Isomeric Compounds Research Articles

Serially coupled columns enhance rapid separation and predictive interaction understanding of 93 fentanyl analogs

BackgroundThe simplicity of synthesis methods has facilitated the illegal manufacture of various fentanyl analogs, leading to numerous fatal overdoses worldwide, particularly in North America. Fentanyl analogs with similar structures are difficult to distinguish due to their fragmentation patterns, making separation using chromatography essential. Additionally, because fentanyl analogs are lethal even in trace amounts, they are easily smuggled, and commonly used fentanyl test strips often fail to detect them due to their low sensitivity. Therefore, the urgent need for analytical methods that can simultaneously identify multiple analogs and swiftly detect them at low concentrations. ResultsIn this study, liquid chromatography-tandem mass spectrometry was conducted to screen 93 types of fentanyl analogs among the illegal fentanyl substances. The phenyl-hexyl columns enhance fentanyl analog separation through strong π–π interactions. The serially coupled column system increased the separation efficiency and mitigated peak distortion, particularly those of polar fentanyl analogs. The selectivity varied significantly, depending on the interactions with the combined columns. The phenyl-hexyl column's superior ability to predict fentanyl analog interactions based on molecular structure was confirmed by retention factor analysis. The resolution of fentanyl isomers increased significantly when methanol was used instead of acetonitrile as an organic modifier in the mobile phase. The approach was validated by determining the limits of detection and quantification, specificity, detection capability, recovery, and relative ion intensity. SignificanceThe fentanyl analogs, including 23 sets of isomeric and isobaric compounds, were analyzed via separation using a phenyl-hexyl column serially coupled with a cyano column. The serially coupled column system increased the separation efficiency and mitigated peak distortion, particularly those of polar fentanyl analogs. The proposed strategy can be adopted in exploring methods of effectively separating mixtures with diverse properties, aiding the prevention of drug abuse and bolstering public health and safety efforts.

DFT and Model Hamiltonian Study of Optoelectronic Properties of Some Low-Symmetry Graphene Quantum Dots.

We have studied the electronic and optical properties of three low-symmetry graphene quantum dots (GQDs), with point-group symmetries C2v and C2h. For the calculations of linear optical absorption spectra, we employed both first-principles time-dependent density-functional theory (TDDFT) and the electron-correlated Pariser-Parr-Pople (PPP) model coupled with the configuration-interaction (CI) approach. In the PPP-CI approach, calculations were performed using both screened and standard parameters, along with efficiently incorporating electron correlation effects using multireference singles-doubles CI for both ground and excited states. We assume that the GQDs are saturated by hydrogen atoms at the edges, making them effectively polycyclic aromatic hydrocarbons (PAHs) dibenzo[bc,ef]coronene (also known as benzo(1,14)bisanthene, C30H14) and two isomeric compounds, dinaphtho[8,1,2abc;2',1',8'klm]coronene and dinaphtho[8,1,2abc;2',1',8'jkl]coronene with the chemical formula C36H16. The two isomers have different point group symmetries; therefore, this study will also help us understand the influence of symmetry on the optical properties. A common feature of the absorption spectra of the three GQDs is that the first peak representing the optical gap is of low to moderate intensity, while the intense peaks appear at higher energies. For each GQD, PPP model calculations performed with the screened parameters agree well with the experimental results of the corresponding PAH and also with the TDDFT calculations. To further quantify the influence of electron-correlation effects, we also computed the singlet-triplet gap (spin gap) of the three GQDs, and we found them to be significant.

Rapid quantitative analysis of semi-volatile organic compounds in indoor surface film using direct analysis in real time mass spectrometry: a case study on phthalates

