Production Of Aldehydes Research Articles

Characterization of methanolysis products from plasmalogenic lipids in horse muscle tissue

Muscle tissue is known to contain plasmalogenic lipids. Traditional methodologies for the analysis of lipids in muscle consists of methanolysis followed by gas chromatography (GC). The resultant dimethylacetals (DMA) are difficult to resolve because of extensive overlap with fatty acid methyl esters. In this study a new two-step procedure was applied to isolate DMAs from FAMEs from methanolysed horse muscle lipids (n=48) after saponification and solvent partitioning. Both total and isolated DMAs were analysed by GC and the extent of overlap was evident. The total methylated mixture was also analyzed using GC with online reduction (GC-OR x GC) which confirmed the identity of the FAME, DMA and aldehyde products. The DMA content in horse muscle tissue was found to be 55.7mg DMAs in 100g of meat, or 3.10% of total lipids. The saturates 16:0 and 18:0 were the predominant DMA isomers, and 18:3n-3 and 18:2n-6 DMA were identified in this tissue. Samples with a higher (> 3g/100g of meat) intramuscular fat (IM) content showed a lower (p ≤ 0.05) absolute content of the DMAs compared to samples with lower IM fat content (15.3 vs 29.3mg/g of fat, respectively).

Saccharomyces cerevisiae whole cell biotransformation for the production of aldehyde flavors and fragrances

9-Carbon aldehydes such as (2E)-nonenal, (3Z)-nonenal, and (2E,6Z)-nonadienal are important melon and cucumber fragrance compounds. Currently, these molecules are produced either synthetically, which faces consumer aversion, or through biotransformation using plant-extracted enzymes, which is costly and inefficient. In this study, we constructed a Saccharomyces cerevisiae platform for the whole cell biotransformation of polyunsaturated fatty acids (PUFAs) to 9-carbon aldehydes. Heterologous expression of lipoxygenase (LOX) from Nicotiana benthamiana and hydroperoxide lyase (HPL) from Cucumis melo (melon) in S. cerevisiae enabled the production of (2E)-nonenal from readily available polyunsaturated fatty acid substrates. A 5.5-fold increase in (2E)-nonenal titer was then achieved utilizing genetic and reaction condition enhancement strategies. The highest titer of (2E)-nonenal was more than 0.11 mM, with about 9% yield. This platform can potentially be used to produce a variety of other aldehyde products by customizing with LOX and HPL enzymes of different regio-selectivities.Key points• Establishment of a S. cerevisiae whole-cell biotransformation platform for cost-efficient, high-yield conversion of PUFAs into high value 9-carbon aldehyde compounds• 5.5-Fold improvement of (2E)-nonenal titer to > 0.11 mM achieved by enhancing reaction conditions and gene expression levels of LOX and HPL

Oxidative Stress-mediated Lipid Peroxidation-derived Lipid Aldehydes in the Pathophysiology of Neurodegenerative Diseases.

Neurodegenerative diseases such as Alzheimer's, Parkinson's, and amyotrophic lateral sclerosis cause damage and gradual loss of neurons affecting the central nervous system. Neurodegenerative diseases are most commonly seen in the ageing process. Ageing causes increased reactive oxygen species and decreased mitochondrial ATP generation, resulting in redox imbalance and oxidative stress. Oxidative stress-generated free radicals cause damage to membrane lipids containing polyunsaturated fatty acids, leading to the formation of toxic lipid aldehyde products such as 4- hydroxynonenal and malondialdehyde. Several studies have shown that lipid peroxidation-derived aldehyde products form adducts with cellular proteins, altering their structure and function. Thus, these lipid aldehydes could act as secondary signaling intermediates, modifying important metabolic pathways, and contributing to the pathophysiology of several human diseases, including neurodegenerative disorders. Additionally, they could serve as biomarkers for disease progression. This narrative review article discusses the biological and clinical significance of oxidative stress-mediated lipid peroxidation-derived lipid aldehydes in the pathophysiology of various neurodegenerative diseases.

