Natural naphthoquinones and their derivatives as potential drug molecules against trypanosome parasites

Chemical structure-biological activity of 1,4-naphthoquinone analogs as potential Aedes aegypti larvicides

BACKGROUND

1,4-Naphthoquinone compounds have shown pesticidal activity against Aedes aegypti larvae, a key vector of diseases such as dengue and Zika. However, limited knowledge of their structure-activity relationships has hindered their optimization for pesticide development. This study investigates the structure-activity relationships of 1,4-naphthoquinone, particularly 2-hydroxy-1,4-naphthoquinone and its derivatives.

RESULTS

A series of 1,4-naphthoquinones with modifications at the C-2, C-5, and C-8 positions were synthesized and tested for larvicidal activities against Ae. aegypti. The presence of chlorine substituents at the C-2 position significantly increased mosquito larval mortality. In contrast, 2-hydroxy and 2-methoxy groups were less effective, highlighting the importance of the C-2 substituent in determining larvicidal activity. The compounds were tested on both pyrethroid-susceptible Orlando 1952 (ORL1952) and permethrin-resistant Puerto Rico (PR) strains of Ae. aegypti. While compound 1d exhibited the lowest median lethal concentration (LC50) against ORL1952 larvae, it showed minimal activity against the PR strain, which is resistant. The most promising compounds, 1 and 4a, showed LC50 values of 2.764 and 4.916 ppm in the ORL strain, and 2.548 and 4.878 ppm in the PR strain, respectively.

CONCLUSION

Chlorine substitution at the C-2 position of 1,4-naphthoquinones enhances larvicidal activity against Ae. aegypti, while 2-hydroxy and 2-methoxy substitutions reduce efficacy. Certain compounds, such as 1 and 4a, show potential as broad-spectrum agents effective against both susceptible and resistant strains of Ae. aegypti, highlighting their promise for further development as mosquito control agents. © 2025 Society of Chemical Industry.

Marine Natural Products as Novel Treatments for Parasitic Diseases

Parasitic diseases including malaria, leishmaniasis, and trypanosomiasis have received significant attention due to their severe health implications, especially in developing countries. Marine natural products from a vast and diverse range of marine organisms such as sponges, corals, molluscs, and algae have been found to produce unique bioactive compounds that exhibit promising potent properties, including antiparasitic, anti-Plasmodial, anti-Leishmanial, and anti-Trypanosomal activities, providing hope for the development of effective treatments. Furthermore, various techniques and methodologies have been used to investigate the mechanisms of these antiparasitic compounds. Continued efforts in the discovery and development of marine natural products hold significant promise for the future of novel treatments against parasitic diseases.

Synthesis and In Silico Evaluation of Piperazine-Substituted 2,3-Dichloro-5,8-dihydroxy-1,4-naphthoquinone Derivatives as Potential PARP-1 Inhibitors

PARP-1 (poly(ADP-ribose)-polymerase 1) inhibitors are vital in synthetic lethality, primarily due to their specificity for PARP-1 over PARP-2 (PARP-1 > PARP-2). This specificity is crucial as it allows precise inhibition of PARP-1 in tumor cells with Breast Cancer 1 protein (BRCA1) or BRCA2 deficiencies. The development of highly specific PARP-1 inhibitors not only meets the therapeutic needs of tumor treatment but also has the potential to minimize the adverse effects associated with nonselective PARP-2 inhibition. In this study, a series of novel 2,3-dichloro-5,8-dihydroxy-1,4-naphthoquinone (DDNO) derivatives were synthesized, characterized, and evaluated regarding their PARP-1 inhibitory and cytotoxic activity. Compound 3 exhibited the highest cytotoxic potential against all cell lines, except for MDA-MB-231 cells. The inhibitory potential of these molecules against PARP-1 was evaluated through in silico molecular docking and molecular dynamics studies. Notably, compounds 5, 9, and 13 exhibited significant inhibitory activity in silico results, interacting with critical amino acids known to be important for PARP-1 inhibition during simulations. These compounds exhibited target-specific and strong binding profiles, with docking scores of -7.17, -7.41, and -7.37 kcal/mol, respectively, and MM/GBSA scores of -52.51, -43.77, and -62.87 kcal/mol, respectively. These novel compounds (DDNO derivatives) hold promise as potential PARP-1 inhibitors for the development of targeted therapeutics against cancer.

