The therapeutic logic behind the work rests on the deep biological overlap between inflammatory and allergic disease. COX-2 catalyzes the conversion of arachidonic acid into prostaglandins when tissues become inflamed, driving pain, fever, and swelling, while histamine acting through H1 receptors triggers vasodilation, smooth muscle contraction, and itching. In conditions such as allergic rhinitis with sinus inflammation or chronic urticaria with an inflammatory component, both pathways fire at once. A compound that engages both could, in principle, deliver synergistic benefit, lower the effective dose of each mechanism, reduce drug-drug interactions, and improve patient adherence. The authors point to rupatadine, which combines H1 antagonism with platelet-activating factor inhibition, as an existing proof that multi-target antihistamines can succeed clinically.

The benzimidazole scaffold was a deliberate choice. This fused benzene-imidazole ring system structurally resembles the purine bases of DNA, which helps it form favorable contacts with a wide range of biological targets. Benzimidazole drugs already span an impressive pharmacological range, from anti-inflammatory and antimicrobial to antiviral, anticancer, and antiparasitic activity. Previous studies have shown that suitably substituted benzimidazoles can act as selective COX-2 inhibitors with improved gastrointestinal safety compared with traditional NSAIDs; one reported series of methyl sulfonyl-substituted analogues achieved sub-micromolar inhibitory potency in enzyme assays. What had not been done before, according to the authors, was a systematic dual-target evaluation of a single benzimidazole series against both COX-2 and the H1 receptor.

The design itself was methodical. All eleven compounds, labeled SP1 through SP11, share a 2-phenyl-1H-benzimidazole core connected through an acetamide linker at the N-1 position to a variable substituent. That substituent was varied deliberately across chemical space: aromatic groups such as aniline and resorcinol, aldehyde-bearing moieties including salicylaldehyde and isovanillin, carboxylic acids ranging from formic to benzoic, chloroacetic, and salicylic acid, and simple aliphatic propanol and butanol chains. Each variation tunes lipophilicity, hydrogen-bonding capacity, and steric profile in a different way, allowing the team to read out structure-activity relationships directly from the docking results.

Before any docking was attempted, the compounds had to pass basic drug-likeness filters. Using the SwissADME web platform, the researchers confirmed that every derivative satisfied Lipinski’s Rule of Five and Veber’s oral bioavailability criteria without a single violation. Molecular weights ranged from 279.29 to 385.42 daltons, comfortably below the 500-dalton ceiling, while calculated LogP values between 1.02 and 3.72 suggested a workable balance between membrane permeability and aqueous solubility. Topological polar surface area values of 46.92 to 84.22 square angstroms and rotatable bond counts of five to seven fell within Veber’s limits, predicting efficient passive diffusion across the gut wall. In short, all eleven molecules looked like plausible oral drugs on paper.

Safety screening came next, using ProTox-III, a machine-learning platform trained on curated toxicological datasets. Predicted acute oral LD50 values ranged from 500 to 2000 milligrams per kilogram, placing every compound in GHS Toxicity Class IV, a category comparable to many approved pharmaceuticals. Human intestinal absorption was predicted to exceed 80 percent for the entire series, and carcinogenicity and mutagenicity predictions were negative for nearly all derivatives. Notably, low predicted blood-brain barrier penetration for most compounds hints at a peripherally acting antihistamine with reduced sedation risk, the defining drawback of first-generation H1 antagonists. One caution did emerge: SP7 and SP8 showed moderate predicted cardiotoxicity, a signal the authors stress must be verified with hERG channel assays, since cardiac liability contributed to the market withdrawal of some earlier COX-2 inhibitors.

The docking results were where the study delivered its headline findings. Using Schrödinger’s Glide Extra Precision protocol against human COX-2, the crystal structure of which was solved bound to ibuprofen, the team found that SP2, a resorcinol derivative, scored minus 8.032 kilocalories per mole and SP8, a salicylic acid derivative, scored minus 9.566 kilocalories per mole, both far ahead of ibuprofen’s benchmark of minus 5.779. The protocol was validated by re-docking the co-crystallized ligands, yielding root-mean-square deviations of 1.83 and 1.78 angstroms for COX-2 and the H1 receptor respectively, both under the accepted 2.0-angstrom threshold. SP8’s strength appears to come from its ortho-hydroxyl and carboxylate groups working in concert: the carboxylate forms a salt bridge with Arg120 while hydrogen bonds anchor to Tyr355 and Ser530, and hydrophobic packing into the enzyme’s channel stabilizes the complex.

Against the histamine H1 receptor, solved by cryo-electron microscopy in complex with desloratadine, the top performers were SP2 at minus 8.021 and SP11, a butanol-bearing derivative, at minus 8.627 kilocalories per mole, both surpassing the reference antihistamine astemizole at minus 6.519. These compounds engage the orthosteric binding pocket through hydrogen bonds with Asp107, Tyr108, Ser111, and Asn198, complemented by aromatic stacking against Trp428, Tyr431, and Phe432. The extended butyl chain of SP11 appears to fill hydrophobic sub-pockets lined by Phe432, Phe435, and Trp428, consistent with established structure-activity rules for lipophilic H1 ligands. Intriguingly, the SAR analysis suggested that lengthening the alkyl chain preferentially boosts H1 affinity over COX-2 affinity, giving medicinal chemists a tunable dial for target balance.