Oxidative Catalytic Depolymerization of Lignin into Value-Added Monophenols by Carbon Nanotube-Supported Cu-Based Catalysts

Lignin valorisation into chemicals and fuels is of great importance in addressing energy challenges and advancing biorefining in a sustainable manner. In this study, on the basis of the high microwave absorption performance of carbon nanotubes (CNTs), a series of copper-oxide-loaded CNT catalysts (CuO/CNT) were developed to facilitate the oxidative depolymerization of lignin under microwave heating. This catalyst can promote the activation of hydrogen peroxide and air, effectively generating a range of reactive oxygen species (ROS). Through the application of electron paramagnetic resonance techniques, these ROS generated under different oxidation conditions were detected to elucidate the oxidation mechanism. The results demonstrate that the •OH and O2•− play a crucial role in the formation of aldehyde and ketone products through the cleavage of lignin Cβ-O and Cα-Cβ bonds. We further evaluated the catalytic performance of the CuO/CNT catalysts with three typical lignin feedstocks to determine their applicability for lignin biorefinery. The bio-enzymatic lignin produced a 13.9% monophenol yield at 200 °C for 20 min under microwave heating, which was higher than the 7% yield via hydrothermal heating conversion. The selectivity of G-/H-/S-type products was slightly affected, while lignin substrate had a noticeable effect on the selective production. Overall, this study explored the structural characteristics of CuO/CNT catalysts and their implications for lignin conversion and offered an efficient oxidation approach that holds promise for sustainable biorefining practices.

Biosensor-Guided Engineering of a Baeyer-Villiger Monooxygenase for Aliphatic Ester Production.

Esters are valuable aroma compounds and can be produced enzymatically by Baeyer-Villiger monooxygenases (BVMOs) from (aliphatic) ketone precursors. However, a genetically encoded biosensor system for the assessment of BVMO activity and the detection of reaction products is missing. In this work, we assembled a synthetic enzyme cascade - featuring an esterase, an alcohol dehydrogenase, and LuxAB - in the heterologous host Escherichia coli. Target esters are produced by a BVMO, subsequently cleaved, and the corresponding alcohol oxidized through the artificial pathway. Ultimately, aldehyde products are detected in vivo by LuxAB, a luciferase from Photorhabdus luminescens that emits bioluminescence upon the oxidation of aldehydes to the corresponding carboxylates. This biosensor system greatly accelerated the screening and selection of active BVMO variants from a focused library, omitting commonly used low-throughput chromatographic analysis. Engineered enzymes accepted linear aliphatic ketones such as 2-undecanone and 2-dodecanone and exhibited improved ester formation.

Sodium thiosulfate modified graphitic carbon nitride for enhancing the photocatalytic production of aldehydes

The oxidation of alcohols to aldehydes is one of the most relevant reactions in organic chemistry. The currently implemented methods based on expensive noble metallic catalysts, toxic solvents, and high temperature and pressure conditions have released the seek for softer and cheaper alternatives such as photocatalysis. In this sense, graphitic carbon nitride has been modified with sodium thiosulfate as a source of S and Na+ incorporation in the structure, aimed at enhancing the photocatalytic performance on the oxidation of alcohols to aldehydes, i.e. cinnamaldehyde, benzaldehyde, and vanillin in aqueous solution. Three g-C3N4 samples synthesized from different precursors, i.e. melamine, thiourea, and urea, were treated with sodium thiosulfate. Urea led to the g-C3N4 with the highest mesoporosity (surface area, 69 m2 g−1) and photocatalytic activity. The modification with 5 % (wt.) of Na2S2O3 enhanced the pseudo-first order rate constant of cinnamyl alcohol oxidation from 0.265 h−1 (bare sample) to 0.792 h−1 (Na2S2O3-modified). The characterization of the material suggests a better charge separation of the photogenerated charges after S and Na+ incorporation in the structure, minimizing the recombination rate of photogenerated charges. The optimum photocatalyst, tested in aqueous solution, was most selective in the production of benzaldehyde (selectivity, >100 %) > cinnamaldehyde (>23 %) > vanillin (∼5 %). The selectivity was considerably boosted under acetonitrile as the solvent medium, raising in the case of cinnamaldehyde the 23 % recorded in water to 51 % in pure acetonitrile. The degradation mechanism suggests a strong influence of the photogenerated holes and the superoxide radical, the latter being more selective in the oxidation of the alcohol.

