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Photodynamic therapy (PDT) has been used for various purposes, including as an antitumor resource in a noninvasive therapy with minimal side effects. Sinningia magnifica (Otto & A. Dietr.) Wiehler is a rupicolous plant found in rock crevices in Brazilian tropical forests. Initial studies indicate the presence of phenolic glycosides and anthraquinones in species of the genus Sinningia (Generiaceae family). It is known that anthraquinones are natural photosensitizers with potential PDT applications. This led us to investigate the potential compounds of S. magnifica for use as a natural photosensitizer against the melanoma (SK-MEL-103) and the prostate cancer (PC-3) cell lines in a bioguided study. Our results showed that singlet oxygen production by the 1,3-DPBF photodegradation assay greatly increased in the presence of crude extract and fractions. The biological activity evaluation showed photodynamic action against melanoma cell line SK-MEL-103 and prostate cell line PC-3. These results suggest the presence of potential photosensitizing substances, as demonstrated in this in vitro antitumor PDT study by the naphthoquinones Dunniol and 7-hydroxy-6-methoxy-α-dunnione for the first time. Naphthoquinones, anthraquinones and phenolic compounds were identified in the crude extract by UHPLC-MS/MS analysis, motivating us to continue with the bioguided phytochemical study aiming to discover more photochemically bioactive substances in Gesneriaceae plants.

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Abstract Due to the severe side effects revealed by most of the currently used antidiabetic medicines, search for finding new and safe drugs to manage diabetes is continued. Naphthoquinones possessing strong antioxidant properties have been employed as candidates for diabetes therapy. Present study is aimed at finding the antioxidant and hypoglycaemic potential of some novel derivatives of 2-phenylamino-1,4-naphthoquinones (PAN) including chloro, nitro, methyl and bromo (5a-d) derivatives synthesized by single pot experiment. Product crystals were purified by TLC and characterized by FT-IR. The antioxidant potential of the compounds was assayed through DPPH radical scavenging and reducing power activities noted as UV-vis. absorbance. The DPPH assay has showed the powerful antioxidant activity of nitro and bromo derivatives, while the nitro derivative showed the significant reduction potential towards FRAP assay. Hypoglycaemic potential of the compounds was studied in rat animal model. All synthesized compounds revealed better hypoglycaemic activity; however, the chloro-derivative exhibited the more potent hypoglycaemic activity showing about 43% reduction in the mean blood glucose levels of the treated animals. As the bioreduction of naphthoquinones may be influenced by changing its redox properties, it has been noticed that the e-donating resonance effect (+R) of chloro group has shown the significant effects on biological activity through stabalization of its imine form which limits the potential of generation of free radicals during bioreduction of quinones and thus has been proposed as the reason of its hypoglycaemic activity. Future studies employing the properties of e-donating groups of PAN may optimize the drug-receptor interaction for better drug designing and drug development strategies against diabetes and also for the clinical trials.

Resumo Em razão dos graves efeitos colaterais causados pela maioria dos medicamentos antidiabéticos atualmente utilizados, continua a busca por novos medicamentos seguros para o controle do diabetes. As naftoquinonas, que possuem fortes propriedades antioxidantes, têm sido empregadas como candidatas à terapia do diabetes. O presente estudo visa encontrar o potencial antioxidante e hipoglicemiante de alguns novos derivados de 2-fenilamino-1,4-naftoquinonas (PAN), incluindo derivados de cloro, nitro, metil e bromo (5a-d) sintetizados por experimento em pote único. Os cristais do produto foram purificados por TLC e caracterizados por FT-IR. O potencial antioxidante dos compostos foi testado por meio de atividades de sequestro de radicais DPPH e redução de energia observada como absorção no UV-vis. O ensaio DPPH mostrou a poderosa atividade antioxidante dos derivados nitro e bromo, enquanto o derivado nitro mostrou o potencial de redução significativo para o ensaio FRAP. O potencial hipoglicêmico dos compostos foi estudado em modelo animal de rato. Todos os compostos sintetizados revelaram melhor atividade hipoglicemiante; no entanto, o derivado cloro apresentou atividade hipoglicêmica mais potente, com redução de 43% nos níveis médios de glicose no sangue dos animais tratados. Como a biorredução de naftoquinonas pode ser influenciada pela alteração de suas propriedades redox, notou-se que o efeito da doação eletrônica por ressonância (+R) do grupo cloro tem sido significativo na atividade biológica por meio da estabilização de sua forma imina, que limita o potencial de geração de radicais livres durante a biorredução de quinonas, e, portanto, tem sido proposto como a razão de sua atividade hipoglicemiante. Estudos futuros empregando as propriedades de grupos de doação eletrônica de PAN podem otimizar a interação droga-receptor para melhor planejamento de medicamentos e estratégias de desenvolvimento de medicamentos contra o diabetes e também para os ensaios clínicos.

