Positional Isomers Research Articles

Side Chain Phenyl Isomerization‐Induced Spatial Conjugation for Achieving Efficient NIR‐II Phototheranostic Agents

The contradiction of near‐infrared II (NIR‐II) emission and photothermal effects limits the development of phototheranostic agents (PTAs) in many emerging cutting‐edge applications. Organic aggregates present a promising opportunity for the balance of competitive relaxation processes through the manipulation of molecular structure and packing. Herein, side chain phenyl isomerization‐induced spatial conjugation was proposed for constructing A‐D‐A type NIR‐II PTAs with simultaneous enhancement of fluorescence brightness and photothermal properties. Three pairs of mutually isomeric fluorophores, whose phenyls respectively located at the outside (o‐series) and inside (i‐series) of the side chain, were designed and synthesized. The positional isomerization of the phenyl endows the o‐series crystals with strong spatial conjugation between the phenyl group on the side chain and the backbone, as well as interlocked planar network, which is different to that observed in the i‐series. Thus, all o‐series nanoparticles (NPs) exhibit red‐shifted absorption, enhanced NIR‐II emission, and superior photothermal properties than their i‐series counterparts. A prominent member of the o‐series, o‐ITNP NPs, demonstrated efficacy in facilitating NIR‐II angiography, tumor localization, and NIR‐II imaging‐guided tumor photothermal therapy. The success of this side chain phenyl isomerization strategy paves the way for precise control of the aggregation behavior and for further development of efficient NIR‐II PTAs.

Side Chain Phenyl Isomerization‐Induced Spatial Conjugation for Achieving Efficient NIR‐II Phototheranostic Agents

The contradiction of near‐infrared II (NIR‐II) emission and photothermal effects limits the development of phototheranostic agents (PTAs) in many emerging cutting‐edge applications. Organic aggregates present a promising opportunity for the balance of competitive relaxation processes through the manipulation of molecular structure and packing. Herein, side chain phenyl isomerization‐induced spatial conjugation was proposed for constructing A‐D‐A type NIR‐II PTAs with simultaneous enhancement of fluorescence brightness and photothermal properties. Three pairs of mutually isomeric fluorophores, whose phenyls respectively located at the outside (o‐series) and inside (i‐series) of the side chain, were designed and synthesized. The positional isomerization of the phenyl endows the o‐series crystals with strong spatial conjugation between the phenyl group on the side chain and the backbone, as well as interlocked planar network, which is different to that observed in the i‐series. Thus, all o‐series nanoparticles (NPs) exhibit red‐shifted absorption, enhanced NIR‐II emission, and superior photothermal properties than their i‐series counterparts. A prominent member of the o‐series, o‐ITNP NPs, demonstrated efficacy in facilitating NIR‐II angiography, tumor localization, and NIR‐II imaging‐guided tumor photothermal therapy. The success of this side chain phenyl isomerization strategy paves the way for precise control of the aggregation behavior and for further development of efficient NIR‐II PTAs.

Steering diffusion selectivity of chemical isomers within aligned nanochannels of metal-organic framework thin film

The movement of molecules (i.e. diffusion) within angstrom-scale pores of porous materials such as metal-organic frameworks (MOFs) and zeolites is influenced by multiple complex factors that can be challenging to assess and manipulate. Nevertheless, understanding and controlling this diffusion phenomenon is crucial for advancing energy-economic membrane-based chemical separation technologies, as well as for heterogeneous catalysis and sensing applications. Through precise assessment of the factors influencing diffusion within a porous metal-organic framework (MOF) thin film, we have developed a chemical strategy to manipulate and reverse chemical isomer diffusion selectivity. In the process of cognizing the molecular diffusion within oriented, angstrom-scale channels of MOF thin film, we have unveiled a dynamic chemical interaction between the adsorbate (chemical isomers) and the MOF using a combination of kinetic mass uptake experiments and molecular simulation. Leveraging the dynamic chemical interactions, we have reversed the haloalkane (positional) isomer diffusion selectivity, forging a chemical pathway to elevate the overall efficacy of membrane-based chemical separation and selective catalytic reactions.

