Search Results (664)

Caffeoylquinic acids (CQAs), a class of phenolic acid metabolites widely distributed in plants, encompass 15 positional isomers from mono- to tetra-esters, with 5-O-caffeoylquinic acid (5-CQA) as the predominant form. The biosynthesis of 5-CQA from phenylalanine proceeds through five primary pathways, which are finely regulated by environmental, hormonal, and transcription factors from families such as MYB, WRKY, and bHLH. These regulators control 5-CQA synthesis by binding specifically to the promoter regions of key structural genes, including PAL, 4CL and HCT/HQT. Subsequently, 5-CQA serves as a central precursor for the biosynthesis of other CQAs. In terms of bioactivity, CQAs possess remarkable pharmacological activities, encompassing antioxidant, antimicrobial, anti-diabetic, anti-inflammatory and anti-tumor properties. For instance, anti-inflammatory effects are demonstrated by the ability of 5-CQA to reduce key pro-inflammatory cytokines (e.g., TNF-α and IL-1β) and downregulate the TLR4/NF-κB pathway. The synergistic action of 5-CQA with ultraviolet-A reduced succinate-coenzyme Q reductase activity by approximately 72%, highlighting its potential to disrupt bacterial metabolism and combat antibiotic resistance. Furthermore, 3,4,5-triCQA exhibits potent anti-influenza virus activity, potentially through a mechanism distinct from existing neuraminidase inhibitors. Beyond medicine, CQAs show promise in light industry. They serve as antibiotic alternatives in livestock feed to enhance gut health, extend food shelf life through their antioxidant activity, and function as active ingredients in UV-protective skincare formulations. CQAs also enhance plant stress tolerance to cold, arsenic, and pests by mechanisms such as scavenging reactive oxygen species and inhibiting pest mobility. While this review consolidates progress in the biosynthesis and bioactivity of CQAs specifically with caffeoyl substituents, future efforts should leverage modern biotechnological tools and interdisciplinary approaches to bridge critical knowledge gaps in their biosynthesis, transport, and clinical translation. Full article

Chemical bonds among carbon atoms are central to chemistry. A general working principle regarding these interactions is that these contacts become stronger as the carbon atoms become closer to each other. Nevertheless, there are long, yet strong single C–C bonds that challenge this interpretation. Herein, we perform a quantitative thorough decomposition of the electronic energy of hexaphenylethane and several derivatives of this molecule with increasingly bulkier substituents. For this purpose, we exploit state-of-the-art methods of wave function analysis for the examination of the chemical bonding scenario in the examined systems, namely, the quantum theory of atoms in molecules (QTAIM) and the interacting quantum atoms (IQA) electronic energy partition. Our results reveal the predominance of collective non-covalent interactions over the central, covalent one in the chemical bonding of the examined molecules, in particular for those that have been synthesized in the laboratory. The QTAIM and IQA methods also showed that, besides London dispersion, electron sharing comprises an important contribution to the abovementioned collective interactions. Overall, our results give valuable insights about the importance of collective interactions in the investigated systems and they aid in the understanding of the nature of long, yet stable single C–C bonds. Full article

The molecular mechanism of the formation of 1,3-diaryl-5-nitropyrazoles via a CHCl₃-elimination reaction was investigated using ωB97xD/6-31+G(d,p) (PCM) calculations. It was found that, regardless of the polarity of the reaction environment or the nature of the substituents on the phenyl rings of the starting molecules, the elimination process proceeds through a single-step mechanism characterized by an extremely asynchronous transition state. The ELF (Electron Localization Function) analysis of selected critical structures confirms the proposed mechanism and reveals a pronounced reorganization of electrons within the heterocyclic ring. The in silico analysis based on ADME (Activity, Distribution, Metabolism, and Excretion) and PASS (Prediction of Activity Spectra for Substances) predictions indicates that the title 1,3-diaryl-5-nitropyrazoles exhibit promising biological potential, showing inhibitory activity against both oxidoreductases and proteases. The most consistent targets include hyponitrite reductase, (R)-6-hydroxynicotine oxidase, acrocylindropepsin, saccharopepsin, and chymosin. Thus, the presented CHCl₃-elimination provides an efficient and versatile route to functionalized pyrazoles, and, together with their promising bioactivity, confirms the utility of this approach for their synthesis. Full article