When docking affinity, drug-likeness, and predicted safety were weighed together, three compounds rose to the top for different reasons. SP2 shows the most balanced dual-target engagement, with its COX-2 and H1 docking scores within 0.1 kilocalories per mole of each other. SP8 is the strongest single COX-2 binder of the series, and SP11 the strongest H1 binder. A fourth compound, SP9, showed promising H1-selective trends thanks to a methoxy group that occupies a hydrophobic sub-pocket absent from COX-2, but its overall dual-target and safety profile did not outperform the three leads, so it was not carried forward. The authors are careful to note that GlideScores are empirical rankings, not thermodynamic binding free energies, and cannot substitute for measured inhibition constants.

That caveat frames the study’s honest limitations. Static docking cannot capture protein flexibility or induced-fit effects, and machine-learning ADMET models can be unreliable for chemotypes poorly represented in their training data. The authors recommend a clear experimental roadmap: synthesize SP2, SP8, and SP11; run in vitro COX-2 inhibition and H1 receptor binding assays; establish COX-1/COX-2 selectivity to gauge gastrointestinal risk; complete full experimental ADMET profiling including hERG testing; and then move to in vivo efficacy studies in inflammation and anaphylaxis models, with molecular dynamics simulations guiding further optimization. Until those experiments are done, the dual-acting promise of these molecules remains a well-supported hypothesis rather than a demonstrated therapy. Still, as a rational, hypothesis-generating screen, the work offers a concrete starting point for a next generation of medicines aimed at the frequent clinical overlap between allergy and inflammation.

Subject of Research: Computational evaluation of novel benzimidazole derivatives as dual COX-2 inhibitors and histamine H1 receptor antagonists

Article Title: Integrated computational evaluation of novel benzimidazole scaffolds as dual COX-2 inhibitory and histamine H1 antagonistic activity

Article References: Pawar, S., & Panzade, P. (2026). Integrated computational evaluation of novel benzimidazole scaffolds as dual COX-2 inhibitory and histamine H1 antagonistic activity. Discover Chemistry, 3(1), Article 566. https://doi.org/10.1007/s44371-026-01024-6

Image Credits: AI Generated

DOI: 10.1007/s44371-026-01024-6

Keywords: benzimidazole, COX-2 inhibition, histamine H1 receptor, molecular docking, drug-likeness, ADMET prediction, SwissADME, ProTox-III, Glide XP docking, structure-activity relationship, computer-aided drug design, dual-target therapeutics

The study, led by Tshwarelo E. Mohale and colleagues, focused on the interplay between docetaxel, a widely used semisynthetic chemotherapy derived from the needles of the European yew, and kaempferol, a natural flavonoid with a growing reputation as an anticancer agent. The team’s central question was whether these two molecules could each bind to and disrupt Bcl-2, an anti-apoptotic protein that acts as a molecular bodyguard for cancer cells. Bcl-2 works by forming heterodimers with pro-apoptotic proteins such as Bax and BAK, blocking mitochondrial outer membrane permeabilization and preventing the release of cytochrome C that would otherwise activate the caspase cascade leading to programmed cell death. Because Bcl-2 is overexpressed in many breast cancer subtypes and is strongly linked to therapy resistance, it has long been considered an attractive drug target.

Docetaxel’s problem is well documented. It kills cancer cells by inducing mitotic arrest followed by apoptosis, but tumours frequently counter by overproducing Bcl-2, which blunts the death signal. Docetaxel is also a poor drug by the standards of oral bioavailability: it violates two of Lipinski’s rule of five criteria, with a molecular weight of 807.88 g/mol and fourteen hydrogen bond acceptors, and it carries a topological polar surface area of 224.45 square angstroms, which explains its low gastrointestinal absorption. Worse, it is a substrate of P-glycoprotein, an efflux pump expressed in the liver and gut lining that actively pumps the drug back out of cells, and it is metabolically inactivated by the CYP3A4 enzyme. Kaempferol, by contrast, is a model of drug-likeness: a molecular weight of just 286.24 g/mol, a single rotatable bond, zero Lipinski violations, a bioavailability score of 0.55 compared with docetaxel’s 0.17, and high predicted gastrointestinal absorption. Crucially, it is not a P-glycoprotein substrate.

To test whether both molecules could engage Bcl-2, the researchers first prepared the human Bcl-2 crystal structure from the Protein Data Bank, removing the co-crystallized ligand to leave an empty receptor. They then performed blind molecular docking using AutoDock Vina, enclosing the entire protein in the search grid so that the algorithm could find the most favourable binding site without bias. The results were striking: docetaxel docked with a score of −7.3 kcal/mol and kaempferol with −7.7 kcal/mol, both outperforming the FDA-approved Bcl-2 inhibitor venetoclax, which scores −6.793 kcal/mol in the same framework, and the potent inhibitor paclitaxel at −7.2 kcal/mol. These scores suggested that both compounds deserve serious consideration as Bcl-2 modulators.