Abstract. Direct analysis in real time mass spectrometry (DART-MS) has recently emerged as a promising approach for measuring semi-volatile organic compounds (SVOCs) on indoor surface films. However, its broader application in indoor environments is limited by low measurement repeatability and no separation of isomers. Herein we developed a sampling suite of indoor surface films for DART-MS analysis, optimized settings of DART to obtain higher analytical performance, and demonstrated the possibility of separating isomeric compounds using tandem mass spectrometry (MS/MS). Two pairs of isomeric phthalate esters, including di(2-ethylhexyl) phthalate (DEHP) and di-n-octyl phthalate (DnOP) and diisobutyl phthalate (DiBP) and di-n-butyl phthalate (DnBP), were used as examples for method optimization and validation. Under optimized conditions, the instrument responses for all four compounds exhibited good linearity (r>0.992) and acceptable repeatability (intraday relative standard deviation (RSD) < 11.0 %). The limits of quantification for the four phthalate esters ranged from 0.042 to 0.24 ng cm−2. The uncertainty in the separation of isomeric components using MS/MS was < 11.4 %, which is acceptable for real sample analysis. To further assess the developed method, we analyzed 10 film samples collected side by side in an occupied office. DnOP was not detected. The RSD among samples was 6.1 % for DEHP, 4.6 % for DnBP, and 10.4 % for DiBP, indicating the overall good repeatability of the collection and measurement method developed. With improved performance, the developed method increases the feasibility of the DART-MS technique for monitoring the dynamics of chemical composition of indoor surface films.

Solvation phenomena in ternary system tetramethylurea-methylacetamide-water: Insights from volumetric, compressibility and FTIR analysis

The properties of the ternary systems N,N,N',N'-tetramethylurea - N-methylacetamide - water were investigated using Fourier-transform infrared spectroscopy (FTIR), volumetric and compression measurements. Densities and sound velocities were determined in order to obtain the apparent molar volumes (VΦ) and apparent molar isentropic compressions (▪S,Φ). These values were then extrapolated to infinite dilution. Additionally, interaction parameters were calculated from the McMillan-Mayer theory. The studies were conducted at 288.15, 298.15, and 308.15 K, at atmospheric pressure (0.1 MPa). The concentration ranges of N-methylacetamide were 2, 4, 6, and 8 moles per kilogram of pure water, and for N,N,N',N'-tetramethylurea from 0 to around 0.35 moles per kilogram of solvent. Discrete changes in isentropic compression were observed. This is the result of the alignment of plots of ▪S,Φ0 as a function of NMA concentration. The results for N,N,N',N'-tetramethylurea were compared with analogous data for the system containing n-butylurea, which is an isomeric compound but exhibits different hydration behaviour. Additionally, large volumetric interaction coefficients were observed, indicating strong interactions between urea derivatives and NMA. This suggests the possibility of strong interactions between protein destabilizers and the protein backbone, differing from those observed for protein structure stabilizers. The observation contributes to understanding the mechanism of osmolyte action and their influence on protein stability.

Combined DFT, Monte Carlo and molecular docking studies of benzene-1,x-diol O,Oʹ-diacetates (x = 2, 3, 4)

In this work, we report detailed computational studies of a series of isomeric compounds, namely benzene-1,2-diol O,Oʹ-diacetate (1), benzene-1,3-diol O,Oʹ-diacetate (2) and benzene-1,4-diol O,Oʹ-diacetate (3), using the DFT/B3LYP/6–311++G(d,p) basis set. The electronic and potential corrosion inhibition properties toward Fe and Cu of 1–3 were revealed. The Monte Carlo simulations were applied to reveal adsorption of the studied compounds on the Fe(110) and Cu(111) surfaces. It was established that all the studied compounds exhibit good molecule-to-metal electron charge transfer for both metals, of which compound 3, followed by 1, exhibit the best results. The Monte Carlo simulations predicted that compound 2 exhibits the lowest adsorption energy with the Fe(110) surface, while the same energy absolute value is about two times lower for the Cu(111) surface. This allowed to conclude that 2 is the most promising candidate among the series of the studied compounds for inhibiting corrosion on both Fe and Cu. Compounds 1–3 were probed in silico as potential inhibitors of a series of the SARS-CoV-2 proteins. The best activity was revealed against Nonstructural protein 3 (Nsp3_range 207–379-MES).