RESUMEN

Due to the severe side effects revealed by most of the currently used antidiabetic medicines, search for finding new and safe drugs to manage diabetes is continued. Naphthoquinones possessing strong antioxidant properties have been employed as candidates for diabetes therapy. Present study is aimed at finding the antioxidant and hypoglycaemic potential of some novel derivatives of 2-phenylamino-1,4-naphthoquinones (PAN) including chloro, nitro, methyl and bromo (5a-d) derivatives synthesized by single pot experiment. Product crystals were purified by TLC and characterized by FT-IR. The antioxidant potential of the compounds was assayed through DPPH radical scavenging and reducing power activities noted as UV-vis. absorbance. The DPPH assay has showed the powerful antioxidant activity of nitro and bromo derivatives, while the nitro derivative showed the significant reduction potential towards FRAP assay. Hypoglycaemic potential of the compounds was studied in rat animal model. All synthesized compounds revealed better hypoglycaemic activity; however, the chloro-derivative exhibited the more potent hypoglycaemic activity showing about 43% reduction in the mean blood glucose levels of the treated animals. As the bioreduction of naphthoquinones may be influenced by changing its redox properties, it has been noticed that the e-donating resonance effect (+R) of 'chloro' group has shown the significant effects on biological activity through stabalization of its imine form which limits the potential of generation of free radicals during bioreduction of quinones and thus has been proposed as the reason of its hypoglycaemic activity. Future studies employing the properties of e-donating groups of PAN may optimize the drug-receptor interaction for better drug designing and drug development strategies against diabetes and also for the clinical trials.

Em razão dos graves efeitos colaterais causados pela maioria dos medicamentos antidiabéticos atualmente utilizados, continua a busca por novos medicamentos seguros para o controle do diabetes. As naftoquinonas, que possuem fortes propriedades antioxidantes, têm sido empregadas como candidatas à terapia do diabetes. O presente estudo visa encontrar o potencial antioxidante e hipoglicemiante de alguns novos derivados de 2-fenilamino-1,4-naftoquinonas (PAN), incluindo derivados de cloro, nitro, metil e bromo (5a-d) sintetizados por experimento em pote único. Os cristais do produto foram purificados por TLC e caracterizados por FT-IR. O potencial antioxidante dos compostos foi testado por meio de atividades de sequestro de radicais DPPH e redução de energia observada como absorção no UV-vis. O ensaio DPPH mostrou a poderosa atividade antioxidante dos derivados nitro e bromo, enquanto o derivado nitro mostrou o potencial de redução significativo para o ensaio FRAP. O potencial hipoglicêmico dos compostos foi estudado em modelo animal de rato. Todos os compostos sintetizados revelaram melhor atividade hipoglicemiante; no entanto, o derivado cloro apresentou atividade hipoglicêmica mais potente, com redução de 43% nos níveis médios de glicose no sangue dos animais tratados. Como a biorredução de naftoquinonas pode ser influenciada pela alteração de suas propriedades redox, notou-se que o efeito da doação eletrônica por ressonância (+R) do grupo "cloro" tem sido significativo na atividade biológica por meio da estabilização de sua forma imina, que limita o potencial de geração de radicais livres durante a biorredução de quinonas, e, portanto, tem sido proposto como a razão de sua atividade hipoglicemiante. Estudos futuros empregando as propriedades de grupos de doação eletrônica de PAN podem otimizar a interação droga-receptor para melhor planejamento de medicamentos e estratégias de desenvolvimento de medicamentos contra o diabetes e também para os ensaios clínicos.

