The motivation behind the research stems from a widening gap in the therapeutic arsenal against parasitic worms. Drugs such as albendazole and mebendazole remain the mainstay of treatment for trichinellosis and related nematode infections, but their limitations are increasingly well documented. Resistance concerns, incomplete efficacy against certain life stages of parasites, and adverse effects, including documented cases of albendazole-induced liver injury, have pushed researchers to explore novel heterocyclic scaffolds with different mechanisms of action. The emergence of drug resistance and the side effect profiles of currently available antiparasitic drugs, the authors note, necessitate the exploration of new chemical frameworks that could form the basis of next-generation anthelmintics.

The scaffold at the heart of the new study is the triazolopyrimidine, a fused bicyclic system that merges a 1,2,4-triazole ring with a pyrimidine ring. This class of nitrogen-rich heterocycles has attracted sustained attention in medicinal chemistry because it appears in compounds with antimicrobial, antiviral, anticancer, anti-inflammatory, and antiparasitic activities. Triazolopyrimidine derivatives have been investigated as inhibitors of DNA gyrase, cyclin-dependent kinases, and microtubule dynamics, and metal complexes of triazolopyrimidines have shown leishmanicidal and trypanocidal activity. Their structural rigidity, multiple hydrogen-bonding sites, and metabolic stability make them attractive pharmacophores, yet their synthesis has often required harsh conditions, long reaction times, and corrosive catalysts, which limits both scalability and environmental sustainability.

To address this synthetic bottleneck, the Egyptian team turned to lanthanum hydroxide nanorods, a rare-earth-based heterogeneous nanocatalyst. The researchers synthesized the La(OH)3 nanorods and subjected them to a thorough battery of characterization techniques, including X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and surface area analysis. These measurements confirmed the nanoscale dimensions, crystalline phase, rod-like morphology, and porous surface architecture of the material. Such one-dimensional lanthanum hydroxide nanostructures have previously found applications ranging from Claisen-Schmidt condensation catalysis to phosphate adsorption from water, and their basic surface sites make them well suited to promoting multicomponent condensation reactions under mild conditions.

Using these nanorods, the team prepared 6,8-diamino-5-(4-nitrophenyl)pyrido[3,2-e][1,2,4]triazolo[1,5-a]pyrimidine-7-carbonitrile, abbreviated DNP-Triazolopyrimidine, a highly functionalized fused heterocycle bearing an aminopyrido ring fused to the triazolopyrimidine core, two amino groups, a para-nitrophenyl substituent, and a nitrile function. The catalytic system demonstrated high efficiency, considerably reducing the reaction time while delivering a high product yield under mild reaction conditions. Compared with conventional approaches that may demand strong bases, elevated temperatures, or stoichiometric reagents, the heterogeneous nanocatalyst offers the additional practical advantage of easy separation from the reaction mixture, a hallmark of green chemistry that reduces waste and facilitates catalyst reuse. The final compound was structurally verified by FT-IR, proton nuclear magnetic resonance, and carbon-13 NMR spectroscopy, confirming the successful construction of the elaborate fused ring system.

With the compound in hand, the parasitology phase of the study began. The researchers evaluated DNP-Triazolopyrimidine in vitro against both the larval and adult stages of Trichinella spiralis, the two life stages most relevant to the pathology of trichinellosis. Adult worms inhabit the intestinal mucosa of the host, while larvae invade and encyst in skeletal muscle, so an effective drug candidate ideally must target both. The results were striking: the compound exhibited significant antiparasitic activity in a dose- and time-dependent manner, achieving complete larval mortality at concentrations of 10 and 20 micrograms per milliliter and complete adult-worm mortality at 20 micrograms per milliliter after 96 hours of exposure.

