Double Bond Research Articles

High glucose enhanced lipoprotein(a) [Lp(a)] oxidation in a manner inhibited by eicosapentaenoic acid (EPA) in vitro

Abstract Background Elevated lipoprotein(a) (Lp(a)) levels are causally and independently associated with increased cardiovascular (CV) risk. Targeted molecular therapies are in development. Levels of oxidized Lp(a) were more predictive of CV events and endothelial dysfunction in type 2 diabetes than non-oxidized forms. EPA administered as icosapent ethyl (IPE) reduced CV events in statin-treated patients (REDUCE-IT) with diabetes and high CV risk. As a fatty acid with multiple conjugated double bonds, EPA inhibits lipoprotein oxidation by a potent lipid-centric scavenging mechanism. We therefore tested the effects of EPA on oxidation of Lp(a) and non-modified LDL under conditions of high glucose to mimic aspects of hyperglycemia in vivo. Methods Lp(a) was enriched to 41% of total ApoB-containing particles from patients with elevated levels by isopycnic centrifugation. Samples of Lp(a) and non-modified LDL were incubated under high glucose (200 mg/dL) conditions at 37°C for 30 min with EPA (50 µM). Samples were then subjected to copper sulfate-induced oxidation (20 µM) monitored by formation of malondialdehyde (MDA) via a colorimetric assay. Results Lp(a) enriched plasma underwent increased oxidation, peaking at 4 hr by 32-fold compared to baseline (0.37 ± 0.04 vs 12.27 ± 0.61 µM, p<0.001) under conditions of high glucose. Non-modified LDL also underwent oxidation in the presence of high glucose with a distinct rate compared to Lp(a), peaking after 3 h (0.28 ± 0.09 vs 10.91 ± 0.93 µM, p<0.001). EPA significantly inhibited both Lp(a) and LDL oxidation in a time-dependent manner. After peak oxidation was achieved in Lp(a) (4 h) and LDL (3 h), EPA inhibited oxidation by 57% (5.29 ± 0.25 µM, p<0.001) and 81% (2.12 ± 0.09 µM, p<0.001), respectively. Conclusions Under hyperglycemic conditions, EPA inhibited oxidation of Lp(a)-enriched plasma and non-modified LDL in a time-dependent manner. The activity of EPA may arise from its lipophilic properties and highly conjugated structure that scavenges free radicals in lipid-concentrated environments. The potent antioxidant activity of EPA may contribute to reduced CV risk in patients with diabetes and elevated Lp(a).

Polymerization kinetics of 3D-printed orthodontic aligners under different UV post-curing conditions

BackgroundThe purpose of the study was to measure the degree of conversion (DC) of direct-printed aligners (DPA) that were post-cured under ambient and nitrogen atmosphere at specific time intervals and investigate the kinetics of polymerization reaction of this material.MethodsA total of 48 aligners were produced in 4 printing series by a 3D printer with TC-85DAC resin (Graphy Inc). From each series of printing, 12 aligners were included. The aligners were divided into two groups according to their post-curing conditions. One group was post-cured under ambient air with the presence of oxygen and the other under a nitrogen atmosphere, both using the same UV post-curing unit recommended by the company. The aligners were post-cured at six different time intervals: 1, 2, 3, 5, 10, and 20 min. Each time interval included 8 aligners, with 2 aligners from each series. The DC of the cured aligners was measured by means of attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) through acquisition of the respective spectra for each UV-curing condition. Statistical analysis was performed to compare the results and differences within each atmosphere post-curing protocol, as well as between the different selected atmosphere conditions. Statistical significance level was set at p-value ≤ 0.05.ResultsPairwise analysis between post-curing protocols showed statistically significant differences only at the first minute of polymerization. Post-curing with nitrogen did not yield statistically significant results across different time intervals. Post-curing in ambient air showed some significant differences on the 1st and 2nd minute of the post-curing process.ConclusionsAlmost complete double bond conversion was observed. Significant differences were observed only during the first minute of polymerization under the nitrogen atmosphere.