Docking scores alone can mislead, so the team subjected each complex to 150-nanosecond molecular dynamics simulations in explicit water using the Amber20 software suite with the ff14SB protein force field and the General Amber Force Field for the ligands. The simulations tracked how the protein-ligand complexes behaved at body temperature over time. Root mean square deviation analysis showed that the unbound Bcl-2 protein averaged 2.89 angstroms of deviation from its starting structure, while the docetaxel-bound complex averaged 3.44 angstroms and the kaempferol-bound complex 2.73 angstroms. In other words, docetaxel loosened the protein’s architecture, increasing its flexibility by 0.55 angstroms relative to the unbound state, whereas kaempferol actually produced a slightly more compact conformation than the protein achieved on its own.

Root mean square fluctuation analysis told a complementary story at the level of individual amino acids. The docetaxel complex showed elevated fluctuations across many regions, indicating that the drug destabilizes the residues that maintain Bcl-2’s function, particularly within the conserved hydrophobic cleft where the protein normally sequesters BH3-only pro-apoptotic proteins. Disrupting this cleft could weaken Bcl-2’s grip on its targets and restore apoptotic signalling. The kaempferol complex, in contrast, remained comparatively rigid. Radius of gyration measurements, which ranged between 14.49 and 14.63 angstroms across all systems, confirmed modest structural rearrangements upon ligand binding, and dynamic cross-correlation matrix analysis revealed that docetaxel increased positively correlated, synchronized motions in the BH3 region spanning residues 40 to 110, while kaempferil restricted movement in ways that preserved conformational stability.

To quantify binding strength more rigorously than docking allows, the researchers applied the Molecular Mechanics Poisson-Boltzmann Surface Area method to the simulation trajectories. The docetaxel-Bcl-2 complex yielded a binding free energy of −28.90 ± 11.93 kcal/mol, stronger than the kaempferol complex at −23.63 ± 4.87 kcal/mol. In both cases van der Waals interactions dominated the binding energy, with docetaxel contributing −37.44 kcal/mol and kaempferol −29.01 kcal/mol, confirming that hydrophobic contacts within the BH3-binding cleft are the principal driver of recognition. Per-residue energy decomposition identified Tyr114, Ala65 and Glu69 as the biggest contributors in the docetaxel complex, while Arg80, Gly79 and Asp37 anchored kaempferol. Notably, the highest-contributing residues in each complex also formed direct hydrogen bonds with their ligands, stabilizing both molecules inside the same binding pocket.

The pharmacokinetic analysis added a provocative twist. Kaempferol was predicted to inhibit CYP3A4 and CYP1A2, the very enzymes responsible for metabolizing docetaxel. In theory, this could raise systemic docetaxel exposure and enhance its anticancer effect, but it also raises the spectre of increased toxicity, a consideration the authors flag as a significant translational caveat. The combination has precedent: kaempferol and docetaxel have previously been reported to act synergistically against pancreatic and prostate cancer cells, and kaempferol alone has been shown to suppress breast cancer proliferation and metastasis by downregulating Bcl-2 and modulating the PI3K/Akt pathway. The new study provides a structural rationale for why the two molecules might cooperate at the level of a single protein target.

The authors are careful to frame these findings as hypothesis-generating rather than clinical. The study relies entirely on computational methods: a single 150-nanosecond trajectory per complex, docking, MM-PBSA energetics and in silico ADME predictions. Key open questions remain, including whether docetaxel and kaempferol can bind Bcl-2 simultaneously and whether a ternary complex would show cooperative effects. The team calls for in vitro studies testing the pair individually and in combination against breast cancer cells, alongside experimental CYP450 inhibition assays to verify the predicted metabolic interaction. If those experiments bear out the simulations, a common dietary flavonoid could become a genuine partner for one of oncology’s workhorse drugs, offering a cheaper and more tolerable route to disarming the survival machinery that keeps breast cancer cells alive.

Subject of Research: Computational study of kaempferol and docetaxel binding to the Bcl-2 anti-apoptotic protein in breast cancer therapy

Article Title: Enhancing therapeutic efficacy through Kaempferol and docetaxel combination: integrative binding and molecular dynamics study targeting Bcl-2 protein in breast cancer

Article References: Mohale, T. E., Machaba, K. E., Hlengwa, N., & Mbazima, V. (2026). Enhancing therapeutic efficacy through Kaempferol and docetaxel combination: integrative binding and molecular dynamics study targeting Bcl-2 protein in breast cancer. Results in Chemistry, 31, Article 103906. https://doi.org/10.1016/j.rechem.2026.103906

Image Credits: AI Generated

DOI: 10.1016/j.rechem.2026.103906

Keywords: breast cancer, Bcl-2, kaempferol, docetaxel, molecular docking, molecular dynamics, MM-PBSA, apoptosis, drug resistance, flavonoid, chemotherapy, drug-likeness

