Recent advances in the therapeutic applications of pyrazolines

Generation and characterization of two acid-resistant macrocin O-methyltransferase variants with a higher enzyme activity at 30 °C from Streptomyces fradiae

Tylosin is an important macrolide antibiotic produced by Streptomyces fradiae. In the biosynthesis of tylosin, macrocin O-methyltransferase TylF catalyzes the conversion of the side-product tylosin C (macrocin) to the primary component tylosin A (C/A conversion). This conversion is the rate-limiting step in the biosynthesis of tylosin, and affects the quality of the end product. To find a high activity and environment-adapted TylF enzyme, a TylF variant pool has been constructed via protein evolution approach in our previous study (Fan et al., 2023 [41]). In this study, the TylF variants with higher C/A conversion rates were expressed in E. coli and purified. The variants TylFY139F, TylFQ138H, F232Y and TylFT36S, V54A were shown to have a higher C/A conversion rate at 30 °C than that of TylF at 38 °C. Moreover, they had a greater acid resistance and showed more adaptable to the pH change during fermentation. Further protein structural and substrate-binding affinity analyses revealed that the T36S, V54A, Q138H, Y139F, and F232Y mutations enlarged the volume of the substrate-binding pocket, thereby increasing the affinity of enzyme variants for their substrates of SAM and macrocin, and decreasing the inhibition of SAH. Three of the TylF variants were overexpressed in the industrial tylosin-producing S. fradiae strain, and the recombinant strains showed the highest C/A conversion at 30 °C without heating up to 38 °C during the last 24 h of fermentation. This is of great energy-saving significance for tylosin industrial production.

Catalytic enantioselective synthesis of 2-pyrazolines via one-pot condensation/6π-electrocyclization: 3,5-bis(pentafluorosulfanyl)-phenylthioureas as powerful hydrogen bond donors

A new conjugate-base-stabilized carboxylic acid (CBSCA) containing a 3,5-bis(pentafluorosulfanyl)phenylthiourea functionality catalyses challenging one-pot condensations/6π-electrocyclizations of hydrazines and α,β-unsaturated ketones under mild conditions. Structurally diverse N-aryl 2-pyrazolines are obtained in good yields and enantioselectivities. The superior performance of 3,5-bis(SF5)phenylthioureas over the widely used 3,5-bis(CF3)phenylthioureas is further demonstrated in the Michael addition of dimethyl malonate to nitrostyrene, using a new Takemoto-type catalyst.

Design, Synthesis, and Evaluation of New Pyrazolines As Small Molecule Inhibitors of Acetylcholinesterase

In pursuit of identifying small molecule inhibitors of acetylcholinesterase (AChE), the synthesis of new 2-pyrazolines was performed efficiently. A modified spectrophotometric method was used to examine their inhibitory effects on AChE as well as butyrylcholinesterase. Four compounds (2a, 2g, 2j, and 2l) were identified as selective AChE inhibitors. Molecular docking studies were conducted to explore their potential interactions with the active site of AChE (PDB code: 4EY7). 1-(3-Nitrophenyl)-3-(thiophen-3-yl)-5-[4-(4-morpholinyl)phenyl]-2-pyrazoline (2l) exerted significant AChE inhibitory action with an IC50 value of 0.040 μM close to donepezil (IC50 = 0.021 μM). In addition to π-π interactions with Tyr341, Tyr124, and Trp86 residues, compound 2l was also capable of forming two hydrogen bonds and a salt bridge at the active site of AChE thanks to its nitro group at the meta position of the phenyl moiety linked to the N 1 position of the pyrazoline scaffold. The higher inhibitory effect of compound 2l on AChE when compared to other compounds in this series might be explained by these additional interactions. Based on the in vitro parallel artificial membrane permeability assay, compound 2l was found to have high blood-brain barrier permeability. In vitro and in silico studies suggest that compound 2l is a potent inhibitor of AChE, which is an important target for neurodegenerative disorders, particularly Alzheimer's disease.

Electrocatalytic dehydrogenative and defluorinative coupling between aldehyde-derived N,N-dialkylhydrazones and fluoromalonates: synthesis of 2-pyrazolines

An electrocatalytic synthesis of 2-pyrazolines via dehydrogenative and defluorinative cross-coupling reactions between (hetero)arylaldehyde-derived N,N-dialkylhydrazones and fluoromalonates is disclosed. Salient features of this work include (i) readily available starting materials, (ii) practical reaction conditions, and (ii) a formal oxidative (4 + 1)-cycloaddition via triple C-H bond functionalization. Cyclic voltammetry analyses support the electrocatalytic formation of an α-fluoromalonyl radical.

Pyrazoline and Analogs: Substrate-based Synthetic Strategies

Among the many reports published on strategies applicable to synthesizing pyrazolines and its analogs, The 1,3-dipolar cycloaddition offers a remarkably wide range of utility. Many 1,3-dipolar cycloaddition reactions used for the synthesis of pyrazolines provide better selectivity, eco-friendly, and less expensive chemical processes. In the presented study, we have reviewed various recently adopted strategies for the synthesis of pyrazoline, which followed the 1,3-dipolar cycloaddition reactions mechanism and classified them based on starting materials such as nitrile imines, diazo compounds, different zwitter ions, chalcones, and isoprene units. The manuscript also focused on the synthesis of pyrazolines starting from Seyferth-Gilbert reagents (SGR) and Psilostachyin (PSH) reagents. We hope this work will help those engaged or have plans to research pyrazoline or its analogs, as synthetic protocols based on starting material are rarely available for pyrazolines. Thus, this article holds a valuable complement to the development of newer pyrazoline and its derivatives.

