New chalcone derivatives as effective against SARS-CoV-2 agent

Structure-Activity Relationship of Natural Dihydrochalcones and Chalcones, and Their Respective Oxyalkylated Derivatives as Anti-Saprolegnia Agents

Saprolegnia sp. is a pathogenic oomycete responsible for severe economic losses in aquaculture. To date, there is no treatment for its control that is effective and does not pose a threat to the environment and human health. In this research, two dihydrochalcones 1 and 2, and three chalcones 3-5, isolated from the resinous plant Adesmia balsamica, as well as their synthesized oxyalkylated derivatives 6-29 already reported and a new synthesized series of oxyalkylchalcones 30-35, were evaluated for their anti-saprolegnia activity and structure-activity relationship as potential control and treatment agents for strains of Saprolegnia parasitica and S. australis. Among the molecules tested, natural 2',4'-dihydroxychalcone (3) and new oxyalkylchalcone 34 were the most potent antisaprolegnia agents against both strains, even with better results than the commercial control bronopol. On the other hand, the structure-activity relationship study indicates that the contributions of steric and electrostatic fields are important to enhance the activity of the compounds, thus the presence of bulky substituents favors the activity.

Synergistic activity between conventional antifungals and chalcone-derived compound against dermatophyte fungi and Candida spp

The scarce antifungal arsenal, changes in the susceptibility profile of fungal agents, and lack of adherence to treatment have contributed to the increase of cases of dermatomycoses. In this context, new antimicrobial substances have gained importance. Chalcones are precursors of the flavonoid family that have multiple biological activities, have high tolerability by humans, and easy synthesis. In this study, we evaluated the in vitro antifungal activity, alone and in combination with conventional antifungal drugs, of the VS02-4'ethyl chalcone-derived compound against dermatophytes and Candida spp. Susceptibility testing was carried out by broth microdilution. Experiments for determination of the target of the compound on the fungal cell, time-kill kinetics, and toxicity tests in Galleria mellonella model were also performed. Combinatory effects were evaluated by the checkerboard method. Results showed high activity of the compound VS02-4'ethyl against dermatophytes (MIC of 7.81-31.25 μg/ml). The compound targeted the cell membrane, and the time-kill test showed the compound continues to exert gradual activity after 5 days on dermatophytes, but no significant activity on Candida. Low toxicity was observed at 250 mg/kg. Excellent results were observed in the combinatory test, where VS02-4'ethyl showed synergistic interactions with itraconazole, fluconazole, terbinafine, and griseofulvin, against all isolates tested. Although further investigation is needed, these results revealed the great potential of chalcone-derived compounds against fungal infections for which treatments are long and laborious.

Organohalogen chalcones: design, synthesis, ADMET prediction, molecular dynamics study and inhibition effect on acetylcholinesterase and carbonic anhydrase

In an effort to discover potential acetylcholinesterase (AChE) and carbonic anhydrase (CA) inhibitors, a novel series of organohalogen chalcone derivatives (12-20, 23-30) was synthesized, and their chemical structures were characterized by spectral analysis. They showed a highly potent inhibition effect on AChE and hCAs (Ki values range from 5.07 ± 0.062 to 65.53 ± 4.36 nM for AChE, 13.54 ± 2.55 to 94.11 ± 10.39 nM for hCA I, and 5.21 ± 0.54 to 57.44 ± 3.12 nM for hCA II). In addition, the chalcone derivatives with the highest inhibitor score docked into the active site of the indicated metabolic enzyme receptors, and their absorption, metabolism, and toxic properties were evaluated according to ADMET's estimation.Compounds 16 and 19 exhibited the highest inhibition score, emerged as lead compounds, and inspired the development of more potent compounds.