The rationale behind the work rests on molecular hybridization, a drug-design strategy in which two pharmacophores are fused into a single molecular entity to achieve synergistic effects. Pyridazine-based compounds have long attracted attention in medicinal chemistry because they can modulate key oncogenic targets; clinically successful kinase inhibitors such as Vatalanib, Talazoparib and Simmiparib all contain the pyridazine heterocycle. Adding a thiophene ring to form the thienopyridazine scaffold increases electron density and enhances the pharmacological profile of the pyridazine system. Thiazole rings, meanwhile, appear in established anticancer drugs including Dasatinib and Tiazofurin, and are known to improve pi-pi stacking, hydrogen bonding and lipophilicity. The researchers reasoned that merging the two frameworks could amplify target binding, cellular uptake and pharmacokinetic behaviour simultaneously.

The synthesis began from 3-chloro-4-cyano-5,6-dimethylpyridazine, which was converted through an addition-elimination reaction with thiourea into a mercapto intermediate and then cyclized to the key building block, 6-acetyl-5-amino-3,4-dimethylthieno[2,3-c]pyridazine. This bifunctional compound served as the branching point for two synthetic routes. In the first, condensation with thiosemicarbazide produced a thiosemicarbazone derivative in 74.4 percent yield, which was then reacted with alpha-halo-carbonyl reagents in Hantzsch-type cyclizations to yield thiazole-bearing hydrazones, or with chloroacetic acid to form a thiazolin-4-one ring that could subsequently undergo Knoevenagel condensations with substituted benzaldehydes. The second route converted the amino group of the building block into a chloroacetamide, which reacted with ammonium thiocyanate to close a thiazolidin-4-one ring, again followed by benzylidene elaboration. All products were verified by infrared, nuclear magnetic resonance and mass spectrometry, together with elemental analysis.

Quantum-chemical calculations at the DFT/B3LYP level with a 6-311++G(d,p) basis set revealed how structural modifications reshape the electronic landscape of the molecules. The optimized geometries were largely non-planar, with torsion angles showing that phenyl substituents introduce significant twisting while thiazolidinone ring closure produces a more rigid, near-planar architecture. Frontier molecular orbital analysis showed that in the parent aminothienopyridazine the highest occupied and lowest unoccupied molecular orbitals both sit on the fused ring system, corresponding to pi-pi* transitions with limited charge separation. In the nitro-substituted benzylidene analogues, by contrast, the LUMO localizes strongly on the benzylidene phenyl group, creating a pronounced donor-acceptor separation. HOMO-LUMO gaps ranged from 2.81 to 3.80 electron volts, with the nitro compounds showing the smallest gaps, the highest softness and the greatest electrophilicity, all hallmarks of strong intramolecular charge-transfer capability. Computed dipole moments, polarizabilities and first hyperpolarizabilities exceeded those of urea by factors of up to 5.25 and 22.80 respectively, underlining the strong charge separation in these conjugated systems.

The biological screening used the MTT assay against three cancer cell lines, HepG2 liver carcinoma, HT-29 colorectal adenocarcinoma and MCF-7 breast cancer, alongside normal WI-38 fibroblasts, with doxorubicin as the reference drug. The results traced a clear structure-activity relationship. The parent compounds, lacking extended heterocyclic conjugation, were weakly active. Introducing a methyl-substituted thiazole boosted activity markedly against HT-29 and MCF-7, while the phenyl-substituted regioisomer acted selectively on HepG2, showing that subtle changes in heteroatom orientation can redirect cellular sensitivity. Benzylidene substitution on the thiazolidinone rings further enhanced potency, particularly with electron-donating methoxy or halogen substituents, whereas the strongly electron-withdrawing nitro group diminished activity across the series.

The standout compound was the chloroacetamide analogue 8, which achieved IC50 values of 12.57 micromolar against HT-29 cells and 17.66 micromolar against MCF-7 cells, close to or better than doxorubicin at the same cell lines, while showing the highest tolerance in normal WI-38 fibroblasts at 88.21 micromolar. The authors attribute this performance to the synergistic effect of the electrophilic chloroacetamide linkage with an optimal electronic distribution, adequate molecular size and enhanced hydrogen-bonding capability. A related thiazolidinone imine analogue showed the strongest inhibition of HepG2 cells at 19.40 micromolar, suggesting that scaffold flexibility can confer organ-specific sensitivity. Most analogues displayed high selectivity indices against the normal cell line, a critical safety signal for any prospective anticancer lead.

To rationalize these findings computationally, the team docked the molecules into the N-terminal ATP-binding domain of Hsp90alpha, a molecular chaperone that stabilizes numerous oncogenic proteins and is an established cancer drug target. Binding scores ranged from -4.9488 to -7.2492 kilocalories per mole, with the lead chloroacetamide compound achieving the strongest score, driven by a hydrogen-acceptor bond between its chlorine atom and Lys58. Derivatives carrying thiazole and thiazolidinone rings consistently bound better than their simpler precursors because those rings increase hydrophobic and pi-stacking interactions within the binding cavity. Docking of doxorubicin itself yielded a score of -6.6103 kilocalories per mole, confirming the protocol and demonstrating that several novel derivatives match or exceed the reference drug’s computed affinity.