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Quinones are chemical compounds produced from the oxidation of phenols. Among the quinones, naphthoquinones stand out as potential antitumor agents. Bladder tumour is the tenth most diagnosed in the world. Based on this, using a urothelial carcinoma cell line (T24), two naphthoquinones had their cytotoxicity tested by the MTT colorimetric method and were submitted to assays of clonogenic survival, morphology, cell cycle, cell migration and species reactive oxygen. The results showed 8-methoxy-α-lapachone and lausone presented selectivity indexes (19.5 and 28.0, respectively) for T24 cells. Moreover, the two naphthoquinones reduced the cell viability, interfered with the process of cell migration, changed the cell cycle kinectics and induced the production of species reactive oxygen (ROS). Additionaly, 8-methoxy-α-lapachone altered the morphology of the cells. In conclusion, the studied naphthoquinones showed potential antiproliferative effects in bladder cancer cells, interfering in cellular processes, possibly through oxidative stress.

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Parkinson's disease (PD) is a degenerative disease that affects approximately 6.1 million people and is primarily caused by the loss of dopaminergic neurons. Naphthoquinones have several biological activities explored in the literature, including neuroprotective effects. Therefore, this review shows an overview of naphthoquinones with neuroprotective effects, such as shikonin, plumbagin and vitamin K, that prevented oxidative stress, in addition to multiple mechanisms. Synthetic naphthoquinones with inhibitory activity on the P2X7 receptor were also found, leading to a neuroprotective effect on Neuro-2a cells. It was found that naphthazarin can act as inhibitors of the MAO-B enzyme. Vitamin K and synthetic naphthoquinones hybrids with tryptophan or dopamine showed inhibition of the aggregation of α-synuclein. Synthetic derivatives of juglone and naphthazarin were able to protect Neuro-2a cells against neurodegenerative effects of neurotoxins. In addition, routes for producing synthetic derivatives were also discussed. With the data presented, 1,4-naphthoquinones can be considered as a promising class in the treatment of PD and this review aims to assist the scientific community in the application of these compounds. The derivatives presented can also support further research that explores their structures as synthetic platforms, in addition to helping to understand the interaction of naphthoquinones with biological targets related to PD.

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Cancer is responsible for high mortality rates worldwide, representing a serious health problem. In this sense, melanoma corresponds to the most aggressive type of skin cancer, being the cause of the highest death rates. Therapeutic strategies for the treatment of melanoma remain limited, with problems associated with toxicity, serious side effects, and mechanisms of resistance. The potential of natural products for the prevention and treatment of melanoma has been reported in different studies. Among these compounds, naphthoquinones (1,2-naphthoquinones and 1,4-naphthoquinones) stand out for their diverse pharmacological properties, including their antitumor activity. Thus, this review covers different studies found in the literature on the application of natural naphthoquinones targeting melanoma, providing information regarding the mechanisms of action investigated for these compounds. Finally, we believe that this review provides a comprehensive basis for the use of natural naphthoquinones against melanoma and that it may contribute to the discovery of promising compounds, specifically naphthoquinones, aimed at the treatment of this cancer.

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Two new naphthoquinones, 7-hydroxy-2-O-methyldunniol (1) and 7-methoxy-2-O-methyldunniol (2) were isolated from the tubers of Sinningia conspicua (Seem.) G. Nicholson (Gesneriaceae). Nine known compounds were also obtained: 7-methoxydunniol (3), dunniol (4), 7-methoxy-α-dunnione (5), 7-hydroxydunnione (6), 2,4,4',6-tetramethoxychalcone (7), loureirin B (8), allo-calceolarioside A (9), ß-sitosterol (10) and stigmasterol (11). This is the first report of compounds 3 and 5 in Sinningia. n-Hexane, ethyl acetate and ethanol extracts, and compounds 1-5 were tested for cytotoxic activity against PC-3 (prostate) and SKMEL 103 (melanoma) human tumour cell lines and also against the 3T3 (fibroblast) non-cancer cell line. All samples were inactive.