Synthesis, evaluation, and mechanism of 1-(4-(arylethylenylcarbonyl)phenyl)-4-carboxy-2-pyrrolidinones as potent reversible SARS-CoV-2 entry inhibitors

A class of 1-(4-(arylethylenylcarbonyl)phenyl)-4-carboxy-2-pyrrolidinones were designed and synthesized via Michael addition, cyclization, aldol condensation, and deprotonation to inhibit the human transmembrane protease serine 2 (TMPRSS2) and Furin, which are involved in priming the SARS-CoV-2 Spike for virus entry. The most potent inhibitor 2f (81) was found to efficiently inhibit the replication of various SARS-CoV-2 delta and omicron variants in VeroE6 and Calu-3 cells, with EC50 range of 0.001-0.026 μM by pre-incubation with the virus to avoid the virus entry. The more potent antiviral activities than the proteases inhibitory activities led to discovery that the synthesized compounds also inhibited Spike's receptor binding domain (RBD):angiotensin converting enzyme 2 (ACE2) interaction as a main target, and their antiviral activities were enhanced by inhibiting TMPRSS2 and/or Furin. To further confirm the blocking effect of 2f (81) on virus entry, SARS-CoV-2 Spike pseudovirus was used in the entry assay and the results showed that the compound inhibited the pseudovirus entry in a ACE2-dependent pathway, via mainly inhibiting RBD:ACE2 interaction and TMPRSS2 activity in Calu-3 cells. Finally, in the in vivo animal model of SARS-CoV-2 infection, the oral administration of 25 mg/kg 2f (81) in hamsters resulted in reduced bodyweight loss and 5-fold lower viral RNA levels in nasal turbinate three days post-infection. Our findings demonstrated the potential of the lead compound for further preclinical investigation as a potential treatment for SARS-CoV-2.

Antiviral and antimicrobial applications of chalcones and their derivatives: From nature to greener synthesis

Chalcones and their derivatives have been widely studied due to their versatile pharmacological and biological activities, such as anti-inflammatory, antibacterial, antiviral, and antitumor effects. These compounds have shown suitable antiviral effects through the selective targeting of a variety of viral enzymes, including lactate dehydrogenase, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), fumarate reductase, protein tyrosine phosphatase, topoisomerase-II, protein kinases, integrase/protease, and lactate/isocitrate dehydrogenase, among others. Chalcones and their derivatives have displayed excellent potential for combating pathogenic bacteria and fungi (especially, multidrug-resistant bacteria). However, relevant mechanisms should be further explored, focusing on inhibitory effects against DNA gyrase B, UDP-N-acetylglucosamine enolpyruvyl transferase (MurA), and efflux pumps (e.g., NorA), among others. In addition, the antifungal and antiparasitic activities of these compounds (e.g., antitrypanosomal and antileishmanial properties) have prompted additional explorations. Nonetheless, systematic analysis of the relevant mechanisms, biosafety issues, and pharmacological properties, as well as clinical translation studies, are vital for practical applications. Herein, recent advancements pertaining to the antibacterial, antiviral, antiparasitic, and antifungal activities of chalcones and their derivatives are deliberated, focusing on the relevant mechanisms of action, crucial challenges, and future prospects. Furthermore, due to the great importance of greener and more sustainable synthesis of these valuable compounds, especially on an industrial scale, the progress made in this field has been briefly discussed. Hopefully, this review can serve as a catalyst for researchers to delve deeper into the exploration and designing of novel chalcone compounds with medicinal properties, especially against pathogenic viruses and multidrug-resistant bacteria as major causes of concern for human health.

