Antitumoral activity of different Amaryllidaceae alkaloids: In vitro and in silico assays.

ETHNOPHARMACOLOGY RELEVANCE: The plants of Amaryllidaceae family, such as Amaryllis belladonna L., have been used as herbal remedies for thousands of years to address various disorders, including diseases that might today be identified as cancer. AIM OF THE STUDY: The objective of this work was to evaluate the potential of three Amaryllidaceae alkaloids against four cancer cell lines. MATERIAL AND METHODS: The alkaloids lycorine, 1-O-acetylcaranine, and montanine were evaluated in vitro against colon adenocarcinoma cell line (HCT-116) and breast carcinoma cell lines (MCF-7, MDAMB231, and Hs578T). Computational experiments (target prediction and molecular docking) were conducted to gain a deeper comprehension of possible interactions between these alkaloids and potential targets associated with these tumor cells. RESULTS: Montanine presented the best results against HCT-116, MDAMB231, and Hs578T cell lines, while lycorine was the most active against MCF-7. In alignment with the target prediction outcomes and existing literature, four potential targets were chosen for the molecular docking analysis: CDK8, EGFR, ER-alpha, and dCK. The docking scores revealed two potential targets for the alkaloids with scores similar to co-crystallized inhibitors and substrates: CDK8 and dCK. A visual analysis of the optimal docked configurations indicates that the alkaloids may interact with some key residues in contrast to the other docked compounds. This observation implies their potential to bind effectively to both targets. CONCLUSIONS: In vitro and in silico results corroborate with data literature suggesting the Amaryllidaceae alkaloids as interesting molecules with antitumoral properties, especially montanine, which showed the best in vitro results against colorectal and breast carcinoma. More studies are necessary to confirm the targets and pharmaceutical potential of montanine against these cancer cell lines.

In silico Prediction of ADMET/Drug-likeness Properties of Bioactive Phloroglucinols from Hypericum Genus.

BACKGROUND: Dimeric acylphloroglucinols occurring in species from sections Brathys and Trigynobrathys of the genus Hypericum exhibit acylfilicinic acid and acylphloroglucinol moieties linked by a methylene bridge. However, this chemical feature differs from hyperforin, from H. perforatum (Hypericum section). Some dimeric acylphloroglucinols, such as uliginosin B, display similar pharmacological activities, namely antidepressant and antinociceptive. However, there is no knowledge about the pharmacokinetic profile and no toxicity studies of these compounds in intact mammals. OBJECTIVE: To perform an in silico evaluation of the similarity, pharmacokinetics and toxicity (ADMET) properties of dimeric acylphloroglucinols from species native to Central and South America. METHODS: ADMET prediction of eleven elected phloroglucinols followed by the chemical space evaluation of thirty-five dimeric acylphloroglucinols derivatives labeled according to their prenylation/ geranylation pattern through principal component analysis (PCA). The similarity analysis was performed using the Tanimoto similarity index. ADMET properties were predicted with the opensource software SwissADME and pkCSM-pharmacokinetics. RESULTS: Several compounds showed good human intestinal absorption. However, they may present difficulties in crossing the blood-brain barrier, probably due to the high tPSA values. The predicted toxicity parameters indicated that most compounds have low toxicity. Most non-prenylated phloroglucinols were disposed into Lipinski's rule limits. Uliginosin B, isouliginosin B and japonicin A seem to be druglike compounds. The PCA model explained 77.49% of the total variance, and molecular similarity analyses revealed some expected similarities between isomers and different compounds. CONCLUSION: Dimeric acylphloroglucinols may be promising drug candidates and deserve further pharmacological and medicinal chemistry studies.

LaSOM 335, active against bladder cancer cells, interferes with Let-60 (hRas) and reduces CD73 expression/activity.

