Anti-Leishmanial and Cytotoxic Activities of a Series of Maleimides: Synthesis, Biological Evaluation and Structure-Activity Relationship

Advances in organocatalyzed synthesis of organic compounds

The recent advancements in utilizing organocatalysts for the synthesis of organic compounds have been described in this review by focusing on their simplicity, effectiveness, reproducibility, and high selectivity which lead to excellent product yields. The organocatalytic methods for various derivatives, such as indoles, pyrazolones, anthrone-functionalized benzylic amines, maleimide, polyester, phthalimides, dihydropyrimidin, heteroaryls, N-aryl benzimidazoles, stilbenoids, quinazolines, quinolines, and oxazolidinones have been specifically focused. The review provides more understanding by delving into potential reaction mechanisms. We anticipate that this collection of data and findings on successful synthesis of diverse compound derivatives will serve as valuable resources and stimulating current and future research efforts in organocatalysis and industrial chemistry.

Cheminformatics-based discovery of new organoselenium compounds with potential for the treatment of cutaneous and visceral leishmaniasis

Leishmaniasis affects more than 12 million humans globally and a further 1 billion people are at risk in leishmaniasis endemic areas. The lack of a vaccine for leishmaniasis coupled with the limitations of existing anti-leishmanial therapies prompted this study. Cheminformatic techniques are widely used in screening large libraries of compounds, studying protein-ligand interactions, analysing pharmacokinetic properties, and designing new drug molecules with great speed, accuracy, and precision. This study was undertaken to evaluate the anti-leishmanial potential of some organoselenium compounds by quantitative structure-activity relationship (QSAR) modeling, molecular docking, pharmacokinetic analysis, and molecular dynamic (MD) simulation. The built QSAR model was validated (R2train = 0.8646, R2test = 0.8864, Q2 = 0.5773) and the predicted inhibitory activity (pIC50) values of the newly designed compounds were higher than that of the template (Compound 6). The new analogues (6a, 6b, and 6c) showed good binding interactions with the target protein (Pyridoxal kinase, PdxK) while also presenting excellent drug-likeness and pharmacokinetic profiles. The results of density functional theory, MD simulation, and molecular mechanics generalized Born surface area (MM/GBSA) analyses suggest the favourability and stability of protein-ligand interactions of the new analogues with PdxK, comparing favourably well with the reference drug (Pentamidine). Conclusively, the newly designed compounds could be synthesized and tested experimentally as potential anti-leishmanial drug molecules.Communicated by Ramaswamy H. Sarma.

Inhibitory Effects of a Maleimide Compound on the Virulence Factors of Candida albicans

Candidiasis caused by Candida albicans infection has long been a serious human health problem. The pathogenicity of C. albicans is mainly due to its virulence factors, which are the novel targets of antifungal drugs for low risk of resistance development. In this study, we identified a maleimide compound [1-(4-methoxyphenyl)-1hydro-pyrrole-2,5-dione, MPD] that exerts effective anti-virulence activity. It could inhibit the process of adhesion, filamentation, and biofilm formation in C. albicans. In addition, it exhibited low cytotoxicity, hemolytic activity and drug resistance development. Moreover, in Galleria mellonella-C. albicans (in vivo) infection model, the survival time of infected larvae was significantly prolonged under the treatment of MPD. Further, mechanism research revealed that MPD increased farnesol secretion by upregulating the expression of Dpp3. The increased farnesol inhibited the activity of Cdc35, which then decreased the intracellular cAMP content resulting in the inhibition of virulence factors via the Ras1-cAMP-Efg1 pathway. In all, this study evaluated the inhibitory effect of MPD on various virulence factors of C. albicans and identified the underlying mechanisms. This suggests a potential application of MPD to overcome fungal infections in clinic.