Studies on the Nonalkaloidal Secondary Metabolites of Hippeastrum vittatum (L'Her.) Herb. Bulbs

Sixteen chemically varied metabolites were isolated from the bulbs of Hippeastrum vittatum (L'Her.) Herb., including eight flavonoids [3'-methyl isoliquiritigenin (2), 7-hydroxyflavan (8), 7-hydroxyflavanone (9), 7-hydroxyflavan-3-ol (10), 7-methoxy-3',4'-methylenedioxyflavan-3-ol (11), 7-hydroxy-3',4'-methylenedioxy flavan (12), 2',4'-dihydroxy-3'-methyl-3,4-methylenedioxychalcone (13), and isoliquiritigenin (14)], four acetophenones [2,6-dimethoxy-4-hydroxyacetophenone (3), 2,4-dihydroxyacetophenone (4), 2,4-dihydroxy-6-methoxy-3-methylacetophenone (6), and 2,4,6-trimethoxyacetophenone (7)], two alkaloids [lycorine (1) and narciprimine (15)], one phenol derivative [p-nitrophenol (5)], and one steroid [β-sitosterol 3-O-β-glucopyranoside (16)]. Their structures were elucidated by combining one- and two-dimensional NMR and ESI-MS techniques and by comparison with the reported literature data and some authentic samples. Except for lycorine (1), the isolated metabolites were obtained herein for the first time from Hippeastrum plants, among which compound 13 was identified as a new chalcone derivative. Additionally, the total phenolic and flavonoid contents of the total ethanol extract and different fractions of the bulbs were determined by the Folin-Ciocalteu and aluminum chloride colorimetric methods, respectively, whereas their antioxidant potential was compared using the phosphomolybdenum and 2,2'-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assays. Finally, the binding affinities of compounds 1-16 to some key target proteins of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), namely, main protease (Mpro), papain-like protease (PLpro), and RNA-dependent RNA polymerase (RdRp), were screened and compared using molecular docking analysis. The possible chemotaxonomic significance of the identified metabolites was also discussed.

Garbage in, garbage out: how reliable training data improved a virtual screening approach against SARS-CoV-2 MPro

Introduction: The identification of chemical compounds that interfere with SARS-CoV-2 replication continues to be a priority in several academic and pharmaceutical laboratories. Computational tools and approaches have the power to integrate, process and analyze multiple data in a short time. However, these initiatives may yield unrealistic results if the applied models are not inferred from reliable data and the resulting predictions are not confirmed by experimental evidence. Methods: We undertook a drug discovery campaign against the essential major protease (MPro) from SARS-CoV-2, which relied on an in silico search strategy -performed in a large and diverse chemolibrary- complemented by experimental validation. The computational method comprises a recently reported ligand-based approach developed upon refinement/learning cycles, and structure-based approximations. Search models were applied to both retrospective (in silico) and prospective (experimentally confirmed) screening. Results: The first generation of ligand-based models were fed by data, which to a great extent, had not been published in peer-reviewed articles. The first screening campaign performed with 188 compounds (46 in silico hits and 100 analogues, and 40 unrelated compounds: flavonols and pyrazoles) yielded three hits against MPro (IC₅₀ ≤ 25 μM): two analogues of in silico hits (one glycoside and one benzo-thiazol) and one flavonol. A second generation of ligand-based models was developed based on this negative information and newly published peer-reviewed data for MPro inhibitors. This led to 43 new hit candidates belonging to different chemical families. From 45 compounds (28 in silico hits and 17 related analogues) tested in the second screening campaign, eight inhibited MPro with IC₅₀ = 0.12-20 μM and five of them also impaired the proliferation of SARS-CoV-2 in Vero cells (EC₅₀ 7-45 μM). Discussion: Our study provides an example of a virtuous loop between computational and experimental approaches applied to target-focused drug discovery against a major and global pathogen, reaffirming the well-known "garbage in, garbage out" machine learning principle.