Bladder cancer is the fourth most common malignancy in men. It can present along the entire continuum of severity, from mild to well-differentiated disease to extremely malignant tumors with low survival rates. Human RAS genes are the most frequently mutated oncogenes in human cancers, and the critical role of aberrant Ras protein function in carcinogenesis is well established. Therefore, considerable efforts have been devoted to the development of anti-Ras inhibitors for cancer treatment. This study presents the biphenyl dihydropyrimidinone LaSOM 335 with high activity against T24 bladder cancer cells (IC50 = 10.73 ± 0.53 µM) and selectivity of cytotoxicity for this cancer cell line compared to two non-cancer cell lines investigated. Furthermore, we also show that this compound reduced vulvar development in the mutant let-60 gene of Caenorhabditis elegans. Let-60 is a homolog of the mammalian Ras gene. In addition, we observed that LaSOM 335 inhibits the enzymatic activity of CD73 and decreases CD73 expression. Possibly, this expression decrease is due to downstream EGFR signaling via the Ras-Raf-ERK pathway, that directly regulates CD73 expression via ERK1/2. Evidence suggests that non-immunomodulating functions of CD73 play an equally important role for cancer cell survival, progression, and migration. Regarding we also notice that LaSOM 335 was safe in the in vivo model of C. elegans. The set of these findings makes this biphenyl dihydropyrimidinone a promising candidate for further investigations in the bladder cancer field.

Antiproliferative activity and toxicity evaluation of 1,2,3-triazole and 4-methyl coumarin hybrids in the MCF7 breast cancer cell line.

Four coumarin-triazole hybrids were selected from our in house library and screened for cytotoxic activity on A549 (lung cancer), HepG2 (liver cancer), J774A1 (mouse sarcoma macrophage), MCF7 (breast cancer), OVACAR (ovarian cancer), RAW (murine leukaemia macrophage), and SiHa (uterus carcinoma) and their in vitro toxicity was assessed on 3T3 (healthy fibroblasts) cell lines. SwissADME pharmacokinetic prediction was performed. Effects on ROS production, mitochondrial membrane potential, apoptosis/necrosis and DNA damage were evaluated. All of the hybrids have good pharmacokinetic predictions. Each of them showed cytotoxic activity against the MCF7 breast cancer cell line, with IC50 between 2.66 and 10.08 µM, lower than cisplatin (45.33 µM) for the same test. One can observe an order of reactivity from the most potent: LaSOM 186 > LaSOM 190 > LaSOM 185 > LaSOM 180, with a better selectivity index than the reference drug cisplatin and the precursor hymecromone, and caused cell death by apoptosis induction. Two compounds showed antioxidant activity in vitro and three disrupted the mitochondrial membrane potential. None of the hybrids caused genotoxic damage to healthy 3T3 cells. All hybrids showed potential for further optimization, mechanism elucidation, in vivo activity and toxicity tests.

Targeting ecto-5'-nucleotidase: A comprehensive review into small molecule inhibitors and expression modulators.

The purinergic signaling has drawn attention from academia and more recently from pharmaceutical industries as a potential therapeutic route for cancer treatment, since ATP may act as chemotactic agent and possess in vitro antineoplastic activity. On the other way, adenosine, produced in extracellular medium by ecto-5'-NT, acts as immunosuppressor and is related to neoangiogenesis, vasculogenesis and evasion to the immune system. Consequently, inhibitors of ecto-5'-NT may prevent tumor progression, reducing adenosine concentrations, preventing escape from the host's immune system and slowing cancer's growth. This review aims to highlight important biochemical and structural features of ecto-5'NT, highlight its expression profile in normal and cancer cell lines detailing compounds which may act as expression regulators and to review the several classes of ecto-5'NT inhibitors developed in the past 12 years, in order to build a general structure-activity relationship model to guide further compound design.

The Role of Alternative Toxicological Trials in Drug Discovery Programs. The Case of Caenorhabditis elegans and Other Methods.