Quantitative analysis of the dose-response relationships revealed LC50 values, the concentrations lethal to half of the parasites, of 9.71 micrograms per milliliter for larvae and, notably, 3.16 micrograms per milliliter for adult worms. The lower LC50 for adults indicates that the intestinal stage of the parasite is particularly susceptible to the compound, an encouraging finding given that eliminating adult worms early in infection can prevent the subsequent establishment of muscle larvae and interrupt the parasite’s life cycle within the host. These potency figures compare favorably with many naturally derived and repurposed antiparasitic candidates previously tested against T. spiralis in vitro, positioning DNP-Triazolopyrimidine as a promising lead for further optimization.

To understand how the compound kills the parasites, the team turned to scanning electron microscopy, which revealed pronounced ultrastructural alterations in treated worms. The exposed cuticular surface of the nematodes suffered cuticular rupture, blebbing, vesicle formation, and loss of annulations, the characteristic transverse ridges of the nematode cuticle. The cuticle is far more than a passive skin; it is a metabolically active interface through which the worm absorbs nutrients, secretes immunomodulatory molecules, and defends itself against host immunity and drugs. Extensive damage to this tegumental barrier, as observed here, compromises osmotic balance, nutrient uptake, and immune evasion, providing a coherent mechanistic picture of nematode death consistent with surface-acting anthelmintic action.

Any prospective drug must spare host cells, so the researchers assessed the cytotoxicity of DNP-Triazolopyrimidine against WI-38 normal human fibroblast cells. The compound showed comparatively low cytotoxicity, with an IC50 of 51.61 plus or minus 2.9 micromolar, a concentration substantially above the levels that killed the parasites. This selectivity margin, while requiring confirmation in more cell types and in vivo models, suggests that the compound’s toxic effects are preferentially directed at the parasite rather than at mammalian tissue, a crucial property for a viable therapeutic candidate. Complementing the experimental data, the team performed in silico ADMET analysis, computational predictions of absorption, distribution, metabolism, excretion, and toxicity, which provided preliminary information on the pharmacokinetic and safety profile of DNP-Triazolopyrimidine and will guide medicinal chemists as they refine the scaffold.

The study, which received no external funding and was conducted with the support of Zagazig University’s Faculty of Science, illustrates a growing convergence between nanocatalysis and drug discovery. By demonstrating that inexpensive, recyclable lanthanum hydroxide nanorods can efficiently assemble a complex, biologically active heterocycle under mild conditions, the researchers have lowered a practical barrier that has historically slowed the exploration of triazolopyrimidine chemistry. At the same time, the potent in vitro activity against both larval and adult T. spiralis, the direct visualization of cuticular damage, and the encouraging selectivity over mammalian cells together argue that DNP-Triazolopyrimidine deserves further development. The path from an in vitro lead to a licensed medicine is long, requiring in vivo efficacy studies, detailed mechanism-of-action elucidation, and safety pharmacology, but this work provides a solid, technically well-documented starting point in the search for alternatives to a strained anthelmintic pharmacopoeia.

Subject of Research: Nanocatalytic synthesis of a triazolopyrimidine compound with in vitro antiparasitic activity against Trichinella spiralis

Article Title: An efficient nanocatalytic synthesis of a triazolopyrimidine carbonitrile with potent activity against Trichinella spiralis

Article References: El-Latif, Y. A. A., Elsayed, D. A., Mohamed, A.-E. A., & Said, R. M. (2026). An efficient nanocatalytic synthesis of a triazolopyrimidine carbonitrile with potent activity against Trichinella spiralis. The Science of Nature, 113(5), Article 111. https://doi.org/10.1007/s00114-026-02153-9

Image Credits: AI Generated

DOI: 10.1007/s00114-026-02153-9

Keywords: DNP-Triazolopyrimidine, La(OH)3 nanorods, heterogeneous nanocatalysis, Trichinella spiralis, trichinellosis, antiparasitic activity, lanthanum hydroxide, LC50, cuticular ultrastructure, WI-38 cytotoxicity, ADMET, medicinal chemistry