Design, Synthesis, and Evaluation of a New Series of 2-Pyrazolines as Potential Antileukemic Agents

In an attempt to identify small molecules for the treatment of leukemia, 12 new pyrazolines (2a-l) were synthesized efficiently. WST-1 assay was performed to examine their cytotoxic features on HL-60 human acute promyelocytic leukemia (APL), K562 human chronic myeloid leukemia (CML), and THP-1 human acute monocytic leukemia cells. Four compounds (2e, 2f, 2g, and 2h) were determined as promising antileukemic agents on HL-60 and K562 cells. IC50 values of compounds 2f, 2h, 2e, 2g, and bortezomib for the HL-60 cell line were found as 33.52, 42.89, 48.02, 62.34, and 31.75 μM, while IC50 values of compounds 2h, 2g, 2f, 2e, and bortezomib for K562 cells were determined as 33.61, 50.23, 57.28, 76.90, and 42.69 μM, respectively. Further studies were carried out to shed light on the mechanism of antileukemic action. According to the data obtained by in vitro experiments, 1-(4-fluorophenyl)-3-(thiophen-3-yl)-5-(4-(4-methylpiperazin-1-yl)phenyl)-2-pyrazoline (2f) and 1-(3-bromophenyl)-3-(thiophen-3-yl)-5-(4-(4-methylpiperazin-1-yl)phenyl)-2-pyrazoline (2h) have proved to be potential antileukemic agents with remarkable cytotoxicity against HL-60 and K562 cells by activation of caspase 3, thereby inducing apoptosis.

Visible-light-induced [3+2] cycloadditions of donor/donor diazo intermediates with alkenes to achieve (spiro)-pyrazolines and pyrazoles

To date, [3 + 2] cycloadditions of diazo esters with alkynes or alkenes have been a robust tool to generate pyrazoles and pyrazolines. However, methods capable of generating donor/donor diazo species from readily available N-tosylhydrazones to furnish [3 + 2] cycloadditions, remain elusive. Herein, we describe the first visible-light-induced [3 + 2] cycloadditions of donor/donor diazo precursors with alkenes to afford pyrazoles and novel (spiro)pyrazolines bearing a quaternary center. This protocol shows a tolerable substrate scope covering versatile carbonyl compounds and alkenes. Late-stage functionalization of bioactive molecules, one-pot approach, and gram-scale synthesis have also been introduced successfully to prove the practicability. At last, mechanistic experiments and DFT studies suggested the formation of non-covalent interactions enabling the activation of N-tosylhydrazones and the formation of the donor/donor diazo intermediates.

Dihydropyrazole Derivatives Act as Potent α-Amylase Inhibitors and Free Radical Scavengers: Synthesis, Bioactivity Evaluation, Structure-Activity Relationship, ADMET, and Molecular Docking Studies

Dihydropyrazole (1-22) derivatives were synthesized from already synthesized chalcones. The structures of all of the synthesized compounds were confirmed by elemental analysis and various spectroscopic techniques. Furthermore, the synthesized compounds were screened against α amylase as well as investigated for antioxidant activities. The synthesized compounds demonstrate good to excellent antioxidant activities with IC₅₀ values ranging between 30.03 and 913.58 μM. Among the 22 evaluated compounds, 11 compounds exhibit excellent activity relative to the standard ascorbic acid IC₅₀ = 287.30 μM. Interestingly, all of the evaluated compounds show good to excellent α amylase activity with IC₅₀ values lying in the range between 0.5509 and 810.73 μM as compared to the standard acarbose IC₅₀ = 73.12 μM. Among the investigated compounds, five compounds demonstrate better activity compared to the standard. In order to investigate the binding interactions of the evaluated compounds with amylase protein, molecular docking studies were conducted, which show an excellent docking score as compared to the standard. Furthermore, the physiochemical properties, drug likeness, and ADMET were investigated, and it was found that none of the compounds violate Lipiniski's rule of five, which shows that this class of compounds has enough potential to be used as a drug candidate in the near future.

Assessing the effect of N-oxidation on the mutagenicity of 1-pyrazolines using the Ames assay