Heterogeneous Asymmetric Hydrogenation of C=C and C=O Double Bonds

Nowadays, heterogeneous catalysts play a crucial role in the field of asymmetric catalysis to produce enantiopure compounds for various applications. The unique properties of heterogeneous systems, such as high stability, reusability, or ease of separation, allow effective catalysis of asymmetric transformations and their further implementation in industrial processes. In this mini review, we address the recent trend in the synthesis of chiral heterogeneous catalysts and their subsequent application in asymmetric hydrogenation reactions. We focus on current advances in asymmetric hydrogenation reactions of C=O and C=C bonds due to their high relevance in the fine chemicals industry. Our main aim is to provide a short overview of this expanding field, its current challenges, and future perspectives.

Gestational Diabetes-like Fuels Impair Mitochondrial Function and Long-Chain Fatty Acid Uptake in Human Trophoblasts

In the parent, gestational diabetes mellitus (GDM) causes both hyperglycemia and hyperlipidemia. Despite excess lipid availability, infants exposed to GDM are at risk for essential long-chain polyunsaturated fatty acid (LCPUFA) deficiency. Isotope studies have confirmed less LCPUFA transfer from the parent to the fetus, but how diabetic fuels impact placental fatty acid (FA) uptake and lipid droplet partitioning is not well-understood. We evaluated the effects of high glucose conditions, high lipid conditions, and their combination on trophoblast growth, viability, mitochondrial bioenergetics, BODIPY-labeled fatty acid (FA) uptake, and lipid droplet dynamics. The addition of four carbons or one double bond to FA acyl chains dramatically affected the uptake in both BeWo and primary isolated cytotrophoblasts (CTBs). The uptake was further impacted by media exposure. The combination-exposed trophoblasts had more mitochondrial protein (p = 0.01), but impaired maximal and spare respiratory capacities (p < 0.001 and p < 0.0001), as well as lower viability (p = 0.004), due to apoptosis. The combination-exposed trophoblasts had unimpaired uptake of BODIPY C12 but had significantly less whole-cell and lipid droplet uptake of BODIPY C16, with an altered lipid droplet count, area, and subcellular localization, whereas these differences were not seen with individual high glucose or lipid exposure. These findings bring us closer to understanding how GDM perturbs active FA transport to increase the risk of adverse outcomes from placental and neonatal lipid accumulation alongside LCPUFA deficiency.

Skeletal Rearrangements in the Enzyme-Catalysed Biosynthesis of Coral-Type Diterpenes from Chitinophaga pinensis.

Two diterpene synthases from the bacterium Chitinophaga pinensis were characterised. The first enzyme mainly produced the rearranged diterpene palmatol, a compound known from octocorals, while the second enzyme made the new coral-type eunicellane chitinol. The mechanisms of both enzymes were deeply studied through isotopic labelling experiments, DFT calculations, and with a substrate analog containing a saturated double bond, resulting in the formation of derailment products that gave additional insights into the nature of the cyclisation cascade intermediates. The formation of coral-type diterpenes poses interesting questions on the functions of these compounds in organisms as different as bacteria and corals.

Direct cleavage of C=O double bond in CO2 by the subnano MoOx surface on Mo2N

Compared to H2-assisted activation mode, the direct dissociation of CO2 into carbonyl (*CO) with a simplified reaction route is advantageous for CO2-related synthetic processes and catalyst upgrading, while the stable C = O double bond makes it very challenging. Herein, we construct a subnano MoO3 layer on the surface of Mo2N, which provides a dynamically changing surface of MoO3↔MoOx (x < 3) for catalyzing CO2 hydrogenation. Rich oxygen vacancies on the subnano MoOx surface with a high electron donating capacity served as a scissor to directly shear the C = O double bond of CO2 to form CO at a high rate. The O atoms leached in CO2 dissociation are removed timely by H2 to regenerate active oxygen vacancies. Owing to the greatly enhanced dissociative activation of CO2, this MoOx/Mo2N catalyst without any supported active metals shows excellent performance for catalyzing CO2 hydrogenation to CO. The construction of highly disordered defective surface on heterostructures paves a new pathway for molecule activation.