A structural and functional model for alkene dioxygenases

In this article, we report sterically-controlled iron sites based on non-chelating bulky imidazole ligands. Adding 6 equiv. of 1,2-dimethylimidazole (1,2-Me2Im) to Fe(OTf)2⋅2CH3CN affords the first example of a 5-coordinate imidazole‑iron complex ([Fe(1,2-Me2Im)5](OTf)2, 1). The structure is distorted square pyramidal (τ5 = 0.41). When an iPr group is substituted for the methyl group at the 2-position on the imidazole (2-iPr-1-MeIm), the 14-electron complex ([Fe(2-iPr-1-MeIm)4](OTf)2, 2) is obtained. This complex exhibits slightly distorted tetrahedral geometry (τ'4 = 0.93) with four N-donors and serves as a 4-His iron structural model complex for carotenoid cleavage dioxygenases (CCD). The electronic structure of 1 and 2 were characterized by Mössbauer spectroscopy. Reactions of 1 and 2 with model olefin substrates (1-R-4-(1-methoxyprop-1-en-2-yl)benzene; R = Me or Br) in the presence of oxygen result in olefin cleavage yielding ketone and aldehyde products, although 2 yields more products than 1. Support for a proposed reaction mechanism for 2 is offered from Density Functional Theory (DFT) calculations.

Vacancy-Engineered 1D Nanorods with Spatially Segregated Dual Redox Sites for Visible-Light-Driven Cooperative CO2 Reduction.

Cooperative CO2 photoreduction with tailored organic synthesis offers a potent avenue for harnessing concurrently generated electrons and holes, facilitating the creation of both solar fuels and specialized chemical compounds. However, controlling the crystallization and morphologies of metal-free molecular nanostructures with exceptional photocatalytic activities toward CO2 reduction remains a significant challenge. These hurdles encompass insufficient CO2 activation potential, sluggish multielectron processes, delayed charge-separation kinetics, inadequate storage of long-lived photoexcitons, unfavorable thermodynamic conditions, and the precise control of product selectivity. Here, melem oligomer 2D nanosheets (MNSs) synthesized through pyrolysis are transformed into 1D nanorods (MNRs) at room temperature with the simultaneous engineering of vacancies and morphology. Transient absorption spectral analysis reveals that vacancies in MNRs trap charges, extending charge carrier lifetimes. Additionally, carbon vacancies enhance CO2 adsorption by increasing amine functional centers. The photocatalytic performance of MNRs for CO2 reduction coupled with benzyl alcohol oxidation is approximately ten times higher (CH3OH and aromatic aldehyde production rate 27 ± 0.5 and 93 ± 0.5 mmol g-1 h-1, respectively) than for the MNSs (CH3OH and aromatic aldehyde production rate 2.9 ± 0.5 and 9 ± 0.5 mmol g-1 h-1, respectively). The CO2 reduction pathway involved the carbon-coordinated formyl pathway through the formation of *COOH and *CHO intermediates, as mapped by in situ Fourier-transform infrared spectroscopy. The superior performance of MNRs is attributed to favorable energy-level alignment, enriched amine surfaces, and unique morphology, enhancing solar-to-chemical conversion.