The substrate in question, ent-pimara-8(14),15-dien-19-oic acid, is a pimarane-type diterpene carboxylic acid, a molecule built around a rigid tricyclic core decorated with two carbon-carbon double bonds, an internal one at position 8(14) and an external vinyl group at position 15. When the researchers added this compound to growing liquid cultures of the fungus, the organism responded by transforming it into four oxidized products. Two of these, 15,16-epoxy-ent-pimar-8(14)-en-19-oic acid and 15,16-dihydroxy-ent-pimar-8(14)-en-19-oic acid, were known compounds, but the other two, 17-hydroxy-15,16-epoxy-ent-pimar-8(14)-en-19-oic acid and 15-oxo-16-hydroxy-ent-pimar-8(14)-en-19-oic acid, had never been described before. In every case, the fungus attacked the vinyl group and left the internal double bond intact.

That selectivity is what makes the result remarkable. Monosubstituted double bonds like the vinyl group are typically more reactive toward chemical oxidants, yet when chemists treated a related pimaradiene with the classic epoxidation reagent meta-chloroperbenzoic acid, they obtained only epoxides at the internal 8(14) position along with rearranged byproducts, the opposite outcome. Previous microbial studies pointed the same way: a strain of Aspergillus niger oxidized the tricyclic ring system of the same substrate at carbons 1, 6, 7, 11 and the internal double bond while ignoring the vinyl group, and the endophytic fungus Preussia minima also hydroxylated positions away from the vinyl moiety. The new work shows that A. sclerotiorum does essentially the reverse, a biotransformation pattern the authors describe as at least uncommon.

To probe whether this apparent regioselectivity was real, the team challenged the fungus with a second diterpene, abietic acid, a resin acid bearing two endocyclic double bonds at positions 7(8) and 13(14). If the fungus simply preferred external double bonds, abietic acid, which has none, should be metabolized differently. Instead, the organism oxidized a methyl group attached at carbon 13, outside the ring system, producing 16-hydroxyabieta-7(8),13(14)-dien-19-oic acid. This mirrors what it did with the pimarane substrate, where the vinyl group and the methyl group both hang off carbon 13, suggesting the enzymes recognize the spatial region around that carbon rather than a particular bond type.

The structural detective work relied on one- and two-dimensional nuclear magnetic resonance spectroscopy and high-resolution mass spectrometry. In the epoxide product, the characteristic ABX spin system of vinylic hydrogens near 5.4 and 4.9 parts per million in the proton spectrum vanished, replaced by new signals between 2.5 and 2.8 parts per million, while carbon-13 signals for the sp2 carbons at 147.2 and 112.9 parts per million gave way to aliphatic signals at 58.9 and 42.5. For the diol product, the carbon-15 resonance appeared at 80.4 parts per million, a deshielded position that literature correlations assign to the 15S configuration. Because an epoxide hydrolase opening the epoxide by an SN2-type attack at carbon 16 would yield only one epimer, whereas an SN1 mechanism through a carbocation would yield both, the researchers could infer that the epoxide products share that same 15S configuration. The hydroxyketone product, carrying a carbonyl signal at 214.8 parts per million, appears to arise from further oxidation of the diol’s C-15 hydroxyl group.

Hunting for the enzyme behind this chemistry, the team scanned publicly available whole-genome shotgun contigs of A. sclerotiorum using tblastn, searching for cytochrome P450 sequences similar to CYP105A1 from Streptomyces griseolus, a bacterial enzyme previously shown to oxidize the C-15 isopropyl group of abietic acid and to epoxidize the vinyl group of an isopimarane diterpene. The search returned two candidate open reading frames, one of 1083 nucleotides encoding 360 amino acids and another of 1641 nucleotides encoding 546 amino acids, with sequence identities of 25 and 24 percent and query coverages of 37 and 35 percent respectively. Crucially, both proteins carry the canonical P450 signature motif FxxGxxxCxG, including the cysteine residue that binds the heme iron, confirming they belong to the cytochrome P450 superfamily.

