High selective leishmanicidal activity of 3-hydroxy-2-methylene-3-(4-bromophenyl)propanenitrile and analogous compounds

Lipase-Catalysed Enzymatic Kinetic Resolution of Aromatic Morita-Baylis-Hillman Derivatives by Hydrolysis and Transesterification

Acylated Morita-Baylis-Hillman (MBH) adducts were synthesised and subjected to enzymatic kinetic resolution (EKR) by hydrolysis employing various lipase enzymes: from P. fluorescens, P. cepacia (PCL), C. antarctica A (CAL-A), C. antarctica B (CAL-B) and Novozyme 435. In a number of instances enantiopure Morita-Baylis-Hillman acetates or butyrates and their corresponding hydrolysed MBH adducts were obtained with ee values of >90 %, at ca. 50 % conversion, corresponding to enantiomeric ratio (E) values of >200. Enantioselective transesterification reactions on MBH adducts was achieved using acyl anhydrides in THF or the greener organic solvent 2-MeTHF in the presence of CAL-A. This is the first report of successful lipase-catalysed EKR of aromatic MBH adducts by transesterification in organic medium.

In Vitro Cytotoxic and Leishmanicidal Activity of Isolated and Semisynthetic ent-Pimaranes from Aldama arenaria

Two pimaranes ent-pimara-8(14),15-dien-19-oic acid (1: ) and ent-8(14),15-pimaradien-3β-ol (2: ), isolated from Aldama arenaria, and six semi-synthetic derivatives methyl ester of the ent-pimara-8(14),15-dien-19-oic acid (3: ), ent-pimara-8(14),15-dien-19-ol (4: ), acetate of ent-pimara-8(14),15-dien-19-ol (5: ), ent-pimara-8(14),15-dien-19-ol succinic acid (6: ), acetate of ent-8(14),15-pimaradien-3β-ol (7: ), ent-8(14),15-pimaradien-3β-ol succinic acid (8: ) were evaluated in vitro for their cytotoxic activities to childhood leukemia cell lines and leishmanicidal activity against the parasite Leishmania amazonensis. Among these compounds, 1: to 6: presented moderate cytotoxic activity, with compound 4: being the most active (GI₅₀ of 2.6 µM for the HL60 line) and the derivatives 7: and 8: being inactive. Against the parasite Leishmania amazonensis, the most promising derivative was the acetate of ent-pimara-8(14),15-dien-19-ol (5: ), with EC₅₀ of 20.1 µM, selectivity index of 14.5, and significant reduction in the parasite load. Pimarane analogues 1: , ent-pimara-8(14),15-dien-19-oic acid, and 2: , ent-8(14),15-pimaradien-3β-ol, presented different activities, corroborating the application of such molecules as prototypes for the design of other derivatives that have greater cytotoxic or leishmanicidal potential.

Biological activity of Morita-Baylis-Hillman adduct homodimers in L. infantum and L. amazonensis: anti-Leishmania activity and cytotoxicity

This study is a report on the anti-Leishmania activity of Morita-Baylis-Hillman (MBH) homodimers adducts against the promastigote and axenic amastigote forms of Leishmania (Leishmania) infantum and Leishmania (Leishmania) amazonensis and on the cytotoxicity of these adducts to human blood cells. Both studied homodimers, MBH 1 and MBH 2, showed activity against the promastigote forms of L. infantum and L. amazonensis, which are responsible for visceral and cutaneous leishmaniasis, respectively. Additionally, the homodimers presented biological activity against the axenic amastigote forms of these two Leishmania species. The adducts exhibited no hemolytic activity to human peripheral blood mononuclear cells or erythrocytes at the tested concentrations and achieved higher selectivity indices than amphotericin B. Evaluation of cell death by apoptosis revealed that the homodimers had better apoptosis/necrosis profiles than amphotericin B in the promastigote forms of both L. infantum and L. amazonensis. In conclusion, these Morita-Baylis-Hillman adducts had anti-Leishmania activity in an in vitro model and may thus be promising molecules in the search for new drugs to treat leishmaniasis.

SO2F2 mediated cascade dehydrogenative Morita–Baylis–Hillman reaction of the C(sp3)–H of primary alcohols with the C(sp2)–H of electron-deficient olefins for the assembly of allylic alcohols

A cascade dehydrogenative Morita–Baylis–Hillman reaction of the C(sp³)–H of primary alcohols with the C(sp²)–H of electron-deficient olefins for forming allylic alcohols mediated by SO₂F₂ was developed. This method provides a mild process for the preparation of allylic alcohol moieties without the requirement of transition metals.