The discovery of a new drug requires over a billion dollars and around 12 years of research efforts, and toxicity is the leading reason for the failure to approve candidate drugs. Many alternative methods have been validated to detect toxicity as early as possible to diminish the waste of resources and efforts in medicinal chemistry research, and in vivo alternative methods are especially valuable for the amount of information they can provide at little cost and in a short time. In this work, we present a review of the literature published between the years 2000 and 2021 on in vivo alternative methods of toxicity screening employed in medicinal chemistry, which we believe will be useful because, in addition to shortening the research time, these studies provide much additional information aside from the toxicity of drug candidate compounds. These in vivo models include zebrafish, Artemia salina, Galleria mellonella, Drosophila melanogaster, planarians, and Caenorhabditis elegans. The most published ones in the last decade were zebrafish, D. melanogaster, and C. elegans due to their reliability, ease, and cost-effectiveness in implementation and flexibility. Special attention is given to C. elegans because of its rising popularity, a wide range of uses, including toxicity screening, and active effects measurement, from antioxidant effects to anthelmintic and antimicrobial activities, and its fast and reliable results. Over time, C. elegans also became a viable high-throughput (HTS) automated drug screening option. Additionally, this manuscript lists briefly the other screening methods used for the initial toxicological analyses and the role of alternative in vivo methods in these scenarios, classifying them as in silico, in vitro and alternative in vivo models that have been receiving a growing increase in interest in recent years.

Exploring the N1 Position of Biginelli Compounds: New Insights and Trends for Chemical Diversity Generation of Bioactive Derivatives.

Dihydropyrimidinones (DHPMs) are heterocycles obtained by the multicomponent Biginelli reaction. Recently, new synthetic protocols have allowed us to explore functionalisation at less explored positions of DHPMs, such as the N1 position. In this context, a full literature survey of N1- substituted DHPMs was performed. We analysed 27 papers and identified 379 compounds with substituents at the N1 position, most of them with alkyl groups, and a total of 28% compounds with aromatic substituents attached at the N1 position. N1-substituted DHPMs were explored mainly due to their effects on cancer cell proliferation via numerous targets, such as kinesin Eg5, heat shock protein 70, heat shock protein 90, and the epidermal growth factor receptor. Similarity analyses were performed using the data of 379 DHPMs from different cheminformatic approaches, i.e., chemical property correlations, principal component analysis, similarity networks, and compound clustering.

Revisiting nature: a review of iridoids as a potential antileishmanial class.

Leishmaniasis still stands as one of the most prevalent neglected tropical diseases in the least developed and emerging countries. The recommended therapeutic arsenal to treat leishmaniasis is characterized by several shortcomings, and resistance has already been reported. Hence, this dramatic background highlights the pressing need to develop novel, affordable, and safe antileishmanial drugs. Multiple classes of natural compounds have been reported to possess antileishmanial activity. Among these classes, iridoids stand out as a special type of monoterpenoids with diverse biological properties-including their antileishmanial potential. This review aims to discuss the available literature between 1991 and 2020 related to the antileishmanial activity of the iridoid class. Throughout the past decades, various investigations attributed antileishmanial action to assorted iridoid types, including inhibitory potential towards validated drug targets and immunomodulatory activity. The latter deserves special attention due to the ability of some iridoids to improve the host's immune response against parasites. It opens the possibility of iridoids become adjuncts in leishmaniasis treatments by improving the efficacy of currently employed drugs. Furthermore, the present study intends to provide a convenient visual representation of which iridoids and Leishmania spp. species have been most investigated as a guide for further researches.

New insights into cytotoxic mechanisms of bozepinib against glioblastoma.

