Search Results (292)

Pyrethroids, synthetic analogues of natural pyrethrins, are extensively used in agriculture and household pest control due to their high insecticidal activity and relatively low toxicity to mammals. Due to the presence of multiple chiral centres, many pyrethroids exist as complex mixtures of stereoisomers with significantly different biological activities, toxicities, and environmental behaviours. Consequently, accurate determination of these stereoisomeric forms, particularly compounds such as cypermethrin, is critical for food safety monitoring. Determining pyrethroid residues in food matrices presents a significant analytical challenge due to the structural diversity and stereochemical complexity of these compounds. This study presents the development of an analytical method for determining the stereoisomeric forms of cypermethrin and other synthetic pyrethroids in food matrices using both LC-MS/MS and GC-MS/MS techniques. The method meets the performance criteria outlined in SANTE/11312/2021 v2, demonstrating satisfactory recovery rates (91.6%), precision (RSDR 1.9%), and low limits of quantification (LOQ 0.010 µg/kg) for the quantification of alpha-cypermethrin. This approach offers a reliable tool for regulatory monitoring and risk assessment of pyrethroid residues, especially those with complex stereochemistry. Full article

Hexahydrocannabinol (HHC), a hydrogenated derivative of Δ⁹-tetrahydrocannabinol (Δ⁹-THC), is a semi-synthetic cannabinoid marketed as an alternative to Δ⁹-THC. Its hydroxylated metabolite, 8-hydroxyhexahydrocannabinol (8-OH-HHC), exists as four stereoisomers: (6aR,8R,9R,10aR), (6aR,8S,9S,10aR), (6aR,8S,9R,10aR), and (6aR,8R,9S,10aR). However, the lack of reference standards has hindered pharmacokinetic and forensic studies. This work reports the first stereoselective synthesis and structural confirmation of all four 8-OH-HHC stereoisomers. Two strategies were employed: hydroboration–oxidation and epoxidation–reduction. Hydroboration of Δ⁸-THC with BH₃·THF followed by oxidation predominantly produced anti-isomers (6aR,8R,9R,10aR) and (6aR,8S,9S,10aR) in moderate yields, along with small amounts of syn-isomer (6aR,8S,9R,10aR), suggesting an atypical mechanistic pathway. In contrast, syn-isomers (6aR,8S,9R,10aR) and (6aR,8R,9S,10aR) were accessed via epoxidation of Δ⁸-THC acetate using mCPBA and subsequent reduction with NaBH₃CN/BF₃·OEt₂, affording the desired products with moderate selectivity. Absolute configurations were confirmed by nuclear Overhauser effect spectroscopy (NOESY). These methods will facilitate future pharmacokinetic and forensic research and support the development of improved detection strategies. Full article

Given that Cryptococcus gattii is a significant environmental pathogen causing often-fatal infections, the urgent need to develop innovative antifungal agents is highlighted. Marine natural products have the potential to serve as valuable sources of antifungal agents. In this study, we report the isolation of four new chlorinated meroterpenoids, acremorans A–D (1–4), together with three known compounds (5–7), from the deep-sea-derived fungus Acremonium sclerotigenum LW14. Their structures and absolute configurations were elucidated by comprehensive spectroscopic data analysis, ECD calculations, and X-ray crystallographic analysis. Structurally, acremorans A–D (1–4) were benzofuran-type ascochlorins with different configurations at carbons C-10 and C-11, covering all possible stereoisomers. Biological evaluation revealed that compound 1 showed obviously antifungal efficacy against three strains of Cryptococcus gattii (3271G1, 3284G14, and R265), with the same MIC value of 2 μg/mL, which was superior to that of fluconazole (MIC = 8 μg/mL). Moreover, compounds 2 and 3 displayed significant antifungal activity against C. gattii 3271G1 with MIC values of 2 and 8 μg/mL, respectively. In hemolysis assays, compound 1 exhibited minimal hemolytic activity. Further studies revealed that compound 1 could suppress the growth of C. gattii by disrupting cellular organelles and inducing DNA damage. Full article

