Synthesis and Evaluation of Novel 2,2-Dimethylthiochromanones as Anti-Leishmanial Agents

Thiourea-functionalized aminoglutethimide derivatives as anti-leishmanial agents

Aim: We aim to develop new anti-leishmanial agents against Leishmania major and Leishmania tropica. Materials & methods: A total of 23 thiourea derivatives of (±)-aminoglutethimide were synthesized and evaluated for in vitro activity against promastigotes of L. major and L. tropica. Results & conclusion: The N-benzoyl analogue 7p was found potent (IC50 = 12.7 μM) against L. major and non toxic to normal cells. The docking studies, indicates that these inhibitors may target folate and glycolytic pathways of the parasite. The N-hexyl compound 7v was found strongly active against both species, and lacked cytotoxicity against normal cells, whereas compound 7r, with a 3,5-bis-(tri-fluoro-methyl)phenyl unit, was active against Leishmania, but was cytotoxic in nature. Compound 7v was thus identified as a hit for further studies.

Synthetic product-based approach toward potential antileishmanial drug development

Leishmaniasis is a parasitic disease and is categorized as a tropically neglected disease (NTD) with no effective vaccines available. The available chemotherapeutics against leishmaniasis are associated with an increase in the incidence of toxicity and drug resistance. Consequently, targeting metabolic pathways and enzymes of parasites which differs from the mammalian host can be exploited to treat and overcome the resistance. The classical methods of identifying the structural fragments and the moieties responsible for the biological activities from the standard compounds and their modification are options for developing more effective novel compounds. Significant progress has been made in refining the development of potent non-toxic molecules and addressing the limitations of the current treatment available. Several examples of synthetic product-based approach utilizing their core heterocyclic rings including furan, pyrrole, thiazole, imidazole, pyrazole, triazole, quinazoline, quinoline, pyrimidine, coumarin, indole, acridine, oxadiazole, purine, chalcone, carboline, phenanthrene and metal containing derivatives and their structure-activity relationships are discussed in this review. It also analyses the groups/fragments interacting with the host cell receptors and will support the medicinal chemists with novel antileishmanial agents.

The role of natural anti-parasitic guided development of synthetic drugs for leishmaniasis

Leishmaniasis is a parasitic disease and categorised as a neglected tropical disease (NTD). Each year, between 70,0000 and 1 million new cases are believed to occur. There are approximately 90 sandfly species which can spread the Leishmania parasites (over 20 species) causing 20,000 to 30,000 death per year. Currently, leishmaniasis has no specific therapeutic treatment available. The prescribed drugs with several drawbacks including high cost, challenging administration, toxicity, and drug resistance led to search for the alternative treatment with less toxicity and selectivity. Introducing the molecular features like that of phytoconstituents for the search of compounds with less toxicity is another promising approach. The current review classifies the synthetic compounds according to the core rings present in the natural phytochemicals for the development of antileishmanial agents (2020-2022). Considering the toxicity and limitations of synthetic analogues, natural compounds are at the higher notch in terms of effectiveness and safety. Synthesized compounds of chalcones (Compound 8; IC₅₀: 0.03 μM, 4.7 folds more potent than Amphotericin B; IC₅₀: 0.14 μM), pyrimidine (compound 56; against L. tropica; 0.04 μM and L. infantum; 0.042 μM as compared to glucantime: L. tropica; 8.17 μM and L. infantum; 8.42 μM), quinazoline and (compound 72; 0.021 μM, 150 times more potent than miltefosine). The targeted delivery against DHFR have been demonstrated by one of the pyrimidine compounds 62 with an IC₅₀ value of 0.10 μM against L. major as compared to the standard trimethoprim (IC₅₀: 20 μM). The review covers the medicinal importance of antileishmanial agents from synthetic and natural sources such as chalcone, pyrazole, coumarins, steroids, and alkaloidal-containing drugs (indole, quinolines, pyridine, pyrimidine, carbolines, pyrrole, aurones, and quinazolines). The efforts of introducing the core rings present in the natural phytoconstituents as antileishmanial in the synthetic compounds are discussed with their structural activity relationship. The perspective will support the medicinal chemists in refining and directing the development of novel molecules phytochemicals-based antileishmanial agents.