Glioblastoma (GBM) is the most frequent and aggressive brain tumor in adults and the current treatments only have a modest effect on patient survival. Recent studies show that bozepinib (BZP), a purine derivative, has potential applications in cancer treatment. The aim of this study was to evaluate the effect of BZP against GBM cells, specially concerning the purinergic system. Thus, GBM cells (C6 and U138 cell lines) were treated with BZP and cell viability, cell cycle, and annexin/PI assays, and active caspase-3 measurements were carried out. Besides, the effect of BZP over the purinergic system was also evaluated in silico and in vitro. Finally, we evaluate the action of BZP against important markers related to cancer progression, such as Akt, NF-κB, and CD133. We demonstrate here that BZP reduces GBM cell viability (IC50 = 5.7 ± 0.3 µM and 12.7 ± 1.5 µM, in C6 and U138 cells, respectively), inducing cell death through caspase-dependent apoptosis, autophagosome formation, activation of NF-κB, without any change in cell cycle progression or on the Akt pathway. Also, BZP modulates the purinergic system, inducing an increase in CD39 enzyme expression and activity, while inhibiting CD73 activity and adenosine formation, without altering CD73 enzyme expression. Curiously, one cycle of treatment resulted in enrichment of GBM cells expressing NF-κB and CD133+, suggesting resistant cells selection. However, after another treatment round, the resistant cells were eliminated. Altogether, BZP presented in vitro anti-glioma activity, encouraging further in vivo studies in order to better understand its mechanism of action.

Discovery, development, chemical diversity and design of isoxazoline-based insecticides.

Isoxazoline is a 5-membered heterocycle present in the active compounds of many commercial veterinary anti-ectoparasitic products. The molecular target of isoxazolines is the inhibition of GABA-gated chloride channels in insects. These facts have inspired the use of the isoxazoline scaffold in the design of novel insecticide compounds. The main strategies used for isoxazoline synthesis are either the 1,3-dipolar cycloaddition between a nitrile oxide and an alkene or the reaction between hydroxylamine and an α,ß-unsaturated carbonyl compound. This review highlights the utilization of isoxazoline as insecticide: its mode of action, its commercial preparations and its consideration in the design of novel insecticides. Similarity analyses were performed with 235 isoxazoline derivatives in three different cheminformatic approaches - chemical property correlations, similarity network and compound clustering. The cheminformatic methodologies are interesting tools to use in evaluating the similarity between commercial isoxazolines and to clarify the main features explored within their derivatives.

Chagas Disease and Coumarins: A Review of Natural and Synthetic Coumarins As Anti-Trypanosoma Cruzi Agents.

The complexity of Chagas disease is still a challenge in endemic regions and an emergent public health problem in non-endemic countries. The causative agent of this neglected tropical disease, Trypanosoma cruzi, is mainly transmitted by triatomine vectors and possesses multiple epidemiologically important strains. Current chemotherapeutics are outdated and their limited efficacy is one of the major reasons for treatment discontinuation. In this context, the development of novel, safe and economically accessible antichagasic drugs is required. Various classes of heterocycles and natural compounds have been described as potential antichagasic scaffolds, and coumarins are no exception. These versatile compounds have a wide spectrum of biological activities, and numerous natural and synthetic coumarins have been reported with antichagasic potential. This review aims to discuss the available literature between 2001 and 2020 regarding natural and synthetic coumarins with anti- Trypanosoma cruzi activity. Moreover, some of the studies herein comprised are dedicated to the potential of coumarins to inhibit promising targets in Trypanosoma cruzi.

Geo-Measures: A PyMOL plugin for protein structure ensembles analysis.

Although molecular dynamics encompasses several applications, studies focusing on biomolecular systems are central issues of this research area. Such simulations require the generation of trajectory files, which provide a path for the analysis and interpretation of results with biological significance. However, although several programs have been developed in Python language for the analyses of molecular dynamics (MD) trajectories, they usually require some knowledge of programming languages in order to write or run the scripts using command lines, which certainly hinders the access of MD simulations to many scientists with the necessary biological background to interpret their results. To ease the access to Python packages focusing on MD trajectory analyses, we built a user-friendly and easy-to-install graphical PyMOL interface. Geo-Measures integrates the PyMOL functionalities with MDTraj, a powerful library of trajectory analyses, allowing the users to access up to 14 different types of analyses. Two sample cases are reported here to demonstrate the use of Geo-Measures. In the first example, which involves the use a MD trajectory file of hemoglobin from the MoDEL MD bank, we exemplified the analyses of the following variables: root mean square deviation, radius of gyration, free energy landscape and principal component analysis. In the second case, we built a trajectory file for the ecto-5'-nucleotidase using the LiGRO program to study the carbon alpha pincer angles, to define the secondary structure of the proteins and to analyze the Modevectors. This user-friendly graphical PyMOL plugin, which can be used to generate several descriptive analyses for protein structures, is open source and can be downloaded at: https://pymolwiki.org/index.php/Geo_Measures_Plugin.