A bidentate ligand concept based on β-carbolines functionalized with a 1,2,4-triazolyl-moiety was designed and realized, enabling the development of a series of neutral rhenium(I) complexes. This new class of anionic ligands, incorporating either an unsubstituted 9H-pyrido[3,4-b]indole core (L_nHo) or a 9-methyl-substitued variant (L_Me-nHo), was developed towards tailored photofunctionality. Structural modification via methyl substitution at the indole moiety was found to enhance overall phosphorescence efficiency. Comparative studies of two monodentate auxiliary units revealed that 1,3,5-triaza-7-phosphaadamantane (PTA) significantly reduces the photoluminescence efficiency compared to pyridine (Py). Solvent-dependent photoluminescence studies indicated that a lowered polarity leads to an increase in photoluminescence quantum yields (Φ_L). The complex Re(L_Me-nHo)Py emerged as the most efficient emitter, displaying a Φ_L of 44% in dichloromethane (DCM). Notably, all complexes exhibited efficient quenching of excited triplet states by diffusional collision with triplet dioxygen (³O₂), yielding good singlet dioxygen (¹O₂) photoproduction efficiencies (Φ_Δ) with a maximum of 45% observed for Re(L_nHo)Py. These results highlight the suitability of these complexes for applications requiring efficient phosphorescence and oxygen photosensitization, such as bioimaging, and photodynamic therapy or photooxidation catalysis, while underscoring the central role of the tailored β-carboline-based chromoluminophores in enabling precise tuneability of photophysical properties. Full article

The similar properties of the nitrogen atoms in azole ring complicate the regioselective N-functionalization of pyrazoles. This work demonstrates the role of the hydrazone substituent in the control of the alkylation selectivity of (trifluoromethyl)pyrazoles. Reaction conditions for the synthesis of 3- and 5-(trifluoromethyl)pyrazoles were developed, and all types of regioisomers formed under the alkylation of bis-pyrazolyl NH-ketazine were isolated. The structures of the synthesized compounds were confirmed by NMR spectroscopy and XRD data. Full article

Tyrosyl-DNA phosphodiesterase 1 (TDP1) is an important DNA repair enzyme and its functioning is considered as one of the possible reasons for tumor resistance to topoisomerase 1 (TOP1) poisons such as topotecan. Thus, TDP1 inhibitors in combination with topotecan may improve the effectiveness of anticancer therapy. TDP1 acts somehow in a phospholipase manner, depleting the phosphodiester bond between lipophilic tyrosine residue and 3′ end of DNA; therefore, lipophilic molecules bearing aromatic substituents can interact with TDP1 and even possess high inhibitory activity, which is evidenced by data from the literature. Previously, we identified lipophilic nucleoside derivative (compound 6d, IC₅₀ = 0.82 µM) as an effective inhibitor of the purified enzyme TDP1 that enhances the cytotoxic, DNA-damaging, and antitumor effects of topotecan. However, the role of TDP1 inhibition in this synergistic effect remained not fully understood. In the present study, we have tested the hypothesis of a TDP1-dependent mechanism of action for compound 6d, showing that it sensitizes wild-type A549 lung cancer cells, but not TDP1 knockout cells, to the cytotoxic effects of topotecan. The sensitizing effect was absent in non-cancerous HEK293A cells regardless of TDP1 status. Additionally, we analyzed the effect of compound 6d and topotecan on the expression level of TOP1 and TDP1 to determine whether the observed synergy was due to direct TDP1 inhibition and/or changes in regulation of these enzymes. The data obtained shows that compound 6d did not affect TDP1 gene expression level in HEK293A and A549 WT cells. Thus, compound 6d most probably does not suppress the transcription or mRNA stability of TDP1, and the synergistic action of 6d with topotecan is related to TDP1 inhibtion. Full article

N-vinylindoles have attracted attention for their promising role in medicinal chemistry. Therefore, developing new synthetic methods that enable access to diverse functionalized N-vinylindoles with potential pharmacological properties is highly valuable. 1-[2-aryl-1-(4,5-dihydro-1H-imidazol-2-yl)vinyl]-1H-indoles 2a-i were prepared via Knoevenagel condensation promoted by 1H-benzotriazole, and characterized by IR, NMR, and MS spectroscopic data as well as a single-crystal X-ray diffraction-based study of the representative derivative 2g. The obtained compounds 2a-i were screened for their cytotoxic potency against human cancer cell lines (HeLa, SKOV-3, AGS) and non-cancerous cell line (HaCaT) using the MTT assay. Additional apoptosis analysis and cell cycle assay on SKOV-3 cells were conducted. Their antimicrobial activity was determined using reference strains of S. aureus, E. coli, C. albicans, and C. glabrata. The potent inhibitory activity against AGE2-BSA/sRAGE interaction of selected N-vinylindoles 2b, 2d-f, and 2h-i was evaluated by ELISA assay. A facile approach has been developed for the synthesis of a novel class of N-vinylindoles. The preliminary structure–activity considerations indicated that the presence of substituents R, such as 4-bromophenyl (compound 2f) or 2-naphthyl (compound 2i) is optimal for anticancer activity and the AGE2-BSA/sRAGE interaction inhibition. The most prominent (Z)-1-[1-(4,5-dihydro-1H-imidazol-2-yl)-2-(naphthalen-2-yl)vinyl]-1H-indole (2i) was found to strongly arrest cell cycle in the SKOV-3 cell line in the subG0 phase, inducing apoptosis. Notably, derivative 2i also exhibited the highest activity against S. aureus and C. albicans strains within the tested series. These findings highlight the substantial potential of N-vinylindole derivative 2i as a lead compound for the development of anticancer drugs with additional inhibitory activity on the AGE/RAGE interaction. Full article