Co-pyrolysis of wheat straw with polyester-based polyurethane for nitrogenous compounds: Pyrolysis kinetic properties and synergistic effects

To re-utilize agricultural waste straw and waste plastic, the co-pyrolysis process of wheat straw (WS) and high-nitrogen polymer polyester-based polyurethane (PU) and the synergistic effects were studied. The results showed that PU facilitated pyrolysis to occur at lower temperatures. The effective apparent activation energies (Eα) of different samples were calculated at different conversion rates with three methods (Kissinger, KAS and Starink). It was found that PU decreased the Eα values and enthalpy change of WS and increased the reactivity. Both ΔG and ΔS results indicate that a heating rate of 5 ℃/min is more favorable for co-pyrolysis. PU greatly promoted the production of pyrolysis oil. Co-pyrolysis oil doped with 75 % PU gave the highest yield of 77 wt%. Co-pyrolysis effectively suppressed the production of acids, aldehydes, and phenols in pyrolysis oils. It increased the levels of alcohols and ketones, improving the pyrolysis oil's stability and calorific value. α, β-unsaturated aldehydes produced by WS during pyrolysis reacted with hydrazine derivatives produced by PU pyrolysis to produce pyrazole compounds after dehydration. In the co-pyrolysis of 50 % doped PU, the reaction of methyl and methylene produced by WS with amines (-NH2) produced by the pyrolysis of PU promotes the production of trimethylamine. The yield of amines in the nitrogenous compounds reached a maximum at this time. PU increased the yield of nitrogenous compounds and their variety. It favored the output of high-value chemicals. FT-IR analyses of pyrolytic charcoal showed that the addition of PU promoted the cleavage of WS and the dehydration and decarboxylation reactions of C-O and C-O-C. Finally, synergistic effects and nitrogen conversion mechanisms in the co-pyrolysis process are proposed. This work provided a theoretical basis for the resource utilization of WS waste and PU waste.

Porous Organic Polymers Supported Heterogeneous Catalysts for Hydroformylation Reactions

AbstractSince Otto Roelen revealed the accidental discovery of the hydroformylation process while exploring Fischer‐Tropsch synthesis, this chemical process of olefins with syngas has subsequently become the main source of aldehyde products. Compared to homogeneous systems, heterogeneous hydroformylation systems can avoid homogenous separation and lower the loss of valuable metals. Porous organic polymers (POPs) are one of porous materials that are interconnected by strong covalent bonds. By modifying the substrate structures, they may encapsulate various metal atoms and show remarkably high selectivity and activity for hydroformylation processes. In this review, we mainly focus on systematically summarizing recent developments, synthesis, and catalytic research on POPs supported catalysts in hydroformylation reactions. Lastly, we also discuss the prospects and challenges for future studies for the POPs supported metal catalysts.

Continuous Flow Approach for Benzylic Photo-oxidations Using Compressed Air.

A continuous flow approach for the aerobic photo-oxidation of benzylic substrates to ketone and aldehyde products is presented. The resulting process exploits UV-A LEDs (375 nm) in combination with a Corning AFR reactor that ensures effective gas-liquid mixing and leads to short residence times of 1 min. A variety of benzylic substrates are converted to their corresponding carbonyl products, and scalability is demonstrated to produce multigram quantities of products within a few hours. Overall, this continuous flow approach offers several improvements over alternative oxidation methods due to the combined use of air as an oxidant and SAS (sodium anthraquinone-2 sulfonate) as a water-soluble photocatalyst. The use of greener and safer conditions together with process intensification principles renders this flow approach attractive for further industrial applications.

Computational Design of an Electro-Organocatalyst for Conversion of CO2 into Long Chain Aldehydes.

