Synthesis and evaluation of naphthyl bearing 1,2,3-triazole analogs as antiplasmodial agents, cytotoxicity and docking studies

Synthesis, crystal structure and Hirshfeld surface analysis of 2-({5-[(naphthalen-1-yl)meth-yl]-4-phenyl-4H-1,2,4-triazol-3-yl}sulfan-yl)-1-(4-nitro-phen-yl)ethanone

The title compound, C27H20N4O3S, crystallizes in the monoclinic system, space group P21/n, with Z = 4. The global shape of the mol-ecule is determined by the orientation of the substituents on the central 4H-1,2,4-triazole ring. The nitro-phenyl ring, phenyl ring, and naphthalene ring system are oriented at dihedral angles of 82.95 (17), 77.14 (18) and 89.46 (15)°, respectively, with respect to the triazole ring. The crystal packing features chain formation in the b-axis direction by S⋯O inter-actions. A Hirshfeld surface analysis indicates that the highest contributions to surface contacts arise from contacts in which H atoms are involved.

Investigation of new 1,2,3-triazolyl-quinolinyl-propan-2-ol derivatives as potential antimicrobial agents: in vitro and in silico approach

A new series of 1-((1-(4-substituted benzyl)-1H-1,2,3-triazol-4-yl)methoxy)-2-(2-substituted quinolin-4-yl)propan-2-ol (9a-x) have been synthesized. The newly synthesized 1,2,3-triazolyl-quinolinyl-propan-2-ol (9a-x) derivatives were screened for in vitro antimicrobial activity against M. tuberculosis H37Rv, E. coli, P. mirabilis, B. subtilis, and S. albus. Most of the compounds showed good to moderate antibacterial activity and all derivatives have shown excellent to good antitubercular activity with MIC 0.8-12.5 μg/mL. To know the plausible mode of action for antibacterial activity the docking study against DNA gyrase from M. tuberculosis and S. aureus was investigated. The compounds have shown significant docking scores in the range of -9.532 to -7.087 and -9.543 to -6.621 Kcal/mol with the DNA gyrase enzyme of S. aureus (PDB ID: 2XCT) and M. tuberculosis (PDB ID: 5BS8), respectively. Against the S. aureus and M. tuberculosis H37Rv strains, the compound 9 l showed good activity with MIC values of 62.5 and 3.33 μM. It also showed significant docking scores in both targets with -8.291 and -8.885 Kcal/mol, respectively. Molecular dynamics was studied to investigate the structural and dynamics transitions at the atomistic level in S. aureus DNA gyrase (2XCT) and M. tuberculosis DNA gyrase (5BS8). The results revealed that the residues in the active binding pockets of the S. aureus and M. tuberculosis DNA gyrase proteins that interacted with compound 9 l remained relatively consistent throughout the MD simulations and thus, reflected the conformation stability of the respective complexes. Thus, the significant antimicrobial activity of derivatives 9a-x recommended that these compounds could assist in the development of lead compounds to treat for bacterial infections.Communicated by Ramaswamy H. Sarma.

Naphthyl bearing 1,3,4-thiadiazoleacetamides targeting the parasitic folate pathway as anti-infectious agents: in silico, synthesis, and biological approach