A cascade dehydrogenative Morita–Baylis–Hillman reaction of the C(sp³)–H of primary alcohols with the C(sp²)–H of electron-deficient olefins for forming allylic alcohols mediated by SO₂F₂ was developed.

One-Electron Reduction Potentials: Calibration of Theoretical Protocols for Morita⁻Baylis⁻Hillman Nitroaromatic Compounds in Aprotic Media

Nitroaromatic compounds—adducts of Morita–Baylis–Hillman (MBHA) reaction—have been applied in the treatment of malaria, leishmaniasis, and Chagas disease. The biological activity of these compounds is directly related to chemical reactivity in the environment, chemical structure of the compound, and reduction of the nitro group. Because of the last aspect, electrochemical methods are used to simulate the pharmacological activity of nitroaromatic compounds. In particular, previous studies have shown a correlation between the one-electron reduction potentials in aprotic medium (estimated by cyclic voltammetry) and antileishmanial activities (measured by the IC₅₀) for a series of twelve MBHA. In the present work, two different computational protocols were calibrated to simulate the reduction potentials for this series of molecules with the aim of supporting the molecular modeling of new pharmacological compounds from the prediction of their reduction potentials. The results showed that it was possible to predict the experimental reduction potential for the calibration set with mean absolute errors of less than 25 mV (about 0.6 kcal·mol⁻¹).

Synthesis of 16 New Hybrids from Tetrahydropyrans Derivatives and Morita-Baylis-Hillman Adducts: In Vitro Screening against Leishmania donovani

Leishmaniases are a group of neglected tropical diseases (NTDs) caused by protozoan parasites from >20 Leishmania species. Visceral leishmaniasis (VL), also known as kala-aza, is the most severe form of leishmaniasis, usually fatal in the absence of treatment in 95% of cases. The Morita-Baylis-Hillman adducts (MBHAs) are being explored as drug candidates against several diseases, one of them being leishmaniasis. We present here the design, synthesis and in vitro screening against Leishmania donovani of sixteen new molecular hybrids from analgesic/anti-inflammatory tetrahydropyrans derivatives and Morita-Baylis-Hillman adducts. First, acrylates were synthesized from analgesic/anti-inflammatory tetrahydropyrans using acrylic acid under TsOH as a catalyst (70%–75% yields). After the 16 new MBHAs were prepared in moderate to good yields (60%–95%) promoted by microwave irradiation or low temperature (0 °C) in protic and aprotic medium. The hybrids were evaluated in vitro on the promastigote stage of Leishmania donovani by determining their inhibitory concentrations 50% (IC₅₀), 50% hemolysis concentration (HC₅₀), selectivity index (HC₅₀/IC₅₀,), and comparing to Amphotericin B, chosen as the anti-leishmanial reference drug. The hybrid which presents the bromine atom in its chemical structure presents high leishmanicide activity and the high selectivity index in red blood cells (SI_rb > 180.19), compared with the highly-toxic reference drug (SI_rb = 33.05), indicating that the bromine hybrid is a promising compound for further biological studies.

Synthesis and In Vitro Anti Leishmania amazonensis Biological Screening of Morita-Baylis-Hillman Adducts Prepared from Eugenol, Thymol and Carvacrol

Leishmaniasis represents a series of severe neglected tropical diseases caused by protozoa of the genus Leishmania and is widely distributed around the world. Here, we present the syntheses of Morita-Baylis-Hillman adducts (MBHAs) prepared from eugenol, thymol and carvacrol, and their bioevaluation against promastigotes of Leishmania amazonensis. The new MBHAs are prepared in two steps from essential oils in moderate to good yields and present IC₅₀ values in the range of 22.30–4.71 μM. Moreover, the selectivity index to the most potent compound is very high (SIrb > 84.92), far better than that of Glucantime^® (SIrb 1.39) and amphotericin B (SIrb = 22.34). Conformational analysis were carried out at the M062X//6-31+G(d,p) level of theory to corroborate a hypothesis about the nitroaromatic bioreduction mechanism.