Viologens are promising candidates for next-generation electrochromic devices due to their reversible color changes, low operating voltages, and structural tunability. However, their practical performance is often constrained by limited color range, stability issues, and poor charge delocalization. In this study, we present a detailed density functional theory (DFT) and time-dependent DFT (TD-DFT) investigation of asymmetric viologens based on the Benzyl-4,4′-dipyridyl-R (BnV-R) framework. A series of electron-donating and electron-withdrawing substituents (CN, COOH, PO₃H₂, CH₃, OH, NH₂) were introduced via either benzyl or phenyl linkers. Geometry optimizations for neutral, radical cationic, and dicationic states were performed at the CAM-B3LYP/6-31+G(d,p) level with C-PCM solvent modeling. Electronic structure, frontier orbital distributions, and redox potentials were correlated with substituent type and linkage mode. Natural Bond Orbital analysis showed that electron-withdrawing groups stabilize reduced states, while electron-donating groups enhance intramolecular charge transfer and switching kinetics. TD-DFT calculations revealed significant bathochromic and hyperchromic shifts dependent on substitution patterns, with phenyl linkers promoting extended conjugation and benzyl spacers minimizing aggregation. Radical cation stability, quantified via ΔE_red and comproportionation constants, highlighted cyano- and amine-substituted systems as particularly promising. These insights provide predictive design guidelines for tuning optical contrast, coloration efficiency, and electrochemical durability in advanced electrochromic applications. Full article

Polysiloxanes are unique polymers used in medicine and materials science and are ideal for various modifications. Classic functionalization methods involve a covalent approach, but finer tuning of the properties of the final polymers can also be achieved through sub-sequent noncovalent modifications. This study introduces a fundamentally new approach to polysiloxane functionalization by incorporating cooperative noncovalent interaction centers: selenium-based chalcogen bonding donors and polyfluoroaromatic π-hole acceptors into a single polymer platform. We developed an efficient nucleophilic substitution strategy using poly((3-chloropropyl)methylsiloxane) as a platform for introducing Se-containing groups with polyfluoroaromatic substituents. Three synthetic approaches were evaluated; only direct modification of Cl-PMS-2 proved successful, avoiding catalyst poisoning and crosslinking issues. The optimized methodology utilizes mild conditions and achieved high substitution degrees (74–98%) with isolated yields of 60–79%. Comprehensive characterization using ¹H, ¹³C, ¹⁹F, ⁷⁷Se, and ²⁹Si NMR, TGA, and contact angle measurements revealed significantly enhanced properties. Modified polysiloxanes demonstrated improved thermal stability (up to 37 °C higher decomposition temperatures, 50–60 °C shifts in DTG maxima) and increased hydrophobicity (water contact angles from 69° to 102°). These systems potentially enable chalcogen bonding and arene–perfluoroarene interactions, providing foundations for materials with applications in biomedicine, electronics, and protective coatings. This dual-functionality approach opens pathways toward adaptive materials whose properties can be tuned through supramolecular modification while maintaining the inherent advantages of polysiloxane platforms—flexibility, biocompatibility, and chemical inertness. Full article