Positional Isomerism: A Novel Paradigm for Enhancing Iodine Adsorption in Functionalized Metal-Organic Frameworks.

Porous metal-organic frameworks (MOFs) have shown great potential as adsorbents for capturing radioiodine, a major fission product generated during the reprocessing of nuclear fuel. However, studies exploring the correlation between the structure of MOFs and iodine uptake capacity remain notably rare. In this study, we introduce a new strategy for enhancing the iodine adsorption efficiency of MOFs by strategically varying the position of functional groups on the organic linkers. Employing ligand-functionalized UiO-67 MOFs, our findings reveal that ortho-amino substitution of UiO-67-o-NH2, proximal to the node of the dicarboxylate linker, markedly accelerates adsorption kinetics of iodine vapor in comparison to meta-amino substitution of UiO-67-m-NH2, where the amino groups are oriented away from the node. In contrast, UiO-67-m-NH2 exhibits a higher adsorption capacity of 2.19 g/g, compared to 1.91 g/g for UiO-67-o-NH2, attributable to its higher porosity. Furthermore, a competitive I2/H2O vapor adsorption study demonstrated that UiO-67-o-NH2 exhibits faster adsorption kinetics and higher selectivity for iodine in the presence of water vapor compared to UiO-67-m-NH2. Additionally, the crucial influence of positional isomerism on enhancing iodine adsorption has been corroborated through Raman spectroscopy, X-ray photoelectron spectroscopy, and density functional theory calculations. These analyses reveal that the nitrogen atom positioned at the ortho site demonstrates a stronger affinity for iodine molecules compared to the nitrogen atom at the meta site, thereby improving adsorption kinetics.

Systematic Characterisation of the Fragmentation of Flavonoids Using High-Resolution Accurate Mass Electrospray Tandem Mass Spectrometry

Flavonoids are a class of polyphenolic secondary metabolites found in plants. Due to their ubiquity in our daily dietary intake and their major anti-oxidative, anti-inflammatory and anti-mutagenic activities, they have been a major focus of wide-ranging research for the past two decades. Mass spectrometry combined with liquid chromatography is one of the most popular techniques for the analysis of flavonoids. In this study, high-resolution accurate mass electrospray tandem mass spectrometry was used to study 30 flavonoids in both positive and negative ionisation modes. From the data obtained, common losses were summarised and compiled. Dominating neutral losses were tabulated. The radical loss of CH3· was observed in flavonoids containing methoxy groups and three key diagnostic product ions were identified. These were m/z 153 (indicative of two OH groups on ring A) m/z 167 (indicative of one OH and one methoxy group on ring A) and m/z 151 (a flavanol, with no ketone oxygen but two OH groups on ring A). These will be useful in structural elucidation of unknown flavonoids and flavonoid metabolites. Energy breakdown graphs were utilised to distinguish between three pairs of structural isomers, and to help rationalise proposed fragmentation pathways. Lastly, a competition of loss of CH3· and methane was reported for rhamnetin and isorhamnetin in the negative ion mode for the first time. Proposed fragmentation pathways were given to rationalise the differences in peak intensities for this competitive process.

From historical drugs to present perils: UHPLC-QqQ-MS/MS determination of methaqualone and its designer analogs (NPS) with comprehensive fragmentation pathways study (QTOF)