Chromium‐Mediated Dearomative Allylic Addition to Arenes

AbstractIn comparison with the well‐established allylic additions to C=O, C=N, and C=C double bonds, the dearomative allylic addition to arene π‐systems is heavily underdeveloped due to the severe challenge in breaking aromatic resonance stabilization. Herein, we disclose a general and efficient dearomative allylic addition to chromium‐bound arenes using allylsilanes as the pronucleophiles, thus affording convenient access to allyl‐functionalized 1,3‐cyclohexadiene building blocks. With commercially available deuterium sources, the versatility of this strategy further enables an arene dearomative 1,2‐deuteroallylation with a high level of deuterium incorporation. Finally, a preliminary try on the asymmetric dearomative hydroallylation based on a chiral auxiliary strategy is described.

Near‐Infinite‐Chain Polymers with Ge=Ge Double Bonds

Despite considerable interest in heteroatom‐containing conjugated polymers, there are only few examples with heavier p‐block elements in the conjugation path. The recently reported heavier acyclic diene metathesis (HADMET) allowed for the synthesis of a polymer containing Ge=Ge double bonds – albeit insoluble and with limited degree of polymerization. By incorporation of long alkyl chains, we now obtained soluble representatives, which exhibit degrees of polymerization near infinity according to diffusion‐ordered NMR spectroscopy (DOSY) and dynamic light scattering (DLS). Analyses of the UV/Vis absorption and the NMR spectroscopic data confirm the presence of σ,π‐conjugation across the silylene‐phenylene linkers between the Ge=Ge double bonds. Favorable intermolecular dispersion interactions lead to ladder‐like cylindrical supramolecular assemblies as confirmed by X‐ray diffraction (XRD), small angle X‐ray scattering (SAXS) and DLS. AFM and TEM images of deposited thin films reveal lamellar ordering of extended polymer bundles.

Near-Infinite-Chain Polymers with Ge=Ge Double Bonds.

Despite considerable interest in heteroatom-containing conjugated polymers, there are only few examples with heavier p-block elements in the conjugation path. The recently reported heavier acyclic diene metathesis (HADMET) allowed for the synthesis of a polymer containing Ge=Ge double bonds - albeit insoluble and with limited degree of polymerization. By incorporation of long alkyl chains, we now obtained soluble representatives, which exhibit degrees of polymerization near infinity according to diffusion-ordered NMR spectroscopy (DOSY) and dynamic light scattering (DLS). Analyses of the UV/Vis absorption and the NMR spectroscopic data confirm the presence of σ,π-conjugation across the silylene-phenylene linkers between the Ge=Ge double bonds. Favorable intermolecular dispersion interactions lead to ladder-like cylindrical supramolecular assemblies as confirmed by X-ray diffraction (XRD), small angle X-ray scattering (SAXS) and DLS. AFM and TEM images of deposited thin films reveal lamellar ordering of extended polymer bundles.

Palladium-Catalyzed Site-Selective Hydrogenation of Unactivated Alkenes Directed by 8-Aminoquinoline Amides.

We have developed a method for the site-selective hydrogenation of unactivated alkenes using 8-aminoquinoline amide as the directing group. For unactivated alkenes with two C-C double bonds, Daugulis's 8-aminoquinoline amide facilitated the site-selective hydrogenation of the desired C-C double bond, producing a product in which one C-C double bond was reduced. Site-selective reduction methodologies using intramolecular directing groups are expected to contribute significantly to the synthesis of molecules with multiple reducible functional groups in the future.