Two series of imidazole-2(3H)-thiones inspired by naturally occurring lepidiline alkaloids, bearing either one or two benzyl-type substituents located at the N(1)/N(3) atoms, respectively, were prepared and examined in reactions with in situ generated C-trifluoromethyl-N-aryl nitrile imines. N,N-Dibenzylated imidazole-2-thiones served exclusively as C=S dipolarophiles to afford hitherto unknown CF₃-functionalized spiro [1,3,4-thiadiazole-5,2′-imidazole] derivatives formed through the (3+2)-cycloaddition pathway. In contrast, the enolizable N-monobenzylated imidazole-2-thiones provided acyclic products, i.e., hydrazonothioates, resulting from nucleophilic addition of the respective en(thio)late onto the C-termini of the 1,3-dipole. The presented results extend the scope of both fluorinated products available via trapping of the in situ generated CF₃-nitrile imines as well as synthetic analogues of lepidilines. In addition, spectroscopic analysis of the obtained products and the known related systems revealed ¹³C NMR chemical shifts attributed to the C-(CF₃) atom as useful probes to differentiate the open-chain hydrazonothioates (δ = 112–120), 2,2-diaryl/dialkyl-2,3-dihydro-1,3,4-thiadiazoles (δ = 130–145), and more strained spiro-1,3,4-thiadiazole derivatives (δ = 166–170) reported herein. Full article

Donor–acceptor (D–A) cyclopropanes are important precursors in the synthesis of complex molecules due to their bidentate character and high reactivity. Among them, cyclopropane-1,1-dicarbonitriles are less commonly reported in modern literature, primarily because of the high reactivity of the nitrile groups and their limited compatibility with metal-catalyzed processes, which is caused by the geometrical constraints imposed by the linear cyano substituents. While the cyano groups can be seen as a limitation, they also offer synthetic versatility by serving as handles for further functionalization. In this work, we performed a cycloaddition reaction with mercaptoacetaldehyde, leading to a new class of DA cyclopropanes bearing a thiazole moiety. This one-pot, two-step transformation requires only a single purification step. The resulting thiazolyl-substituted cyclopropanes were subjected to ring strain-release reactions, showing reactivity comparable to the parent cyclopropane-1,1-dicarbonitriles. Full article

The synthesis and crystal structure of 4,11-dimethyl-2,13-di-m-tolyltribenzo[b,e,g][1,4]dioxocine-7,8-dicarbonitrile are reported. X-ray diffraction analysis reveals a rigid dioxocine core with m-tolyl substituents adopting torsional angles of 25–40°. The crystal packing is stabilized by C-H···N hydrogen bonds (2.6 Å) and π-π stacking interactions (3.4 Å) between dicarbonitrile groups, forming dimeric motifs. These structural insights provide a foundation for designing dioxocine-based functional materials. Full article

This theoretical work investigates the linear (absorption and emission) and nonlinear (first hyperpolarizability and TPA) optical properties of donor–$\pi$–acceptor (D–$\pi$–A) molecular architectures based on functionalized benzoxazoles, with potential applications in optoelectronic technologies such as OLEDs and solar cells. Four $\pi$-conjugated compounds were studied in the gas phase and in polar (methanol) and nonpolar (toluene) solvents, employing DFT with the B3LYP and CAM-B3LYP functionals and the 6-311++G(d,p) basis set, as implemented in Gaussian and Dalton. The results reveal that the chemical environment induces spectral shifts and modulates the intensity of electronic transitions. In particular, the compound 2-((4-((5-nitro-2-oxo-1,3-benzoxazol-3(2H)-yl)amino)phenyl)methyl)-1,3-benzoxazole exhibited outstanding behavior in methanol, with a significant increase in dipole moment, polarizability, and first hyperpolarizability (static and dynamic at 1064 nm), reaching a TPA cross-section close to 150 GM. These findings highlight the key role of ionic substituents in tuning the optical response of $\pi$-conjugated systems and underscore their potential as functional materials for high-performance light-emitting and energy-conversion devices. Full article

Neutral and protonated histamine tautomers, mono-substituted with twelve functional groups, were studied theoretically as isolated molecules and complexes with the H₁ receptor. Geometry and energy of tautomers were optimized using the DFT method with the B3LYP functional and the aug-cc-pVTZ basis set. The approach was based on the charge of the substituent active region (cSAR) parameters and the Harmonic Oscillator Model of Aromaticity (HOMA) indices. The cSAR parameters characterized the electron density better than the conventional Hammett’s constants σ. In general, the cSAR parameters correlate with other characteristics of the charge distribution, particularly those for substituents at the carbon atom in the ring adjacent to the side chain. Substituents at this atom affected the aromaticity less strongly than those located between two nitrogen atoms, which confirmed recent reports. Our results suggest that the 3H tautomer isomerizes into the 1H one after binding to the H₁ receptor. Moreover, the electron structure of the molecule hydrogen-bonded to the receptor may significantly depend on the electron donor-acceptor properties of the substituent. The strong electron-accepting substituents, e.g., NO₂, favor the imidazole configuration of the ring in the bonded molecule, while the strong electron-donating ones, e.g., NH₂, promote the imidazolium one. Full article