Methaqualone, introduced in the 1960s as a sedative-hypnotic alternative to barbiturates, was withdrawn from the market due to its side effects and growing recreational use. Despite this, interest in methaqualone and its analogs remains high, raising concerns about potential abuse in the future. An ultra-high-performance liquid chromatography method coupled with triple quadrupole tandem mass spectrometry (UHPLC-QqQ-MS/MS) was developed to determine nine methaqualone-related compounds simultaneously. Biological samples were prepared using liquid-liquid extraction with ethyl acetate at pH 9, quantification was performed in blood using multiple reaction monitoring (MRM) mode. Methaqualone-d7 served as an internal standard. The limit of quantification (LOQ) ranged from 0.1 to 0.2 ng/mL, with precision and accuracy within 20%. Recovery ranged from 84.2% to 113.7%. The developed method allowed chromatographic separation of all compounds tested, including two structural isomers: methtylmethaqualone and etaqualone. The mass spectra aquired from quadrupole time-of-flight mass spectrometer allowed for the elucidation of comprehensive fragmentation study of methaqualone derivatives. The described situation poses a significant problem from the analytical point of view, as well as interpretation and forensic toxicological expertise. The developed method will contribute to increased analytical capabilities and enhanced detection of compounds from the methaqualone group that may appear on the illicit market.

Conversion of CO2 into Synthetic Motor Fuels

The process of CO2 conversion into synthetic hydrocarbons including the stages of synthesis gas production on the catalyst NIAP 06-06 and hydrocarbon synthesis by the Fischer-Tropsch method on a bifunctional zeolite-containing catalyst has been investigated. Experimental studies of the process of catalytic conversion of CO2 into synthesis gas were carried out in order to obtain gas with the ratio of H2/CO close to the required ratio for Fischer-Tropsch synthesis. The possibility of obtaining gasoline and diesel fractions of hydrocarbons with a high content of isomeric structures that increase the performance characteristics of motor fuels has been shown. The yield of hydrocarbons C5+ with 1 m3 of initial CO2 and H2 at the synthesis temperature of 220 °C is found to be 44.5 g.

Comparative Ecotoxicity Assessment of highly bioactive Isomeric monoterpenes carvacrol and thymol on aquatic and edaphic indicators and communities

The growing demand for sustainable natural products to replace harmful synthetic ones requires comprehensive ecotoxicity assessments to ensure their eco-friendly nature. This study explored for the first time the changes in microbial community growth and metabolic profiles from river and natural soil samples exposed to the two structural isomers, thymol (THY) and carvacrol (CARV), utilizing Biolog EcoPlate™ assays and 16S rRNA gene sequencing for taxonomic analysis. In addition, we addressed existing ecotoxicity data gaps for these two compounds by using aquatic (Daphnia magna and Vibrio fischeri) and soil (Eisenia fetida and Allium cepa) indicators. Results show acute toxicity of both CARV and THY on all indicators. V. fischeri (LC50=0.59 mg/L) >D. magna (4.75 mg/L) >A. cepa (6.47 mg/L) for CARV, and V. fischeri (LC50=1.71 mg/L) >A. cepa (4.05 mg/L) >D. magna (8.13 mg/L) for THY. E. fetida showed LC50 = 7.68 mg/Kg for THY and 1.04 for CARV. River and soil microbial communities showed resilience, likely because they contain taxa capable of biodegrading these products. No significant growth inhibition effects were observed up to 100 mg/L, though substrate utilization decreased at higher concentrations, particularly for polymers and amines in soil microorganisms and polymers in aquatic communities. Soil microorganisms were more affected than aquatic ones, with CARV being more toxic than THY (EC50120h = THY 94.13 and CARV 29.79 mg/L in soil microorganisms). These findings suggest that an increase in the consumption of these products and their subsequent ecotoxicity effects from environmental discharge should still be monitored before being ruled out. However, long-term effects are unlikely due to microbial degradation of these natural products, potentially reducing risks to other target species and opening the way for their use as substitutes for commercial antibiotics.

