Julio C. Borges

Synthesis and antiviral activity of new 4-(phenylamino)/4-[(methylpyridin-2-yl)amino]-1-phenyl-1H-pyrazolo[3,4-b]pyridine-4-carboxylic acids derivatives

The synthesis of new 4-(phenylamino)-1-phenyl-1H-pyrazolo[3,4-b]pyridine-4-carboxylic acid (3a-l) derivatives and the new 4-[(methylpyridin-2-yl)amino]-1-phenyl-1H-pyrazolo[3,4-b]pyridine-4-carboxylic acid (5a–c) derivatives was achieved with an efficient synthetic route. Ethyl 4-chloro-1-phenyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylate (1) on fusion with appropriate substituted anilines or aminopicolines gave the required new ethyl 4-(phenylamino)-1-phenyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylates (2a–l) (52–82%) or new ethyl 4-[(methylpyridin-2-yl)amino]-1-phenyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylates (4a–c) (50–60%), respectively. Subsequent hydrolysis of the esters afforded the corresponding carboxylic acids (3a–l) (86–93%) and (5a–c) in high yield (80–93%). Inhibitory effects of 4-(phenylamino)/4-[(methylpyridin-2-yl)amino]-1-phenyl-1H-pyrazolo[3,4-b]pyridine-4-carboxylic acids. Derivatives on Herpes simplex virus type 1 (HSV-1), Mayaro virus (MAY) and vesicular stomatitis virus (VSV) were investigated. Compounds 2d, 3f, 3a, and 3c exhibited antiviral activity against HSV-1, MAY, and VSV virus with EC50 values of 6.8, 2.2, 4.8, 0.52, 2.5, and 1.0. None of these compounds showed toxicity for Vero cells.

Antibacterial profile against drug-resistant Staphylococcus epidermidis clinical strain and structure-activity relationship studies of 1H-pyrazolo(3,4-b)pyridine and thieno(2,3-b)pyridine derivatives

Antibacterial resistance is a complex problem that contributes to health and economic losses worldwide. The Staphylococcus epidermidis is an important nosocomial pathogen that affects immunocompromised patients or those with indwelling devices. Currently, there are several resistant strains including S. epidermidis that became an important medical issue mainly in hospital environment. In this work, we report the biological and theoretical evaluations of a 4-(arylamino)-1-phenyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acids series (1, 1a-m) and the comparison with a new isosteric ring nucleus series, 4-(arylamino)thieno[2,3-b]pyridine-5-carboxylic acids derivatives (2, 2a-m). Our results revealed the 1H-pyrazolo[3,4-b]pyridine derivatives significant antibacterial activity against a drug-resistant S. epidermidis clinical strain in contrast to the thieno[2,3-b]pyridine series. The minimal inhibitory concentration (MIC) of the most active derivatives (1a, 1c, 1e, and 1f) against S. epidermidis was similar to that of oxacillin and twofold better than chloramphenicol. Interestingly, the position of the functional groups has a great impact on the activity as observed in our structure-activity relationship (SAR) study. The SAR of 1H-pyrazolo[3,4-b]pyridine derivatives shows that the highest inhibitory activity is observed when the meta position is occupied by electronegative substituents. The molecular modeling analysis of frontier molecular orbitals revealed that the LUMO density is less intense in meta than in ortho and para positions for both series (1 and 2), whereas HOMO density is overconcentrated in 1H-pyrazolo[3,4-b]pyridine ring nucleus compared to the thieno[2,3-b]pyridine system. The most active derivatives of series 1 were submitted to in silico ADMET screening, which confirmed these compounds as potential antibacterial candidates.

4-(1H-Pyrazol-1-yl) benzenesulfonamide derivatives: identifying new active antileishmanial structures for use against a neglected disease.

Leishmaniasis is a neglected disease responsible for about 56,000 deaths every year. Despite its importance, there are no effective, safe and proper treatments for leishmaniasis due to strain resistance and/or drug side-effects. In this work we report the synthesis, molecular modeling, cytotoxicity and the antileishmanial profile of a series of 4-(1H-pyrazol-1-yl)benzenesulfonamides. Our experimental data showed an active profile for some compounds against Leishmania infantum and Leishmania amazonensis. The profile of two compounds against L. infantum was similar to that of pentamidine, but with lower cytotoxicity. Molecular modeling evaluation indicated that changes in electronic regions, orientation as well as lipophilicity of the derivatives were areas to improve the interaction with the parasitic target. Overall the compounds represent feasible prototypes for designing new molecules against L. infantum and L. amazonensis.