Azobenzene-Based Main-Chain Liquid Crystalline Polymers Bearing Periodically Installed Alkyl, PEG, or Fluoroalkyl Segments and Photoisomerization Studies

ABSTRACT In the present study, liquid crystalline polymers (LCPs) were prepared by melt-transesterification of azobenzene-bearing diols and diethyl malonate (DEM) derivatized monomers. The effect of the nature and length of the installed pendant segments on the mesomorphic properties of the prepared LCPs was investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD), and polarized optical microscopy (POM) studies. The formation of layered morphology was inferred from X-ray scattering analysis arising from the colocation of rigid azobenzene moieties in one layer and the flexible pendant segments in alternate layers due to the zigzag folding of the polymer backbone. The linear variation of the interlamellar spacing with the number of carbon atoms in the pendant alkyl segments corroborates the proposed zigzag backbone folding in the polymers. The rate constant values obtained from the photoisomerization studies of the isomeric polymers and model compound, which are in the same ballpark, reveal that the photoisomerization process of such polymers is not affected by the position or size of the azobenzene unit.

B-150 Chromatographic Separation and Quantitation of Human Insulin and Lispro Analog in Serum Using Liquid Chromatography High-Resolution Mass Spectrometry

Abstract Background Factitious hypoglycemia, a deliberate attempt to induce low blood glucose levels occurring secondary to the surreptitious administration of exogenous insulin, can be difficult to diagnose due to a variety of factors including the increased use of synthetic insulin analogs in clinical practice. Traditional insulin immunoassays demonstrate variable cross-reactivity with commonly prescribed insulin analogues and their metabolites, making it difficult to measure specific analogs. The development of liquid chromatography high resolution accurate mass (LC-HRAM)-mass spectrometry (MS) assays has largely circumvented the limitations of traditional immunoassays for detection and quantitation of insulin analogs. Analytical challenges remain, however, specifically in differentiating lispro, an isomeric human insulin analog formed by the transposition of proline and lysine near the C-terminal end of the B chain, from human insulin in patient samples due to the equivalent mass-to-charge ratios of their precursor ions. Methods Immunoaffinity purification of insulin from calibrators and quality control material prepared by spiking insulin-depleted serum with pharmaceutical insulin preparations, as well as patient samples, was performed using tips coupled with anti-insulin monoclonal antibody. An automated liquid handler was programmed to perform aspiration and dispense cycles. Eluate from the purification protocol was submitted for analysis using a TLX-2 multiplex LC system paired with a Thermo Scientific Q Exactive Plus mass spectrometer. Various HPLC column chemistries were evaluated, a column passivation procedure was established, and column heater temperature was optimized to identify a combination of parameters yielding the best chromatographic separation of human insulin and lispro. Additionally, parallel reaction monitoring (PRM) targeted tandem mass spectrometry (MS/MS) analysis was utilized in combination with the full scan data to increase specificity through the monitoring of fragment ions produced from human insulin and each insulin analog. Results We found that a 1000 Å Diphenyl, 2.7 µm, 2.1 x 100 mm analytical column in a column heater maintained at a temperature of 80°C allowed for human insulin and lispro to be differentiated as two chromatographically separated extracted ion chromatographic peaks (XICs) and quantified down to 2.5 mcIU/mL with near-baseline separation. Before use, the column required passivation with a high protein buffer (0.05% bovine serum albumin in 20% acetonitrile [ACN] + 0.2% acetic acid) followed by increasingly organic buffers (20% ACN + 0.2% acetic acid and 50% ACN + 0.2% acetic acid). MS/MS was used to confirm the presence of analogs detected. Conclusions The LC-HRAM-MS method described here, coupled with optimized column chemistry, column passivation, and proper column temperature control allows for chromatographic separation of human insulin and lispro. Incorporating a PRM scan into the mass spectrometry full scan method provides confirmation of the insulin detected in the XICs. The results obtained from preliminary studies suggest this method is appropriate for use to facilitate the clinical investigation of suspected factitious hypoglycemia with the ability to differentiate isomeric compounds, such as human insulin and lispro.