A multiple linear regression analysis connecting quantum-chemical descriptors to measured IC50 values produced determination coefficients between 0.9567 and 0.9823 across the four cell lines, indicating that frontier orbital energies largely account for the biological variation. Lower LUMO energies favoured cytotoxicity, consistent with the importance of electron-accepting ability in stabilizing interactions with biological targets, while the positive contribution of the HOMO-LUMO gap suggested that optimal activity requires balanced reactivity rather than excessive molecular softness. Electronegativity enhanced activity in all models, whereas hardness and softness effects varied by cell line, reflecting differences in how each tumour type responds to electronic flexibility.

In silico pharmacokinetic profiling with SwissADME added a further layer of assessment. The lead compound 8, together with analogues 9 and 10a, showed high gastrointestinal absorption, good aqueous solubility and full Lipinski compliance, although several were predicted to be P-glycoprotein substrates, which could modestly limit oral bioavailability. Importantly, none of the synthesized analogues were predicted to cross the blood-brain barrier, which the authors interpret as evidence that the series is best suited to peripheral, non-CNS diseases rather than central nervous system indications.

The authors caution that the cytotoxic data represent a preliminary screening; mechanistic studies involving apoptosis markers, cell cycle analysis and Western blotting on the most active analogues are the logical next step. Nevertheless, the convergence of potent and selective antiproliferative activity, docking affinities rivalling a clinical drug, and acceptable predicted drug-likeness positions the thienopyridazine-thiazole hybrids, and the chloroacetamide lead in particular, as promising starting points for further optimization in the search for safer and more effective anticancer agents.

Subject of Research: Synthesis, computational modelling and cytotoxic evaluation of thienopyridazine-thiazole hybrid compounds as potential anticancer agents

Article Title: Synthesis, molecular modelling, and cytotoxic activity of new thienopyridazine analogues clubbed thiazole ring systems

Article References: Mazi, W., & Alenazi, N. A. (2026). Synthesis, molecular modelling, and cytotoxic activity of new thienopyridazine analogues clubbed thiazole ring systems. Journal of Saudi Chemical Society, 30(4), Article 46. https://doi.org/10.1007/s44442-026-00076-8

Image Credits: AI Generated

DOI: 10.1007/s44442-026-00076-8

Keywords: thienopyridazine, thiazole, anticancer agents, cytotoxicity, DFT, molecular docking, Hsp90alpha, drug-likeness, molecular hybridization, HT-29, MCF-7, structure-activity relationship

The fascination with organic molecules as NLO materials is not new. Photonic technologies, including second-harmonic generation, optical switching, frequency conversion, and electro-optical modulation, all depend on substances whose electrons respond nonlinearly to intense light. Inorganic crystals have long dominated the field, but organic systems offer synthetic versatility, easily tunable structures, and extended pi-electron delocalization. When electron density sloshes between donor and acceptor regions inside a conjugated molecule, the result is a large dipole moment, high polarizability, and, most importantly, a sizable first-order hyperpolarizability, the parameter that governs second-order NLO behavior. What makes the new study distinctive is its proposal that drug molecules, whose structures often already contain aromatic rings, heteroatoms, and donor-acceptor subunits, could serve double duty as optoelectronic components.

Hydroxyzine, chemically designated 2-[2-[4-[(4-chlorophenyl)(phenyl)methyl]piperazin-1-yl]ethoxy]ethanol, turns out to be structurally well suited for such scrutiny. Its architecture stacks two phenyl rings, a piperazine heterocyclic core, ether linkages, and a terminal hydroxyl group into a framework rich in electron donors and acceptors. The researchers optimized the molecule’s geometry at the B3LYP/6-311G(d,p) level of theory, a workhorse combination of hybrid functional and triple-zeta basis set widely trusted for organic pharmaceuticals. The computed structural parameters told a coherent story: aromatic carbon-carbon bond lengths between 1.389 and 1.399 angstroms, midway between single and double bonds, confirmed substantial pi-electron delocalization, while the carbon-oxygen bonds in the ether linkages, at 1.411 to 1.419 angstroms, were shorter than standard single bonds, indicating partial double-bond character as oxygen lone pairs delocalize into the adjacent carbon framework.