N-Nitrosamines are well known as environmental carcinogens. We have reported that N-nitroso-N-methylbutylamine was oxidized by Fe2+-Cu2+-H2O2 to 5-methyl-5-nitro-1-pyrazoline, a direct-acting N-oxide. 1-Pyrazolines have not been reported to exhibit genotoxicity. In this study, we investigated the effect of N-oxidation on the mutagenicity of 1-pyrazolines using the Ames assay. The mutagenicity of 5-alkyl-5-nitro-1-pyrazoline 1-oxide (1a; methyl, 1b; ethyl), the N-oxide isomer (3-alkyl-3-nitro-1-pyrazoline 1-oxide; 2a; methyl, 2b; ethyl), and the corresponding nonoxides (3-alkyl-3-nitro-1-pyrazoline; 3a; methyl, 3b; ethyl) was assayed in Salmonella typhimurium TA1535 and Escherichia coli WP2uvrA. The ratios of mutagenic potency in S. typhimurium TA1535 versus E. coli WP2uvrA were compared with those of N-alkylnitrosoureas. To predict the reaction site on the pyrazolines with nucleophiles, the electron density of the pyrazolines was obtained by theoretical calculations. The pyrazolines were mutagenic in S. typhimurium TA1535 and E. coli WP2uvrA. The ratio of S. typhimurium TA1535 to E. coli WP2uvrA 1a (87:13) or 1b (90:10) was similar to that of N-ethyl-N-nitrosourea (70:30). In contrast, the mutagenic ratio of 2a (22:78) or 2b (52:48) was similar to that of N-propyl-N-nitrosourea (48:52) or N-butyl-N-nitrosourea (14:86). The ratio of 3a (53:47) or 3b (54:46) was similar to that of N-propyl-N-nitrosourea or N-butyl-N-nitrosourea. The pyrazolines exhibit genotoxicity, and the mutagenic potency of the 1-pyrazolines is influenced by N-oxidation. We estimated that the mutagenicity of 1a or 1b was caused by DNA ethylation, and the isomers or the nonoxides were mutagenic via formation of alkylated DNA, which contains an alkyl chain longer than the propyl.

Pyrazoline Containing Compounds as Therapeutic Targets for Neurodegenerative Disorders

Pyrazolines are a significant class of heterocyclic compounds with essential biological activities. They are quite stable, which has inspired medicinal chemists to experiment with the ring's structure in many different ways to create a variety of pharmacological activities. The structures of numerous commercially available therapeutic agents contain a pyrazoline ring. Pyrazolines are well-known for their ability to treat neurodegenerative diseases. The neurodegenerative diseases that affect huge populations globally include Alzheimer's disease (AD), Parkinson's disease (PD), and psychiatric disorders. The neuroprotective properties of pyrazolines published since 2003 are covered in the current review. Structure-activity relationships (SARs), molecular docking simulation, anticholinesterase (anti-AChE), and monoamine oxidase (MAO A/B) inhibitory actions are all covered in this article. Pyrazolines were discovered to have beneficial effects in the management of AD and were revealed to be inhibitors of acetylcholine esterase (AChE) and beta-amyloid (Aβ) plaques. They were discovered to be efficient against PD and also targeted MAO B and COMT. It was discovered that the pyrazolines block MAO A to treat psychiatric diseases. Pyrazolines are significant heteroaromatic scaffolds with a variety of biological functions. They were discovered to be remarkably stable and serve as an indispensable anchor for the development of new drugs. By blocking AChE and MAOs, they may be used to treat neurodegenerative diseases. The discussion outlined here is an essential and helpful resource for medicinal chemists who are investigating and applying pyrazolines in neurodegenerative research initiatives as well as to expedite future research programs on neurodegenerative disorders.

Synthesis, Anticancer and Antitubercular Properties of New Chalcones and Their Nitrogen-Containing Five-Membered Heterocyclic Hybrids Bearing Sulfonamide Moiety

A new series of sulfonamides, 8a-b, 10, 12, and 14a-b, were synthesized by N-sulfonation reaction with sulfonyl chlorides 6a-b. Five new series of chalcone-sulfonamide hybrids (16-20)a-f were prepared via Claisen–Schmidt condensation of the newly obtained sulfonamides with aromatic aldehydes 15a-f in basic medium. Chalcones substituted with chlorine at position 4 of each series were used as precursors for the generation of their five-membered heterocyclic pyrazoline (22-23)a-d, (24-25)a-b and carbothioamide 27a-f derivatives. The synthesized compounds were evaluated for their anticancer and antituberculosis activities. To determine their anticancer activity, compounds were screened against sixty human cancer cell lines at a single dose (10 μM). Compounds 17a-c were highly active against LOX IMVI (melanoma), with IC₅₀ values of 0.34, 0.73 and 0.54 μM, respectively. Chalcone 18e showed remarkable results against the entire panel of leukemia cell lines with IC₅₀ values between 0.99–2.52 μM. Moreover, compounds 20e and 20f displayed growth inhibition of Mycobacterium tuberculosis H37Rv at concentrations below 10 μM. Although they showed low selectivity in cytotoxicity tests against the Vero cell line, further optimization could advance the potential biological activity of the selected compounds.

Rational Design, Synthesis and Biological Evaluation of Novel Pyrazoline-Based Antiproliferative Agents in MCF-7 Cancer Cells

Breast cancer is a disease in which cells in the breast divide continuously without control. There are great limitations in cancer chemotherapy. Hence, it is essential to search for new cancer therapeutics. Herein, a novel series of EGFR/HER2 dual inhibitors has been designed based on the hybridization of thiazole and pyrazoline fragments. The synthesized compounds were screened for their anti-proliferative activity against MCF-7 breast cancer cell line and MCF-10 normal breast cell line. Interestingly, synthesized compounds 6e and 6k showed very potent antiproliferative activity towards MCF-7 with IC50 values of 7.21 and 8.02 µM, respectively. Furthermore, enzymatic assay was performed against EGFR and HER2 to prove the dual inhibitory action. Compounds 6e and 6k showed potent inhibitory activity for EGFR with IC50 of 0.009 and 0.051 µM, respectively, and for HER2 with IC50 of 0.013 and 0.027 µM, respectively. Additionally, compounds 6e and 6k significantly stimulated apoptotic breast cancer cell death. Compound 6e was further explored for its anticancer activity in vivo using a Xenograft model. Moreover, computational modeling studies, ADMET studies and toxicity prediction were performed to investigate their potential drug candidates.