New pharmacological findings linked to biphenyl DHPMs, kinesin Eg5 ligands: anticancer and antioxidant effects.

Background: Dihydropyrimidin-2-thiones (DHPMs) are a class of heterocyclic compound which have been intensively investigated mainly due to their anticancer activity as kinesin Eg5 inhibitors. Materials & methods: A library of N1 aryl substituted DHPMs were tested against glioma and bladder cancer cell lines. Quantitative structure-activity relationship (QSAR) investigation was performed in order to identify key elements of DHPMs linked with their antiproliferative effect. The toxicity of most active compounds was investigated using Caenorhabditis elegans as the model. Results & conclusion: DHPMs 9, 13 and 17 have been identified as having improved activity against glioma and bladder cell lines as compared with monastrol. Flow cytometry investigations showed that the new compounds induce cell cycle arrest in phase G2/M and cell death by apoptosis. In addition, compound 13 was able to modulate the reactive oxygen species production in vivo in C. elegans. The biphenyl dihydropyrimidinthiones provided a safety profile in C. elegans.

Insight into Out-of-Layer Fluctuations in the Smectic A Stability of 3,5-Diarylisoxazole Liquid Crystals.

Polar-terminated 3,5-diarylisoxazole liquid crystals (ILCs) were synthetized and characterized. ILCs are composed by rigid core 3,5-diarylisoxazol, alkyl chain and polar-terminated flexible spacer. Hydroxyl-, ketal- and 1,2-diol-terminated ILCs rendered smectic C and A mesophase, while bromine-terminated ILCs showed smectic A and B mesophase, for monosubstituted and linear ILCs. For branched alkyl chain monotropic SmA was detected and for disubstituted ILCs no mesophase was detected. Out-of-layer fluctuations (OLFs) are discussed based on X-ray diffraction date and textures. The OLFs are dependent on the bromine atom hardness, hydrogen bonding through collective actions and conformational effects at the interface between layers. Smectic translational order parameter (TOP) Σ was also obtained for orientated bromine- and hydroxyl-terminated ILCs and related it with OLFs. For 1,2-diol-terminated ILCs two SmC sublayers were founded, probably related to the intramolecular hydrogen bond favoring the 5-membered and 6-membered formation.

The use of isoxazoline and isoxazole scaffolding in the design of novel thiourea and amide liquid-crystalline compounds.

A series of novel thiourea and amide liquid crystals containing 5-membered isoxazoline and isoxazole rings were synthetized and the liquid crystal properties studied. Thioureas were obtained using a condensation reaction of benzoyl chlorides, arylamines and ammonium thiocyanate. The amides, on the other hand, were the byproduct of a quantitative reaction which used potassium cyanate as the starting material. Thiourea and amide derivatives were predominantly SmA mesophase inductors. A nematic mesophase was observed only for thioureas and amides containing an isoxazole ring. Additionaly, the liquid crystal behavior was also dependent on the relative position of nitrogen and oxygen atoms on the 5-membered heterocycle.

Piperazine designer drugs elicit toxicity in the alternative in vivo model Caenorhabditis elegans.

