C8 C18 Research Articles

Robust biocatalyst for the green continuous flow synthesis of esters from biomass-derived furfuryl alcohol and C8–C18 carboxylic acids

A sustainable method suitable for industrial-scale continuous flow synthesis of esters from biomass-derived furfuryl alcohol (FA) and C8–C18 carboxylic acids was developed.

The role of serum acylcarnitine profiling for the detection of multiple solid tumors in humans

Metabolic reprogramming is an essential hallmark of cancer. Several studies have reported the dysregulation of acylcarnitine (ACar) metabolism in tumor cells, suggesting that changes in the blood ACar may be related to tumor growth. Accordingly, this study aimed to understand the alteration of serum ACar profiles in various solid tumors and explore the potential of differential serum ACars as diagnostic biomarkers. A series of 69 relatively abundant ACars were identified via untargeted analysis. Then, targeted metabolomics was used to describe the metabolic alterations in ACars between normal controls and patients with six types of solid tumors. The results suggested that changes in ACars correlated with their carbon chain length and saturation. The six tumor types had highly similar ACar metabolic profiles, indicating similar fatty acid oxidation (FAO) metabolic pathways. Moreover, the receiver operating curve analysis of differential ACars showed that 16 ACars (C8–C14) had high diagnostic capability towards the studied solid tumors. Specifically, the area under the curve of ACar 10:2 isomer2 and ACar 12:2 isomer2 was greater than 0.95. In conclusion, the marked decrease in the levels of medium- and long-chain ACars (C8–C18) in the six solid tumors suggests that they may have similar FAO-based metabolic pathways, which could afford a common target for cancer therapy. Additionally, 16 ACars (C8–C14) were identified as potential biomarkers for diagnosing six types of solid tumors.

Enzyme Engineering for High‐Yielding Amide Formation: Lipase‐Catalyzed Synthesis of N‐Acyl Glycines in Aqueous Media

AbstractAmide syntheses remain a key challenging green chemistry reaction. For instance, green synthesis of N‐acyl glycines as biosurfactants and therapeutics is highly desirable to replace chemical pathways using toxic phosgene. Herein, we report a novel concept for enzymatic amidation in an aqueous system via glycerol activation of fatty acids and theirsubsequent aminolysis with glycine to synthesize N‐acyl glycines. We then engineer an enzyme (proRML) by reshaping its catalytic pocket to enhance its aminolysis activity and catalytic efficiency by 103‐fold and 465‐fold, respectively. The evolved proRML (D156S/L258K/L267N/S83D/L58K/R86K/W88V) catalyzed the amidation of a fatty acid with glycine to give N‐lauroylglycine with high yield (80 %). It accepts a broad range of medium‐ to long‐chain fatty acids (C8–C18), giving high yields of N‐decanoyl‐, N‐myristoyl‐, and N‐oleoylglycine. The developed amidation concept may be general, and the engineered enzyme is useful for the green synthesis of N‐acyl glycines.

Fast and simplified quantitative multiresidue analytical method for pesticides in surface waters by UHPLC-MS/MS with online sample preparation

A quantitative multiresidue analytical method for the simultaneous analysis of current-use agricultural pesticides in surface waters is reported. The method involves minimal sample manipulation and small sample collection volumes (for 1 mL and 5 mL injections) with online sample clean-up and analyte preconcentration on a hydrophilic-lipophilic balance (HLB) column. To our knowledge, this online approach with the use of an HLB column has not yet been reported for multiresidue pesticide analysis in surface waters. Chromatographic separations of isomeric pesticides were achieved through the sequential coupling of C8 and polar endcapped C18 analytical columns. High resolution accurate mass (HRAM) quadrupole Orbitrap spectrometry was performed in full scan mode followed by data-dependent MS/MS fragmentation (FS-ddMS2) with concurrent electrospray ionization in both positive and negative modes. The method was validated for thirty-one (31) diverse current-use pesticides and demonstrated strong linearity (R2 > 0.9912) and precision (% RSD <8.4%) with low quantitation limits (average LOQ of 41 ng L−1). The majority of target analytes experienced minimal matrix effects (<±20%) in fortified environmental water samples. When applied to surface water samples, the method detected fourteen of the target analytes, including twelve herbicides, one insecticide, and one fungicide. This method offers a fast, simple, and reliable approach for the quantitative analysis of diverse current-use pesticides in surface water samples within hours of sample collection in the field. The robust nature of the method may allow for potential application to other types of water and the targeted or untargeted screening of other emerging contaminants.