Co(III)-Catalyzed Regioselective Functionalization of Isoquinolones with Naphthoquinones

A strategy for Co(III)-catalyzed C(sp2)-H alkenylation of N-protected isoquinolones with 1,4-naphthoquinones has been disclosed. The developed protocol was efficiently applied for diversely substituted isoquinolones. Preliminary mechanistic experiments revealed the involvement of a five-membered cobaltacycle as an intermediate. Deuterium labeling experiments suggested the reversible nature of the C-H activation step. The scale-up reaction was also carried out, and the product was utilized as a chemosensor to detect Fe3+ ions.

Intracellular ROS production and apoptotic effect of quinoline and isoquinoline alkaloids on the growth of Trypanosoma evansi

Trypanosoma evansi, a hemoflagellate poses huge economic threat to the livestock industry of several countries of Asia, Africa, South America and Europe continents of the world. Limited number of available chemical drugs, incidents of growing drug resistance, and related side effects encouraged the use of herbal substitutes. In the present investigation, the impact of six alkaloids of quinoline and isoquinoline group was evaluated on the growth and multiplication of Trypanosoma evansi and their cytotoxic effect was examined on horse peripheral blood mononuclear cells in an in vitro system. Quinine, quinindine, cinchonine, cinchonidine, berbamine and emetine showed potent trypanocidal activities with IC50/24 h values 6.631 ± 0.244, 8.718 ± 0.081, 16.96 ± 0.816, 33.38 ± 0.653, 2.85 ± 0.065, and 3.12 ± 0.367 µM, respectively, which was comparable to the standard anti-trypanosomal drug, quinapyramine sulfate (20 µM). However, in the cytotoxicity assay, all the drugs showed dose dependent cytotoxic effect and quinine, berbamine and emetine showed selectivity index more than 5, based of ration of CC50 to IC50. Among the selected alkaloids, quinidine, berbamine and emetine exhibited higher apoptotic effects in T. evansi. Likewise, drug treated parasites showed a dose-dependent and time-dependent increase in reactive oxygen species (ROS) production. Therefore, increased apoptosis in combination with ROS generation could be responsible for the observed trypanocidal effect which could be further evaluated in T. evansi-infected mice model.

Plumbagin: A Promising In Vivo Antiparasitic Candidate against Schistosoma mansoni and In Silico Pharmacokinetic Properties (ADMET)