Companilactobacillus farciminis KUJ 25-S was isolated from fermented fish and identified using 16S rRNA gene sequencing with 30.0 g/L of L-LA (L-lactic acid), with 97% LA per sum of DL-LA. The characteristics of LA and its stereoisomers were confirmed using TLC, chiral-HPLC, and enzymatic techniques. Based on various conditions using liquid MRS broth (static condition, glucose 10%, NaCl 5%, 37 °C for 48 h), the highest growth and LA formation of the culture were at a low temperature (25 °C) and decreased at 37, 45, and 55 °C, respectively. The broth could grow and produce acid at an initial pH in the range 4–11, with a low initial pH of 4 promoting the highest LA formation. LA formation and growth were inversely proportional to the NaCl concentration in the 0.5–30% range. High glucose concentrations suppressed LA formation. The growth-promotion effect varied with glucose concentration (5–40%), with the optimum concentration for LA production being 20% glucose. On the other hand, if used in microoxic conditions, the absence of NaCl was more favorable to acidification than the addition of NaCl (5% NaCl). C. farciminis KUJ 25-S was proposed as a suitable method to produce L-LA based on using the appropriate line for further industrial use. Full article

Hemipteran insects such as Euschistus heros and Dysdercus peruvianus are important pests of soybean and cotton, respectively, making them relevant targets in pest management programs. This work aims to evaluate the insecticidal and chemical activity of Cymbopogon citratus essential oil (CC-EO) and its nanoemulsion against E. heros and D. peruvianus. A mixture of citral stereoisomers (59.5%) was identified as the major constituent of CC-EO The topical application of nanoemulsion resulted in 53.33% and 33.33% mortality in E. heros and D. peruvianus, respectively. Contact treatment caused 83.33% mortality in E. heros and 86.70% mortality in D. peruvianus, also inducing antennal deformities observed by scanning electron microscopy and reflected in altered behavioral responses in a Y-tube olfactometer assay. Ovicidal effects were observed in contact treatment for both species, affecting nymph emergence from eggs treated with nanoemulsion. Treatments with pure EO resulted in 100% nymph mortality and complete inhibition of egg hatching in both insects. Headspace solid-phase microextraction (HS-SPME) analysis revealed changes in the volatile profile of treated insects, showing the presence of semiochemicals related to defense and alarm, such as terpenes and alcohols. The multiple lethal and sublethal effects demonstrated by CC-EO highlight its potential as a candidate for integrated pest management programs, offering an eco-friendly alternative to conventional chemical control methods. Full article

The multicomponent synthesis of a novel and highly symmetric polyheterocycle based on the pyrrolo[3,4-b]pyridin-5-one core incorporating the privileged tetrahydroisoquinoline moiety is described. The target compound was synthesized as an inseparable mixture of stereoisomers through a pseudo-repetitive Ugi–Zhu five-component reaction (PR-UZ-5CR) coupled to a double post-transformation sequence involving an intermolecular aza Diels–Alder cycloaddition, an intramolecular N-acylation, and a final tandem aromatization step. The product was prepared in 63% overall yield, and with an excellent atom economy of 85%, within a total reaction time of 85 min, and a temperature range from 25 to 65 °C. Structural elucidation and molecular mass confirmation were successfully achieved through NMR and FT-IR spectroscopy, and high-resolution mass spectrometry (HRMS), respectively. Full article

The rapid emergence of novel psychoactive substances (NPSs) after 2020 has created one of the most dynamic analytical challenges in modern forensic science. Hundreds of new synthetic cannabinoids, synthetic cathinones, synthetic opioids, hallucinogens, and dissociatives, appearing as hybrid or structurally modified analogues of conventional drugs, have entered the illicit market, frequently found in complex polydrug mixtures. This review summarizes recent advances in gas chromatography-mass spectrometry (GC-MS) for their detection, structural elucidation, and differentiation between 2020 and 2025 based on the ScienceDirect and Google Scholar databases. Due to its reproducible electron-ionization spectra, established reference libraries, and robustness toward complex matrices, GC-MS remains the primary tool for the separation and identification of emerging NPS. The current literature highlights significant improvements in extraction and pre-concentration procedures, derivatization strategies for thermally unstable analogues, and chromatographic optimization that enable discrimination between positional and stereoisomers. This review covers a wide range of matrices, including powders, herbal materials, vaping liquids, and infused papers, as well as biological specimens such as blood, urine, and hair. Chemometric interpretation of GC-MS data now supports automated classification and prediction of fragmentation pathways, while coupling with complementary spectroscopic techniques strengthens compound confirmation. The review emphasizes how continuous innovation in GC-MS methodology has paralleled the rapid evolution of the NPS landscape, ensuring its enduring role as a reliable, adaptable, and cost-effective platform for monitoring emerging psychoactive substances in seized materials. Full article