Mechanism of methyl elaidate on the thermal oxidation behavior

The effects of cis–trans isomerization on the oxidation products of oleic acid (composites and structure characterization) were investigated. The reduction of thermal oxidation reaction of methyl elaidate (ME) was 6.72 % lower than that of methyl oleate (MO), and the oxidation products (core aldehydes) first increased and then decreased with the prolongation of thermal oxidation time. ME exhibited better oxidation stability than MO in free radicals, hydroperoxides, double bonds, aldehydes, and glycerides. The oxidation products were mainly 11-oxo-9-undecenoate (initial stage) and methyl 9-oxononanoate (later stage), following the free radical chain reaction mechanism. The H8 in double bond was more easily dehydrogenated in the chain initiation stage than H11, followed by the formation of core aldehyde through three intermediates and two transition states each pathway. ME required a higher energy barrier (1.3–13.6 kJ/mol) than MO reaction, making it more difficult for ME to undergo thermal oxidation reaction. The transition state 4 and 5 were rate determining steps of chain initiation reaction and proliferation reaction, respectively. This study was of great significance to further control the formation of these trans fats and their oxidation products.

Metabolic Syndrome in Reproductive Age Women of Various Ethnic Groups. Neuroendocrine Status and Lipid Peroxidation System.

We analyzed the state of neuroendocrine regulation and LPO-antioxidant defense systems in reproductive age women with metabolic syndrome (MetS), representatives of the Russian and Buryat ethnic groups. Compared to the corresponding control groups, women from the Russian ethnic group with MetS had elevated levels of thyroid-stimulating hormone and free androgen index (FAI) and reduced levels of sex hormone-binding globulin, while women from the Buryat ethnic group had increased levels of prolactin and FAI. Changes in the LPO system in women of the Russian ethnic group with MetS consisted in an increase in the levels of substrates with double bonds, TBA-reactive substances, and fat-soluble vitamins. Buryat women with MetS had a higher content of primary oxidation products and reduced levels of glutathione. The results of the study indicate a hyperandrogenic shift in the neuroendocrine regulation system, as well as compensatory influences from different parts of the antioxidant defense system in women of reproductive age with MetS, depending on their ethnicity. These findings indicate the need for assessing and monitoring the levels of these metabolites in women with MetS, considering their ethnicity.

Efficient Visible‐Light‐Induced π‐Extension of Perylene Tetraesters: An Investigation on Regioselectivity

The present study discloses a highly efficient visible‐light‐induced π‐extension of perylene tetraesters and discussion on the regioselectivity in the photocyclization. We initially found that π‐extension reaction of 3,4‐dimethoxyphenyl perylene tetraester smoothly proceeded by only irradiating blue LED with a complete regioselectivity. Investigations of the photocyclization with various substrates revealed the relationship between the regioselectivity and electron‐donating/withdrawing effects of the substituents on the aromatic groups. Moreover, theoretical investigation suggested the importance of bond alteration in the aromatic groups: cyclization proceeds preferentially at shorter C‐C bonds with higher double bond characters. The findings will open new possibilities for the practical synthesis of custom‐designed π‐extended perylene materials.

Effect of load-resisting force on photoisomerization mechanism of a single second generation light-driven molecular rotary motor.

A pivotal aspect of molecular motors is their capability to generate load capacity from a single entity. However, few studies have directly characterized the load-resisting force of a single light-driven molecular motor. This research provides a simulation analysis of the load-resisting force for a highly efficient, second-generation molecular motor developed by Feringa et al. We investigate the M-to-P photoinduced nonadiabatic molecular dynamics of 9-(2,3-dihydro-2-methyl-1H-benz[e]inden-1-ylidene)-9H-fluorene utilizing Tully's surface hopping method at the semi-empirical OM2/MRCI level under varying load-resisting forces. The findings indicate that the quantum yield remains relatively stable under forces up to 0.003a.u., with the photoisomerization mechanism functioning typically. Beyond this threshold, the quantum yield declines, and an alternative photoisomerization mechanism emerges, characterized by an inversion of the central double bond's twisting direction. The photoisomerization process stalls when the force attains a critical value of 0.012a.u. Moreover, the average lifetime of the excited state oscillates around that of the unperturbed system. The quantum yield and mean lifetime of the S1 excited state in the absence of external force are recorded at 0.54 and 877.9fs, respectively. In addition, we analyze a time-dependent fluorescence radiation spectrum, confirming the presence of a dark state and significant vibrations, as previously observed experimentally by Conyard et al.