Fluorescence "Turn-off" Sensing of Iron (III) Ions Utilizing Pyrazoline Based Sensor: Experimental and Computational Study

A simple pyrazoline-based ''turn off'' fluorescent sensor 5-(4-methoxyphenyl)-3-(5-methylfuran-2-yl)-1-phenyl-4,5-dihydro-1H-pyrazole (PFM) was synthesized and well characterized by different techniques such as FT-IR, ¹H-NMR, ¹³C-NMR, and mass spectrometry. The synthesized sensor PFM was utilized for the detection of Fe³⁺ ions. Fluorescence emission selectively quenched by Fe³⁺ ions compared to other metal ions (Mn²⁺, Al³⁺, Fe²⁺, Hg²⁺, Cu²⁺, Co²⁺, Ni²⁺, Cd²⁺, Pb²⁺, and Zn²⁺) via paramagnetic fluorescence quenching and showed good anti-interference ability over the existence of other tested metals. Under optimum conditions, the fluorescence intensity of sensor quenched by Fe³⁺ in the range of 0 to 3 μM with detection limit of 0.12 μM. Binding of Fe³⁺ ions to PFM solution were studied by fluorescent titration, revealed formation of 1:1 PFM-Fe metal complex and binding constant of complex was found to be of 1.3 × 10⁵ M^-1. Further, the fluorescent sensor has been potentially used for the detection of Fe³⁺ in environmental samples (river water, tap water, and sewage waste water) with satisfactory recovery values of 99-101%.

Methyltransferases: Functions and Applications

In this review the current state-of-the-art of S-adenosylmethionine (SAM)-dependent methyltransferases and SAM are evaluated. Their structural classification and diversity is introduced and key mechanistic aspects presented which are then detailed further. Then, catalytic SAM as a target for drugs, and approaches to utilise SAM as a cofactor in synthesis are introduced with different supply and regeneration approaches evaluated. The use of SAM analogues are also described. Finally O-, N-, C- and S-MTs, their synthetic applications and potential for compound diversification is given.

Recent advances on synthesis and biological activities of C-17 aza-heterocycle derived steroids

Steroids modification for improving their biological activities is one of the most efficient and fruitful methods to develop novel medicines. Steroids with aza-heterocycles attaching to the C-17 owing various biological activities have received great attentions and some of the compounds are developed successfully as drugs. In this review, the research of the syntheses and biological activities of steroids bearing various aza-heterocycles published in the last 8 years is assembled, and some important structure-activity relationships (SARs) of active compounds are presented. According to the analysis of the literatures and our experiences in this field, the potential of aza-heterocyclic steroids as medicinal drugs is proposed.

Novel 2-(5-Aryl-4,5-Dihydropyrazol-1-yl)thiazol-4-One as EGFR Inhibitors: Synthesis, Biological Assessment and Molecular Docking Insights

Introduction

Epidermal growth factor receptor (EGFR) regulates several cell functions which include cell growth, survival, multiplication, differentiation, and apoptosis. Currently, EGFR kinase inhibitors are of increasing interest as promising targeted antitumor therapeutic agents.

Methods

Different thiazolyl-pyrazoline derivatives (7a-o) were synthesized and were first tested for anti-proliferative effect towards the A549 lung cancer cell line and the T-47D breast cancer cell line in MTT assay. Thereafter, thiazolyl-pyrazolines (7b, 7g, 7l, and 7m) were subsequently evaluated for their PK inhibition for EGFR. Moreover, representative promising derivatives (7g and 7m) in cytotoxic and PK inhibition assays were tested to investigate their impact on the apoptosis and cell cycle phases in T-47D cells in order to explore more insights into the antitumor actions of the target thiazolyl-pyrazolines. Furthermore, docking studies were accomplished to evaluate the patterns of binding of thiazolyl-pyrazolines 7b, 7g, 7l, and 7m in the EGFR active pocket (PDB ID: 1M17).

Results

Testing the thiazolyl pyrazoline compounds 7a-o on A549 and T-47D cell lines showed IC₅₀ arrays between 3.92 and 89.03 µM, and between 0.75 and 77.10 µM, respectively. Also, the tested thiazolyl-pyrazolines (7b, 7g, 7l, and 7m) demonstrated significant sub-micromolar EGFR inhibitory actions with IC₅₀ values 83, 262, 171 and 305 nM, respectively, in comparison to erlotinib (IC₅₀ =57 nM).

Discussion

Generally, it was observed that the tested thiazolyl pyrazolines showed more potent antiproliferative activity toward breast cancer cells T-47D than toward lung cancer cell lines A549. In particular, thiazolyl pyrazolines 7g and 7m showed the best activity against A549 cells (IC₅₀ = 3.92 and 6.53 µM) and T-47D cells (IC₅₀ = 0.88 and 0.75 µM). Compounds 7g and 7m provoked a sub-G1 phase arrest and cell apoptosis which are in agreement with the expected outcome of EGFR inhibition. Finally, the molecular docking of 7g and 7m in the active site of EGFR revealed a common binding pattern similar to that of erlotinib which involves the accommodation of the 1,3 thiazol-4-one ring and pyrazoline ring of target compounds in the binding region of erlotinib’s quinazoline ring and anilino moiety.