Effects of the surface ligands of quantum dots on the intaglio transfer printing process

High-resolution semiconductor nanocrystal quantum dot (QD) patterns are required for applications in display devices. For this, the dry transfer printing of QDs is promising because it does not degrade the inherent properties of QDs. However, the effect of the surface ligands on this process remains poorly understood, despite its importance. Herein, we investigate the effect of the surface ligands on the intaglio transfer printing process. Colloidal QDs with organic (C8–C18) or inorganic (I−) ligands are prepared. In various pattern-printing tests, including patterns with a sub-10-μm width, the patterning yield is ∼100% for QDs with long-chain ligands (C18). However, the patterning yield decreases with decrease in the chain length for the organic-ligand-passivated QDs and is the lowest for the QDs passivated with I−. Using surface energy characterization and finite element method simulations, we suggest two printing failure mechanisms: (i) Inorganic-ligand-passivated QDs are not effectively picked-up by the stamp because of poor adhesion, and, (ii) for the organic-ligand-passivated QDs, internal crack formation is easier for QDs having short-chain ligands because of the weak interparticle attraction between QDs. Our findings reveal previously unknown defects of the intaglio printing process and provide guidance for mitigating these problems for preparing high-resolution QD patterns.

Mechanistic insight into the role of mevalonate kinase by a natural fatty acid-mediated killing of Leishmania donovani

We evaluated the anti-leishmanial efficacy of different saturated medium-chain fatty acids (FAs, C8–C18) where FA containing C8 chain, caprylic acid (CA), was found to be most potent against Leishmania donovani, the causative agent for visceral leishmaniasis (VL). Different analogs of CA with C8 linear chain, but not higher, along with a carboxyl/ester group showed a similar anti-leishmanial effect. Ergosterol depletion was the major cause of CA-mediated cell death. Molecular docking and molecular dynamic simulation studies indicated the enzyme mevalonate kinase (MevK) of the ergosterol biosynthesis pathway as a possible target of CA. Enzyme assays with purified recombinant MevK and CA/CA analogs confirmed the target with a competitive inhibition pattern. Using biochemical and biophysical studies; strong binding interaction between MevK and CA/CA analogs was established. Further, using parasites with overexpressed MevK and proteomics studies of CA-treated parasites the direct role of MevK as the target was validated. We established the mechanism of the antileishmanial effect of CA, a natural product, against VL where toxicity and drug resistance with current chemotherapeutics demand an alternative. This is the first report on the identification of an enzymatic target with kinetic parameters and mechanistic insights against any organism for a natural medium-chain FA.

Synthesis of the C1‐C18 fragment of Neaumycin B

AbstractStereoselective synthesis of the C1–C18 fragment 2 of Neaumycin B (1), 28‐membered macrolide compound with 19‐chiral centers and 6,6‐spiroketal structure, has been described. Brown syn‐crotylation and olefin metathesis reaction were used as key steps from (R)‐roche ester in the synthesis of C8–C18 fragment 3. C1–C7 fragment 4 was constructed from 1,3‐propanediol using diastereoselective allylation, syn‐aldol reaction, and olefin metathesis reaction as key steps. Finally, NHK reaction and (S)‐CBS reduction as key steps led to the of synthesis of C1–C18 fragment 2 of Neaumycin B (1).

Quaternary Ammonium Compounds: Bioaccumulation Potentials in Humans and Levels in Blood before and during the Covid-19 Pandemic.