A review on new natural and synthetic anti-leishmanial chemotherapeutic agents and current perspective of treatment approaches

Leishmaniases are considered among the most neglected yet dangerous parasitic diseases worldwide. According to the recent WHO report (Weekly Epidemiological Record, Sep, 2021), 200 countries and territories reported leishmanises cases in 2020; of which 89 (45%) for CL, and 79 (40%) for VL were endemic. Indian subcontinent (India, Bangladesh and Nepal), one of the three eco-epidemiological hotspots of VL, currently reported 18% of the total cases of VL worldwide. Eastern Mediterranean region and the Region of the Americas together reported >90% of the new CL cases, of which >80% were from Afghanistan, Algeria, Brazil, Colombia, Iraq, Pakistan and the Syrian Arab Republic. While considering the current therapeutic options, conventional anti-leishmanial drugs have long been proved to be toxic and/or expensive and have resulted in extensive drug resistance in India. Recent searches for novel anti-leishmanial drugs have led to find out the prime cellular targets and metabolic pathways to bridge the gap between the known facts and unexplored data. Cutting edge knowledge based drug designing has simplified the search for novel molecules with leishmanicidal efficacy by identifying ligand-receptor interactions and has accelerated the cost effective primary discovery of molecules through computational validation against Leishmaniases. This review focuses on the limitations of conventional drugs, and discusses the chemotherapeutic potential of many novel natural and synthetic anti-leishmanial agents reported since the last decade. It is also interpreted that some of the reported molecules might be tested singly or as a part of combinatorial therapy on pre-clinical and clinical level.

High Value-Added Application of Natural Plant Products in Crop Protection: Construction and Pesticidal Activities of Piperine-Type Ester Derivatives and Their Toxicology Study

To discover new potential pesticide candidates, recently, structural modification of natural bioactive products has received much attention. In this work, a series of new piperine-type ester derivatives were regio- and stereoselectively synthesized based on a natural alkaloid piperine isolated from Piper nigrum. Their structures were characterized by IR, mp, ¹H NMR (¹³C NMR), and high-resolution mass spectrometry (HRMS). Against Tetranychus cinnabarinus Boisduval (Acari: Tetranychidae), compounds 4e, 4f, 4u, and 4v displayed the most significant acaricidal activity with LC₅₀ values of 0.155, 0.117, 0.177, and 0.164 mg/mL, respectively. Particularly, compound 4f showed >120-fold higher acaricidal activity than piperine (LC₅₀: 14.198 mg/mL). Notably, the acaricidal activity of 4f was equivalent to that of the commercial acaricide spirodiclofen (LC₅₀: 0.115 mg/mL). Additionally, against Eriosoma lanigerum Hausmann (Hemiptera: Aphididae), compounds 4w and 4b' showed 1.8-fold aphicidal activity of piperine. Furthermore, via the scanning electron microscope (SEM) imaging method, the obvious destruction of the construction of the cuticle layer of 4f-treated T. cinnabarinus was observed. Compound 4f could be further studied as a lead acaricidal agent.

Antimicrobial Activity and DFT Studies of a Novel Set of Spiropyrrolidines Tethered with Thiochroman-4-one/Chroman-4-one Scaffolds

A novel series of 14 spiropyrrolidines bearing thiochroman-4-one/chroman-4-one, and oxindole/acenaphthylene-1,2-dione moieties were synthesized and characterized by spectroscopic techniques, as well as by three X-ray diffraction studies, corroborating the stereochemistry. Quantum chemical calculations studies, using the DFT approach, were performed to rationalize the stereochemical outcome. These N-heterocycles were evaluated for their antibacterial and antifungal activities against some pathogenic organisms. Several compounds displayed moderate to excellent activity towards the screened microbe strains in the study compared to Amoxicillin (AMX), Ampicillin (AMP), and Amphotericin B. Furthermore, a structural activity relationship (SAR) was established considering the synthesized compounds. Pharmacokinetic studies reveal that these derivatives exhibit an acceptable predictive ADMET profile (Absorption, Distribution, Metabolism, Excretion and Toxicity) and good drug-likeness.

Facile access to chiral chromanone-2-carboxylic acids enabled by Rhodium-catalyzed chemo- and enantioselective hydrogenation

Rh-catalyzed highly chemo- and enantioselective hydrogenation of chromone-2-carboxylic acids was first successfully established, providing a wide range of enantiopure chromanone-2-carboxylic acids with excellent results (up to 97% yield and 99%...