Schistosomiasis, a potentially fatal chronic disease whose etiological agents are blood trematode worms of the genus Schistosoma spp., is one of the most prevalent and debilitating neglected diseases. The treatment of schistosomiasis depends exclusively on praziquantel (PZQ), a drug that has been used since the 1970s and that already has reports of reduced therapeutic efficacy, related with the development of Schistosoma-resistant or -tolerant strains. Therefore, the search for new therapeutic alternatives is an urgent need. Plumbagin (PLUM), a naphthoquinone isolated from the roots of plants of the genus Plumbago, has aroused interest in research due to its antiparasitic properties against protozoa and helminths. Here, we evaluated the in vivo schistosomicidal potential of PLUM against Schistosoma mansoni and the in silico pharmacokinetic parameters. ADMET parameters and oral bioavailability were evaluated using the PkCSM and SwissADME platforms, respectively. The study was carried out with five groups of infected mice and divided as follows: an untreated control group, a control group treated with PZQ, and three groups treated orally with 8, 16, or 32 mg/kg of PLUM. After treatment, the Kato-Katz technique was performed to evaluate a quantity of eggs in the feces (EPG). The animals were euthanized for worm recovery, intestine samples were collected to evaluate the oviposition pattern, the load of eggs was determined on the hepatic and intestinal tissues and for the histopathological and histomorphometric evaluation of tissue and hepatic granulomas. PLUM reduced EPG by 65.27, 70.52, and 82.49%, reduced the total worm load by 46.7, 55.25, and 72.4%, and the female worm load by 44.01, 52.76, and 71.16%, for doses of 8, 16, and 32 mg/kg, respectively. PLUM also significantly reduced the number of immature eggs and increased the number of dead eggs in the oogram. A reduction of 36.11, 46.46, and 64.14% in eggs in the hepatic tissue, and 57.22, 65.18, and 80.5% in the intestinal tissue were also observed at doses of 8, 16, and 32 mg/kg, respectively. At all doses, PLUM demonstrated an effect on the histopathological and histomorphometric parameters of the hepatic granuloma, with a reduction of 41.11, 48.47, and 70.55% in the numerical density of the granulomas and 49.56, 57.63, and 71.21% in the volume, respectively. PLUM presented itself as a promising in vivo antiparasitic candidate against S. mansoni, acting not only on parasitological parameters but also on hepatic granuloma. Furthermore, in silico, PLUM showed good predictive pharmacokinetic profiles by ADMET.

α-amylase inhibition and in silico studies of novel naphtho[2,3-d]imidazole-4,9-dione linked N-acyl hydrazones

Aim: To enrich the pool of α-amylase inhibitors to manage Type 2 diabetes. Methods: Synthesis, conformational study, α-amylase inhibitory action and various in silico studies of novel N'-(arylbenzylidene)-2-(4,9-dioxo-4,9-dihydro-1H-naphtho[2,3-d]imidazol-1-yl)acetohydrazides carried out. Results: Compound H6 demonstrated the highest activity (IC50 = 0.0437 μmol mL-1) among the tested compounds. Structure-activity relationship study suggested that variable substitution at the aryl ring has a pivotal role in determining the inhibitory action of tested compounds. Docking simulations of the most active compound (H6) confirmed its interaction potential with active site residues of A. oryzae α-amylase. The root-mean-square deviation fluctuations substantiated the stability of protein-ligand complex. Absorption, distribution, metabolism and excretion prediction revealed optimal values for absorption, distribution, metabolism and excretion parameters. Conclusion: The developed molecules could be beneficial for the development of novel α-amylase inhibitors to treat Type 2 diabetes.

Natural Products for Pesticides Discovery: Structural Diversity Derivation and Biological Activities of Naphthoquinones Plumbagin and Juglone

Plant diseases and insect pests seriously affect the yield and quality of crops and are difficult to control. Natural products are an important source for the discovery of new pesticides. In this work, naphthoquinones plumbagin and juglone were selected as parent structures, and a series of their derivatives were designed, synthesized and evaluated for their fungicidal activities, antiviral activities and insecticidal activities. We found that the naphthoquinones have broad-spectrum anti-fungal activities against 14 types of fungus for the first time. Some of the naphthoquinones showed higher fungicidal activities than pyrimethanil. Compounds I, I-1e and II-1a emerged as new anti-fungal lead compounds with excellent fungicidal activities (EC₅₀ values: 11.35-17.70 µg/mL) against Cercospora, arachidicola Hori. Some compounds also displayed good to excellent antiviral activities against the tobacco mosaic virus (TMV). Compounds I-1f and II-1f showed similar level of anti-TMV activities with ribavirin, and could be used as new antiviral candidates. These compound also exhibited good to excellent insecticidal activities. Compounds II-1d and III-1c displayed a similar level of insecticidal activities with matrine, hexaflumuron and rotenone against Plutella xylostella. In current study, plumbagin and juglone were discovered as parent structures, which lays a foundation for their application in plant protection.