Synthesis of 2-Hydroxynaphthyl Pyrazolines Containing Isoniazid Moiety: A Potential Antitubercular Agent

Abstract:

The new series of pyrazolines derivatives containing isoniazid moiety were synthesized from 2-hydroxynaphthyl functionalized chalcones and isoniazid using sodium hydroxide as a base in 2- ethoxy ethanol. We evaluated their antitubercular activity against Mycobacterium tuberculosis strain (H37Rv) by Microplate Alamar Blue Assay (MABA). Some of the tested compounds 3a, 3b, and 3c, were found to have higher antitubercular activity than the selected standard drugs, whereas compounds 3d, 3e, 3i and 3j were found to have higher antitubercular activity than Streptomycin and same as that of Pyrazinamide and Ciprofloxacin, while remaining compound showed moderate activity. Whereas it is found that the disubstituted halogen compound and electron-withdrawing group on the phenyl ring are important substitutions for an increase in antitubercular activity.

A medicinal chemist's perspective towards structure activity relationship of heterocycle based anti-cancer agents

AIM

To describe structure activity relationship of heterocyclic derivatives with multi-targeted anticancer activity.

OBJECTIVES

With the following goals in mind, this review tries to describe significant recent advances in the medicinal chemistry of heterocycle-based compounds: (1) To shed light on recent literature focused on heterocyclic derivatives' anticancer potential; (2) To discuss recent advances in the medicinal chemistry of heterocyclic derivatives, as well as their biological implications for cancer eradication; (3) To summarise the comprehensive correlation of structure activity relationship (SAR) with pharmacological outcomes in cancer therapy.

BACKGROUND

Cancer remains one of the major serious health issues devastating the world today. Cancer is a complex disease in which improperly altered cells proliferate at an uncontrolled, rapid, and severe rate. Variables such as poor dietary habits, high stress, age, and smoking, can all contribute to the development of cancer. Cancer can affect almost any organ or tissue, although the brain, breast, liver, and colon are the most frequently affected organs. From several years, surgical operations and irradiation are in use along with chemotherapy as a primary treatment of cancer but still effective treatment of cancer remains a huge challenge. Chemotherapy is now one of the most effective strategies to eradicate cancer, although it has been shown to have a number of cytotoxic and unfavourable effects on normal cells. Despite all of these cancer treatments, there are several other targets for anticancer drugs. Cancer can be effectively eradicated by focusing on these targets, which include both cell-specific and receptor-specific targets such as tyrosine kinase receptors (TKIs). Heterocyclic scaffolds also have a variety of applications in drug development and are a common moiety in the pharmaceutical, agrochemical, and textile industries.

METHODS

The association between structural activity relationship data of many powerful compounds and their anticancer potential in vitro and in vivo has been studied. SAR of powerful heterocyclic compounds can also be generated using molecular docking simulations, as reported vastly in literature.

CONCLUSIONS

Heterocycles have a wide range of applications, from natural compounds to synthesised derivatives with powerful anticancer properties. To avoid cytotoxicity or unfavourable effects on normal mammalian cells due to a lack of selectivity towards the target site, as well as to reduce the occurrence of drug resistance, safer anticancer lead compounds with higher potency and lower cytotoxicity are needed. This review emphasizes on design and development of heterocyclic lead compounds with promising anticancer potential.

Novel metabolic enzyme inhibitors designed through the molecular hybridization of thiazole and pyrazoline scaffolds

New hybrid thiazolyl-pyrazoline derivatives (4a-k) were obtained through a facile and versatile synthetic procedure, and their inhibitory effects on the human carbonic anhydrase (hCA) isoforms I and II as well as on acetylcholinesterase (AChE) were determined. All new thiazolyl-pyrazolines showed activity at nanomolar levels as hCA I, hCA II, and AChE inhibitors, with K_I values in the range of 13.35-63.79, 7.01-115.80, and 17.89-48.05 nM, respectively. 1-[4-(4-Cyanophenyl)thiazol-2-yl]-3-(4-piperidinophenyl)-5-(4-fluorophenyl)-2-pyrazoline (4f) and 1-(4-phenylthiazol-2-yl)-3-(4-piperidinophenyl)-5-(4-fluorophenyl)-2-pyrazoline (4a) against hCAs and 1-[4-(4-chlorophenyl)thiazol-2-yl]-3-(4-piperidinophenyl)-5-(4-fluorophenyl)-2-pyrazoline (4d) and 1-[4-(4-nitrophenyl)thiazol-2-yl]-3-(4-piperidinophenyl)-5-(4-fluorophenyl)-2-pyrazoline (4b) against AChE were identified as highly potent inhibitors, superior to the standard drugs, acetazolamide and tacrine, respectively. Compounds 4a-k were also evaluated for their cytotoxic effects on the L929 mouse fibroblast (normal) cell line. Moreover, a comprehensive ligand-receptor interaction prediction was performed using the ADME-Tox, Glide XP, and MM-GBSA modules of the Schrödinger Small-Molecule Drug Discovery Suite to elucidate the potential binding modes of the new hybrid inhibitors against these metabolic enzymes.