Malaria is still a complex and lethal parasitic infectious disease, despite the availability of effective antimalarial drugs. Resistance of malaria parasites to current treatments necessitates new antimalarials targeting P. falciparum proteins. The present study reported the design and synthesis of a series of a 2-(4-substituted piperazin-1-yl)-N-(5-((naphthalen-2-yloxy)methyl)-1,3,4-thiadiazol-2-yl)acetamide hybrids for the inhibition of Plasmodium falciparum dihydrofolate reductase (PfDHFR) using computational biology tools followed by chemical synthesis, structural characterization, and functional analysis. The synthesized compounds were evaluated for their in vitro antimalarial activity against CQ-sensitive PfNF54 and CQ-resistant PfW2 strain. Compounds T5 and T6 are the most active compounds having anti-plasmodial activity against PfNF54 with IC50 values of 0.94 and 3.46 μM respectively. Compound T8 is the most active against the PfW2 strain having an IC50 of 3.91 μM. Further, these active hybrids (T5, T6, and T8) were also evaluated for enzyme inhibition assay against PfDHFR. All the tested compounds were non-toxic against the Hek293 cell line with good selectivity indices. Hemolysis assay also showed non-toxicity of these compounds on normal uninfected human RBCs. In silico molecular docking studies were carried out in the binding pocket of both the wild-type and quadruple mutant Pf-DHFR-TS to gain further insights into probable modes of action of active compounds. ADME prediction and physiochemical properties support their drug-likeness. Additionally, they were screened for antileishmanial activity against L. donovani promastigotes to explore broader applications. Thus, this study provides molecular frameworks for developing potent antimalarials and antileishmanial agents.

Current development of 1,2,3-triazole derived potential antimalarial scaffolds: Structure- activity relationship (SAR) and bioactive compounds

Malaria is among one of the most devastating and deadliest parasitic disease in the world claiming millions of lives every year around the globe. It is a mosquito-borne infectious disease caused by various species of the parasitic protozoan of the genus Plasmodium. The indiscriminate exploitation of the clinically used antimalarial drugs led to the development of various drug-resistant and multidrug-resistant strains of plasmodium which severely reduces the therapeutic effectiveness of most frontline medicines. Therefore, there is urgent need to develop novel structural classes of antimalarial agents acting with unique mechanism of action(s). In this context, design and development of hybrid molecules containing pharmacophoric features of different lead molecules in a single entity represents a unique strategy for the development of next-generation antimalarial drugs. Research efforts by the scientific community over the past few years has led to the identification and development of several heterocyclic small molecules as antimalarial agents with high potency, less toxicity and desired efficacy. Triazole derivatives have become indispensable units in the medicinal chemistry due to their diverse spectrum of biological profiles and many triazole based hybrids and conjugates have demonstrated potential in vitro and in vivo antimalarial activities. The manuscript compiled recent developments in the medicinal chemistry of triazole based small heterocyclic molecules as antimalarial agents and discusses various reported biologically active compounds to lay the groundwork for the rationale design and discovery of triazole based antimalarial compounds. The article emphasised on biological activities, structure activity relationships, and molecular docking studies of various triazole based hybrids with heterocycles such as quinoline, artemisinins, naphthyl, naphthoquinone, etc. as potential antimalarial agents which could act on the dual stage and multi stage of the parasitic life cycle.

Biological activity of 1,2,3-triazole-2-amino-1,4-naphthoquinone derivatives and their evaluation as therapeutic strategy for malaria control

Malaria can be caused by several Plasmodium species and the development of an effective vaccine is challenging. Currently, the most effective tool to control the disease is the administration of specific chemotherapy; however, resistance to the frontline antimalarials is one of the major problems in malaria control and thus the development of new drugs becomes urgent. The study presented here sought to evaluate the antimalarial activities of compounds derived from 2-amino-1,4-naphthoquinones containing 1,2,3-triazole using in vivo and in vitro models. 1H-1,2,3-Triazole 2-amino-1,4-naphthoquinone derivatives were synthesized and evaluated for antimalarial activity in vitro, using P. falciparum W2 chloroquine (CQ) resistant strain and in vivo using the murine-P. berghei ANKA strain. Acute toxicity was determined as established by the OECD (2001). Cytotoxicity was evaluated against HepG2 and Vero mammalian cell lines. Transmission electron microscopy of the Plasmodium falciparum trophozoite (early and late stages) was used to evaluate the action of compounds derived at ultra-structural level. The compounds displayed low cytotoxicity CC₅₀ > 100 μM, neither did they cause hemolysis at the tested doses and nor the signs of toxicity in the in vivo acute toxicity test. Among the five compounds tested, one showed IC₅₀ values in submicromolar range of 0.8 μM. Compounds 7, 8 and 11 showed IC₅₀ values < 5 μM, and selectivity index (SI) ranging from 6.8 to 343 for HepG2, and from 13.7 to 494.8 for Vero cells. Compounds 8 and 11 were partially active against P. berghei induced parasitemia in vivo. Analysis of the ultrastructural changes associated with the treatment of these two compounds, showed trophozoites with completely degraded cytoplasm, loss of membrane integrity, organelles in the decomposition stage and possible food vacuole deterioration. Our results indicated that compounds 8 and 11 may be considered hit molecules for antimalarial drug discovery platform and deserve further optimization studies.