Selective catalytic conversion of model olefin and diolefin compounds of waste plastic pyrolysis oil: Insights for light olefin production and coke minimization

The primary challenges in ex-situ catalytic pyrolysis of plastic waste to produce light olefins lie in the selective conversion of larger olefins and diolefins downstream of the pyrolyzer. Hence, the catalytic cracking mechanism of plastic pyrolysis oil was explored using an α-olefin (1-decene) and a diolefin (1,9-decadiene) model compounds over an HZSM-5 zeolite-based catalyst in a fixed-bed reactor. Key objectives were to elucidate the reaction pathways for light olefin production, aromatization, and coke formation in catalytic cracking of larger olefins and diolefins. The investigation explored the impact of HZSM-5 steam treatment severity, contact time (∼58–226 ms), and reaction temperature (250–450 °C) on product yields. The severity of steam treatment was found to increase the 1-decene isomerization rate while decreasing the cracking rate and conversion of 1-decene to C3-4 light olefins. In the catalytic cracking of 1-decene, major product types included olefins (linear and nonlinear) and a few naphthenes, while in the case of 1,9-decadiene catalytic cracking, non-linear olefins were absent, with abundant naphthenes followed by lighter diolefins and C3-5 linear olefins. Temperature and contact time variations revealed that the catalytic cracking of 1-decene initiated with double bond rearrangement isomerization, progressing to skeletal isomerization, and intensified cracking reactions producing light C3-4 olefins. Conversely, in the catalytic cracking of 1,9-decadiene, cyclization was the primary reaction pathway, followed by β-scission, resulting in lighter conjugated dienes and light linear olefins. Thermal gravimetric analysis (TGA) of spent catalysts confirmed a higher coke amount generated during 1,9-decadiene cracking compared to 1-decene cracking, indicating that diene compounds serve as precursors for significant coke formation in plastic pyrolysis oil. These insights provide valuable understanding for catalytic upgrading of pyrolysis oil from polyolefin pyrolysis.

Non-Ionic Peterson-Type Olefination Reactivity and its Use in a Silicon-Promoted Carbonyl-Carbonyl Cross Coupling Reaction.

The [2+2] cycloaddition reaction between the Si=C double bond of adamantylsilene and the carbonyl group of aliphatic, aromatic or acetylenic ketones and aldehydes is demonstrated. The product of this reaction that is central to a non-ionic version of the Peterson olefination is an unusual four-membered 1,2-silaoxetane heterocycle that was characterized spectroscopically and crystallographically. In the presence of SiO2, the silaoxetane undergoes retro-cycloaddition with the formation of alkene products. As the [2+2] cycloaddition proceeds without the necessity of any base, enolizable ketones can be converted into olefins. In addition, it is shown that the adamantylsilene can be produced in situ by a sila-Peterson reaction, providing valuable input for the development of a new one-pot silicon-based reductive carbonyl-carbonyl cross coupling methodology.

Investigation on induced smectic phases in double hydrogen bond liquid crystal complexes derived from aromatic carboxylic acids: Experimental and quantum chemical approaches