Density functional theory calculations employing a hybrid implicit/explicit solvation method were used to demonstrate that an electro-organocatalyst designed in our previous work for reducing CO2 to formaldehyde could also be capable of coupling formaldehyde to form long chain aldehydes. The catalytic activity is enabled by an electron-rich vicinal enediamine (>N-C═C-N<) backbone that activates formaldehyde by reversing the polarity on the carbon atom, enabling it to act as a nucleophile in the subsequent aldol addition step. The catalyst then enables reductive dehydroxylation of the aldol addition product by facilitating outer-sphere electron transfer. The optimal pH as well as the limiting potential and formaldehyde concentration are identified and related to the kinetic balance between several rate limiting steps. Finally, the optimal conditions for coupling with the CO2 reduction cycle are discussed, demonstrating that the electro-organocatalyst is capable of efficiently converting CO2 into aldehyde products with a turnover frequency (per carbon atom) on the order of 0.1-1 s-1.

Heme-catalyzed degradation of linoleate 9-hydroperoxide (9-HPODE) forms two allylic epoxy-ketones via a proposed pseudo-symmetrical diepoxy radical intermediate

Heme-initiated decomposition of unsaturated fatty acid hydroperoxides creates alkoxyl radicals that propagate a complex series of reactions to hydroxy, keto, epoxy and aldehydic products. Herein, among the products from the hematin-catalyzed degradation of 9-hydroperoxy-linoleic acid (9-HPODE), we observed a double peak on normal-phase HPLC that resolved on RP-HPLC into equal proportions of two epoxy-allylic ketones with identical UV spectra. Their proton NMR spectra were also indistinguishable and consistent with 9,10-trans-epoxy-11E-13-keto- and 9-keto-10E-12,13-trans-epoxy-octadecenoic acids. Acid hydrolysis to the corresponding dihydroxy-ketones and GC-MS analysis identified the earlier eluting product on RP-HPLC as the 9,10-epoxy regio-isomer. Starting from the C9-hydroperoxide, recovery of the two epoxy-ketones in equal proportions suggests their formation from a common intermediate. Earlier work has proposed formation of a pseudo-symmetrical diepoxy radical (9,10-epoxy-11(•)-12,13-epoxy, derived from an epoxy allylic hydroperoxide precursor) in the carbon chain fragmentation leading to aldehydic products. This intermediate in pathways of alkoxyl radical reactions forms equal pairs of aldehydes, and now also a pair of epoxy-ketones, and based on mechanism the same products arise from either 9-HPODE or 13-HPODE. Our results point to the intermediacy of this diepoxy-carbinyl radical in the origin of at least two classes of linoleate peroxidation products, and it should be considered as a viable intermediate for homo-conjugated diene peroxidation in general. The reactions could contribute to the aldehydes and epoxy-ketones in tissues undergoing oxidative transformations of polyunsaturated fatty acids.

A comprehensive study on the steric impact of phosphine ligands on propene hydroformylation

This research examines the steric impact of ligand structure on Rhodium-catalyzed hydroformylation, specifically, the significant impact of substituent positioning of monodentate phosphine ligands on the catalytic activity in propene hydroformylation. Focusing on methyl-substituted triphenylphosphine ligands, it explores how the placement of methyl groups influences the selection between mono- and bis-ligated coordination modes and, consequently, the selectivity towards linear versus branched aldehydes. Findings highlight that substituents' proximity to the ligand's phosphorus atom alters the dominant reaction step, depending on the coordination mode favored by the ligand's structural configuration. Substituents positioned further from the phosphorus atom tend to favor a bis-ligated coordination mode, wherein olefin insertion predominantly influences the aldehyde product profile. Conversely, closer substituents lead to a preference for a mono-ligated mode, shifting the decisive step from olefin insertion to other reactions, changing selectivity and catalytic activity. The result refined understanding facilitates catalyst optimization through targeted modifications of ligand structures, advancing the more effective design of hydroformylation catalysis.