Synthesis, characterization, antioxidant and antiparasitic activities new naphthyl-thiazole derivatives

In this work, 13 thiosemicarbazones (1a - m) and 16 thiazoles (2a - p) were obtained, which were properly characterized by spectroscopic and spectrometric techniques. The pharmacokinetic properties obtained in silico revealed that the derivatives are in accordance with the parameters established by lipinski and veber, showing that such compounds have good bioavailability or permeability when administered orally. In assays of antioxidant activity, thiosemicarbazones showed moderate to high antioxidant potential when compared to thiazoles. In addition, they were able to interact with albumin and DNA. Screening assays to assess the toxicity of compounds to mammalian cells revealed that thiosemicarbazones were less toxic when compared to thiazoles. In relation to in vitro antiparasitic activity, thiosemicarbazones and thiazoles showed cytotoxic potential against the parasites Leishmania amazonensis and Trypanosoma cruzi. Among the compounds, 1b, 1j and 2l stood out, showing inhibition potential for the amastigote forms of the two parasites. As for the in vitro antimalarial activity, thiosemicarbazones did not inhibit Plasmodium falciparum growth. In contrast, thiazoles promoted growth inhibition. This study shows in a preliminary way that the synthesized compounds have antiparasitic potential in vitro.

Expanding the scope of novel 1,2,3-triazole derivatives as new antiparasitic drug candidates

We have previously shown that prenyl and aliphatic triazoles are interesting motifs to prepare new chemical entities for antiparasitic and antituberculosis drug development. In this opportunity a new series of prenyl-1,2,3-triazoles were prepared from isoprenyl azides and different alkynes looking for new antimalarial drug candidates. The compounds were prepared by copper(i) catalyzed dipolar cycloaddition of the isoprenyl azide equilibrium mixture providing exclusively 1,4-disubstituted 1,2,3-triazoles in a regiospecific fashion. The complete collection of 64 compounds was tested on chloroquine-sensitive (CQ sensitive), Sierra Leone (D6), and the chloroquine-resistant, Indochina (W2), strains of Plasmodium falciparum and those compounds which were not previously reported were also tested against Leishmania donovani, the causative agent for visceral leishmaniasis. Thirteen analogs displayed antimalarial activity with IC50 below 10 μM, while the antileishmanial activity of the newly reported analogs could not improve upon those previously reported. Compounds 1o and 1r were identified as the most promising antimalarial drug leads with IC50 below 3.0 μM for both CQ-sensitive and resistant P. falciparum strains with high selectivity index. Finally, a chemoinformatic in silico analysis was performed to evaluate physicochemical parameters, cytotoxicity risk and drug score. The validation of a bifunctional farnesyl/geranylgeranyl diphosphate synthase PfFPPS/GGPPS as the potential target of the antimalarial activity of selected analogs should be further investigated.