To make sure the quantum picture was not a computational mirage, the team validated it against experiment. The simulated FT-IR spectrum matched the measured one across a broad range, reproducing the telltale broad hydroxyl stretch between 3400 and 3200 inverse centimeters, the split aromatic and aliphatic C-H stretching regions, and the ether C-O-C fingerprint bands between 1250 and 1050 inverse centimeters. The ultraviolet-visible spectrum, measured experimentally with peaks near 260 and 300 nanometers, was reproduced by time-dependent DFT calculations across seven solvent environments spanning gas phase to water, with computed absorptions falling between 259 and 273 nanometers. The dominant electronic transitions, assigned as HOMO-1 to LUMO, HOMO to LUMO, and HOMO-1 to LUMO+1 with near-complete contributions, confirmed that excitation is dominated by the delocalized aromatic pi-system. Curiously, the solvatochromic shifts were tiny, less than 3 nanometers across every solvent tested, suggesting the electronic excitations are localized well within the aromatic core and only weakly coupled to their surroundings.

The frontier molecular orbital analysis supplied the electronic heart of the story. The highest occupied molecular orbital sat at minus 6.24 electron volts, the lowest unoccupied one at minus 1.08 electron volts, yielding a gap of 5.16 electron volts. That figure places hydroxyzine in the same electronic stability neighborhood as other biologically active pharmaceuticals, such as the cyclic dipeptide cyclo(L-phenylalanyl-L-proline) at 5.19 electron volts, and implies a molecule that is neither too chemically inert nor too fragile, a balance quantified by derived descriptors like a chemical hardness of 2.58 electron volts. Mulliken population analysis then mapped the charge landscape: the two oxygen atoms and two piperazine nitrogens carried the deepest negative charges, between minus 0.37 and minus 0.40 elementary units, marking them as the principal nucleophilic centers, while positively polarized hydrogens completed an effective donor-pi-acceptor architecture that channels intramolecular charge transfer through the conjugated scaffold.

That charge asymmetry is precisely what drives the headline result. The calculated first-order hyperpolarizability came out at 1.79 times ten to the minus thirty electrostatic units, roughly 4.81 times larger than the benchmark value for urea, the traditional reference compound in NLO studies. The dominant tensor components, beta-zxx at 172.69 atomic units and beta-xxx at minus 75.92 atomic units, pointed to charge redistribution along specific molecular directions as the engine of the response. The researchers were careful to keep expectations grounded: the absolute magnitude places hydroxyzine among moderate NLO materials, well below star chromophores like para-nitroaniline derivatives and push-pull stilbenes, whose hyperpolarizabilities can exceed urea’s by one to two orders of magnitude. Yet the conceptual payoff is considerable. A clinically approved molecule already produced at industrial scale exhibits optical nonlinearity, implying that the structural features responsible for biological activity, aromatic rings, heteroatoms, and charge-transfer pathways, can be recruited for photonic purposes without designing a new scaffold from scratch.

The study went further, connecting molecular topology to electronic behavior through graph-theoretical descriptors. Representing the molecule as a graph of 28 vertices and 29 edges, the authors computed a battery of degree-based topological indices, including a first Zagreb index of 116, a second Zagreb index of 128, a hyper Zagreb index of 528, and a forgotten index of 272. These values, noticeably higher than those of simple aromatic molecules, quantify the structural complexity introduced by the piperazine bridge, the two chemically distinct phenyl rings, and the ether-linked side chain. In the authors’ framework, this topological complexity underwrites the extended electronic delocalization and donor-acceptor charge transfer responsible for the optical response, establishing a quantitative bridge between the shape of a molecular graph and its electro-optical performance.

The pharmaceutical side of the analysis held its own surprises. SwissADME predictions placed hydroxyzine squarely in the yellow yolk of the Boiled-Egg model, indicating high passive gastrointestinal absorption and probable blood-brain barrier penetration, findings consistent with its known sedative and anxiolytic actions. The molecule passed Lipinski’s rule of five with zero violations and was predicted not to be a P-glycoprotein substrate, easing concerns about efflux at the barrier. Molecular docking against histamine N-methyltransferase, a key enzyme of the histaminergic pathway, using the protein with PDB identifier 3Q01, yielded a binding energy of minus 6.01 kilocalories per mole, stabilized by hydrogen bonds to asparagine 200 and glycine 199 at 2.1 and 2.6 angstroms, plus a cluster of hydrophobic contacts. Laboratory agar well diffusion assays added a microbial footnote: compounds identified during characterization showed moderate antibacterial activity, generally stronger against Staphylococcus aureus than against Escherichia coli, a selectivity the authors attribute to the impermeable outer membrane of Gram-negative bacteria.

Not every piece of the puzzle snapped cleanly into place, and the authors were candid about it. Several computed proton NMR shifts, particularly for the flexible ethoxy side chain, diverged substantially from experimental values, with one proton predicted near 2.6 parts per million measured at 8.72. The team attributes these discrepancies to solvent-induced deshielding, concentration-dependent aggregation, possible assignment issues, and the limitations of relying on a single lowest-energy conformer rather than the full conformational ensemble present in solution, flagging conformational sampling and explicit solvent models as priorities for future work. Still, the overall verdict is that a familiar allergy pill, viewed through the combined lenses of quantum chemistry, spectroscopy, topology, and biology, reveals itself as a genuine structure-property laboratory. The findings suggest that piperazine-based drug scaffolds, already synthetically accessible and pharmacologically validated, could seed the next generation of sustainable, multifunctional organic materials, blurring the boundary between the pharmacy shelf and the photonics bench.