Trypanosoma cruzi cell death induced by the Morita-Baylis-Hillman adduct 3-Hydroxy-2-methylene-3-(4-nitrophenylpropanenitrile)

Chagas disease, caused by the protozoan Trypanosoma cruzi, remains a serious health concern due to the lack of effective vaccines or satisfactory treatment. In the search for new compounds against this neglected disease, we have previously demonstrated that the compound 3-Hydroxy-2-methylene-3-(4-nitrophenylpropanenitrile) (MBHA3), derived from the Morita-Baylis-Hillman reaction, effectively caused a loss of viability in both the epimastigote and trypomastigote forms. However, the mechanisms of parasite death elicited by MBHA3 remain unknown. The aim of this study was to better understand the morphophysiological changes and the mechanism of cell death induced by MBHA3 treatment on T. cruzi. To perform this analysis, we used confocal microscopy and flow cytometry to monitor the fluorescent probes such as annexin-V/propidium iodide (AV/PI), calcein-AM/ethidium homodimer (CA/EH), acridine orange (AO) and rhodamine 123 (Rho 123). Lower concentrations of MBHA3 led to alterations in the mitochondrial membrane potential and AO labeling, but did not decrease the viability of the epimastiogote forms, as determined by the CA/EH and AV/PI assays. Conversely, treatment with higher concentrations of MBHA3 led to extensive plasma membrane damage, loss of mitochondrion membrane potential, DNA fragmentation and acidification of the cytoplasm. Our findings suggest that at higher concentrations, MBHA3 induces T. cruzi epimastigote death by necrosis in a mitochondrion-dependent manner.

Morita-Baylis-Hillman adduct shows in vitro activity against Leishmania (Viannia) braziliensis associated with a reduction in IL-6 and IL-10 but independent of nitric oxide

Current treatments for different clinical forms of leishmaniasis are unsatisfactory, highly toxic and associated with increasing failure rates resulting from the emergence of resistant parasites. Leishmania (Viannia) braziliensis is the main aetiological agent of different clinical forms of American tegumentary leishmaniasis, including the mucosal form for which treatment has high failure rates. The aim of this work was to investigate the activity of the Morita-Baylis-Hillman adduct, methyl 2-{2-[hydroxy(2-nitrophenyl)methyl])acryloyloxy} benzoate in vitro against isolates of L. (V.) braziliensis obtained from patients with different clinical manifestations of tegumentary leishmaniasis: localized cutaneous leishmaniasis, mucosal leishmaniasis and disseminated cutaneous leishmaniasis. The adduct effectively inhibited the growth of promastigotes of the different isolates of L. (V.) braziliensis (IC50 ⩽ 7·77 μg/ml), as well as reduced the infection rate of macrophages infected with these parasites (EC50 ⩽ 1·37 μg/ml). It is remarkable to state that the adduct was more effective against intracellular amastigotes (P ⩽ 0·0045). The anti-amastigote activity correlated with an immunomodulatory effect, since the adduct was able to decrease the production of IL-6 and IL-10 by the infected macrophages. However, its effect was independent of nitric oxide production. This work demonstrates the anti-leishmanial activity of methyl 2-{2-[hydroxy(2-nitrophenyl)methyl])acryloyloxy} benzoate and suggests its potential in the treatment of human infections caused by L. (V.) braziliensis.

Morita-Baylis-Hillman adducts: biological activities and potentialities to the discovery of new cheaper drugs

This review aims to present by the first time the Morita-Baylis-Hillman adducts (MBHA) as a new class of bioactive compounds and highlight its potentialities to the discovery of new cheaper and efficient drugs. Now, most these compounds can be prepared fast and on a single synthetic step (one-pot reaction) in high yields and using ecofriendly synthetic protocols. We highlight here the aromatic MBHA, which have shown diverse biological activities as anti-Leishmania chagasi and Leishmania amazonensis (parasites that cause cutaneous and visceral leishmaniasis), anti-Trypanosoma cruzi (parasite that cause Chagas disease), anti-Plasmodium falciparum and Plasmodium berghei (parasites that cause malaria), lethal against Biomphalaria glabrata (the snail transmitter of schistosomiasis), antibacterial, antifungal, herbicide and actives against some human tumor cell lines. Understanding of the biological mechanisms of action of this new class of molecules is still in the infancy stage. However, we report here which has been described to date on the possibilities of biological mechanisms of action, and we present new analyzes based on literature in this area. The academic and industrial interest in selecting green and cheaper experiments to the drugs development has been the prime mover of the growth on the subject.