Quaternary ammonium compounds (QACs) are commonly used in a variety of consumer, pharmaceutical, and medical products. In this study, bioaccumulation potentials of 18 QACs with alkyl chain lengths of C8–C18 were determined in the in vitro–in vivo extrapolation (IVIVE) model using the results of human hepatic metabolism and serum protein binding experiments. The slowest in vivo clearance rates were estimated for C12-QACs, suggesting that these compounds may preferentially build up in blood. The bioaccumulation of QACs was further confirmed by the analysis of human blood (sera) samples (n = 222). Fifteen out of the 18 targeted QACs were detected in blood with the ΣQAC concentrations reaching up to 68.6 ng/mL. The blood samples were collected during two distinct time periods: before the outbreak of the COVID-19 pandemic (2019; n = 111) and during the pandemic (2020, n = 111). The ΣQAC concentrations were significantly higher in samples collected during the pandemic (median 6.04 ng/mL) than in those collected before (median 3.41 ng/mL). This is the first comprehensive study on the bioaccumulation and biomonitoring of the three major QAC groups and our results provide valuable information for future epidemiological, toxicological, and risk assessment studies targeting these chemicals.

Migration of (non-) intentionally added substances and microplastics from microwavable plastic food containers

Microwavable plastic food containers (MPFCs) are extensively used for food storage, cooking, rapid heating and as take-out containers. There is an urgent need to investigate whether MPFCs pose potential health risks, as a result of the migration of chemicals into foods. Herein, 42 intentionally added substances (IAS) and > 100 non-IAS (NIAS) migrating from MPFCs were identified in food simulants according to Regulation (EU). The migration of major IAS and NIAS was higher in 95% ethanol compared to other simulants, and gradually decreased following repeated use. NIAS, including Cramer class III toxic compounds, such as PEG oligomers of N,N-bis(2-hydroxyethyl) alkyl(C8–C18)amines, isomers of hexadecanamide and oleamide, and Irgafos 168 OXO were detected and exceeded the recommended limits in some MPFCs. Furthermore, microplastics (MPs) were detected with high values of over one million particles/L in some MPFCs in a single test, and migration behaviors of MPs in different MPFCs were diverse. Surprisingly, this rigorous migration might result in an annual intake of IAS/NIAS up to 55.15 mg and 150 million MPs particles if take-out food was consumed once a day. Multi-safety evaluation studies on the migration of various chemicals from MPFCs to foodstuffs during food preparation should be assessed.

Synthesis, characterization, and ethylene oligomerization with star iminopyridine nickel(II) complexes

A series of star iminopyridine ligands, containing different groups (H, CH3, Br) in the pyridine ring, have been synthesized and characterized by FT-IR, 1H NMR, and UV-vis. The corresponding nickel(II) complexes have been prepared in good yields. The nature of the Ni complexes has been established by FT-IR, UV-vis, ESI-MS, and ICP. Upon activation with methylaluminoxane (MAO), the nickel complexes were able to oligomerize ethylene to produce C4–C18 fractions at activity of up to 105 g (mol Ni h)−1. The influence of substituent, catalyst structure, solvent, co-catalyst, and reaction conditions on the catalytic activity and product selectivity was investigated. The results showed that substitution on the pyridine ring had large influence on the catalytic activity and product selectivity. The catalytic activity increased at first and then decreased with the increase of reaction temperature and Al/Ni molar ratio. However, the catalytic activity continuously increased with increasing reaction pressure. When toluene was used as solvent and MAO was used as co-catalyst, catalytic activity of 4.39 × 105 g (mol Ni h)−1 and 31.93% selectivity of higher carbon olefins (C8–C18) were obtained at 10 °C, Al/Ni molar ratio 500, and the reaction pressure 1.0 MPa.

Saturated Fatty Acid-Based In Situ Forming Matrices for Localized Antimicrobial Delivery