Access to 3-Aminomethylated Maleimides via a Phosphine-Catalyzed Aza-Morita-Baylis-Hillman Type Coupling

A designed method for the preparation of 3-aminomethylated maleimides via Morita-Baylis-Hillman (MBH) reaction was developed. This phosphine-catalyzed coupling adopted maleimides and 1,3,5-triazinanes as the substrate, giving a series of 3-aminomethylated maleimide derivatives with a double bond retained on the maleimide ring in 41-90% yield. Acylation, isomerization, and Michael addition of the obtained products demonstrated the synthetic application of the present protocol. The results of control experiments indicated that phosphorus ylide formation and elimination take place during the reaction pathway.

Computational design, molecular properties, ADME, and toxicological analysis of substituted 2,6-diarylidene cyclohexanone analogs as potent pyridoxal kinase inhibitors

Leishmaniasis is one of the tropical diseases which affects over 12 million people mainly in the tropical regions of the world and is caused by the leishmanial parasites transmitted by the female sand fly. The lack of vaccines to prevent leishmaniasis, as well as limitations of existing therapies necessitated this study which was focused on a combined virtual docking screening and 3-D QSAR modeling approach to design some diarylidene cyclohexanone analogs, while also performing pharmacokinetic analysis and Molecular Dynamic (MD) simulation to ascertain their drug-ability. As a result, the built 3-D QSAR model was found to satisfy the requirement of a good model with R2 = 0.9777, SDEC = 0.0593, F-test = 105.028, and Q2 LOO = 0.6592. The template (compound 9, MolDock score =  - 161.064) and all seven newly designed analogs were found to possess higher docking scores than the reference drug (Pentamidine, Moldock score = - 137.827). The results of the pharmacokinetic analysis suggest 9 and the new molecules (9a, b, c, e, and f) as orally bioavailable with good ADME and safe toxicological profiles. These molecules also showed good binding interactions with the receptor (pyridoxal kinase). Additionally, the MD simulation result confirmed the stability of the tested protein-ligand complexes, with an estimated ∆G binding (MM/GBSA) of - 65.2177 kcal/mol and - 58.433 kcal/mol for 9_6K91 and 9a_6K91 respectively. Hence, the new compounds, especially 9a could be considered potential anti-leishmanial inhibitors.

Models for cytotoxicity screening of antileishmanial drugs: what has been done so far?

A growing number of studies have demonstrated the in vitro potential of an impressive number of antileishmanial candidates in the past years. However, the lack of uniformity regarding the choice of cell types for cytotoxicity assays may lead to uncomparable and inconclusive data. In vitro assays relying solely on non-phagocytic cell models may not represent a realistic result as the effect of an antileishmanial agent should ideally be presented based on its cytotoxicity profile against reticuloendothelial system cells. In the present review, we have assembled studies published in the scientific literature from 2015 to 2021 that explored leishmanicidal candidates, emphasising the main host cell models used for cytotoxicity assays. The pros and cons of different host cell types as well as primary cells and cell lines are discussed in order to draw attention to the need to establish standardised protocols for preclinical testing when assessing new antileishmanial candidates.

Total Synthesis of Aqabamycin G, a Nitrophenyl Indolylmaleimide Marine Alkaloid from Vibrio sp. WMBA

The first total synthesis of the marine alkaloid aqabamycin G is disclosed. The synthetic sequence involved the stepwise addition to maleimide of an indole motif and a substituted diazo-benzenoid unit derived from acetaminophen. An alternative strategy using a protected phenol is also reported.

Maleimide structure: a promising scaffold for the development of antimicrobial agents

Natural compounds bearing maleimide rings are a series of secondary metabolites derived from fungi/marine microorganisms, which are characterized by a general structure -CO-N(R)-CO-, and the R group is normally substituted with alkyl or aryl groups. Maleimide compounds show various biological activities such as antibacterial, antifungal, and anticancer activity. In this review, the broad-spectrum antimicrobial activities of 15 maleimide compounds from natural sources and 32 artificially synthesized maleimides were summarized, especially against Candida albicans, Sclerotinia sclerotiorum, and Staphylococcus aureus. It highlights that maleimide scaffold has tremendous potential to be utilized in the development of novel antimicrobial agents.