To visualize how such an enzyme might steer the substrate, the researchers turned to molecular docking using the crystal structure of a bacterial cytochrome P450 as a proxy, since no structure exists for the Aspergillus enzyme. In the docked complex, the diterpene sits in the active site with its vinyl group and the C-13 methyl group positioned closest to the heme catalytic center, exactly where an oxygenating iron-oxo species would deliver its atom. Basic amino acids, including arginine and asparagine, appear to anchor the molecule through hydrogen bonding and electrostatic interactions with the carboxylic acid at carbon 4, holding the substrate in the orientation that favors oxygenation at the side chain rather than the ring system. The docking picture closely resembles calculations published for CYP105A1 acting on abietic acid, reinforcing the idea that a similar P450 in the fungus drives the observed regioselectivity.

The practical payoff came from antiparasitic testing. The parent diterpene and its four derivatives were evaluated against promastigote forms of Leishmania amazonensis and epimastigote forms of Trypanosoma cruzi, the parasites responsible for cutaneous leishmaniasis and Chagas disease, both neglected tropical diseases that affect millions of people in Latin America and beyond. Oxidation consistently improved activity. Against L. amazonensis, the epoxide and the hydroxyketone derivatives showed IC50 values less than half that of the parent compound. Most strikingly, the hydroxyketone inhibited the trypomastigote stage of T. cruzi with an IC50 of 21.4 micromolar, slightly better than the reference drug benznidazole, which came in at 34.5 micromolar under the same assay conditions. Equally important, cytotoxicity assays against healthy Vero cells showed very low toxicity, particularly for the hydroxyketone, yielding favorable selectivity indices.

The structure-activity picture that emerges suggests that chemical modifications at the vinyl side chain matter more for antiparasitic potency than variations on rings A and B of the ent-pimarane skeleton. Earlier studies had found that hydroxylation near ring A did not substantially enhance activity against another T. cruzi strain, while ent-pimaranes modified at ring B showed IC50 values in the 15 to 20 micromolar range. The new derivatives, functionalized precisely at the side chain, now extend that trend and hint that the side chain is a promising handle for drug design.

Beyond the immediate antiparasitic results, the study validates a broader strategy: mining endophytic fungi from diterpene-producing plants for enzymes that recognize the very molecules their hosts biosynthesize. The intimate evolutionary relationship between endophytes and plant biochemistry may predispose their enzymatic machinery to accept plant terpenes as substrates, and expanding the pool of such microorganisms helps overcome the classic unpredictability of whole-cell biotransformation. With two new diterpenes in hand, a candidate P450 enzyme identified, and a docking model that explains the selectivity, the researchers have laid out a complete chain of evidence from genome to molecule to bioactivity, offering a template for turning humble tree-dwelling fungi into factories for medicinally relevant chemistry.

Subject of Research: Regioselective epoxidation of a plant diterpene by the endophytic fungus Aspergillus sclerotiorum and the antiparasitic activity of the resulting oxidized products.

Article Title: Epoxidation of ent-pimara-8(14),15-dien-19-oic acid by whole cells of the endophytic fungus Aspergillus sclerotiorum

Article References: Din, Z. U., de Medeiros, L. S., Abreu, L. M., Lazarin-Bidóia, D., Scariot, D. B., Garcia, F. P., de Paula, J. C., Nakamura, C. V., Fill, T. P., & Rodrigues-Filho, E. (2026). Epoxidation of ent-pimara-8(14),15-dien-19-oic acid by whole cells of the endophytic fungus Aspergillus sclerotiorum. International Microbiology. https://doi.org/10.1007/s10123-026-00895-0

Image Credits: AI Generated

DOI: 10.1007/s10123-026-00895-0

Keywords: Aspergillus sclerotiorum, biotransformation, diterpene, ent-pimaradienoic acid, epoxidation, cytochrome P450, endophytic fungus, Cupressus lusitanica, Leishmania amazonensis, Trypanosoma cruzi, antiparasitic activity, regioselectivity