Generation of Diazomethyl Radicals by Hydrogen Atom Abstraction and Their Cycloaddition with Alkenes

A general catalytic methodology for the synthesis of pyrazolines from α-diazo compounds and conjugated alkenes is reported. The direct hydrogen atom transfer (HAT) process of α-diazo compounds promoted by the tert-butylperoxy radical generates electrophilic diazomethyl radicals, thereby reversing the reactivity of the carbon atom attached with the diazo group. The regiocontrolled addition of diazomethyl radicals to carbon-carbon double bonds followed by intramolecular ring closure on the terminal diazo nitrogen and tautomerization affords a diverse set of pyrazolines in good yields with excellent regioselectivity. This strategy overcomes the limitations of electron-deficient alkenes in traditional dipolar [3+2]-cycloaddition of α-diazo compounds with alkenes. Furthermore, the straightforward formation of the diazomethyl radicals provides umpolung reactivity, thus opening new opportunities for the versatile transformations of diazo compounds.

Identification of a new class of potent aldose reductase inhibitors: Design, microwave-assisted synthesis, in vitro and in silico evaluation of 2-pyrazolines

Aldose reductase (AR) acts as a multi-disease target for the design and development of therapeutic agents for the management of diabetic complications as well as non-diabetic diseases. In the search for potent AR inhibitors, the microwave-assisted synthesis of twenty new compounds with a 1,3-diaryl-5-(4-fluorophenyl)-2-pyrazoline moiety as a common fragment in their structure (1-20) was carried out efficiently. Compounds 1-20 were subjected to in vitro studies, which were conducted to assess their AR inhibitory effects and cytotoxicity towards L929 mouse fibroblast (normal) cells. Among these compounds, 1-(3-bromophenyl)-3-(4-piperidinophenyl)-5-(4-fluorophenyl)-2-pyrazoline (20) was identified as the most promising AR inhibitor with an IC₅₀ value of 0.160 ± 0.005 μM exerting competitive inhibition with a K_i value of 0.019 ± 0.001 μM as compared to epalrestat (IC₅₀ = 0.279 ± 0.001 μM; K_i = 0.801 ± 0.023 μM) and quercetin (IC₅₀ = 4.120 ± 0.123 μM; K_i = 6.082 ± 0.272 μM). Compound 20 displayed cytotoxicity towards L929 cells with an IC₅₀ value of 18.75 ± 1.06 μM highlighting its safety as an AR inhibitor. Molecular docking studies suggested that π-π stacking interactions occurred between the m-bromophenyl moiety of compound 20 and Trp21. Based on in silico pharmacokinetic studies, compound 20 was found to possess favorable oral bioavailability and drug-like properties. It can be concluded that compound 20 is a potential orally bioavailable AR inhibitor for the management of diabetic complications as well as non-diabetic diseases.

Synthesis and Structural Characterization of Isostructural 4-(4-Aryl)-2-(5-(4-fluorophenyl)-3-(1-(4-fluorophenyl)-5-methyl-1H-1,2,3-triazol-4-yl)-4,5-dihydro-1H-pyrazol-1-yl)thiazoles

4-(4-Chlorophenyl)-2-(5-(4-fluorophenyl)-3-(1-(4-fluorophenyl)-5-methyl-1H-1,2,3-triazol-4-yl)-4,5-dihydro-1H-pyrazol-1-yl)thiazole (4) and 4-(4-fluorophenyl)-2-(5-(4-fluorophenyl)-3-(1-(4-fluorophenyl)-5-methyl-1H-1,2,3-triazol-4-yl)-4,5-dihydro-1H-pyrazol-1-yl)thiazole (5) have been synthesized in high yields. Crystallization of 4 and 5 from dimethylformamide solvent produced samples suitable for structure determination by single crystal diffraction. The materials are isostructural with triclinic, PĪ and symmetry and comprise two independent molecules in the asymmetric unit. The two independent molecules in the asymmetric unit assume similar conformation. The molecule is essentially planar apart from one of the two fluorophenyl groups, which is oriented roughly perpendicular to the plane of the rest of the molecule.

Development of Halogenated Pyrazolines as Selective Monoamine Oxidase-B Inhibitors: Deciphering via Molecular Dynamics Approach

Halogens have been reported to play a major role in the inhibition of monoamine oxidase (MAO), relating to diverse cognitive functions of the central nervous system. Pyrazoline/halogenated pyrazolines were investigated for their inhibitory activities against human monoamine oxidase-A and -B. Halogen substitutions on the phenyl ring located at the fifth position of pyrazoline showed potent MAO-B inhibition. Compound 3-(4-ethoxyphenyl)-5-(4-fluorophenyl)-4,5-dihydro-1H-pyrazole (EH7) showed the highest potency against MAO-B with an IC₅₀ value of 0.063 µM. The potencies against MAO-B were increased in the order of –F (in EH7) > –Cl (EH6) > –Br (EH8) > –H (EH1). The residual activities of most compounds for MAO-A were > 50% at 10 µM, except for EH7 and EH8 (IC₅₀ = 8.38 and 4.31 µM, respectively). EH7 showed the highest selectivity index (SI) value of 133.0 for MAO-B, followed by EH6 at > 55.8. EH7 was a reversible and competitive inhibitor of MAO-B in kinetic and reversibility experiments with a Ki value of 0.034 ± 0.0067 µM. The molecular dynamics study documented that EH7 had a good binding affinity and motional movement within the active site with high stability. It was observed by MM-PBSA that the chirality had little effect on the overall binding of EH7 to MAO-B. Thus, EH7 can be employed for the development of lead molecules for the treatment of various neurodegenerative disorders.