De novo synthesis of α-Alk-β-CD: An organic–inorganic hybrid chiral stationary phase for enhanced enantioseparation efficiency and its recognition mechanism research

Herein, two highly stable β-CD and α-Alkenyl-β-CD (α-Alk-β-CD) monolithic columns were fabricated by copolymerizing β-CD and α-Alk-β-CD with GMA onto the pretreated capillary by a simple one-pot strategy. 1H NMR, SEM, FT-IR, TGA and BET surface area analyses were applied to characterize the prepared monolithic columns. The monoliths were evaluated on the enantioseparations of antibiotic drugs, antihistamine drugs, anticholinergic agents, antifungal drugs and pesticides. In contrast to the native β-CD monolith, the derived α-Alk-β-CD reveals significantly improved enantiodiscrimination performance for the analytes especially for pesticides. Through run-to-run (n = 6), day-to-day (n = 9), and column-to-column (n = 9) investigations, the RSDs values were all lower than 3.72 %. Molecular simulation reveled that the chiral recognition between α-Alk-β-CD and chiral drugs was an exothermic process mainly governed by interaction hydrogen bindings, resulting in different binding strength between a pair of isomers compounds and α-Alkenyl-β-CD, and then leading to different migration and finally achieving effective chiral separation.

Utilizing ESI-MS/MS and ion mobility spectrometry for structural characterization and isomer differentiation of 1, 2-unsaturated (1-4) linked disaccharide derivatives and their 2-C-functionalized analogues.

The 1, 2-unsaturated derivatives of (1-4) linked disaccharides serve as versatile building blocks for synthesizing biologically active compounds. Distinguishing between four pairs of stereoisomers in mixtures presents a challenging task. In this study, disaccharide derivatives are analyzed as alkali metal adducts using electrospray ionization tandem mass spectrometry (ESI-MS/MS), both as individual compounds and in mixtures by ion mobility mass spectrometry (IMS). Electrospray ionization (ESI) in combination with tandem mass spectrometry (MS/MS) in positive mode was employed to differentiate lithium adduct ions of hexa-acetyl/hexa-benzyl-D-lactals, and hexa-acetyl/hexa-benzyl-D-maltals, along with their corresponding 2-C-branched malonates. The high resolving power of trapped ion mobility spectrometry (TIMS) with the imeX™ functionality rapidly identified different metal adducts (Li, Na, Cs) as individual isomers and separated mixtures of stereoisomers. The measured collisional cross section (CCS) values were analyzed in relation to predicted CCS values. MS/MS spectra of the [M + Li]+ ions of glycal disaccharide analogues exhibited typical cross-ring and glycosidic bond cleavages. Collision-induced dissociation (CID) spectra provided insights into their fragmentation behavior, allowing differentiation of (1-4) linked disaccharides. TIMS technology delivered adjustable ion mobility resolution for suitable separation of the four sets of stereo isomeric compounds. However, accurately predicting CCS values to differentiate between respective isomeric pairs using the SigmaCCS program for sodium adducts is only partially achievable. ESI CID spectra of [M + Li]+ adduct ions for individual glycal disaccharide analogues facilitate the discrimination between alpha and beta (1-4) linked unsaturated disaccharides and their 2-C-branched analogues. Through optimized experimental conditions, complete baseline ion mobility separation of stereoisomer pairs of the Cs adducts is achieved.

Thermoplasmonic Effect Enables Indirect ON-OFF Control over the Z-E Isomerization of Azobenzene-Based Photoswitch.

Proper formulation of systems containing plasmonic and photochromic units, such as gold nanoparticles and azobenzene derivatives, yields materials and interfaces with synergic functionalities. Moreover, gold nanoparticles are known to accelerate the Z-E isomerization of azobenzene molecules in the dark. However, very little is known about the light-driven, plasmon-assisted Z-E isomerization of azobenzene compounds. Additionally, most of the azobenzene-gold hybrids are prepared with nanoparticles of small, isotropic shapes and azobenzene ligands covalently linked to the surface of nanostructures. Herein, a formulation of an innovative system combining azobenzene derivative, gold nanorods, and cellulose nanofibers is proposed. The system's structural integrity relies on electrostatic interactions among components instead of covalent linkage. Cellulose, a robust scaffold, maintains the material's functionality in water and enables monitoring of the material's plasmonic-photochromic properties upon irradiation and at elevated temperatures without gold nanorods aggregation. Experimental evidence supported by statistical analysis suggests that the optical properties of plasmonic nanometal enable indirect control over the Z-E isomerization of the photochromic component with near-infrared irradiation by triggering the thermoplasmonic effect. The proposed hybrid material's dual plasmonic-photochromic functionality, versatility, and ease of processing render a convenient starting point for further advanced azobenzene-related research and 3D printing of macroscopic light-responsive structures.