In recent years, the world has faced the issue of antibiotic resistance. Methicillin-resistant Staphylococcus aureus (MRSA) is a significant problem in various treatments and control of infections. Biocompatible materials with saturated fatty acids of different chain lengths (C8–C18) were studied as matrix formers of localized injectable vancomycin HCl (VCM)-loaded antisolvent-induced in situ forming matrices. The series of fatty acid-based in situ forming matrices showed a low viscosity (5.47–13.97 cPs) and pH value in the range of 5.16–6.78, with high injectability through a 27-G needle (1.55–3.12 N). The preparations exhibited low tolerance to high concentrations of KH2PO4 solution (1.88–5.42% v/v) and depicted an electrical potential change during phase transformation. Their phase transition and matrix formation at the microscopic and macroscopic levels depended on the chain length of fatty acids and solvent characteristics. The VCM release pattern depended on the nucleation/crystallization and solvent exchange behaviors of the delivery system. The 35% w/v of C12–C16 fatty acid-based in situ forming matrix prolonged the VCM release over seven days in which C12, C14, C16 –based formulation reached 56, 84, and 85% cumulative drug release at 7th day. The release data fitted well with Higuchi’s model. The developed formulations presented efficient antimicrobial activities against standard S. aureus, MRSA, Escherichia coli, and Candida albicans. Hence, VCM-loaded antisolvent-induced fatty acid-based in situ forming matrix is a potential local delivery system for the treatment of local Gram-positive infection sites, such as joints, eyes, dermis of surgery sites, etc., in the future.

Migration of dihydroxyalkylamines from polypropylene coffee capsules to Tenax® and coffee by salt-assisted liquid–liquid extraction and liquid chromatography–mass spectrometry

Migration of N,N-Bis(2-hydroxyethyl) alkyl(C8–C18)amines from five different polypropylene capsules to Tenax® and coffee powder have been studied. A single step extraction-cleanup procedure using salting out liquid–liquid extraction (SALLE) method followed by ultra-high performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS) was applied. The critical parameters on the SALLE procedure such as extracting solvent, extracting volume, sample pH, salt and its concentration were optimized. The recovery values were in the range of 87.5%–106.5%. The %RSD were lower than 3.7%. The limit of detection was improved from 2.3 ng/g in Tenax® to 0.8 ng/g in coffee. The results indicated that the analyzed compounds have the potential to migrate from the polypropylene capsule containers to the coffee. In most of the cases, the migrated values were higher in Tenax® than in coffee in a range between 1.8 and 61%. One sample did not comply with the specific migration limit established by the European Commission.

High efficiency enzymatic synthesis of triglycerides with varying chain length and degree of unsaturation in a solvent‐free system under vacuum

AbstractBACKGROUNDTriglycerides with varying chain length and unsaturation degree are now in high demand in the food and pharmaceutical industries. Enzymatic catalyzed synthesis methods are favored over chemical‐based processes in the commercial production of triglycerides. This study found that the application of vacuum can improve the efficiency and productivity of enzymatic synthesis of various triglycerides using Novozym 435 (EC 3.1.1.3), an immobilized lipase B from Candida antarctica. The system was used for esterification of fatty acids varying in chain length, unsaturation degree, and oxidation degree.RESULTSThe vacuum condition was not applicable to short chain fatty acids (C4–C6) due to loss of fatty acids in the reaction. The conversions of C4–C6 saturated fatty acids were low (15–35%) under atmospheric pressure. Under vacuum, high conversions (&gt;95%) and triglyceride yields (approximately 90%) were achieved in the esterification of glycerol with several medium‐chain and long‐chain (C8–C18) saturated fatty acids. Moreover, unsaturation degree of fatty acids also affected the triglyceride yield. The triglyceride contents synthesized from C18:2n‐6 (76.17 ± 0.45%) was significantly lower (P &lt; 0.05) than those from C18:0 (91.59 ± 1.58%) and C18:1n‐9 (90.77 ± 0.85%). Furthermore, fatty acids with a high oxidation degree had negative effect on triglyceride synthesis. This vacuum solvent free system allowed the synthesis enzyme to be reused 11 times without significant decrease in the lipase activity for esterification of fatty acids.CONCLUSIONThe studied vacuum facilitated triglyceride synthesis process provides an economically attractive yet sustainable solution for the production of a wide range of triglyceride products. © 2020 Society of Chemical Industry

Synthesis and Thermophysical Characterization of Fatty Amides for Thermal Energy Storage.