Pyrazol(in)e derivatives of curcumin analogs as a new class of anti-Trypanosoma cruzi agents

Aim: We report the synthesis and biological evaluation of a small library of 15 functionalized 3-styryl-2-pyrazolines and pyrazoles, derived from curcuminoids, as trypanosomicidal agents. Methods & results: The compounds were prepared via a cyclization reaction between the corresponding curcuminoids and the appropriate hydrazines. All of the derivatives synthesized were investigated for their trypanosomicidal activities. Compounds 4a and 4e showed significant activity against epimastigotes of Trypanosoma cruzi, with IC₅₀ values of 5.0 and 4.2 μM, respectively, accompanied by no toxicity to noncancerous mammalian cells. Compound 6b was found to effectively inhibit T. cruzi triosephosphate isomerase. Conclusion: The up to 16-fold higher potency of these derivatives compared with their curcuminoid precursors makes them a promising new family of T. cruzi inhibitors.

Diversity of the reaction mechanisms of SAM-dependent enzymes

S-adenosylmethionine (SAM) is ubiquitous in living organisms and is of great significance in metabolism as a cofactor of various enzymes. Methyltransferases (MTases), a major group of SAM-dependent enzymes, catalyze methyl transfer from SAM to C, O, N, and S atoms in small-molecule secondary metabolites and macromolecules, including proteins and nucleic acids. MTases have long been a hot topic in biomedical research because of their crucial role in epigenetic regulation of macromolecules and biosynthesis of natural products with prolific pharmacological moieties. However, another group of SAM-dependent enzymes, sharing similar core domains with MTases, can catalyze nonmethylation reactions and have multiple functions. Herein, we mainly describe the nonmethylation reactions of SAM-dependent enzymes in biosynthesis. First, we compare the structural and mechanistic similarities and distinctions between SAM-dependent MTases and the non-methylating SAM-dependent enzymes. Second, we summarize the reactions catalyzed by these enzymes and explore the mechanisms. Finally, we discuss the structural conservation and catalytical diversity of class I-like non-methylating SAM-dependent enzymes and propose a possibility in enzymes evolution, suggesting future perspectives for enzyme-mediated chemistry and biotechnology, which will help the development of new methods for drug synthesis.

Synthesis of New Bis-pyrazolines Endowed with Potent Antifungal Activity against Candida albicans and Aspergillus niger

Background:

Due to the increasing number of cases of invasive fungal infections (IFIs), there is an urgent need to identify potent antifungal agents capable of combating IFIs. Pyrazolines are one such class of therapeutically active agents that could be considered to fulfill this need.

Objective:

In this context, this paper aims to identify two new series of bis-pyrazolines endowed with potent antifungal activity against Candida albicans and Aspergillus niger.

Methods:

Two new series of bis-pyrazolines (4a-i, 5a-e) were synthesized through an efficient and versatile synthetic procedure. The compounds were screened for their antifungal effects on C. albicans and A. niger using a broth microdilution method. Their cytotoxic effects on NIH/3T3 mouse embryonic fibroblast cells were determined using MTT assay. Molecular docking studies were performed in the active site of lanosterol 14α-demethylase (CYP51) to shed light on their antifungal effects using Schrödinger’s Maestro molecular modeling package.

Results:

5,5'-(1,4-Phenylene)bis[1-(2-(5-phenyl-1,3,4-oxadiazol-2-yl)thio)acetyl)-3-(2-thienyl)-4,5- dihydro-1H-pyrazole] (4a) and 5,5'-(1,4-phenylene)bis[1-(2-(4-(2-hydroxyethyl)-1-piperazinylthiocarbamoyl) thio)acetyl)-3-(2-thienyl)-4,5-dihydro-1H-pyrazole] (5a) were found as the most promising antifungal agents in this series. Compounds 4a and 5a showed pronounced antifungal activity against C. albicans (MIC= 0.016 mg/mL) and A. niger (MIC= 0.008 mg/mL). Based on MTT assay, their antifungal effects were selective (IC50 > 0.500 mg/mL for NIH/3T3 cell line). Molecular docking studies suggested that compounds 5a-e might show their anticandidal effects via CYP51 inhibition in regard to their stronger interactions in the active site of CYP51.

Conclusion:

Compounds 4a and 5a stand out as potential antifungal agents for the management of IFIs caused by C. albicans and A. niger.

Pharmacophore hybridization approach to discover novel pyrazoline-based hydantoin analogs with anti-tumor efficacy

In search for new and safer anti-cancer agents, a structurally guided pharmacophore hybridization strategy of two privileged scaffolds, namely diaryl pyrazolines and imidazolidine-2,4-dione (hydantoin), was adopted resulting in a newfangled series of compounds (H1-H22). Herein, a bio-isosteric replacement of "pyrrolidine-2,5-dione" moiety of our recently reported antitumor hybrid incorporating diaryl pyrazoline and pyrrolidine-2,5-dione scaffolds with "imidazoline-2,4-dione" moiety has been incorporated. Complete biological studies revealed the most potent analog among all i.e. compound H13, which was at-least 10-fold more potent compared to the corresponding pyrrolidine-2,5-dione, in colon and breast cancer cells. In-vitro studies showed activation of caspases, arrest of G0/G1 phase of cell cycle, decrease in the expression of anti-apoptotic protein (Bcl-2) and increased DNA damage. In-vivo assay on HT-29 (human colorectal adenocarcinoma) animal xenograft model unveiled the significant anti-tumor efficacy along with oral bioavailability with maximum TGI 36% (i.p.) and 44% (per os) at 50 mg/kg dose. These findings confirm the suitability of hybridized pyrazoline and imidazolidine-2,4-dione analog H13 for its anti-cancer potential and starting-point for the development of more efficacious analogs.