Subject of Research: Density functional theory investigation of the charge transfer and nonlinear optical properties of the antihistamine hydroxyzine

Article Title: Computational insight into charge transfer and nonlinear optical response of hydroxyzine: a DFT-guided approach towards sustainable optoelectronic and pharmaceutical applications

Article References: Sasikala, L., Kumar, K. B., Vimal, S., Prabhaharan, M., & Amirthakumar, C. (2026). Computational insight into charge transfer and nonlinear optical response of hydroxyzine: a DFT-guided approach towards sustainable optoelectronic and pharmaceutical applications. Results in Chemistry, 30, Article 103890. https://doi.org/10.1016/j.rechem.2026.103890

Image Credits: AI Generated

DOI: 10.1016/j.rechem.2026.103890

Keywords: hydroxyzine, density functional theory, nonlinear optics, hyperpolarizability, intramolecular charge transfer, piperazine, TD-DFT, topological indices, molecular docking, drug-likeness, antimicrobial activity, optoelectronics

The synthesis strategy combined two complementary fabrication routes. First, the team prepared tantalum-doped nickel oxide nanoparticles through a solvothermal procedure: nickel nitrate hexahydrate was dissolved in ethylene glycol, treated with aqueous ammonia to raise the pH to roughly 10 or 11, and mixed with a small quantity of tantalum pentachloride as the doping agent. The mixture was sealed in a Teflon-lined autoclave and held at 140 degrees Celsius for 12 hours, after which the solid product was washed, dried, and calcined at 550 degrees Celsius. Pure ZIF-8 was then grown from zinc nitrate and 2-methylimidazole in water at ambient temperature. To build the final hybrid, pre-sonicated Ta-doped NiO nanoparticles were mixed with the zinc and linker solutions in an ultrasound bath, and the resulting suspension underwent hydrothermal treatment at 110 degrees Celsius for 24 hours. The product emerged as a light beige solid in which the oxide nanorods were integrated into the porous framework.

A battery of structural and morphological techniques confirmed that the hybrid was real, crystalline, and well-formed. X-ray diffraction showed that the doped nickel oxide phase matched the reference pattern for cubic NiO with sharp, high-intensity peaks indicating high crystallinity and no impurity phases; applying the Scherrer equation gave an average crystallite size of 29.39 nanometers. The ZIF-8 scaffold displayed its characteristic strong reflection near 7.42 degrees in two-theta. Notably, when the two components were combined, the NiO reflections shifted slightly toward lower angles while the ZIF-8 peaks stayed put. According to Bragg’s law, that shift signals a modest expansion of the interplanar spacing within the oxide lattice, which the authors attribute to interfacial strain at the heterojunction boundaries, arising from lattice mismatch and potential coordination between the NiO surface and the nitrogen-donor sites of the imidazole linkers. The preserved ZIF-8 pattern confirmed the framework survived the integration intact.

Microscopy and spectroscopy reinforced the picture. Energy-dispersive X-ray spectroscopy mapping verified the expected elements in each material, with oxygen, nickel, and tantalum uniformly distributed in the doped oxide, carbon, oxygen, nickel, and zinc in pure ZIF-8, and carbon, nitrogen, oxygen, nickel, and tantalum spread across the final composite. Field-emission scanning electron microscopy revealed that the pure Ta-doped NiO particles formed nanorods roughly 266 nanometers long, while pure ZIF-8 crystallized as cubic particles averaging about 215 nanometers. In the hybrid, the in-situ incorporation of the oxide nanorods reshaped the final morphology into nanorods averaging 218 nanometers in length. Transmission electron microscopy confirmed that these rods formed homogeneously, with high uniformity and no agglomeration. Infrared spectroscopy picked up the expected Ni-O and Ni-O-Ta vibrations in the oxide, the imidazole ring and Zn-N stretch signatures of ZIF-8, and all of these features in the final composite, sealing the case for successful hybridization.

Porosity measurements told a subtler story. Nitrogen adsorption and desorption isotherms classified pure ZIF-8 as type IV with an H1-type hysteresis loop, while the composite showed type III behavior with an H3-type loop. The Brunauer-Emmett-Teller surface area of the hybrid came in at 183.73 square meters per gram, far below the 1187.71 square meters per gram of pure ZIF-8, and the total pore volumes and pore size distributions differed markedly as well. Hybridization, in other words, costs the framework much of its iconic surface area. Yet the catalytic performance did not suffer, because the Ta-doped NiO nanostructures brought their own active sites to the partnership, and a synergic interaction between those sites and the organic starting materials more than compensated for the loss of internal surface.