In-situ catalytic upgrading of lignin pyrolysis volatiles over red mud

Red mud (RM) is a solid waste of Bayer's alumina industry production process, which comprises a mixture of diverse minerals. After calcination, the minerals in RM are present in the form of oxides, exhibiting remarkable catalytic performance for biomass pyrolysis. It is thought that pyrolysis of lignin generates renewable aromatic chemicals. In this paper, the effect of in-situ catalysis of calcinated RM on the distribution of lignin pyrolysis volatile products is investigated. In addition, upgrading of tar by components in RM, including SiO2, Al2O3, Fe2O3, and Na2O is also discussed. The results show that the addition of RM in lignin pyrolysis leads to lower char yield and higher gas yield. RM catalyzes the breaking and rearrangement of methoxy groups and induces the generation of hydroxyl groups, which leads to an increase from 1.96 to 3.96 wt% in monophenol content of the tar. Furthermore, the activation of C-O bonds by Fe2O3 and the redox properties of Fe2O3 (FeSi) combine to stimulate the production of monophenols and aldehydes by 30.8 % and 148.2 %, while Al2O3 (AlSi) boosts the production of guaiacols by 32.0 % comparing with SiO2 (Si). It is found that synergistic effect between multiple species improves the catalytic performance, the yield of tar reaches 24.5 wt% and the selectivity of oxygenated compounds achieves 94.4 % (FeAlSiNa). The catalytic performances of RM for product yield and tar component distribution are similar to that of FeSi, indicating that Fe2O3 and SiO2 play a main catalytic role in RM.

Selective Oxidation of Alcohol to Valuable Aldehydes Using Water as a Promoter in a Photoelectrochemical Cell.

Artificial photoelectrochemistry (PEC) has emerged as a promising and efficient technology for the sustainable conversion of solar energy into chemicals. In this study, we present a refined PEC process that enables the highly selective and stable production of piperonal and other valuable aldehydes through the oxidation of the corresponding alcohols. By employing Fe2O3 or TiO2 as the photoanode material and 2,2,6,6-tetramethylpiperidinooxy (TEMPO) as a redox mediator in an H2O/acetonitrile solution, we achieve 100% selectivity and a >95% Faradaic efficiency for piperonal production from piperonyl alcohol (PA) oxidation. Remarkably, we reveal the enhancing effect on the PA oxidation reactivity of appropriate-amount water in the solvent as it plays a crucial role in inhibiting the photoelectron-hole recombination efficiency and facilitating charge transfer. Mechanistic analysis suggests that TEMPO-mediated PA oxidation involves the formation of •O2- radicals by the reduction of oxygen on the cathode, resulting in water as the sole byproduct. Furthermore, our PEC oxidation system exhibits applications on the 100%-selective production of various conjugated aldehydes, including 4-anisaldehyde, cuminaldehyde, and the vitamin B6 derivative. By implementing a TiO2//Fe2O3 dual-photoanode system, we achieve an enhanced piperonal production rate of 31.2 μmol h-1 cm-2 at 1.0 V vs Ag/Ag+ and demonstrate its stability over a 102 h cyclic test, ensuring near-quantitative yield. This research illuminates the potential of the PEC strategy as a generally applicable method for the efficient production of high-value aldehydes.

Selective Oxidations of Toluenes and Benzyl Alcohols by an Unspecific Peroxygenase (UPO)

Unspecific Peroxygenases (UPOs) have emerged as robust biocatalysts for selective oxygenation reactions, as they are easily produced at scale and require only hydrogen peroxide as the external oxidant. UPOs can catalyze the oxygenation of the primary benzylic carbons of toluenes to give alcohol, aldehyde and carboxylic acid products. They can also catalyze hydroxylation at the benzylic position of ethylbenzenes, and the subsequent oxidation of the secondary alcohols to ketones. In this study, we have investigated factors that affect the balance of products in UPO‐catalyzed benzylic oxygenations using a range of functionalised toluenes and ethyl benzenes, and a UPO from Agrocybe aegerita (rAaeUPO‐PaDa‐I‐H variant). The product distribution is dependent upon a mixture of steric and electronic effects and, in selected cases, controlling the reaction conditions permits products from each product series to be generated chemoselectively. In this way, electron poor toluenes were converted directly into carboxylic acids in isolated yields of 36–99% on preparative scale.