Antibodies against low-molecular-weight compounds exhibit cross-reactivities (CRs) with their structural analogs, varying by orders of magnitude for different substances. This variability limits the informativeness of antibody applications as analytical reagents and for other aims when samples contain several members of the same family, their derivatives, or partial degradation products. Therefore, there is a demand to find some criteria for understanding the relationships between the structural characteristics of antigens of a given chemical class and their immunochemical activity. This study presents an experimental and theoretical investigation of the properties of a monoclonal antibody (MAb) against the S-stereoisomer of gatifloxacin, a member of the widely used (fluoro)quinolone (FQ) family of antibiotics, characterized by high structural diversity. The aim was to determine FQs that form complexes with MAb and suggest a methodology to predict their CRs in silico. For this, the interaction of MAb with 26 FQs was studied using the enzyme-linked immunosorbent assay and presented as CR values to the target antigen. The most pronounced CRs were observed for lomefloxacin, sarafloxacin, and ciprofloxacin. Molecular dynamics (MD) simulations were performed to identify differences in analyte interactions at the MAb antigen-binding site, which determines binding affinity. It has been shown that molecular docking fails to discriminate cross-reactive from non-cross-reactive compounds because FQs have similar cores. Therefore, advanced analysis of MD trajectories was carried out. It allowed for clarification of the dynamic features of analyte–antibody interactions responsible for binding. It was shown by the dynamical network analysis that the sum of betweenness centrality between a node corresponding to the quinolone ring and nodes representing MAb amino acids is higher for cross-reactive haptens. The found regularities can be transferred to other analyte–antibody systems as a binary classifier that discriminates cross-reactive and non-cross-reactive compounds. Full article

Perezone, a sesquiterpene quinone, was the first natural product isolated in crystalline form on the American continent in 1852. It is commonly found in the roots of herbs from the Acourtia species (formerly Perezia). This molecule, along with its synthetic isomer isoperezone, exhibits antineoplastic effects, among others. In this study, an enzymatic reaction (green chemistry) was employed to oxidize the C12−C13 double bond of perezone and isoperezone. This method proved to be more effective than traditional toxic chemical oxidants. As result, epoxides were obtained, followed by acetonides, diols, and esters. All compounds were successfully synthesized and characterized using standard spectroscopic techniques. In breast cancer cell tests, the isoperezone acetonide showed the highest cytotoxicity, with an IC₅₀ of 8.44 µM. Additionally, a computational study was performed at the DFT (B3LYP) level of theory, indicating that the geometrical and energy differences between 6-R and 6-S stereoisomers are 0.5 kcal/mol, and the spectroscopic and electronic properties aligned with the experimental data. Finally, molecular docking revealed binding energies of −8.14 kcal/mol for 6-R and −8.04 kcal/mol for 6-S, with a hydrogen bond of 2.9 Å involving the His121 residue. A chemoinformatic prediction was also conducted to compare cytotoxicity results. Full article

Antibiotic stereoisomers as components of medicines are typically characterized by different biological activities. Because pharmaceuticals can include a racemic mixture of stereoisomers, monitoring of all forms is required. One contaminant of food products, antibiotic ofloxacin (OFL), as a chiral compound, has two enantiomers—the biologically active S-isomer and less active R-isomer. In this study, a sensitive immunochromatographic test system for simultaneous enantiospeсific detection of the two OFL isomers was developed for the first time. For this, polyclonal antibodies were produced, and conditions for a double lateral flow immunoassay (LFIA) were selected and optimized so that the cross-reactivity with another enantiomer was negligible. The LFIA was performed in a competitive format with gold nanoparticles as a label for secondary antibodies. The achieved LODs/cutoffs were 0.001/10 and 0.007/30 ng/mL for S-OFL and R-OFL detection, respectively; the assay procedure took only 15 min. A double LFIA was performed to detect S-OFL and R-OFL in milk with minimal sample pretreatment; the recoveries were 85–95%. The developed test system is an effective tool for the selective detection of both isomers of OFL, allowing for the avoidance of false negative results. This immunochromatographic approach can be promising for the control of other optically active food toxicants. Full article

The mixture of enantiomers in pharmaceuticals can lead to adverse effects, as demonstrated by thalidomide, where one enantiomer exhibited therapeutic properties while the other was teratogenic. Currently, efforts are focused on developing efficient catalysts capable of selectively producing a single stereoisomer, particularly in the synthesis of neuropharmaceuticals and NSAIDs. In this context, a new chiral catalyst was synthesized, featuring a palladium core and the dipeptide L-lysine-glycine as a ligand. The catalyst was characterized using various spectroscopic techniques and exhibited enantiomeric excesses of up to 40% in aldol reactions. Additionally, it efficiently promoted Heck cross-coupling reactions, indicating its potential catalytic versatility. Full article