Synthesis and photochemistry of novel 1,2,3-triazole di-heterostilbenes. An experimental and computational study

The synthesis, photoreactivity, and spectroscopic characterization of novel 1,2,3-triazole di-heterostilbenes bearing various aliphatic and aromatic substituents on the triazole rings were thoroughly explored. By introducing triazole rings into the o-divinylbenzene moiety, compared with the 2-furyl and 2-thienyl heteroanalogues, these compounds did not show any photochemical reactivity toward intramolecular cycloaddition reactions or electrocyclization processes. The research is further extended to the more in-depth examination of photochemical and photophysical characteristics of the investigated triazolo-stilbenes to explain the lack of reactivity in intramolecular photochemical cyclizations by configuration and substituent effects. Conformations of synthetically obtained novel triazoles are examined by Density Functional Theory (DFT). The time dependent-DFT approach was employed to obtain additional insight into the properties observed with UV/Vis spectroscopy. The frontier orbital energy was computationally investigated to determine the influence of cis-trans isomerism and the nature of substituents on the spectroscopic properties of the triazoles. Along with our previous studies of similar compounds containing furan and thiophene, respectively, this study shows that introducing various heteroaromatic rings induces diverse photochemistry and photophysics due to the conformational changes and change in electronic distribution within the molecular system.

Glioblastoma-specific anticancer activity of newly synthetized 3,5-disubstituted isoxazole and 1,4-disubstituted triazole-linked tyrosol conjugates

Two series of 3,5-disubstituted isoxazoles (6a-e) and 1,4-disubstituted triazoles (8a-e) derivatives have been synthesized from tyrosol (1), a natural phenolic compound, detected in several natural sources such as olive oil, and well-known by its wide spectrum of biological activities. Copper-catalyzed microwave-assisted 1,3-dipolar cycloaddition reactions between tyrosol-alkyne derivative 2 and two series of aryl nitrile oxides (5a-e) and azides (7a-e) regiospecifically afforded 3,5-disubstituted isoxazoles (6a-e) and 1,4-triazole derivatives (8a-e), respectively in quantitative yields. Synthesized compounds were purified and characterized by spectroscopic means including 1D and 2D NMR techniques and HRMS analysis. The newly prepared hybrid molecules have been evaluated for their anticancer and hemolytic activities. Results showed that most derivatives displayed significant antiproliferative activity against human glioblastoma cancer cells (U87) in a dose-dependent manner. Compounds 6d (IC₅₀ = 15.2 ± 1.0 μg/mL) and 8e (IC₅₀ = 21.0 ± 0.9 μg/mL) exhibited more potent anticancer activity. Moreover, most derivatives displayed low hemolytic activity, even at higher concentrations which suggested that these classes of compounds are suitable candidates for further in vivo investigations. The obtained results allow us to consider the newly synthesized isoxazole- and triazole-linked tyrosol derivatives as promising scaffolds for the development of effective anticancer agents.

Design, synthesis and molecular docking studies of thymol based 1,2,3-triazole hybrids as thymidylate synthase inhibitors and apoptosis inducers against breast cancer cells

Natural product produced by plants has been the backbone for numerous anticancer agents. In the present work, natural bioactive thymol based 1,2,3-triazole hybrids have been synthesized and evaluated for anticancer activity in MCF-7 and MDA-MB-231 cancer cells. The synthesized molecules displayed desired pharmacokinetic predictions for an orally available drug. Among the synthesized hybrids, compound 4-((2-isopropyl-5-methylphenoxy)methyl)-1-o-tolyl-1H-1,2,3-triazole (10) was the most potent (IC₅₀ 6.17 μM) showing comparable cytotoxity to tamoxifen (IC₅₀ 5.62 μM) and 3.2 fold inhibition to 5-fluorouracil (IC₅₀ 20.09 μM) against MCF-7 cancer cells. Whereas against MDA-MB-231 cancer cells, compound 10 (IC₅₀ 10.52 μM) and 3-(4-((2-isopropyl-5-methylphenoxy)methyl)-1H-1,2,3-triazol-1-yl)benzoic acid (12) (IC₅₀ 11.41 μM) displayed 1.42 and 1.3 fold inhibition, respectively to tamoxifen (IC₅₀ 15.01 μM) whereas 2.4 fold and 2.2 activity to 5-Florouracil (IC₅₀ 25.31 μM). Furthermore, 10 and 12 significantly inhibited thymidylate synthase enzyme with 2.4 and 1.26 fold activity to standard drug, Pemetrexed (IC₅₀ 5.39 μM) suggesting their mode of action as thymidylate synthase inhibitors. Cell cycle arrest and annexin V induced apoptosis study of compound 10 showed cell cycle arrest at the G2/M phase and induction of apoptosis in MCF-7 cells. The molecular docking was accomplished onto thymidylate synthase (TS) protein. The active compounds exhibited promising binding interactions and binding affinities into active sites. Finally, density functional theory (DFT) calculations including chemical reactivity and molecular electrostatic potential (MEP) have been performed to confirm the data obtained from docking and biological experiments. The results from this study inferred that compound 10 could be served as a lead molecule for the treatment of breast cancer.