Synthesis and anti-HSV-1 evaluation of new 3H-benzo[b]pyrazolo[3,4-h]-1,6-naphthyridines and 3H-pyrido[2,3-b]pyrazolo[3,4-h]-1,6- naphthyridines

Background Herpes simplex virus type-1 (HSV-1) is the primary cause of facial lesions (mouth, lips, and eyes) in humans. The widespread use of acyclovir and nucleoside analogues has led to emergence of HSV strains that are resistant to these drugs. Recently, non-nucleoside anti-HSV compounds have received considerable attention. 1,6-Naphthyridines are a class of heterocyclic compounds that exhibit a broad spectrum of biological activities such as inhibitor of HIV-1 integrase, HCMV, FGF receptor-1 tyrosine kinase, and the enzyme acetylcholinesterase. We previously reported the synthesis, SAR studies, and evaluation anti-HSV-1 activity of 3H-benzo[b]pyrazolo[3,4-h]-1,6-naphthyridines. In the course of our search for new 1,6-naphthyridines derivatives with potential activity against HSV-1, we have synthesized and evaluated new 3H-benzo[b]pyrazolo[3,4-h]-1,6-naphthyridines (1a-k) and 3H-pyrido[2,3-b]pyrazolo[3,4-h]-1,6-naphthyridines (2a-c). Results A known synthetic approach was used for preparing new 3H-benzo[b]pyrazolo[3,4-h]-1,6-naphthyridines (1a-k) and 3H-pyrido[2,3-b]pyrazolo[3,4-h]-1,6-naphthyridines (2a-c), starting from ethyl 4-chloro-1-phenyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylate (7). All compounds were identified by FTIR, 1H NMR, and mass spectrometry. The antiviral effect on HSV-1 virus replication was determined. Conclusions The compounds 1d, 1f, 1g, and 1h exhibited the highest anti-HSV-1 activity. In general, 3H-benzo[b]pyrazolo[3,4-h]-1,6-naphthyridines were more effective inhibitors than their corresponding 3H-pyrido[2,3-b]pyrazolo[3,4-h]-1,6-naphthyridines. The compound 1h reduced the virus yield in 91% at 50 μM and exhibited a low cytotoxicity (CC50 600 μM).

Identification of a Potential Lead Structure for Designing New Antimicrobials to Treat Infections Caused by Staphylococcus epidermidis-Resistant Strains

Bacterial infections are a significant cause of morbidity and mortality among critically ill patients. The increase of antibiotic resistance in bacteria from human microbiota—such as Staphylococcusepidermidis, an important nosocomial pathogen that affects immunocompromised patients or those with indwelling devices—increased the desire for new antibiotics. In this study we designed, synthesized, and determined the antimicrobial activity of 27 thieno[2,3-b]pyridines (1, 2, 2a–2m, 3, 3a–3m) derivatives against a drug-resistant clinical S. epidermidis strain. In addition, we performed a structure-activity relationship analysis using a molecular modeling approach, and discuss the drug absorption, distribution, metabolism, excretion, and toxicity profile and Lipinski’s “rule of five,” which are tools to assess the relationship between structures and drug-like properties of active compounds. Our results showed that compound 3b (5-(1H-tetrazol-5-yl)-4-(3`-methylphenylamino)thieno[2,3-b]pyridine) was as active as oxacillin and chloramphenicol but with lower theoretical toxicity risks and a better drug likeness and drug score potential than chloramphenicol. All molecular modeling and biological results reinforced the promising profile of 3b for further experimental investigation and development of new antibacterial drugs.

Synthesis and in vitro evaluation of new benzenesulfonamides as antileishmanial agents

This paper describes the synthesis and the antileishmanial activity of new pyrazolyl benzenesulfonamide derivatives. These were elucidated by spectrometric methods. Some compounds showed a significant in vitro activity against Leishmania amazonensis, highlighting the derivative 1e. These pyrazolyl benzenesulfonamide derivatives did not show any toxicity in murine macrophage.