Antimicrobial potential of 3-hydroxy-2-methylene-3-phenylpropionic acid derivatives

Twenty Baylis-Hillman adducts were synthesized from different aromatic aldehydes and activated vinyl derivatives. The adducts, which are differently substituted 3-hydroxy-2-methylene-3-phenylpropionic acid derivatives, were screened for their antimicrobial activity in vitro by the serial dilution method. Many of these molecules displayed potent antibacterial and antifungal activities. The ease of synthesis from low-cost starting materials along with potent antimicrobial activity of these molecules provide the lead for further improvement of activity and reflect the possibility of therapeutic use.

In silico screening, structure-activity relationship, and biologic evaluation of selective pteridine reductase inhibitors targeting visceral leishmaniasis

In this study we utilized the concept of rational drug design to identify novel compounds with optimal selectivity, efficacy and safety, which would bind to the target enzyme pteridine reductase 1 (PTR1) in Leishmania parasites. Twelve compounds afforded from Baylis-Hillman chemistry were docked by using the QUANTUM program into the active site of Leishmania donovani PTR1 homology model. The biological activity for these compounds was estimated in green fluorescent protein-transfected L. donovani promastigotes, and the most potential analogue was further investigated in intracellular amastigotes. Structure-activity relationship based on homology model drawn on our recombinant enzyme was substantiated by recombinant enzyme inhibition assay and growth of the cell culture. Flow cytometry results indicated that 7-(4-chlorobenzyl)-3-methyl-4-(4-trifluoromethyl-phenyl)-3,4,6,7,8,9-hexahydro-pyrimido[1,2-a]pyrimidin-2-one (compound 7) was 10 times more active on L. donovani amastigotes (50% inhibitory concentration [IC(50)] = 3 μM) than on promastigotes (IC(50) = 29 μM). Compound 7 exhibited a K(i) value of 0.72 μM in a recombinant enzyme inhibition assay. We discovered that novel pyrimido[1,2-a]pyrimidin-2-one systems generated from the allyl amines afforded from the Baylis-Hillman acetates could have potential as a valuable pharmacological tool against the neglected disease visceral leishmaniasis.

Identification of potent chemotypes targeting Leishmania major using a high-throughput, low-stringency, computationally enhanced, small molecule screen

Patients with clinical manifestations of leishmaniasis, including cutaneous leishmaniasis, have limited treatment options, and existing therapies frequently have significant untoward liabilities. Rapid expansion in the diversity of available cutaneous leishmanicidal chemotypes is the initial step in finding alternative efficacious treatments. To this end, we combined a low-stringency Leishmania major promastigote growth inhibition assay with a structural computational filtering algorithm. After a rigorous assay validation process, we interrogated ∼200,000 unique compounds for L. major promastigote growth inhibition. Using iterative computational filtering of the compounds exhibiting >50% inhibition, we identified 553 structural clusters and 640 compound singletons. Secondary confirmation assays yielded 93 compounds with EC₅₀s ≤ 1 µM, with none of the identified chemotypes being structurally similar to known leishmanicidals and most having favorable in silico predicted bioavailability characteristics. The leishmanicidal activity of a representative subset of 15 chemotypes was confirmed in two independent assay formats, and L. major parasite specificity was demonstrated by assaying against a panel of human cell lines. Thirteen chemotypes inhibited the growth of a L. major axenic amastigote-like population. Murine in vivo efficacy studies using one of the new chemotypes document inhibition of footpad lesion development. These results authenticate that low stringency, large-scale compound screening combined with computational structure filtering can rapidly expand the chemotypes targeting in vitro and in vivo Leishmania growth and viability.

Leishmaniasis is a parasitic disease with cutaneous, mucocutaneous and visceral clinical manifestations, depending on the Leishmania spp. and human host. Globally, there are 350 million people at risk of leishmaniasis, but current treatment options rely predominantly on ancient pentavalent antimonials, which have the potential to cause serious systemic toxicity. Our research focuses on the rapid expansion of potential anti-leishmanial compounds that could function as novel chemical structures for future drug development and offer additional therapeutic options to patients with leishmaniasis. We combined high throughput screening methodologies with computational algorithms and multiple confirmatory assay formats to identify and characterize new potent L. major promastigote growth inhibitors, including one that displays in vivo activity without toxicity to human cells. Our use of a large, broadly distributed compound library enabled the identification of these new chemotypes. In addition, since this chemical library is publicly available and annotated, we were able to cross-query archived bioassays and to identify new molecular targets that may be involved in L. major growth and viability as well as identify new protein targets for future leishmanicidal drug discovery.