Evaluating black wattle bark industrial residue as a new feedstock for bioenergy via pyrolysis and multicomponent kinetic modeling

This work presents an evaluation of the industrial residue from exhausted black wattle bark after the extraction of tannin for use as a new feedstock for biofuel production, without competing with food production. The physicochemical and thermodynamic properties, the influence of temperature on pyrolysis products and multicomponent kinetics were evaluated. Principal component analysis showed that sugars, carboxylic acids, ethers/esters, furans and aldehydes were formed as primary products of pyrolysis at 450 °C. At 550 °C, phenols and mainly ketones were favored, especially acetone and 2,3-butanedione. Pyrolysis at 650 °C favored the production of aldehydes, alcohols, and 1-alkene, polyene and alkane hydrocarbons. After an upgrade, the series of 1-alkenes produced, with carbons C7 to C16, could be suitable for a range of gasoline and jet fuels. Kinetic modeling was based on the deconvolution of the mass loss of three events of the pseudo-components: hemicellulose (DE-HC), cellulose (DE-CL) and lignin (DE-LG). The activation energy for kinetic models Friedman, Flynn-Wall-Ozawa, Kissinger-Akahira-Sunose and Starink presented average values of ∼141.4–149.4 for DE-HC, ∼190.5–200.9 for DE-CL and ∼237.2–252.3 kJ mol−1 for DE-LG. This study encourages using agro-industrial waste to produce second-generation drop-in biofuels and bio-based chemicals, aiming at industrial decarbonization.

Ozonolysis of phospholipids at the air-water interface intervened by polyfluoroalkyl substances

Perfluoroalkyl substances (PFASs) are ubiquitous in the environment and even accumulate in the human body associated with their excellent stability and persistence. However, the effect and reaction mechanism at the molecular level on the cell phospholipid peroxidation remained unclear. In this work, the interfacial reaction of model phospholipids (POPG) intervened by per- and polyfluoroalkyl substances (PFASs) at the air-water interface of a hanged droplet exposed to ozone (O3) was investigated. Perfluorinated carboxylates and sulfonates were evaluated. Four-carbon PFASs promoted interfacial ozonolysis, but PFASs with longer carbon skeletons impeded this chemistry. A model concerning POPG packing was proposed and it was concluded that the interfacial chemistry was mediated by chain length rather than their functional groups. Four-carbon PFASs could couple into POPG ozonolysis by mainly reacting with aldehyde products along with minor Criegee intermediates, but this was not observed for longer PFASs. This is different from that condensed-phase Criegee intermediates preferred to reacting with per-fluoroalkyl carboxylic acids. These results provide insight into the adverse health of PFASs on cell peroxidation.

The role of hydrogen-rich water in delaying the pulp breakdown of litchi fruit during postharvest storage

Previous studies have indicated that hydrogen-rich water (HW) treatment can delay fruit ripening and senescence. However, little is known about the HW-delaying pulp breakdown. In this study, eight physiological characteristics revealed that HW treatment delayed both pericarp browning and pulp breakdown of litchi fruit. To gain a comprehensive understanding of the changes in litchi pulp, a combination of multiple metabolomics and gene expression analyses was conducted, assessing 67 primary metabolites, 103 volatiles, 31 amino acids, and 13 crucial metabolite-related genes. Results showed that HW treatment promoted starch degradation, decelerated cell wall degradation and glycolysis, and maintained the flavor and quality of litchi fruit. Furthermore, HW treatment stimulated the production of volatile alcohols, aldehydes, ketones, olefins, and amino acids, which might play a vital role in HW-delaying pulp breakdown. This study sheds light on the mechanism by which HW delayed pulp breakdown by investigating small molecule metabolites and metabolic pathways.