Piperazine designer drugs are a group of synthetic drugs of abuse that have appeared on the illicit market since the second half of the 1990s. The most common derivatives are 1-benzylpiperazine (BZP), 1-(4-methoxyphenyl)piperazine (MeOPP) and 1-(3,4-methylenedioxybenzyl)piperazine (MDBP). They can be consumed as capsules, tablets, but also in powder or liquid forms. Generally, although less potent than amphetamines, piperazines have dopaminergic and serotonergic activities. The aim of this work was to evaluate the toxic effects of BZP, MeOPP and MDBP using Caenorhabditis elegans as in vivo model for acute toxicity, development, reproduction and behavior testing. The LC50 for BZP, MeOPP and MDBP were 52.21, 5.72 and 1.22 mm, respectively. All concentrations induced a significant decrease in the body surface of the worms, indicating developmental alterations, and decrease in the brood size. Worms exposed to piperazine designer drugs also presented a decrease in locomotor activity and mechanical sensitivity, suggesting the possible dysfunction of the nervous system. Neuronal damage was confirmed through the decrease in fluorescence of BY200 strains, indicating loss of dopaminergic transporters. In conclusion, we suggest that piperazine designer drugs lead to neuronal damage, which might be the underlying cause of the altered behavior observed in humans.

Melatonin-loaded lipid-core nanocapsules protect against lipid peroxidation caused by paraquat through increased SOD expression in Caenorhabditis elegans.

BACKGROUND: Melatonin has been described in the literature as a potent antioxidant. However, melatonin presents variable, low bioavailability and a short half-life. The use of polymeric nanoparticulated systems has been proposed for controlled release. Thus, the purpose of this study was to investigate the action of melatonin-loaded lipid-core nanocapsules (Mel-LNC) in the antioxidant system of Caenorhabditis elegans, and the possible protective effect of this formulation against lipid peroxidation caused by paraquat (PQ). METHODS: The suspensions were prepared by interfacial deposition of the polymer and were physiochemically characterized. C. elegans N2 wild type and transgenic worm CF1553, muls84 [sod-3p::gfp; rol6(su1006)] were obtained from the Caenorhabditis Genetics Center (CGC). The worms were divided into 5 groups: Control, PQ 0.5 mM, PQ 0.5 mM + Mel-LNC 10 µg/mL, PQ + unloaded lipid-core nanocapsules (LNC), and PQ + free melatonin (Mel) 10 µg/mL. The lipid peroxidation was assessed through thiobarbituric acid (TBARS) levels and the fluorescence levels of the transgenic worms expressing GFP were measured. RESULTS: The LNC and Mel-LNC presented a bluish-white liquid, with pH values of 5.56 and 5.69, respectively. The zeta potential was - 6.4 ± 0.6 and - 5.2 ± 0.2, respectively. The mean particle diameter was 205 ± 4 nm and 203 ± 3 nm, respectively. The total melatonin content was 0.967 mg/ml. The TBARS levels were significantly higher in the PQ group when compared to the control group (p < 0.001). Mel-LNC reduced TBARS levels to similar levels found in the control group. Moreover, only Mel-LNC significantly enhanced the SOD-3 expression (p < 0.05). Mel-LNC was capable of protecting C. elegans from lipid peroxidation caused by PQ and this was not observed when free melatonin was used. Moreover, Mel-LNC increased the fluorescence intensity of the transgenic strain that encodes the antioxidant enzyme SOD-3, demonstrating a possible mechanism of protection from PQ-induced damage. CONCLUSION: These findings demonstrated that melatonin, when associated with nanocapsules, had improved antioxidant properties and the protective activity against PQ-induced lipid peroxidation could be associated with the activation of antioxidant enzymes by Mel-LNC in C. elegans.

Novel coumarins active against Trypanosoma cruzi and toxicity assessment using the animal model Caenorhabditis elegans.