In the present study, double Hydrogen bond liquid crystal (HBLC) complexes in different mole ratio (1:1 and 1:2) have been isolated from symmetrical aromatic dicarboxylic acid of non-mesogenic compound 1,3-Phenylenediacetic acid (1,3-PDA) and mesogenic compound 4-n-dodecyloxybenzoic acid (12 OBA). Fourier transform infrared Spectroscopy (FTIR) explores the presence of functional groups in the title complexes. Formation of H-bond between 1,3-PDA and 12 OBA is experimentally confirmed by observing the FTIR peak at 3639 cm−1 (1:1 ratio). Induced mesophases and its textures along with transition temperatures are analyzed using polarizing optical microscope (POM) and differential scanning calorimetry (DSC). The layered structures (smectic phases) and their molecular mechanism has been analyzed using density functional theory (DFT). Further, the establishment of H-bond in the title complex has been investigated with the aid of optimized geomentry, molecular electrostatic potential (MEP) and reduced density gradient (RDG) analysis. The band gap energy of title complex (1:1) is calculated by UV–Vis spectrometer and the same has been justified by HOMO-LUMO studies. Maximum absorption in the UV region and moderate bandgap energy (Eg = 4.22 eV) of the title complex clearly indicates its potential application in NLO, optoelectronics and laser tuning devices. In addition to that, LC parameters and its effect on mesophase are reported using experimental and computational methods.

The Interaction Mechanism Between C14-Polyacetylene Compounds and the Rat TRPA1 Receptor: An In Silico Study.

Polyacetylene (PA) compounds, as natural products, exhibit remarkable properties and distinctive chemical activities. Three structurally similar C14-PA compounds-Echinophorin D, Echinophorin B, and Echinophorin A-extracted from plants demonstrate varying biological activities on the Transient Receptor Potential Channel A1 (TRPA1) protein, which belongs to the TRP (Transient Receptor Potential) family. In the current study, we investigated the binding modes of these three PA compounds with TRPA1 using molecular dynamics (MD), molecular docking, binding free energy calculations, and quantum mechanics/molecular mechanics (QM/MM) methods. Initially, a putative binding site (site-II) in TRPA1 was identified for these compounds; Echinophorin B was found to stabilize the upward A-loop of TRPA1, which is critical for its activation. Furthermore, the binding affinity calculations of PA compounds through molecular fragment decomposition indicate that the arrangement of two triple bonds and one double bond in C14-PA compounds is vital for regulating TRPA1 bioactivity. Additionally, the lipophilic and electronic properties of the three molecules were analyzed in relation to binding affinity, establishing a correlation between TRPA1 activity and these molecular properties.

On the interaction of uric acid with ammonium molybdate in acidic medium

This communication is a theoretical organic chemistry study on the interaction of uric acid with ammonium molybdate in acidic medium (Gigli test for uric acid). Colour tests give rapid, visible, results. However, it is interesting know what is happening in the test tube at molecular level. In the present paper we describe the reaction route of the above mentioned assay. Each step is fully commented and the electron flow is also given. The key stages are: addition of molybdic acid to the C-C double bond, acidolysis of the organometallic ester with reduction to molybdenum (IV) and epoxide formation (oxidation step). Ring opening of the oxirane and reaction with water. A glycol is formed followed by opening of the five-member ring giving a carbonyl and an ureido chain. Finally, elimination of urea gives rise to 2,4,5,6-tetraoxo-hexahydropyrimidine (alloxan) which is hydrated. The blue colour observed (molybdenum blue) is a mixture of several oxides.

Rapid evaluation of vegetable oil varieties and geographical origins by ambient corona discharge ionization mass spectrometry

The composition and ratio of unsaturated fatty acids in vegetable oils play a crucial role in determining their overall quality. In this study, we present a corona discharge ionization mass spectrometry (MS) method for the rapid differentiation of vegetable oil varieties and their geographical origins under environmental conditions. Abundant water dimer radical cations, (H2O)2+•, were generated by the ionization setup, which effectively activated carbon‑carbon double bonds (C=C) to form epoxidized products. These epoxidation products were analyzed using tandem MS, generating diagnostic fragment ions that precisely identified CC bond positions. Statistical analysis models were subsequently developed using the resulting MS fingerprint data, revealing significant differences between various vegetable oils and olive oils from different origins. Key advantages of this method include minimal sample preparation, rapid analysis, and easily interpretable spectra. This study provides a new MS-based strategy for food quality assessment and offers a promising tool for identifying CC positional isomers in complex systems.