Nine monoamides were synthesized from carboxylic acids (C8–C18) and crude glycerol. The final monoamides were the result of a rearrangement of the acyl chain during the final hydrogenation process. The purity of the final compounds was determined by spectroscopic and mass spectrometry (MS) techniques. The thermophysical properties of solid monoamides were investigated to determine their capability to act as phase change materials (PCM) in thermal energy storage. Thermophysical properties were determined with a differential scanning calorimeter (DSC). The melting temperatures of the analyzed material ranged from 62.2 °C to 116.4 °C. The analyzed enthalpy of these monoamides ranged from 25.8 kJ/kg to 149.7 kJ/kg. Enthalpy values are analyzed considering the carbon chain and the formation of hydrogen bonds.

Volatile Aroma Compounds of Brandy 'Lozovača' Produced from Muscat Table Grapevine Cultivars (Vitis vinifera L.).

Grape brandy, known as ‘Lozovača’, is one of the most produced alcoholic beverages in the Republic of Serbia. Muscat cultivars are highly priced in grape brandy manufacturing. Among the numerous factors, cultivar-specific characteristics have a significant influence on its quality and aroma profile. Pectolytic enzymes play a part in increasing intensity of the prefermentative aroma by hydrolysis of terpenic glycosides, from which the compounds that contribute to the aroma of brandy are released. In this study, grape brandy samples were produced from five Muscat table grapevine cultivars (Vitis vinifera L.) namely, Early Muscat, Radmilovac Muscat, Banat Muscat, Italia Muscat, and Muscat Hamburg, with the addition of pectolytic enzyme in two different concentrations or without it (control). A total of 58 volatile aroma compounds were detected by means of combined gas chromatographic-mass spectrometric (GC/MS) method. Ethyl esters of C8–C18 fatty acids (21) and terpene (16) compounds were considerably more abundant in all grape brandy samples compared to the other volatile compounds identified. Pectolytic enzyme, positively affected terpenes content in the brandy of all studied cultivars. The similarities between brandy samples produced from Muscat Hamburg (MH) and other Muscat cultivars may be attributed to the parentage of MH to those cultivars.

Functionalized 2-Substituted Allyl Bromides in the Barbier Allylation of (R)-2,3-O-Isopropylideneglyceraldehyde. Synthesis of the C8–C17, C8–C18, and C5–C17 Building Blocks of Laulimalides and Their Synthetic Analogs

Several new 2-substituted allyl bromides were synthesized through cyclopropanol intermediates and were then involved in the Barbier allylation of (R)-2,3-O-isopropylideneglyceraldehyde in the presence of zinc in a mixture of tetrahydrofuran and saturated aqueous ammonium chloride to obtain the corresponding homoallylic alcohols with high diastereoselectivity. The possibility of using the latter as building blocks for macrocyclic antitumor agents (laulimalides) and their synthetic analogs was demonstrated.

Bifunctional Co/Al-SBA-15 Catalyst with Tunable Acidity for Selective Production of Aviation Fuel

Production of alternative, clean aviation fuel from biomass synthesis gas via Fischer–Tropsch (FT) synthesis has attracted much attention. In this paper, Al-SBA-15 supported cobalt catalysts with different Al/Si ratios were successfully prepared for the production of aviation fuel by FT synthesis. The physical and acidic properties of the Co/Al-SBA-15 catalysts were characterized by XRF, XRD, N2 adsorption–desorption, TEM, H2-TPR, 27Al NMR, NH3-TPD, and Py-FTIR. The formation of long-chain hydrocarbons was inhibited by the ordered mesoporous structure. Fischer–Tropsch activity and selectivity were demonstrated to be affected by the acidity of the Al-SBA-15 supports. The selectivity turned to lighter iso-paraffin products. Co-based catalyst with Al/Si ratio of 0.01 exhibited the highest selectivity (52.4%) for aviation fuel (C8–C18 products) and much higher ratio of iso-paraffin/normal-paraffin (iso/n) (20.2%). This study might provide useful information for the selective production of aviation fuel via FT...