Bioactive 1,2,3-Triazoles: An Account on their Synthesis, Structural Diversity and Biological Applications

The triazole heterocycle is a privileged scaffold in medicinal chemistry, since its structure is present in a large number of biologically active molecules, including several drugs currently in the market. Due to their vast applications, a wide variety of methods are described for their preparation, such as the 1,3-dipolar cycloaddition and processes involving diazo compounds and diazo transfer reactions. Considering the significant number of contributions from our research group to this chemistry in recent decades, in this account we discuss both the development of new methods for the synthesis of 1,2,3-triazoles and the preparation of new triazole-functionalized biologically active molecules using classical approaches.

Synthesis and antibiofilm activity of 1,2,3-triazole-pyridine hybrids against methicillin-resistant Staphylococcus aureus (MRSA)

Antibiotic-resistant bacteria are emerging at an alarming rate, posing a potential threat to human health. A series of 1,2,3-triazole-pyridine hybrids were synthesised as promising antibiofilm agents against planktonic and sessile MRSA.

Recent accomplishments on the synthetic/biological facets of pharmacologically active 1H-1,2,3-triazoles

The continuous demand of medicinally important scaffolds has prompted the synthetic chemists to identify simple and efficient routes for their synthesis. 1H-1,2,3-triazole, obtained by highly versatile, efficacious and selective "Click Reaction" has become a synthetic/medicinal chemist's favorite not only because of its ability to mimic different functional groups but also due to enhancement in the targeted biological activities. Triazole ring has also been shown to play a critical role in biomolecular mimetics, fragment-based drug design, and bioorthogonal methodologies. In addition, the availability of triazole containing drugs such as fluconazole, furacyclin, etizolam, voriconazole, triozolam etc. in market has underscored the potential of this biologically enriched core in expediting development of new scaffolds. The present review, therefore, is an attempt to highlight the recent synthetic/biological advancements in triazole derivatives that could facilitate the in-depth understanding of its role in the drug discovery process.

Water-Compatible Synthesis of 1,2,3-Triazoles under Ultrasonic Conditions by a Cu(I) Complex-Mediated Click Reaction

A new monophosphine Cu(I) complex bearing bis(pyrazolyl)methane (L 1 ) (CuIL 1 PPh 3 ) was synthesized and used as a catalyst for the three-component click reaction from an alkyl halide, sodium azide, and terminal alkyne to furnish 1,4-disubstituted 1,2,3-triazoles in up to 93% yield. The catalyst is highly stable, compatible with oxygen/water, and works with total efficiency under ultrasonic condition. The structure of the complex was studied and confirmed by X-ray crystallography, finding a riveting relationship with its catalytic activity. This sustainable triazoles synthesis is distinguished by its high atom economy, low catalyst loading (up to 0.5 mol %), broad substrate scope, short reaction times, operational simplicity, and an easy gram-scale supply of a functionalized product for subsequent synthetic applications.