BACKGROUND: Chagas disease (CD) is a tropical parasitic disease. Although the number of people infected is very high, the only drugs available to treat CD, nifurtimox (Nfx) and benznidazole, are highly toxic, particularly in the chronic stage of the disease. Coumarins are a large class of compounds that display a wide range of interesting biological properties, such as antiparasitic. Hence, the aim of this work is to find a good antitrypanosomal drug with less toxicity. The use of simple organism models has become increasingly attractive for planning and simplifying efficient drug discovery. Within these models, Caenorhabditis elegans has emerged as a convenient and versatile tool with significant advantages for the toxicological potential identification for new compounds. METHODS: Trypanocidal activity: Forty-two 4-methylamino-coumarins were assayed against the epimastigote form of Trypanosoma cruzi (Tulahuen 2 strain) by inhibitory concentration 50% (IC50). Toxicity assays: Lethal dose 50% (LD50) and Body Area were determined by Caenorhabditis elegans N2 strain (wild type) after acute exposure. Structure-activity relationship: A classificatory model was built using 3D descriptors. RESULTS: Two of these coumarins demonstrated near equipotency to Nifurtimox (IC50 = 5.0 ± 1 µM), with values of: 11 h (LaSOM 266), (IC50 = 6.4 ± 1 µM) and 11 g (LaSOM 231), (IC50 = 8.2 ± 2.3 µM). In C. elegans it was possible to observe that Nfx showed greater toxicity in both the LD50 assay and the evaluation of the development of worms. It is possible to observe that the efficacy between Nfx and the synthesized compounds (11 h and 11 g) are similar. On the other hand, the toxicity of Nfx is approximately three times higher than that of the compounds. Results from the QSAR-3D study indicate that the volume and hydrophobicity of the substituents have a significant impact on the trypanocidal activities for derivatives that cause more than 50% of inhibition. These results show that the C. elegans model is efficient for screening potentially toxic compounds. CONCLUSION: Two coumarins (11 h and 11 g) showed activity against T. cruzi epimastigote similar to Nifurtimox, however with lower toxicity in both LD50 and development of C. elegans assays. These two compounds may be a feasible starting point for the development of new trypanocidal drugs.

Targeting pteridine reductase 1 and dihydrofolate reductase: the old is a new trend for leishmaniasis drug discovery.

Leishmaniasis is one of the major neglected tropical diseases in the world and it is considered endemic in 88 countries. This disease is transmitted by a Leishmania spp. infected sandfly and it may lead to cutaneous or systemic manifestations. The preconized treatment has low efficacy and there are cases of resistance to some drugs. Therefore, the search for new efficient molecular targets that can lead to the preparation of new drugs must be pursued. This review aims to evaluate both Leishmania enzymes PTR1 and DHFR-TS as potential drug targets, highlight their inhibitors and to discuss critically the use of chemoinformatics to elucidate interactions and propose new molecules against these enzymes.

In vitro and in silico Activity of Iridoids Against Leishmania amazonensis.

BACKGROUND: Leishmaniasis reaches millions of people around the world. The control of the disease is difficult due to the restricted access to the diagnosis and medication, and low adherence to the treatment. Thus, more efficient drugs are needed and natural products are good alternatives. Iridoids, natural products with reported leishmanicidal activity, can be exploited for the development of anti- Leishmania drugs. The aim of this study was to isolate and to investigate the in vitro activity of iridoids against Leishmania amazonensis and to compare the activity in silico of these compounds with those reported as active against this parasite. METHODS: Iridoids were isolated by chromatographic methods. The in vitro activity of asperuloside (1) and geniposide (2) from Escalonia bifida, galiridoside (3) from Angelonia integerrima and theveridoside (4) and ipolamiide (5) from Amphilophium crucigerum was investigated against promastigote forms of Leishmania amazonensis. Molecular modeling studies of 1-5 and iridoids cited as active against Leishmania spp. were performed. RESULTS: Compounds 1-5 (5-100 µM) did not inhibit the parasite survival. Physicochemical parameters predicted for 1-5 did not show differences compared to those described in literature. The SAR and the pharmacophoric model confirmed the importance of maintaining the cyclopentane[C]pyran ring of the iridoid, of oxygen-linked substituents at the C1 and C6 positions and of bulky substituents attached to the iridoid ring to present leishmanicidal activity. CONCLUSION: The results obtained in this study indicate that iridoids are a promising group of secondary metabolites and should be further investigated in the search for new anti-Leishmania drugs.