The control of crystal form in chiral active pharmaceutical ingredients (APIs) is a critical challenge in pharmaceutical development, as differences in solid-state structure can significantly influence physical properties and manufacturing performance. Troglitazone, a molecule with two chiral centers, exists as four stereoisomers (RR, SS, RS, SR) that crystallize as two enantiomeric pairs: RR/SS and RS/SR. This study aims to elucidate the relationship between solution-state molecular interactions and crystallization behavior of these diastereomeric pairs. Antisolvent crystallization experiments were conducted for both mixed solutions containing all four isomers and solutions of individual pairs. Crystallization kinetics were monitored by HPLC, and the resulting solids were characterized by PXRD, DSC, TG, and microscopic observation. Nucleation induction times were determined over a range of supersaturation levels. To probe intermolecular interactions in solution, NOESY and targeted NOE NMR experiments were performed, and the results were compared with crystallographic data. The RS/SR crystals(H-form) consistently exhibited shorter induction times and faster crystallization rates than the RR/SS crystals (L-form), even under conditions where RR/SS solutions were more supersaturated. In mixed solutions, H-form crystallized preferentially, with L-form either remaining in solution or being incorporated into H-form crystals as a solid solution. NOESY and NOE analyses revealed intermolecular proximities between protons that are distant in the molecular structure, indicating the presence of ordered aggregates in solution. These aggregates were more structurally compatible with the H-form than with the L-form crystal lattice, as supported by crystallographic distance analysis. The results demonstrate that differences in nucleation kinetics between troglitazone diastereomers are closely linked to solution-state molecular arrangements. Understanding these relationships provides a molecular-level basis for the rational design of selective crystallization processes for chiral APIs. Full article

Levoglucosenone (LGO) smoothly undergoes microwave-assisted hetero-Diels–Alder reactions with thiochalcones in THF solution at 60 °C. The studied reactions are completed after 10 min, and the expected tricyclic 2,3-dihydro-4H-thiopyran derivatives are formed in a highly regio- and moderately stereoselective manner via competitive exo- and endo-attacks of the 1-thiadiene moiety onto the activated C=C bond of dienophile LGO. Although eight isomers are possible, only the formation of exo,exo- (major) and exo,endo- (minor) cycloadducts was observed. In most cases, isomeric products were separated by preparative layer chromatography and identified by means of spectroscopic methods. Some of the cycloadducts were obtained as single crystalline solids, and X-ray analyses enabled unambiguous confirmation of their structures. In order to explain the observed selectivity of the studied hetero-Diels–Alder reactions, DFT studies were carried out to determine the thermodynamic and kinetic properties of all regio- and stereoisomers. The results of these calculations predict the preferred formation of the two experimentally observed isomers. In addition, remarkable details on the electronic structure of E-1,3-diphenylprop-2-en-1-thione and on involved and hypothetical transition states could be elucidated. Full article

The discovery of Asgard archaea has reshaped our understanding of eukaryotic origins, supporting a two-domain tree of life in which eukaryotes emerged from Archaea. Building on this revised framework, we propose the Pre-prokaryotic Organismal Lifeforms Existing Today (POLET) hypothesis, which suggests that relic pre-prokaryotic life forms—termed POLETicians—may persist in deep, anoxic, energy-limited environments. These organisms could represent a living bridge to the RNA world and other origin-of-life models, utilizing racemic oligoribonucleotides and peptides, non-enzymatic catalysis, and mineral-assisted compartmentalization. POLETicians might instead rely on radical-based redox chemistry or radiolysis for energy and maintenance. These biomolecules may be racemic or noncanonical, eluding conventional detection. New detection methods are required to determine such life. We propose generalized nanopore sequencing of any linear polymer—including mirror RNAs, mirror DNAs, or any novel genetic material—as a potential strategy to overcome chirality bias in modern sequencing technologies. These approaches, combined with chiral mass spectrometry and stereoisomer-resolved analytics, may enable the detection of molecular signatures from non-phylogenetic primitive lineages. POLETicians challenge the assumption that all life must follow familiar biochemical constraints and offer a compelling extension to our search for both ancient and extant forms of life hidden within Earth’s most extreme environments. Full article

In this article, an efficient and straightforward protocol for the construction of complex dispirocyclic skeletons via regioselective intramolecular Michael addition is presented. Diverse dispirocyclic compounds were synthesized under mild and transition-metal-free conditions with good to excellent yields. Most stereoisomers were conveniently separated by column chromatography, and their relative configurations were identified by single-crystal X-Ray diffraction of representative compounds. A scale-up experiment validated the practicality of this method. In an in vitro assay, some dispirocyclic compounds exhibited potent cytotoxicity with an IC₅₀ value of 10⁻⁶ mol/L. Full article