Evaluation of the ionization efficiency in phosphatidylcholine positional isomers with docosahexaenoic acid bound to the sn-1 or sn-2 position

Phosphatidylcholine (PC), a key phospholipid, contains 2 fatty acids that can be bound at the sn-1 and sn-2 positions, resulting in positional isomers when different fatty acids are attached. Currently, there is no established method for identifying phospholipid molecular species and quantifying individual isomers using authentic standards of each PC isomer. In this study, we prepare authentic analytical standards for PC positional isomers through chemical synthesis and preparative purification. These isomers contain docosahexaenoic acid (DHA, 22:6) and palmitic acid (16:0) attached at the sn-1 and sn-2 positions and are denoted as PC(22:6/16:0) and PC(16:0/22:6), respectively. Standard solutions of PC(22:6/16:0) and PC(16:0/22:6) were analyzed using liquid chromatography-tandem mass spectrometry, and calibration curves of the PC positional isomers were generated to compare their ionization efficiencies. The ionization efficiency of PC(22:6/16:0) was 2.32 times higher than that of PC(16:0/22:6), indicating that the ionization efficiency depends on the binding position of the fatty acid. Elucidating and correcting the differences in the ionization efficiencies of the PC positional isomers will enable the accurate quantitative analysis of lipidomes in the future.

Determination of endogenous GHB in ante-mortem whole blood, urine, and oral fluid by LC–MS/MS: The effect of different additives and storage conditions on the stability of GHB in blood

Two challenges in detecting γ-hydroxybutyric acid (GHB) intake are its endogenous presence and in vitro production after sampling. This study developed an LC–MS/MS method for selective GHB determination in human antemortem blood, urine, and oral fluid at endogenous concentrations. Furthermore, the stability of GHB in blood samples and its endogenous concentrations in samples taken under controlled circumstances were investigated. Samples were extracted in methanol/acetonitrile and processed by anion exchange solid-phase extraction. GHB was separated from structural isomers using a reversed–phase LC column with anion properties. The validated limit of quantification was 0.005 µg/mL in blood and 0.010 µg/mL in urine and oral fluid, at which the relative reproducibility standard deviation and bias were <15 %. The mean extraction recovery was ≥90 %. The average GHB concentration increased by 1.2 µg/mL in fluoride/citrate- preserved blood after 28 days of storage at 4°C; however, in fluoride/oxalate (FX)-preserved blood, the mean concentration increased by only 0.055 µg/mL. No change was observed at −20°C. In 105 randomly selected samples of FX-preserved blood collected for forensic antemortem toxicological analysis, all concentrations were <0.066 µg/mL, even after long-term storage at −20°C. In blood, urine, and oral fluid samples from a clinical study of GHB intake, endogenous baseline levels from 30 participants ranged from 0.0069–0.050, 0.024–0.38, and 0.034–0.93 µg/mL, respectively. These results demonstrate that the current cut-off level of 5 µg/mL for discriminating between endogenous and exogenous GHB in antemortem blood could be considerably lower for FX-preserved blood stored at −20°C.

플라보노이드류의 하위 그룹을 구성하는 기본 분자들에 대한 양자 화학적 연구

A quantum study was carried out the structure and the characteristics of the basic molecules that constituting the subgroup of flavonoid i.e. flavan, flavanone, flavonol, anthocyanidine, flavone, isoflavone, and flavonol. We have reported and discussed the stable structure of isomers and physical quantities associated with the frontier energy, which are HOMO-LUMO energy difference, electronegativity, chemical potential, molecular hardness, softness, electrostatic potential, electrophilicity, electrodonating power and electro-accepting power. And we also have presented and discussed the physical quantities associated with the frontier orbital, such as frontier orbital figure, electrostatic potential diagram, polarizability, dipole moments etc., and also the values of free energy and entropy of each molecule obtained as a result of the vibration-rotation analysis The physical quantities reported and discussed are considered important data for understanding the reactivity, biological, pharmacological activity, and antioxidant properties of molecules belonging to flavonoid in the future

In-situ Forming Multipolymeric Glucose-Responsive Hydrogels.