Structure-based virtual screening of novel natural products as chalcone derivatives against SARS-CoV-2 Mpro

Coronavirus disease 2019 (COVID-19), which is caused by SARS-CoV-2, has spread quickly around the world, causing a global pandemic. It has infected more than 500 million people as of April 28, 2022. Much research has been reported to stop the virus from spreading, but there are currently no approved medicines to treat COVID-19. In this work, a dataset of 142 natural products collected from various medicinal plants was used to perform structure-based virtual screening (SBVS) through the combined application of molecular docking and molecular dynamics (MD) simulation methods. First, the dataset of compounds was optimized using the density functional theory (DFT) approach. The optimized compounds were then submitted to the first screening, which was done by the pKCM web server to look for drug-likeness and the PyRx to look for binding affinity. Among the 142 natural substances, 10 compounds were selected for docking validation. Compounds that interact with CYS145 and LEU141, the essential catalytic residues, as well as compounds with binding affinities less than -8.0 kcal/mol, are considered promising anti-SARS-CoV-2 drug candidates. The top-ranked compounds were then evaluated by MD simulations and MM-GBSA method. These results could help researchers come up with new natural compounds that could be used to treat SARS-CoV-2.Communicated by Ramaswamy H. Sarma.

Recruitment of chalcone's potential in drug discovery of anti-SARS-CoV-2 agents

Chalcone is an interesting scaffold found in the structure of many naturally occurring molecules. Medicinal chemists are commonly interested in designing new chalcone-based structures because of having the α, β-unsaturated ketone functional group, which allows these compounds to participate in Michael's reaction and create strong covalent bonds at the active sites of the targets. Some studies have identified several natural chalcone-based compounds with the ability to inhibit the severe acute respiratory syndrome coronavirus and Middle East respiratory syndrome coronavirus proteases. A few years after the advent of the coronavirus disease 2019 pandemic and the publication of many findings in this regard, there is some evidence that suggests chalcone scaffolding has great potential for use in the design and development of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) inhibitors. Artificial placement of this scaffold in the structure of optimized anti-SARS-CoV-2 compounds can potentially provide irreversible inhibition of the viral cysteine proteases 3-chymotrypsin-like protease and papain-like protease by creating Michael interaction. Despite having remarkable capabilities, the use of chalcone scaffold in drug design and discovery of SARS-CoV-2 inhibitors seems to have been largely neglected. This review addresses issues that could lead to further consideration of chalcone scaffolding in the structure of SARS-CoV-2 protease inhibitors in the future.

Chalcone: A Promising Bioactive Scaffold in Medicinal Chemistry

Chalcones are a class of privileged scaffolds with high medicinal significance due to the presence of an α,β-unsaturated ketone functionality. Numerous functional modifications of chalcones have been reported, along with their pharmacological behavior. The present review aims to summarize the structures from natural sources, synthesis methods, biological characteristics against infectious and non-infectious diseases, and uses of chalcones over the past decade, and their structure–activity relationship studies are detailed in depth. This critical review provides guidelines for the future design and synthesis of various chalcones. In addition, this could be highly supportive for medicinal chemists to develop more promising candidates for various infectious and non-infectious diseases.

The green chemistry of chalcones: Valuable sources of privileged core structures for drug discovery

The sustainable use of resources is essential in all production areas, including pharmaceuticals. However, the aspect of sustainability needs to be taken into consideration not only in the production phase, but during the whole medicinal chemistry drug discovery trajectory. The continuous progress in the fields of green chemistry and the use of artificial intelligence are contributing to the speed and effectiveness of a more sustainable drug discovery pipeline. In this light, here we review the most recent sustainable and green synthetic approaches used for the preparation and derivatization of chalcones, an important class of privileged structures and building blocks used for the preparation of new biologically active compounds with a broad spectrum of potential therapeutic applications. The literature here reported has been retrieved from the SciFinder database using the term "chalcone" as a keyword and filtering the results applying the concept: "green chemistry", and from the Reaxys database using the keywords "chalcone" and "green". For both databases the time-frame was 2017-2022. References were manually selected based on relevance.