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AIMS: The aim of this study was to investigate the antibacterial and antibiofilm potential of cordiaquinones B, E, L, N, and O against different Staphylococci strains, in addition to analyzing in silico the observed effect. METHODS AND RESULTS: The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) were determined according to CLSI guidelines. The inhibition of biofilm formation was investigated at sub-MICs. Atomic force microscopy (AFM) and density functional theory method were performed. The tested strains of Staphylococcus spp. were susceptible to cordiaquinones B, E, and L, among which cordiaquinone B exerted a bactericidal effect, confirmed by a bacterial growth curve study, against Staphylococcus saprophyticus. Cordiaquinones B and E showed lowest MBC values against S. saprophyticus. AFM revealed that cordiaquinone L reduced the mean cell size of S. saprophyticus. Cordiaquinones B and E inhibited the biofilm formation ability of S. aureus by ∼90%. The in silico analysis suggested that the antimicrobial activity of cordiaquinones is driven by their electron donation capability. CONCLUSIONS: Cordiaquinones inhibit the growth and biofilm formation (virulence factor) of both methicillin-sensitive and methicillin-resistant Staphylococci strains, indicating their antimicrobial potential.

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Natural product derivatives are essential in searching for compounds with important chemical, biological, and medical applications. Naphthoquinones are secondary metabolites found in plants and are used in traditional medicine to treat diverse human diseases. Considering this, the synthesis of naphthoquinone derivatives has been explored to contain compounds with potential biological activity. It has been reported that the chemical modification of naphthoquinones improves their pharmacological properties by introducing amines, amino acids, furan, pyran, pyrazole, triazole, indole, among other chemical groups. In this systematic review, we summarized the preparation of nitrogen naphthoquinones derivatives and discussed their biological effect associated with redox properties and other mechanisms. Preclinical evaluation of antibacterial and/or antitumoral naphthoquinones derivatives is included because cancer is a worldwide health problem, and there is a lack of effective drugs against multidrug-resistant bacteria. The information presented herein indicates that naphthoquinone derivatives could be considered for further studies to provide drugs efficient in treating cancer and multidrug-resistant bacteria.

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ATP acts in the extracellular environment as an important signal, activating a family of receptors called purinergic receptors. In recent years, interest in the potential therapeutics of purinergic components, including agonists and antagonists of receptors, has increased. Currently, many observations have indicated that ATP acts as an important mediator of inflammatory responses and, when found in high concentrations in the extracellular space, is related to the activation of the P2X7 purinergic receptor. In this sense, the search for new inhibitors for this receptor has attracted a great deal of attention in recent years. Sulfonamide derivatives have been reported to be potent inhibitors of P2X receptors. In this study, ten naphthoquinone sulfonamide derivatives and five naphthoquinone sulfonate ester derivatives were tested for their inhibitory activity on the P2X7 receptor expressed in peritoneal macrophages. Some compounds showed promising results, displaying IC50 values lower than that of A740003. Molecular docking and dynamic studies also indicated that the active compounds bind to an allosteric site on P2X7R. The binding free energy indicates that sulfonamides have an affinity for the P2X7 receptor similar to A740003. Therefore, the compounds studied herein present potential P2X7R inhibition.