Stimuli-responsive hydrogels (HGs) have shown promise for smart drug delivery applications. Specifically, glucose-responsive HGs having phenylboronic acid (PBA) functional groups are extensively pursued for insulin delivery in hyperglycemia. Current polymeric glucose-responsive HGs are cumbersome to fabricate and show a limited insulin release profile. Herein, we develop a straightforward fabrication of glucose-responsive multipolymer HGs (MPHGs) using a three-component in situ mixing. Molecular cargo, such as insulin, was loaded during the gelation. Heterobifunctional formylphenylboronic acid (FPBA) crosslinkers were used to interconnect polyvinyl alcohol (PVA) and branched polyethyleneimine (PEI) via boronate ester and imine bonds, respectively. Three positional isomers of FPBA (2FPBA, 3FPBA, and 4FPBA) resulted in HGs with distinct viscoelastic behaviors under the same conditions. HGs derived from 4FPBA exhibited more solid-like properties compared to 2FPBA and 3FPBA due to a higher crosslinking density. All the HGs exhibited glucose-responsive dissolution and release of embedded insulin cargo without disrupting the native structure. Insulin release profiles show a higher glucose-responsive release from 4FPBA-derived MPHGs. All the HGs were injectable, self-healing, and noncytotoxic below 10 μg/ml concentrations. The MPHGs developed in this study uncover new directions in creating glucose-responsive matrices for self-regulating drug delivery applications. In the future, detailed in vivo studies will be performed for clinical applications.

Theoretical investigation of isomeric structures of B2O3. Kinetic and thermodynamic study of the transformation of boric oxide to metaboric acid HBO2. Complexation of HBO2: from dimer to hexamer

In this study, Density Functional Theory was adopted. Isomeric structures of boric oxide B 2 O 3 were investigated at B3LYP/6-311G++(d,p), M052X, M062X, M08HX, M11/6-311G++(d,p) levels of theory. For validation of stable states, optimisation was performed using the correlated coupled cluster with single, double, and perturbative triple excitations (CCSD(T)) method in conjunction with the augmented correlation-consistent polarisation valence Double Zeta (aug-cc-pVDZ) (AVDZ) basis sets. Intrinsic Reaction Coordinates (IRCs) calculations were carried out to give kinetics of reactions B 2 O 3 +H 2 O ⇌ 2HBO 2 , B 2 O 3 +HCl ⇌ HBO 2 + OBCl. Complexation of HBO 2 was considered using B3LYP-D3, B97-D, MN15 and wB97X-D dispersion-corrected functionals. Counterpoise-corrected complexation energies as well as frontier orbital HOMO-LUMO energy gaps of (HBO 2 ) n (n = 2, 3, 4, 5, 6) clusters were derived in order to study their stability owed to hydrogen bonds.

Boosting spontaneous orientation polarization of polar molecules based on fluoroalkyl and phthalimide units

Polar organic molecules form spontaneous polarization in vacuum-deposited films by permanent dipole orientations in the films, originating from the molecule’s potential ability to align itself on the film surface during deposition. This study focuses on developing polar molecules that exhibit spontaneous orientation polarization (SOP) and possess a high surface potential. In the proposed molecular design, a hexafluoropropane (6F) unit facilitates spontaneous molecular orientation to align the permanent dipoles, and a phthalimide unit induces strong molecular polarization. Furthermore, the introduction of phthalimides into the molecular backbone raises the glass transition temperature of the molecules, leading to the suppression of molecular mobility on the film surface during film deposition and an improvement in the dipole orientation. The resulting surface potential slope is approximately 280 mV nm−1 without substrate temperature control. Furthermore, this work proposes a method using position isomers as a design strategy to tune the SOP polarity. The substitution position of the strong polar units influences the direction of the total molecular dipoles and affects the SOP polarity of the 6F-based molecules. The proposed molecular designs in this study provide wide tunability of the SOP intensity and polarity, which contributes to highly efficient organic optoelectronic and energy-harvesting devices.

