the western Pacific and Southern Ocean (35°N to 65°S). On average, oxalic (mean, −16.8‰), adipic (−17.2‰), and glyoxylic (−17.6‰) acids showed heavier δ13C, whereas maleic (−24.2‰), methylmalonic (−23.6‰), and phthalic (−23.1‰) acids were more depleted in 13C. Oxalic acid presented very diverse δ13C values (−27 to −7‰), which increased from midlatitudes toward the equator. A similar latitudinal trend of δ13C was also found for malonic, succinic, and adipic acids. However, such a trend was not observed for phthalic, maleic, and glyoxylic acids. We suggest that the δ13C increase toward the equator is associated with photochemically aged air masses, in which kinetic isotope effects for photochemical degradation of DCAs may be important. Differences in δ13C of some saturated DCAs were also found to increase from midlatitudes to the equator.

Degradation of dicarboxylic acids (C2-C9) upon liquid-phase reactions with O3 and its atmospheric implications.

Aerosols are considered major players in climate change and represent health hazards. Dicarboxylic acids are among a major class of components that form secondary organic atmospheric aerosols. To understand the atmospheric transformation of these compounds, kinetic studies on the ozonolysis and the photoinduced ozonolysis (lambda > or = 250 nm) of aqueous solutions of seven (C2-C9) dicarboxylic acids, which have been identified in atmospheric aerosols, were performed using Fourier transform infrared and ultraviolet-visible spectroscopy. The measured apparent rate constants for dicarboxylic acids in 0.1 mol L(-1) aqueous solutions at 298 +/- 2 K are as follows: oxalic, (2.7 +/- 0.1) x 10(-2); malonic, (5.5 +/- 0.1); succinic, (6.7 +/- 0.4) x 10(-4); glutaric, (1.3 +/- 0.2) x 10(-3); adipic, (1.7 +/- 0.1) x 10(-3); pimelic, (4.4 +/- 0.1) x 10(-3); and pinic, (2.5 +/- 0.1) x 10(-2) (L mol(-1) s(-1)). An empirical equation is provided to estimate the ozonolysis rate constant of dicarboxylic acids containing more than three carbon atoms for which no experimental data exists. A mechanism for malonic acid ozonolysis, which explains its fast ozonolysis rate constant, is also suggested. The implications of our results to atmospheric chemistry indicate that ozonolysis and photoinduced ozonolysis are not significant removal pathways for dicarboxylic acids.

152 INCREASED URINARY EXCRETION OF DICARBOXYLIC ACIDS AND 4 HYDROXYPHENYLLACTIC ACID IN PATIENTS WITH ZELLWEGER SYNDROME

s-Oxidation of dicarboxylic acids has been shown to occur in mitochondria iind peroxisomes of rat liver in vitro. Patients with Zellweger syndrome (ZS) offer a unique possibility to study the importance of peroxisomes in the degradation of dicarboxylic acids in vivo. Methods: We quantified urinary organic acids in seven ZS patients with impaired peroxisomal s-oxidation but normal mitochondrial s-oxidation capacity by GCMS. Results: Increased amounts of dicarboxylic acids with an odd number of carbon atoms (e.g. azelaic (up to 23 vs <0.1 mmol/mol creatinine in controls), pimelic acid (up to 15 vs <0.1)) or an even number of carbon atoms (e.g. adipic (up to 180 vs <0.1 nmol/mol creatinine in controls), suberic (up to 140 vs <0.1), sebacic acid (up to 200 vs <0.1)) and 2-hydroxysebacic acid, a medium-chain hydroxydicarboxylic acid (up to 50 vs <0.1 mmol/mol creatinine in controls), were found in the urines of these patients. In addition, patients with ZS Slowed an highly elevated excretion of 4-hydroxyphenyllactic acid (up to 98 vs <0.1 mmol/mol creatinine in controls). Conclusion: These results prove the functional importance of peroxisomes in the s-oxidation of these compounds in vivo. The characteristic pattern of urinary organic acids in ZS should prompt for specific diagnostic procedures for peroxisomal disorders, when found in patients undergoing selective screening for inherited metabolic diseases.

Formation and degradation of dicarboxylic acids in relation to alterations in fatty acid oxidation in rats

Dicarboxylic acids are excreted in urine when fatty acid oxidation is increased (ketosis) or inhibited (defects in β-oxidation) and in Reye's syndrome. ω-Hydroxylation and ω-oxidation of C 6–C 12 fatty acids were measured by mass spectrometry in rat liver microsomes and homogenates, and β-oxidation of the dicarboxylic acids in liver homogenates and isolated mitochondria and peroxisomes. Medium-chain fatty acids formed large amounts of medium-chain dicarboxylic acids, which were easily β-oxidized both in vitro and in vivo, in contrast to the long-chain C 16-dicarboxylic acid, which was toxic to starved rats. Increment of fatty acid oxidation in rats by starvation or diabetes increased C 6:C 10 dicarboxylic acid ratio in rats fed medium-chain triacylglycerols, and increased short-chain dicarboxylic acid excretion in urine in rats fed medium-chain dicarboxylic acids. Valproate, which inhibits fatty acid oxidation and may induce Reye like syndromes, caused the pattern of C 6–C 10-dicarboxylic aciduria seen in β-oxidation defects, but only in starved rats. It is suggested, that the origin of urinary short-chain dicarboxylic acids is ω-oxidized medium-chain fatty acids, which after peroxisomal β-oxidation accumulate as C 6–C 8-dicarboxylic acids. C 10–C 12-dicarboxylic acids were also metabolized in the mitochondria, but did not accumulate as C 6–C 8-dicarboxylic acids, indicating that β-oxidation was completed beyond the level of adipyl CoA.