Searching for new antileishmanial lead drug candidates: Synthesis, biological and theoretical evaluations of promising thieno(2,3-b)pyridine derivatives

Cutaneous leishmaniasis is a parasitic disease associated with high morbidity and mortality rates. This work reports the synthesis, biological and theoretical evaluations of a new antileishmanial series of 5(4,5-dihydro-1H-imidazol-2-yl)-4-(arylamino)thieno[2,3-b]pyridine derivatives - 3 (H), 3a (m-CH3), 3b (mOCH3), 3c (m-NO2), 3d (m-F), 3e (m-Br), 3f (p-CH3), 3g (p-OCH3), 3h (p-NO2), 3i (p-F), 3j (p-Br). Interestingly 3f and 3g showed a better profile against Leishmania amazonensis (EC50=29.49 and 32.23 μM, respectively) than glucantime, the current drug on the market (EC50=163.7 μM). The theoretical analysis pointed a correlation among the antileishmanial profile and the conformational and

Interactions between 4-aminoquinoline and heme: Promising mechanism against Trypanosoma cruzi.

Chagas disease is a neglected tropical disease caused by the flagellated protozoan Trypanosoma cruzi. The current drugs used to treat this disease have limited efficacy and produce severe side effects. Quinolines, nitrogen heterocycle compounds that form complexes with heme, have a broad spectrum of antiprotozoal activity and are a promising class of new compounds for Chagas disease chemotherapy. In this study, we evaluated the activity of a series of 4-arylaminoquinoline-3-carbonitrile derivatives against all forms of Trypanosoma cruzi in vitro. Compound 1g showed promising activity against epimastigote forms when combined with hemin (IC50<1 μM), with better performance than benznidazole, the reference drug. This compound also inhibited the viability of trypomastigotes and intracellular amastigotes. The potency of 1g in combination with heme was enhanced against epimastigotes and trypomastigotes, suggesting a similar mechanism of action that occurs in Plasmodium spp. The addition of hemin to the culture medium increased trypanocidal activity of analog 1g without changing the cytotoxicity of the host cell, reaching an IC50 of 11.7 μM for trypomastigotes. The mechanism of action was demonstrated by the interaction of compound 1g with hemin in solution and prevention of heme peroxidation. Compound 1g and heme treatment induced alterations of the mitochondrion-kinetoplast complex in epimastigotes and trypomastigotes and also, accumulation of electron-dense deposits in amastigotes as visualized by transmission electron microscopy. The trypanocidal activity of 4-aminoquinolines and the elucidation of the mechanism involving interaction with heme is a neglected field of research, given the parasites lack of heme biosynthetic pathway and the importance of this cofactor for parasite survival and growth. The results of this study can improve and guide rational drug development and combination treatment strategies.

Synthesis of New Conjugates 1H-Pyrazolo[3,4-b]pyridine-phosphoramidate and Evaluation against Leishmania amazonensis

In this research three series of substituted 1H-pyrazolo[3,4-b]pyridine phosphoramidates were synthesized and characterized by infrared, H, C, and P nuclear magnetic resonance (NMR) spectroscopy and high-resolution mass spectrometry. The products were obtained in good yields (67-83%) under mild conditions by nucleophilic aromatic substitution reaction of aminoalkylphosphoramidates over 4-chloro-1H-pyrazolo[3,4-b]pyridines. These compounds were evaluated as antileishmanials against Leishmania amazonensis promastigotes in vitro. Among all, compounds of a series showed expressive antileishmanial activity. Two of them emerged as the most active, with IC50 values of 6.44 ± 1.49 and 12.25 ± 0.68 μM. The cytotoxicity of this series was assessed on murine cells and presented values similar to the reference drug pentamidine.

Thieno[2,3-b]pyridine derivatives: a new class of antiviral drugs against Mayaro virus

Mayaro virus (MAYV) is an arthropod-borne virus and a member of the family Togaviridae, genus Alphavirus. Its infection leads to an acute illness accompanied by long-lasting arthralgia. To date, there are no antiviral drugs or vaccines against infection with MAYV and resources for the prevention or treatment of other alphaviruses are very limited. MAYV has served as a model to study the antiviral potential of several substances on alphavirus replication. In this work we evaluated the antiviral effect of seven new derivatives of thieno[2,3-b]pyridine against MAYV replication in a mammalian cell line. All derivatives were able to reduce viral production effectively at concentrations that were non-toxic for Vero cells. Molecular modeling assays predicted low toxicity risk and good oral bioavailability of the substances in humans. One of the molecules, selected for further study, demonstrated a strong anti-MAYV effect at early stages of replication, as it protected pre-treated cells and also during the late stages, affecting virus morphogenesis. This study is the first to demonstrate the antiviral effect of thienopyridine derivatives on MAYV replication in vitro, suggesting the potential application of these substances as antiviral molecules against alphaviruses. Additional in vivo research will be needed to expand the putative therapeutic applications.