Syntheses and Properties of Two Isomeric Phenanthroacephenanthrylene Derivatives

Cyclopenta‐annulated polycyclic aromatic hydrocarbons (CP‐PAHs) are of significant interest due to their unique optoelectronic properties and applications in organic electronic devices. Phenanthroacephenanthrylene (PAP) isomers are CP‐PAHs that have been rarely investigated, and only the [9,10‐e]PAP isomer was explored to date. Herein, we report the syntheses, crystal structure and optoelectronic properties of two PAP isomers, 7‐ethoxy[2,1‐e]PAP 1 and 9‐ethoxy[1,2‐e]PAP 2. The structural isomers were synthesized in multi‐steps, and structural elucidations were performed using NMR, mass, and single‐crystal X‐ray diffraction analyses, revealing planar backbone of the isomers. UV‐visible absorption and fluorescence spectra of compound 1 were red‐shifted than that of 2, suggesting smaller HOMO–LUMO energy gap which is further validated by DFT calculations that suggested the lowering of HOMO–LUMO spacing could be attributed to the greater destabilization of HOMO for 1.

Revisiting Butafulvene formation by Thermal Dimerization of Fluorene-Based Dialkynes - Effects of Aromatic Substitutents.

Butafulvenes, together with pentafulvenes and [3]radialenes, form a series of constitutional benzene isomers in which aromaticity changes significantly and can be strongly substituent dependent. Butafulvene, as a member of this series, is frequently proposed to be antiaromatic. Based on butafulvenes Hopf, Zimmerman and coworkers first time described, derivatives thereof were synthesized and the effects of substituents on both the stability of the intermediate isobenzenes and on their optoelectronic and (anti)aromatic properties are discussed.

Comprehensive targeted profiling of multiple steroid classes in rodent plasma using liquid chromatography-mass spectrometry

BackgroundReliable quantification of multiple steroid classes in biological fluids within a single method remains an analytical challenge despite many previously published methods. Crosstalk of positional isomers, overlap of stereoisomer fragmentation patterns, differing proton affinities, in-source fragmentation, varying stability of protonated ions in the gas phase across steroid classes, and non-existence of steroid-free matrix are the main challenges limiting the number of simultaneously profiled steroids. ResultsIn this study, we focused on the development of a derivatization-free, achiral, high-throughput, and cost-effective UHPLC-MS/MS approach that allows simultaneous profiling of a spectrum of 38 steroids covering progestogens, androgens, corticosteroids, and estrogens, while properly addressing the hurdles of steroid analysis. Within a 20-min method, 16 stereoisomers and 15 positional isomers were fully resolved within a single run while separated from 7 additional non-interfering steroids and matrix interferences in rodent plasma. Protein precipitation (PP) and supported liquid extraction (SLE) methods using only 40 μL of sample were developed to achieve the lowest possible limits of quantification. Nevertheless, 5α-dihydroprogesterone and 3α,5α-THDOC could be only qualitatively assessed when using PP. In contrast, DHEA-S could not be quantified or identified when using SLE. A novel surrogate matrix-background subtraction approach, using rat plasma after the animal's adrenalectomy, has been implemented into the optimized PP-UHPLC-MS/MS workflow, successfully validated according to the unified ICH/EMA M10 guidelines, and compared to the traditional quantification strategies. Moreover, the validity of the newly adopted approach has been verified by the targeted profiling of multiple biologically active endogenous steroids in more than 500 samples of mouse plasma in total. SignificanceUnderestimation of hurdles associated with steroid analysis often compromises the accurate steroid quantification. Our comprehensive, fully validated UHPLC-MS/MS method targeting a wide spectrum of endogenous steroids, mitigating steroid crosstalk and using a minimal sample volume together with a novel surrogate matrix-background subtraction approach significantly advances steroid analysis for research and clinical applications covering multiple biological scopes.

Accelerating Additive-Assisted Defect Passivation via the Structural Isomer Effect for Highly Efficient and Stable Perovskite Solar Cells.

Defects in hybrid perovskites have hindered the development of highly efficient and stable hybrid perovskite solar cells (PSCs). Therefore, researchers have used additives to passivate defects in hybrid perovskites; however, detailed studies on multifunctional group additives with structural isomers are limited. In this letter, we report the improved defect passivation ability of additives through the structural isomer effect and enhanced photovoltaic performance using this effect. l-Alanine methyl ester hydrochloride (l-AMECl) and its structural isomer, β-AMECl, were used to understand the influence of structural variations in functional groups. The structural isomer β-AMECl effectively reduced the trap density in the hybrid perovskite, thereby enhancing the photovoltaic parameters. Consequently, we achieved a power conversion efficiency of 24.25% with β-AMECl, which is the best result among PSCs using additives. Additionally, the PSCs with β-AMECl maintained an initial efficiency of 94% over 2500 h at 25 °C and 25% relative humidity, showing improved long-term stability.