Combined Computational and Experimental Studies on the Asymmetric Michael Addition of α-Aminomaleimides to β-Nitrostyrenes Using an Organocatalyst Derived from Cinchona Alkaloid

Maleimides are often used as electrophiles in conventional reactions; however, their application as nucleophiles is limited to only a few reactions, and reactions utilizing α-aminomaleimides as asymmetric Michael donors have not been reported to date. Thus, in this work, asymmetric Michael addition of α-aminomaleimides as Michael donors to β-nitrostyrenes was conducted for the first time using an organocatalyst derived from a Cinchona alkaloid. Density functional theory investigations were crucial to improve the enantioselectivity of the adduct.

Recent advancements in anti-leishmanial research: Synthetic strategies and structural activity relationships

Leishmaniasis is a parasitic neglected tropical disease caused by various species of Leishmania parasite. Despite tremendous advancements in the therapeutic sector and drug development strategies, still the existing anti-leishmanial agents are associated with some clinical issues like drug resistance, toxicity and selectivity. Therefore, several research groups are continuously working towards the development of new therapeutic candidates to overcome these issues. Many potential heterocyclic moieties have been explored for this purpose including triazoles, chalcones, chromone, thiazoles, thiosemicarbazones, indole, quinolines, etc. It is evident from the literature that the majority of anti-leishmanial agents act by interacting with key regulators including PTR-I, DHFR, LdMetAP1, MAPK, 14 α-demethylase and pteridine reductase-I, etc. Also, these tend to induce the production of ROS which causes damage to parasites. In the present compilation, authors have summarized various significant synthetic procedures for anti-leishmanial agents reported in recent years. A brief description of the pharmacological potentials of synthesized compounds along with important aspects related to structural activity relationship has been provided. Important docking outcomes highlighting the possible mode of interaction for the reported compounds have also been included. This review would be helpful to the scientific community to design newer strategies and also to develop novel therapeutic candidates against leishmaniasis.

Rh(III)-Catalyzed Regioselective C8-Alkylation of Quinoline N-Oxides with Maleimides and Acrylates

Herein, we disclose the Rh(III)-catalyzed selective C8-alkylation of quinoline N-oxides with maleimides and acrylates. The main features of the reaction include complete C8-selectivity and broad substrate scope with good to excellent yields. The reaction also proceeded well with unprotected maleimide. The applicability of the developed methodology is demonstrated with gram-scale synthesis and post-modification of the alkylated product. Preliminary mechanistic study revealed that the reaction proceeds through a five-membered rhodacycle and involves proto-demetalation step.

Biochemical characterization and chemical validation of Leishmania MAP Kinase-3 as a potential drug target

Protozoan parasites of the Leishmania genus have evolved unique signaling pathways that can sense various environmental changes and trigger stage differentiation for survival and host infectivity. MAP kinase (MAPK) plays a critical role in various cellular activities like cell differentiation, proliferation, stress regulation, and apoptosis. The Leishmania donovani MAPK3 (LdMAPK3) is involved in the regulation of flagella length and hence plays an important role in disease transmission. Here, we reported the gene cloning, protein expression, biochemical characterizations, inhibition studies and cell proliferation assay of LdMAPK3. The recombinant purified LdMAPK3 enzyme obeys the Michaelis-Menten equation with K_m and V_max of LdMAPK3 was found to be 20.23 nM and 38.77 ± 0.71 nmoles ATP consumed/mg LdMAPK3/min respectively. The maximum kinase activity of LdMAPK3 was recorded at 35 °C and pH 7. The in-vitro inhibition studies with two natural inhibitors genistein (GEN) and chrysin (CHY) was evaluated against LdMAPK3. The K_i value for GEN and CHY were found to be 3.76 ± 0.28 µM and K_i = 8.75 ± 0.11 µM respectively. The IC₅₀ value for the compounds, GEN and CHY against L. donovani promastigotes were calculated as 9.9 µg/mL and 13 µg/mL respectively. Our study, therefore, reports LdMAPK3 as a new target for therapeutic approach against leishmaniasis.