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Quinones are naturally or synthetically occurring secondary metabolites that have various bio-dynamics, highlighting their antitumor potential. This has been explored through their selective cytotoxicity, and studies in medicinal chemistry about the relation between biological activity versus chemical structure may lead to the solution of the toxicity problems associated with quinones. In this context, the antitumor effect of a synthetic naphthoquinone, named Ethyl 2-(1,4-Dioxo-1,4-Dihydronaphthalen-2-Ylamino) Acetate, was tested using mice transplanted with Ehrlich ascitic tumor as an experimental model. The acute toxicity test was performed using 30 mice that received the aminoquinone at doses of 100, 200, 300, and 600 mg/kg. After evaluation of the clinical findings in the spontaneous activity tests, the LD50 calculation for the test substance showed low levels of toxicity at doses lower than 244.11 ± 23.29 mg/kg. Thus, three experimental groups were established, where animals transplanted with tumor cells received NaCl vehicle solution (control, n = 6), and the others were treated with 71.7 mg/kg of Methotrexate (n = 6) or 20 mg/kg of Aminoquinone (n = 6). All administrations were intraperitoneal, in a single dose. Three days after the implantation of the tumor cells the animals were weighed daily and evaluated for tumor biometry and development. The treatments occurred five days after the implantation of the tumor cells and were extended for 7 more days. At the end of the 12-day experimental period, all animals were euthanized for biochemical and histopathological analyses of the tumors and vital organs. The spontaneous activity test showed that the amount of responses associated with the nervous system tends to increase with the increase in dosage, highlighting the excitatory effect on the central nervous system in almost all dosages employed, followed by depressant activities on this system. There was a significant tumor reduction, both in animals treated with methotrexate (71.7 %) and in those treated with aminoquinone (91.6 %) in the control group. There was no significant difference in tumor volume between the animals treated with aminoquinone or methotrexate. The histopathological analysis revealed that in both treatments there were fewer mitoses in the tumor mass compared to the control group. However, there was apparent toxicity to the liver, heart, and left kidney in the treatment with methotrexate compared to aminoquinone. The significant capacity for tumor reduction presented by aminoquinone allows pointing it as a promising alternative for the development of a more efficient drug to control tumor development, being necessary for the development of new studies to deepen the knowledge about its mechanisms of action.

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Three new naphthoquinones, 5,6,7-trimethoxydunnione (1), 6,7-dimethoxy-α-dunnione (2), and 5,6,7-trimethoxydunniol (3) were isolated from the tubers of Sinningia mauroana Chautems, together with eleven known compounds: 5-hydroxy-6,7-dimethoxy-α-dunnione (4), 6-hydroxy-7-methoxy-α-dunnione (5), 7-hydroxy-6-methoxy-α-dunnione (6), cedrol (7), tectoquinone (8), plantainoside A (9), calceolarioside A (10), calceolarioside B (11), sanangoside (12), allo-calceolarioside A (13), and conandroside (14). The known compounds 4, 7-9 and 11-13 are being reported for the first time in this species. Hexane, ethyl acetate and ethanol extracts were tested for antioxidant activity by the ORAC-FL method, and the antioxidant capacity was measured as trolox equivalent (TE). The ethyl acetate (8808 µg TE g-1) and ethanol (7911 µg TE g-1) extracts showed high antioxidant capacity, while the hexane extract displayed weak antioxidant capacity (860 µg TE g-1).

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Leishmaniasis is a neglected disease that affects millions of people worldwide, and special attention should be given to treatment because the available drugs have limitations, which can lead to low therapeutic adherence and parasitic resistance. This study evaluated the activity of the bioactive naphthoquinones, lapachol and β-lapachone, against Leishmania amazonensis. The cell alterations were evaluated in vitro on promastigote and amastigote forms. The lethal dose (LD50) at 24, 48, and 72 h on the promastigote's forms using lapachol was 75.60, 72.82, and 58.85 μg/mL and for β-lapachone was 0.65, 1.24, and 0.71 μg/mL, respectively. The naphthoquinones significantly inhibited the survival rate of L. amazonensis amastigotes at 83.11, 57.59, and 34.95% for lapachol (82.28, 41.14, and 20.57 µg/mL), and 78.49, 83.25, and 80.22% for β-lapachone (3.26, 1.63, and 0.815 µg/mL). The compounds on the promastigote's forms led to the loss of mitochondrial membrane potential, induced changes in the integrity of the membrane, caused damage to cells suggestive of the apoptotic process, and showed inhibition of tumor necrosis factor (TNF)-α and interleukin (IL)-6 production. The results showed that these naphthoquinones are promising candidates for research on new drugs with anti-Leishmania activity derived from natural products.