The model reaction chosen to test the catalyst was a three-component condensation of 4-bromoaniline, 4-nitrobenzaldehyde, and methyl 2-cyanoacetate to form a substituted quinoline-3-carbonitrile. After screening solvents, catalyst doses, and reaction conditions, the team settled on 14 milligrams of the Ta-doped NiO/ZIF-8 composite in ethanol under probe-ultrasound irradiation at 60 watts, which delivered a 97 percent yield. Ethanol beat water, chloroform, and acetonitrile on the combined grounds of yield, environmental friendliness, and accessibility. Raising the catalyst dose from 6 to 14 milligrams steadily improved the yield, but pushing beyond 14 milligrams brought no further gain. Under conventional reflux the reaction was slower and less productive, and without any catalyst the reaction essentially failed. The ultrasound advantage stems from acoustic cavitation: microscopic bubbles form, grow, and implode in the liquid, releasing bursts of mechanical and thermal energy directly into the reaction mixture without the need for bulk heating, which accelerates the reaction dramatically compared with conventional heating, where energy must diffuse through vessel walls and solvent.

The substrate scope proved impressively broad. Various substituted benzaldehydes bearing both electron-withdrawing and electron-donating groups, positioned at the para, meta, and ortho sites of the aryl ring, coupled with different anilines to give the desired quinoline-3-carbonitriles in consistently high yields, with electron-withdrawing substituents particularly effective, consistent with the electrophilic and nucleophilic interactions in the proposed mechanism. The authors propose that the carbonyl group is first activated by the catalyst’s active centers through interaction with the lone-pair electrons of the carbonyl oxygen, enabling a Knoevenagel condensation to form the first intermediate. The aniline nitrogen then attacks, the catalyst facilitates intramolecular cyclization and water removal, and a final aromatization step delivers the quinoline product. Unsaturated Zn-N centers on the ZIF-8 surface, together with defects and the doped oxide sites, provide the electrophilic character that drives the cascade.

Practical considerations for real-world use were also addressed. The catalyst was recovered after each run by washing with dry acetone, drying overnight at 60 degrees Celsius, and reused across six consecutive cycles with no major loss in performance. X-ray diffraction, infrared spectra, and electron microscopy of the recuperated material were essentially indistinguishable from the fresh sample, demonstrating robust structural and morphological stability. A hot filtration test, in which the catalyst was removed after only 45 seconds of stirring and the filtrate allowed to continue reacting, produced less than 10 percent yield, confirming that the reaction proceeds through genuine heterogeneous surface catalysis rather than leached species, a crucial credential for any catalyst aspiring to industrial relevance.

The second act of the study turned to medicine. Molecular docking simulations placed all 17 synthesized quinoline derivatives into the binding pocket of the histamine H1 receptor, the G protein-coupled receptor that mediates inflammation, smooth muscle contraction, and the classic symptoms of allergy. Every derivative blocked histamine activation, with interaction analysis revealing two key binding motifs: a hydrogen bond between the ligand’s nitrogen and the tyrosine 108 residue, at distances of 1.8 to 2.1 angstroms, and pi-pi stacking interactions with tyrosine 431 and phenylalanine 432, at 3.4 to 3.8 angstroms, the same aromatic contacts that stabilize known antihistamines and enable competitive displacement of histamine itself. Pharmacokinetic predictions using Lipinski’s Rule of Five and QikProp modeling showed excellent drug-likeness across the series: molecular weights under 500 grams per mole, logP values below 5, acceptable hydrogen bond donor and acceptor counts, and predicted human oral absorption of 88 to 100 percent, comfortably exceeding the 80 percent threshold for oral drug candidates. Most compounds also showed favorable Caco-2 intestinal permeability, although predicted transdermal absorption was poor, pointing to oral rather than topical delivery. The study, supported by the University of Kashan’s Department of Organic Chemistry, thus offers a rare double contribution: a green, reusable, ultrasound-driven catalytic platform for building biologically active quinolines, and a computationally validated set of anti-allergy leads poised for further preclinical development.

Subject of Research: Ta-doped NiO/ZIF-8 nanorod composites used as green nanocatalysts for quinoline-3-carbonitrile synthesis and as a platform for anti-allergy drug design targeting the histamine H1 receptor

Article Title: Nanomaterial-driven innovation: integrating catalytic quinoline synthesis and anti-allergy drug design using Ta-doped NiO/ZIF-8 nanorod composites

Article References: Mireei, N. S., Babaei, P., Kharazm, A. M., Ghasemi-Ghahsareh, A., Ebrahimi, S. M., & Rashki, S. (2026). Nanomaterial-driven innovation: integrating catalytic quinoline synthesis and anti-allergy drug design using Ta-doped NiO/ZIF-8 nanorod composites. Journal of Saudi Chemical Society, 30(5), Article 70. https://doi.org/10.1007/s44442-026-00125-2

Image Credits: AI Generated

DOI: 10.1007/s44442-026-00125-2

Keywords: Ta-doped NiO/ZIF-8 nanocomposites, Green chemistry catalysis, Ultrasound irradiation, Quinoline-3-carbonitrile derivatives, Molecular docking, Histamine H1 receptor (HRH1), Heterogeneous catalysis, Solvothermal synthesis, Drug-likeness, ADMET, ZIF-8, Nanorods