An insight into the recent development of the clinical candidates for the treatment of malaria and their target proteins

Malaria is an endemic disease, prevalent in tropical and subtropical regions which cost half of million deaths annually. The eradication of malaria is one of the global health priority nevertheless, current therapeutic efforts seem to be insufficient due to the emergence of drug resistance towards most of the available drugs, even first-line treatment ACT, unavailability of the vaccine, and lack of drugs with a new mechanism of action. Intensification of antimalarial research in recent years has resulted into the development of single dose multistage therapeutic agents which has advantage of overcoming the antimalarial drug resistance. The present review explored the current progress in the development of new promising antimalarials against prominent target proteins that have the potential to be a clinical candidate. Here, we also reviewed different aspects of drug resistance and highlighted new drug candidates that are currently in a clinical trial or clinical development, along with a few other molecules with excellent antimalarial activity overs ACTs. The summarized scientific value of previous approaches and structural features of antimalarials related to the activity are highlighted that will be helpful for the development of next-generation antimalarials.

Discovery of fast-acting dual-stage antimalarial agents by profiling pyridylvinylquinoline chemical space via copper catalyzed azide-alkyne cycloadditions

To identity fast-acting, multistage antimalarial agents, a series of pyridylvinylquinoline-triazole analogues have been synthesized via CuAAC. Most of the compounds display significant inhibitory effect on the drug-resistant malarial Dd2 strain at low submicromolar concentrations. Among the tested analogues, compound 60 is the most potent molecule with an EC₅₀ value of 0.04 ± 0.01 μM. Our current study indicates that compound 60 is a fast-acting antimalarial compound and it demonstrates stage specific action at the trophozoite phase in the P. falciparum asexual life cycle. In addition, compound 60 is active against both early and late stage P. falciparum gametocytes. From a mechanistic perspective, compound 60 shows good activity as an inhibitor of β-hematin formation. Collectively, our findings suggest that fast-acting agent 60 targets dual life stages of the malarial parasites and warrant further investigation of pyridylvinylquinoline hybrids as new antimalarials.

Plasmodium falciparum Knockout for the GPCR-Like PfSR25 Receptor Displays Greater Susceptibility to 1,2,3-Triazole Compounds That Block Malaria Parasite Development

The search for new compounds with antimalarial activity is urgent, as resistance to ones in the classical drug, has already been described in more than one continent. Compounds derived from 1,2,3-triazoles are effective against parasites and bacteria. Here, we evaluated the potential antimalarial activity against the human malaria parasite Plasmodium falciparum in a culture of fifty-four triazole compounds derived from 1H-and 2H-1,2,3-triazole. We identified thirty-one compounds with potential antimalarial activity at concentrations in the micromolar order (µM) and IC₅₀ values ranging from 2.80 µM (9) to 29.27 µM (21). Then, we selected some of these compounds to perform the same tests on the PfSR25- strain (knockout for P. falciparum G-protein coupled receptor-like, SR25). Our experiences with the PfSR25- strain showed that both compounds with higher antimalarial activity for the 3D7 strain and those with less activity resulted in lower IC₅₀ values for the knockout strain. The cytotoxicity of the compounds was evaluated in human renal embryonic cells (HEK 293), using MTT assays. This demonstrated that the compounds with the highest activity (9, 13, 19, 22, 24, 29), showed no toxicity at the tested concentrations.

An epigrammatic status of the 'azole'-based antimalarial drugs

The development of multidrug resistance in the malarial parasite has sabotaged majority of the eradication efforts by restraining the inhibition profile of first line as well as second line antimalarial drugs, thus necessitating the development of novel pharmaceutics constructed on appropriate scaffolds with superior potency against the drug-resistant and drug-susceptible Plasmodium parasite. Over the past decades, the infectious malarial parasite has developed resistance against most of the contemporary therapeutics, thus necessitating the rational development of novel approaches principally focused on MDR malaria. This review presents an epigrammatic collation of the epidemiology and the contemporary antimalarial therapeutics based on the 'azole' motif.