Synthesis of Chalcones Derivatives and Their Biological Activities: A Review

Chalcone derivatives are considered valuable species because they possess a ketoethylenic moiety, CO-CH=CH-. Due to the presence of a reactive α,β-unsaturated carbonyl group, chalcones and their derivatives possess a wide spectrum of antiproliferative, antifungal, antibacterial, antiviral, antileishmanial, and antimalarial pharmacological properties. Recent developments in heterocyclic chemistry have led to the synthesis of chalcone derivatives, which had been biologically investigated toward certain disease targets. The major aspect of this review is to present the most recent synthesis of chalcones bearing N, O, and/or S heterocycles, revealing their biological potential during the past decade (2010-2021). Based on a review of the literature, many chalcone-heterocycle hybrids appear to exhibit promise as future drug candidates owing to their similar or superior activities compared to those of the standards. Thus, this review may prove to be beneficial for the development and design of new potent therapeutic drugs based on previously developed strategies.

Progress of isolation, chemical synthesis and biological activities of natural chalcones bearing 2-hydroxy-3-methyl-3-butenyl group

Chalcones have a three-carbon α,β-unsaturated carbonyl system composed of two phenolic rings. Many chalcones have shown broad spectrum of biological activities with clinical potentials against various diseases. They are usually abundant in seeds, fruit skin, bark and flowers of most edible plants. Among them, chalcones bearing 2-hydroxy-3-methyl-3-butenyl (HMB) group have been reported several times in the past few decades due to their novel scaffolds and numerous interesting biological activities. In this paper, we reviewed the isolation of twelve natural chalcones and a natural chalcone-type compound bearing 2-hydroxy-3-methyl-3-butenyl group discovered so far, and reviewed their synthesis methods and biological activities reported in the literature. We anticipate that this review will inspire further research of natural chalcones.

The Main Protease of SARS-CoV-2 as a Target for Phytochemicals against Coronavirus

In late December 2019, the first cases of COVID-19 emerged as an outbreak in Wuhan, China that later spread vastly around the world, evolving into a pandemic and one of the worst global health crises in modern history. The causative agent was identified as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Although several vaccines were authorized for emergency use, constantly emerging new viral mutants and limited treatment options for COVID-19 drastically highlighted the need for developing an efficient treatment for this disease. One of the most important viral components to target for this purpose is the main protease of the coronavirus (Mpro). This enzyme is an excellent target for a potential drug, as it is essential for viral replication and has no closely related homologues in humans, making its inhibitors unlikely to be toxic. Our review describes a variety of approaches that could be applied in search of potential inhibitors among plant-derived compounds, including virtual in silico screening (a data-driven approach), which could be structure-based or fragment-guided, the classical approach of high-throughput screening, and antiviral activity cell-based assays. We will focus on several classes of compounds reported to be potential inhibitors of Mpro, including phenols and polyphenols, alkaloids, and terpenoids.

Transcription factor Fli-1 as a new target for antitumor drug development

The transcription factor Friend leukemia virus integration 1 (Fli-1) belonging to the E26 Transformation-Specific (ETS) transcription factor family is not only expressed in normal cells such as hematopoietic stem cells and vascular endothelial cells, but also abnormally expressed in various malignant tumors including Ewing sarcoma, Merkel cell sarcoma, small cell lung carcinoma, benign or malignant hemangioma, squamous cell carcinoma, adenocarcinoma, bladder cancer, leukemia, and lymphoma. Fli-1 binds to the promoter or enhancer of the target genes and participates in a variety of physiological and pathological processes of tumor cells, including cell growth, proliferation, differentiation, and apoptosis. The expression of Fli-1 gene is related to the specific biological functions and characteristics of the tissue in which it is located. In tumor research, Fli-1 gene is used as a specific marker for the occurrence, metastasis, efficacy, and prognosis of tumors, thus, a potential new target for tumor diagnosis and treatment. These studies indicated that Fli-1 may be a specific candidate for antitumor drug development. Recent studies identified small molecules regulating Fli-1 thanks to our screened strategy of natural products and their derivatives. Therefore, in this review, the advanced research on Fli-1 as a target for antitumor drug development is analyzed in different cancers. The inhibitors and agonists of Fli-1 that regulate its expression are introduced and their clinical applications in the treatment of cancer, thus providing new therapeutic strategies.