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1,4-naftoquinone (NQ) molecules have been extensively evaluated as potent antibacterial compounds; however, their use is limited, since they have low water solubility and exhibit toxicities in healthy eukaryotic cells. A possible path to overcoming these challenges is the use of particulate vehicles, such as SBA-15, which is a biocompatible and biodegradable mesoporous silica material, that may enhance drug delivery and decrease dosages. In this work, an isotherm model-based adsorption of three NQs into SBA-15 microparticles was evaluated. Interactions between NQs and SBA-15 microparticles were modeled at the B3LYP/6-31+G(d,p) level of theory to understand the nature of such interactions. The results demonstrated that the adsorption of NQ, 2NQ, and 5NQ into SBA-15 fit the Freundlich adsorption model. According to theorical studies, physisorption is mediated by hydrogen bonds, while the most stable interactions occur between the carbonyl group of NQ and silica surfaces. Both experimental and theoretical results contribute to a deeper understanding of the use of SBA-15 or similar particles as nanovehicles in such a way that NQs can be modified in carbonyl or C3 to enhance adsorptions. The theoretical and experimental results were in accordance and contribute to a deeper understanding of how interactions between NQ-type molecules and SiO2 materials occur.

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The P2X7 receptor (P2X7R) is an ion channel that promotes the passage of ions through the membrane through brief stimulation once activated by ATP, its endogenous opener. However, prolonged stimulation with ATP, which occurs in pathological processes, opens a nonselective pore in the plasma membrane, allowing the passage of large molecules and leading to cytokine release or even cell death. In this sense, the search for new inhibitors for this receptor has attracted a great deal of attention in recent years. Considering the booming of biomass upgrading reactions in recent years and the continued efforts to synthesize biologically active molecules containing the 1,2,3-triazole ring, in the present work, we aimed to investigate whether triazole-linked menadione-furan derivatives could present P2X7R inhibitory activity. The novel compounds were tested for their inhibitory activity on ATP-induced dye uptake in peritoneal macrophages. Some have shown promising results, having displayed IC50 values lower than that of the P2X7R inhibitor BBG. Molecular docking studies also indicated that the active compounds bind to an allosteric site on P2X7R, presenting potential P2X7R inhibition.

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The genus Handroanthus Mattos (Bignoniaceae) is widely used for the treatment of cancer in traditional medicine in Brazil and other South American countries. The anticancer potential of species of this genus has been reported in the literature, indicating that their chemical compounds may be effective against different tumor cell lines. In this perspective, the present study aimed to conduct a systematic review of ethnobotanical, pharmacological, phytochemical and toxicological information on Handroanthus species related to cancer treatment. Searches were conducted in the Google Scholar, PubMed®, ScienceDirect® and SciELO databases. A total of 78 articles published in the last thirty-two years (1990-2022) were eligible and included in the review. According to the scientific documents analyzed, five species of Handroanthus are widely used for the treatment of cancer in the traditional medicine of Brazil and other South American countries, including Bolivia and Argentina. The bark (88%) is the main part used in traditional preparations. Extracts and fractions from Handroanthus showed cytotoxicity against the following tumor cell lines: HL-60, MDA-MB-435, MDA-MB-231, MCF-7, HT-29, HCT-8, HCT-116, HEp-2, HepG2, CACO-2, SF-295, NCI-H292, NCI-H460, HeLa, and OVCAR-8. ß-Lapachone, a naphthoquinone isolated from some species of this genus, is the most investigated compound for anticancer potential and has proved effective against some lung cancer cell lines (CL1-1, CL1-5 and A549). Results related to toxicological studies were not conclusive, considering that some extracts and compounds isolated from plants of this genus may present some degree of toxicity depending on the time of use and the concentration/dose used. Thus, despite the promising effects against various cancer cell lines, caution is needed when making use of these products.

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Oral squamous cell carcinoma (OSCC) is a global public health problem with high incidence and mortality. The chemotherapeutic agents used in the clinic, alone or in combination, usually lead to important side effects. Thus, the discovery and development of new antineoplastic drugs are essential to improve disease prognosis and reduce toxicity. In the present study, acridine-core naphthoquinone compounds were synthesized and evaluated for their antitumor activity in OSCC cells. The mechanism of action, pharmacokinetics, and toxicity parameters of the most promising compound was further analyzed using in silico, in vitro, and in vivo methods. Among the derivatives, compound 4e was highly cytotoxic (29.99 µM) and selective (SI 2.9) at levels comparable and generally superior to chemotherapeutic controls. Besides, compound 4e proved to be non-hemolytic, stable, and well tolerated in animals at all doses tested. Mechanistically, compound 4e promoted cell death by apoptosis in the OSCC cell, and molecular docking studies suggested this compound possibly targets enzymes important for tumor progression, such as RSK2, PKM2, and topoisomerase IIα. Importantly, compound 4e presented a pharmacological profile within desirable parameters for drug development, showing promise for future preclinical trials.