Malaria Hybrids: A Chronological Evolution

Malaria, an upsetting malaise caused by a diverse class of Plasmodium species affects about 40% of the world's population. The distress associated with it has reached colossal scales owing to the development of resistance to most of the clinically available agents. Hence, the search for newer molecules for malaria treatment and cure is an incessant process. After the era of a single molecule for malaria treatment ended, there was an advent of combination therapy. However, lately there had been reports of the development of resistance to many of these agents as well. Subsequently, at present most of the peer groups working on malaria treatment aim to develop novel molecules, which may act on more than one biological processes of the parasite life cycle, and these scaffolds have been aptly termed as Hybrid Molecules or Double Drugs. These molecules may hold the key to hitherto unknown ways of showing a detrimental effect on the parasite. This review enlists a few of the recent advances made in malaria treatment by these hybrid molecules in a sequential manner.

Triazole derivatives and their antiplasmodial and antimalarial activities

Malaria, caused by protozoan parasites of the genus Plasmodium especially by the most prevalent parasite Plasmodium falciparum, represents one of the most devastating and common infectious disease globally. Nearly half of the world population is under the risk of being infected, and more than 200 million new clinical cases with around half a million deaths occur annually. Drug therapy is the mainstay of antimalarial therapy, yet current drugs are threatened by the development of resistance, so it's imperative to develop new antimalarials with great potency against both drug-susceptible and drug-resistant malaria. Triazoles, bearing a five-membered heterocyclic ring with three nitrogen atoms, exhibit promising in vitro antiplasmodial and in vivo antimalarial activities. Moreover, several triazole-based drugs have already used in clinics for the treatment of various diseases, demonstrating the excellent pharmaceutical profiles. Therefore, triazole derivatives have the potential for clinical deployment in the control and eradication of malaria. This review covers the recent advances of triazole derivatives especially triazole hybrids as potential antimalarials. The structure-activity relationship is also discussed to provide an insight for rational designs of more efficient antimalarial candidates.

Design, Synthesis, and Biological Evaluation of New 1-(Aryl-1 H-pyrrolyl)(phenyl)methyl-1 H-imidazole Derivatives as Antiprotozoal Agents

We have designed and synthesized a series of new imidazole-based compounds structurally related to an antiprotozoal agent with nanomolar activity which we identified recently. The new analogues possess micromolar activities against Trypanosoma brucei rhodesiense and Leishmania donovani and nanomolar potency against Plasmodium falciparum. Most of the analogues displayed IC₅₀ within the low nanomolar range against Trypanosoma cruzi, with very high selectivity toward the parasite. Discussion of structure-activity relationships and in vitro biological data for the new compounds are provided against a number of different protozoa. The mechanism of action for the most potent derivatives (5i, 6a-c, and 8b) was assessed by a target-based assay using recombinant T. cruzi CYP51. Bioavailability and efficacy of selected hits were assessed in a T. cruzi mouse model, where 6a and 6b reduced parasitemia in animals >99% following intraperitoneal administration of 25 mg/kg/day dose for 4 consecutive days.

Biological evaluation and structure-activity relationships of imidazole-based compounds as antiprotozoal agents

We discovered a series of azole antifungal compounds as effective antiprotozoal agents. They displayed promising inhibitory activities within the micromolar-submicromolar range against P. falciparum, L. donovani, and T. b. rhodesiense. Moreover, most of such compounds showed excellent nanomolar IC₅₀ against T. cruzi, showing also very low cytotoxicity. Discussion of structure-activity relationships and biological data for these compounds are provided against the different parasites. To assess the mechanism of action against T. cruzi we proved that the most potent compounds (3b, 3j-l) inhibited the T. cruzi CYP51. Moreover, the most active derivative 3j dramatically reduced parasitemia in T. cruzi mouse model without acute toxicity.