Determination of Height Equivalent to a Theoretical Plate and Van Deemter Constants for C8 and C18 Columns by using High Performance Liquid Chromatography

This paper reports C8 and C18 columns efficiency which were determined for separation mixture of Methylparaben (MP), Propylparaben (PP) as solutes test and Uracil (Ura) for measuring the dead time to by applying new chromatographic conditions on two columns. Determination mixture of Methylparaben, Propylparaben and Uracil on two columns was effected by using an isocratic mobile phase of water:acetonitrile 55:45 (v/v) on a Shim-pack clc- C8 (25 cm × 4.6 mm, 5 µm) and SGE C18 HQ 105 column (25 cm x 4.6 mm, 5 µm) with different flow rates: (0.05 ,0.10 ,0.15, 0.20 ,0.40 ,0.60, 0.80, 1.00, 1.20, 1.40, 1.60) mL/min. The detector wavelength was set at 245 nm and sample injection volume 20 µL. Under these conditions efficiency, performance of column, height equivalent to a theoretical plate H, velocity u and Van Deemter curves HETP = f (u) were determined. In addition, a specific, rapid and simple RP-HPLC method has been developed for the simultaneous quantification of Paracetamol (Par), Diclofenac potassium (Dic.p) in standard solutions and tablets. The separation was carried out by using a mobile phase consisting of acetonitrile:phosphoric acid pH=2.43in ratio of 60/40 (v/v). Due to good column efficiency of Shim-pack clc- C8 (25 cm x 4.6 mm i.d., 5 µm), it was used to separate Paracetamol and Diclofenac Potassium, with flow rate of 1.0 ml/min using UV detection at 274 nm. The retention times of Paracetamol and Diclofenac Potassium were found to be 3.03 min and 6.68 min respectively. The analytical method can be successfully adopted for quality control tests for these drugs in tablet dosage forms.

Interaction of quaternary ammonium ionic liquids with bacterial membranes – Studies with Escherichia coli R1–R4-type lipopolysaccharides

Here we investigated the interaction between quaternary ammonium ionic liquids and the bacterial membrane of five different Escherichia coli strains. The strains were K-12 and R1–R4-type lipopolysaccharide strains. Additionally, Bacillus cereus was used as a typical Gram-positive bacterium for comparison. The ionic liquids used in the studies were theophylline- based quaternary ammonium salts with C8–C18 alkane chains. The studied compounds belong to third-generation ionic liquids comprising hydrophobic anions of natural origin, and they potentially exhibit biological activity. The interactions were studied using zeta potential measurements, a membrane lateral diffusion estimate based on the excimerization of pyrene, and cell surface hydrophobicity measurements. The minimum inhibitory and bactericidal concentrations were also studied to compare the responses of the bacterial strains to the ionic liquids. We found that the toxicity of the ionic liquids was strain-dependent, and that they strongly affected the Gram-negative bacterial membrane, causing changes of the zeta potential and membrane lateral diffusion. The results indicate that the interaction of ionic liquids with the bacteria depended significantly on the rough or smooth type of E. coli strains. Such relationships were not explained easily, however, some interesting correlations were found, e.g., the correlation between membrane lateral diffusion and ionic liquid toxicity. The results are important for further studies searching for new antibiotics and other drugs that affect the bacterial membrane. The ionic-liquid-mediated changes of the membrane zeta potential are also important for assessing the interactions of membranes and biofilms with nanoparticles.

Organic Monolayers by B(C6F5)3-Catalyzed Siloxanation of Oxidized Silicon Surfaces.

Inspired by the homogeneous catalyst tris(pentafluorophenyl) borane [B(C6F5)3], which acts as a promotor of Si–H bond activation, we developed and studied a method of modifying silicon oxide surfaces using hydrosilanes with B(C6F5)3 as the catalyst. This dedihydrosiloxanation reaction yields complete surface coverage within 10 min at room temperature. Organic monolayers derived from hydrosilanes with varying carbon chain lengths (C8–C18) were prepared on oxidized Si(111) surfaces, and the thermal and hydrolytic stabilities of the obtained monolayers were investigated in acidic (pH 3) medium, basic (pH 11) medium, phosphate-buffered saline (PBS), and deionized water (neutral conditions) for up to 30 days. DFT calculations were carried out to gain insight into the mechanism, and the computational results support a mechanism involving silane activation with B(C6F5)3. This catalyzed reaction path proceeds through a low-barrier-height transition state compared to the noncatalyzed reaction path.