Contamination in LIB Pouch Cells Promoting Self‐Discharge and Crosstalk

AbstractStorage studies of lithium‐ion battery electrolyte within bags made of commercial pouch foils, commonly used as encasing material of battery cells, revealed the presence of contamination leaching from the pouch foil material into the electrolyte. By analyzing the stored electrolyte via GC‐MS the appearing compound was identified as 2,4‐di‐tert‐butylphenol (2,4‐DTBP). To investigate the influence of DTBP on the battery cell performance, full cells employing commercial LiNi1/3Mn1/3Co1/3O2 based cathodes and graphite‐type anodes were assembled using 1 M LiPF6 in ethylene carbonate/ dimethyl carbonate mixture as the electrolyte with/out the intentional addition of either 2,4‐DTBP or its constitutional isomer 2,6‐DTBP. Furthermore, dimethyl terephthalate (DMT), a literature known redox shuttle triggering impurity leaching from PET‐based fixing tape used in LIBs, was added to compare the effect of DMT to DTBPs. It was revealed that either DTBP contaminations have a significant impact on the self‐discharge behavior of the studied cells, which exceed the effect of present DMT. Moreover, all contaminants heavily increase transition metal dissolution‐migration‐deposition (TM DMD) processes and irreversible capacity loss. When vinylene carbonate, an SEI forming additive, is added to the electrolyte mixtures self‐discharge, as well as TM DMD are suppressed to a different degree depending on the type of contaminant added.

Acyclic sesquiterpenes nerolidol and farnesol: mechanistic insights into their neuroprotective potential.

Sesquiterpenes are a class of organic compounds found in plants, fungi, and some insects. They are characterized by the presence of three isoprene units, resulting in a molecular formula that typically contains 15 carbon atoms (C₁₅H₂₄). Nerolidol and farnesol are both sesquiterpene alcohols present in the essential oils of numerous plants. They have drawn attention due to their potential neuroprotective properties. Nerolidol and farnesol are structural isomers, specifically geometric isomers, haring the same molecular formula (C₁₅H₂₄O) but differing in the spatial arrangement of their atoms. This variation in structure may contribute to their distinct biological activities. Scientific evidence suggests that nerolidol and farnesol exhibit antioxidant and anti-inflammatory characteristics which are crucial for neuroprotection. Nerolidol has been specifically noted for its ability to alleviate conditions such as Alzheimer's disease, Parkinson's disease, encephalomyelitis, depression, and anxiety by modulating inflammatory and oxidative stress pathways. Moreover, research indicates that both nerolidol and farnesol may modulate the Nrf-2/HO-1 antioxidant signaling pathway to mitigate oxidative stress-induced neurological damage. Activation of Nrf-2/HO-1 signaling cascade promotes cell survival and enhances the brain's ability to resist various insults. Nerolidol has also been reported to alleviate neuroinflammation by inhibiting the TLR-4/NF-κB and COX-2/NF-κB inflammatory signaling pathway. Besides, this nerolidol also modulates BDNF/TrkB/CREB signaling pathway to improve neuronal health. To date, limited research has delved into the anti-inflammatory properties of farnesol concerning neurodegenerative diseases. Further investigation is warranted to comprehensively elucidate the mechanisms underlying its action and potential therapeutic uses in neuroprotection. Initial observations indicate that farnesol exhibits promising prospects as a natural agent for safeguarding brain functions. Henceforth, drawing upon existing literature elucidating the neuroprotective attributes of nerolidol and farnesol, the current review endeavors to provide a detailed analysis of their mechanistic underpinnings in neuroprotection.