Comparative studies of the NOx impacts on the photooxidation mechanisms of isomeric monoterpenes of β-pinene and limonene

It is highly challenging to precisely compare the impacts of anthropogenic pollutants on the photooxidation of isomeric volatile organic compounds with respect to molecular compositions and particle number/mass concentrations of secondary organic aerosols (SOAs). In this study, we conducted a series of well-defined indoor chamber experiments to compare the effects of NOx (NO and NO2) on the photooxidation of isomeric monoterpenes of β-pinene and limonene. For the photooxidation of β-pinene with NOx, the increase of the initial concentrations of NO ([NO]0) shows a monotonous suppression of the particle mass concentration, whereas the increase of [NO2]0 shows a monotonous enhancement of the particle mass concentration. For the photooxidation of limonene with NOx, the increase of [NO]0 exhibits a monotonous suppression of the particle mass concentration, whereas the increase of [NO2]0 shows a parabolic trend of the particle mass concentration. Utilizing a newly developed vacuum ultraviolet free electron laser (VUV-FEL), the online threshold photoionization mass spectrometry reveals a series of novel compounds at molecular weight (MW) = 232 and 306 for the β-pinene + NOx system and MW = 187, 261, 280, and 306 for the limonene + NOx system. The molecular structures and formation pathways of these species were inferred, which led to the prediction of the diversity and difference of SOA products (i.e., ester and peroxide accretion products) formed from different monoterpene precursors. To improve the predictions of future air quality, it is recommended that climate models should incorporate the NOx-driven diurnal photooxidation of monoterpenes for SOA formation mechanisms.

Assembling of Nitropyrazoles into Tetranitroacetimidic Acid (TNAA): A Pathway to High-Performance Energetic Oxidizers through Dual C/N-Functionalization.

In this work, incorporating nitropyraozles into tetranitroacetimidic acid (TNAA) resulted in two analogues of isomeric TNAA-like compounds (3 and 5). These compounds exhibit excellent densities, detonation performance, and high specific impulse, which are promising high-energy oxidizers that are comparable to AP and ADN. This structural modification strategy may have the potential to contribute significantly to the development of versatile, high-performance energetic oxidizers.

The retention features of nitrogen-containing heterocyclic compounds in reversed-phase and hydrophilic HPLC-MS modes

Aromatic five- and six-membered nitrogen-containing heterocyclic compounds are biologically active substances and are widely used in biochemistry and medicine. In addition, such compounds are known as ecotoxicants formed during oxidation processes in industrial wastewater. High-performance liquid chromatography-mass spectrometry is widely used to determine nitrogen-containing heterocycles in various complex mixtures. Octadecyl silica gel is the main sorbent for chromatographic separation. However, octadecyl silica gel does not always enable satisfactory separation in the presence of highly polar isomeric molecules, and more selective chromatographic approaches are required. One of these is hydrophilic chromatography, which facilitates the separation of polar compounds. The aim of the study was to comparatively characterize the retention of a number of five- and six-membered nitrogen-containing heterocyclic compounds during reversed-phase and hydrophilic liquid chromatography with mass spectrometric detection. In addition, spectrophotometric detection at a wavelength of 210 nm was carried out. In the study, we used sorbents based on octadecyl silica gel and unmodified silica gel. High-resolution mass spectrometry was used in the electrospray ionization mode. We studied 19 nitrogen-containing heterocyclic compounds. We used aqueous acetonitrile mobile phases with added aqueous solutions of formic acid and diethylamine as acid-base modifiers. An ammonium formate solution was used as a modifier during hydrophilic chromatography. Reversed-phase chromatography showed that the introduction of 0.1% aqueous formic acid solution increased the ionization and the mass spectrometer signal intensity, but did not always result in a satisfactory separation of isomers upon elution from the octadecyl silica gel surface. The introduction of 0.01% diethylamine solution provided no significant improvement in the separation compared to the mobile phase without modifiers. The use of unmodified silica gel in hydrophilic chromatography mode allowed us to separate isomeric five-membered heterocycles, which was demonstrated by narrow symmetric peaks, but did not result in selective separation of isomeric diazines. Thus, we studied the retention of 19 nitrogen-containing heterocyclic compounds using reversed-phase and hydrophilic liquid chromatography with electrospray ionisation. It was determined that hydrophilic chromatography on unmodified silica gel could be used for satisfactory separation of isomeric five-membered heterocyclic compounds of different classes. For six-membered heterocycles, satisfactory separation was achieved by elution from the surface of octadecyl silica gel using aqueous acetonitrile mobile phase without modifiers.