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Chagas and leishmaniasis are two neglected diseases considered as public health problems worldwide, for which there is no effective, low-cost, and low-toxicity treatment for the host. Naphthoquinones are ligands with redox properties involved in oxidative biological processes with a wide variety of activities, including antiparasitic. In this work, in silico methods of quantitative structure-activity relationship (QSAR), molecular docking, and calculation of ADME (absorption, distribution, metabolism, and excretion) properties were used to evaluate naphthoquinone derivatives with unknown antiprotozoal activity. QSAR models were developed for predicting antiparasitic activity against Trypanosoma cruzi, Leishmania amazonensis, and Leishmania infatum, as well as the QSAR model for toxicity activity. Most of the evaluated ligands presented high antiparasitic activity. According to the docking results, the family of triazole derivatives presented the best affinity with the different macromolecular targets. The ADME results showed that most of the evaluated compounds present adequate conditions to be administered orally. Naphthoquinone derivatives show good biological activity results, depending on the substituents attached to the quinone ring, and perhaps the potential to be converted into drugs or starting molecules.

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To develop novel chemotherapeutic alternatives for the treatment of Chagas disease, in this study, a set of new amino naphthoquinone derivatives were synthesised and evaluated in vitro on the epimastigote and trypomastigote forms of Trypanosoma cruzi strains (NINOA and INC-5) and on J774 murine macrophages. The design of the new naphthoquinone derivatives considered the incorporation of nitrogenous fragments with different substitution patterns present in compounds with activity on T. cruzi, and, thus, 19 compounds were synthesised in a simple manner. Compounds 2e and 7j showed the lowest IC50 values (0.43 µM against both strains for 2e and 0.19 µM and 0.92 µM for 7j). Likewise, 7j was more potent than the reference drug, benznidazole, and was more selective on epimastigotes. To postulate a possible mechanism of action, molecular docking studies were performed on T. cruzi trypanothione reductase (TcTR), specifically at a site in the dimer interface, which is a binding site for this type of naphthoquinone. Interestingly, 7j was one of the compounds that showed the best interaction profile on the enzyme; therefore, 7j was evaluated on TR, which behaved as a non-competitive inhibitor. Finally, 7j was predicted to have a good pharmacokinetic profile for oral administration. Thus, the naphthoquinone nucleus should be considered in the search for new trypanocidal agents based on our hit 7j.

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Leishmaniasis affects millions of people worldwide, and available treatments have severe limitations. Natural and derivative products are significant sources of innovative therapeutic agents. Naphthoquinones are natural or synthetic chemical compounds with broad biological activity. This systematic review aimed to evaluate the potential anti-Leishmania activity of bioactive compounds derived from naphthoquinones in animal models. Conducted in accordance with PRISMA guidelines, two blocks of MeSH terms were assembled: group I, Leishmania OR Leishmaniasis; group II, Atovaquone OR Lapachol OR Beta lapachone OR Naphthoquinones. The search was performed on PubMed, Web of Science, SCOPUS, EMBASE, and Lilacs databases. Twenty-four articles were retrieved and submitted for quality assessment using the SYRCLE critical appraisal tool. The in vivo anti-Leishmania potential of naphthoquinones was evaluated in visceral and cutaneous leishmaniasis using several measurement parameters. Analyzed compounds varied in structure, association with reference drugs, and encapsulation using a drug delivery system. The study design, including treatment protocol, differed between studies. The findings of the studies in this systematic review indicate the anti-Leishmania potential of naphthoquinones in vivo, with different treatment regimens directed against different Leishmania species. The employed drug delivery systems improve the results concerning selectivity, distribution, and required therapeutic dose. The immunomodulatory action was shown to be beneficial to the host, favoring an adequate immune response against infection by Leishmania parasites since it favored Th1 responses. All studies presented a moderate to high risk of bias. These findings suggest that more studies are needed to assess the overall effectiveness and safety of these treatments.

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