Heterogeneous hydrogenation and isomerization of carbocyclic compounds of the norbornene series (review)

Heterogeneous hydrogenation and isomerization of carbocyclic compounds of the norbornene series (review)

Assessing the Difference in the Effects of NOx on the Photooxidation Mechanisms of Isomeric Compounds of α-Pinene and Δ3-Carene

Assessing the Difference in the Effects of NO_<i>x</i> on the Photooxidation Mechanisms of Isomeric Compounds of α-Pinene and Δ³-Carene

Gas chromatography/mass spectrometry analysis of reaction products of Chemical Weapons Convention-related 2-(N,N-dialkylamino)ethylchlorides with 2-(N,N-dialkylamino)ethanols.

The Chemical Weapons Convention (CWC) mandates rigorous screening of chemical weapons and their potential degradation/reaction products, which is essential to identify such products in suspected samples. The reaction between 2-(N,N-dialkylamino)ethylchlorides and 2-(N,N-dialkylamino)ethanols (precursors/degradation products of VX agents) produces a new class of reaction products that are not explored. The reaction products, bis(2-N,N-dialkylaminoethyl)ethers (1-10), were synthesized using established synthetic procedures, and gas chromatography/mass spectrometry (GC/MS) (electron ionization [EI] and chemical ionization [CI]) methods were developed for their identification. The GC/MS experiments were performed on an Agilent GC/MSD system using an HP-5MS capillary column. Methane gas was used as the CI reagent gas for GC/CIMS experiments. GC/retention index (RI) values of 1-10 were calculated using the retention times of the hydrocarbon mixture and the analytes. The GC/EI spectra of 1-10 exhibited [M-H]+ ions and distinctive fragments that provided valuable structural information. The selective fragmentation of the alkyl groups on nitrogen facilitated the discrimination of possible isomeric compounds. Interpretation of EI fragments in the high mass region is important for unambiguous identification of 1-10, because the major ions significantly match other CWC-related compounds containing the 2-(N,N-dialkylaminoethyl) group. GC/CI (methane) spectra included M+., [M + H]+, [M-H]+, reagent-specific adduct ions, and a few structure-indicative fragments. The spiking experiments in soil and water samples revealed that the target analytes were stable, easily extractable, and detectable using GC/MS. The reaction products, 1-10, could be successfully synthesized and characterized using GC/MS (EI and CI). The GC/MS and GC/RI data provide important insights into the unambiguous identification of the target molecules in challenging CWC verification and are helpful in participation in the Organization for the Prohibition of Chemical Weapons proficiency tests.

An analytical evaluation of tools for lipid isomer differentiation in imaging mass spectrometry

Imaging mass spectrometry has emerged as a powerful tool to map the spatial distributions of lipids and metabolites in biological tissues. However, these analyses are challenged by the multitude of isobaric (i.e., same nominal mass) and isomeric compounds present in most samples. Failure to adequately separate these compounds results in inaccurate or incomplete chemical identifications and produces composite images of spatial distribution arising from multiple compounds. A number of techniques have been developed to more completely resolve and identify this complex chemical milieu. These include methods that rely on condensed-phase chemical derivatization and gas-phase ion chemistry, or some combination thereof. This Young Scientist Feature focuses on summarizing the analytical figures of merit of these tools, highlighting their relative speeds, limits of detection, molecular specificities, and eases-of-use. It will also include current challenges and future perspectives for resolving structural isomers in imaging mass spectrometry experiments.

Carvacrol and Thymol Hybrids: Potential Anticancer and Antibacterial Therapeutics

Cancer is ranked among lethal diseases globally, and the increasing number of cancer cases and deaths results from limited access to effective therapeutics. The use of plant-based medicine has been gaining interest from several researchers. Carvacrol and its isomeric compound, thymol, are plant-based extracts that possess several biological activities, such as antimalarial, anticancer, antifungal, and antibacterial. However, their efficacy is compromised by their poor bioavailability. Thus, medicinal scientists have explored the synthesis of hybrid compounds containing their pharmacophores to enhance their therapeutic efficacy and improve their bioavailability. Hence, this review is a comprehensive report on hybrid compounds containing carvacrol and its isomer, thymol, with potent anticancer and antibacterial agents reported between 2020 and 2024. Furthermore, their structural activity relationship (SAR) and recommended future strategies to further enhance their therapeutic effects will be discussed.

Surface assisted laser desorption/ionization mass spectrometry of lithium cationized lignans – A tool for rapid screening of plant extracts

Lignans are one of the most widespread classes of plant secondary metabolites possessing unique biological activities. The search for new sources of such compounds, their screening and identification in plant biomass is an urgent task, requiring the use of advanced analytical methods. In the present study, matrix-free surface assisted laser desorption/ionization (SALDI) mass spectrometry was proposed for its solution. The combination of carbon nanocoating sputtered on a target plate with lithium cationization allowed obtaining high-quality mass spectra of eight coniferous wood lignans with different bonds between aromatic units (secoisolariciresinol, matairesinol, 7-hydroxymatairesinol, nortrachelogenin, pinoresinol, guaiacylglycerol-β-guaiacyl ether, dehydrodihydrodiisoeugenol, and divanillin). Three types of fragmentation methods (post-source decay, high- and low-energy collision induced dissociation) for the first time were implemented on two types of MALDI instruments. Regardless of tandem mass spectrometry technique, lignans demonstrated the similar fragmentation patterns including the cleavage of bonds between aromatic units with the formation of mostly lithiated product ions. The low-energy collision induced dissociation in quadrupole ion trap provided the most informative tandem mass spectra and multi-stage fragmentation capabilities in structural studies. On this basis, an approach to rapid, high-throughput, and low-cost screening and tentative identification of lignans including isomeric compounds in plant biomass was developed and successfully tested on real samples of pine, fir, spruce, and larch knotwood extracts.

A review on hydrothermal treatments for solid, liquid and gaseous fuel production from biomass

The rise in the population and rapid industrialization has resulted in a rise in the global energy consumption. In order to minimize the load on the conventional energy sources, various studies are being conducted for the production of biofuels by hydrothermal operations. Unlike conventional processes of biofuel production, wet biomass can be directly utilised without drying in turn reducing the energy consumption. Feedstocks such as agricultural residue, forest residue, energy crops, algae, sludge, litter and food waste can be utilised for the production of biofuels. The operation intensities (temperature and pressure) can be varied from pressurized hot water to supercritical water. Hydrothermal operations depending on the operating parameters are further subcategorised into four types namely wet torrefaction (WT), hydrothermal carbonization (HTC), hydrothermal liquefaction (HTL) and hydrothermal gasification (HTG). Even though the operating conditions of wet torrefaction and hydrothermal carbonization lie in similar categories, the difference is clearly visible in the level of carbonization. Due to the wide range of operating temperature and pressure, mainly three different products are produced through hydrothermal operations. The temperature range for wet torrefaction can be limited between 150 and 220 °C, whereas the HTC process can be between 200 and 260 °C. At higher temperatures (260 – 370 °C) in hydrothermal liquefaction (HTL), increased isomerization, depolymerization and repolymerization of organic compounds within the biomass occurred, causing liquid product (bio-oil) to be formed as the major product. Hydrothermal gasification can be further subcategorised into three types: namely aqueous phase refining, near critical water gasification and supercritical water gasification (SCWG). This paper has reviewed different hydrothermal operations based on biofuel production from different biomass.