Design, synthesis, and photophysics of bi- and tricyclic fused pyrazolines

A three series of bi-cyclic and tri-cyclic functionalised pyrazoline fluorophores with high quantum yields and positive solvato(fluoro)chromism were designed and synthesised by improved method.

Dual EGFR/VEGFR2 inhibitors and apoptosis inducers: Synthesis and antitumor activity of novel pyrazoline derivatives

Novel derivatives of the pyrazoline scaffold were synthesized and investigated for their cytotoxicity against prostate (PC-3), hepatocellular (HepG2), and breast (MDA-MB-231) carcinoma cells. The most active compounds, 4a, 4b, 5b, and 7c, revealed significant and broad-spectrum anticancer activities with IC₅₀ values of 1.30-7.18 μM in comparison with doxorubicin (IC₅₀  = 5.12-7.33 μM). Additionally, they exhibited lower cytotoxicity against normal WI-38 cells, indicating their high safety profiles. Aiming to enlighten the inhibitory potential on receptor tyrosine kinases (RTKs), compounds 4a, 4b, 5b, and 7c were assessed for their activities against four different RTKs (EGFR, FGFR2, HER2, and VEGFR2) and their apoptotic potencies on PC-3 cells. The results revealed that compounds 5b and 7c are potent dual EGFR and VEGFR2 inhibitors (IC₅₀  = 0.21 and 0.23 μM, respectively, against EGFR; 0.22 and 0.21 μM, respectively, against VEGFR2), whereas they displayed moderate inhibitory activities against HER2 and FGFR2. Besides, compounds 4a, 4b, 5b, and 7c prompted apoptosis via the upregulation of Bax, p53, and caspase-3, together with the downregulation of the levels of Bcl-2. Also, it was found that compounds 5b and 7c are more potent as apoptosis inducers than the other tested derivatives. Furthermore, molecular docking analyses of compounds 4a, 4b, 5b, and 7c in the EGFR and VEGFR ATP binding sites were performed, to confirm the in vitro assays.

Pyrazoline Hybrids as Promising Anticancer Agents: An Up-to-Date Overview

Pyrazolines are five-membered heterocycles possessing two adjacent nitrogens. They have attracted significant attention from organic and medicinal chemists due to their potent biological activities and the numerous possibilities for structural diversification. In the last decade, they have been intensively studied as targets for potential anticancer therapeutics, producing a steady yearly rise in the number of published research articles. Many pyrazoline derivatives have shown remarkable cytotoxic activities in the form of heterocyclic or non-heterocyclic based hybrids, such as with coumarins, triazoles, and steroids. The enormous amount of related literature in the last 5 years prompted us to collect all these published data from screening against cancer cell lines, or protein targets like EGFR and structure activity relationship studies. Therefore, in the present review, a comprehensive account of the compounds containing the pyrazoline nucleus will be provided. The chemical groups and the structural modifications responsible for the activity will be highlighted. Moreover, emphasis will be given on recent examples from the literature and on the work of research groups that have played a key role in the development of this field.

Recent advancements in the development of bioactive pyrazoline derivatives

Pyrazolines remain privileged heterocycles in drug discovery. 2-Pyrazoline scaffold has been proven as a ubiquitous motif which is present in a number of pharmacologically important drug molecules such as antipyrine, ramifenazone, ibipinabant, axitinib etc. They have been widely explored by the scientific community and are reported to possess wide spectrum of biological activities. For combating unprecedented diseases and worldwide increasing drug resistance, 2-pyrazoline has been tackled as a fascinating pharmacophore to generate new molecules with improved potency and lesser toxicity along with desired pharmacokinetic profile. This review aims to summarizes various recent advancements in the medicinal chemistry of pyrazoline based compounds with the following objectives: (1) To represent inclusive data on pyrazoline based marketed drugs as well as therapeutic candidates undergoing preclinical and clinical developments; (2) To discuss recent advances in the medicinal chemistry of pyrazoline derivatives with their numerous biological significances for the eradication of various diseases; (3) Summarizes structure-activity relationships (SAR) including in silico and mechanistic studies to afford ideas for the design and development of novel compounds with desired therapeutic implications.

Synthesis, In vitro and In silico Evaluation of a Series of Pyrazolines as New Anticholinesterase Agents

Background:

Pyrazolines, electron-rich nitrogen carriers, are of great importance due to their potential applications for the treatment of many diseases including inflammation, infectious diseases and neurodegenerative disorders.

Objectives:

The purpose of this work was to synthesize new pyrazoline derivatives and evaluate their anticholinesterase effects.

Methods:

1-Aryl-5-[4-(piperidin-1-yl)phenyl]-3-(3,4-dimethoxyphenyl)-4,5-dihydro-1H-pyrazoles (1-7) were synthesized via the treatment of 1-(3,4-dimethoxyphenyl)-3-[4-(piperidin-1-yl)phenyl]prop-2- en-1-one with arylhydrazine hydrochloride derivatives in acetic acid, whereas 1-aryl-5-[4- (morpholin-4-yl)phenyl]-3-(3,4-dimethoxyphenyl)-4,5-dihydro-1H-pyrazoles (8-14) were obtained by the treatment of 1-(3,4-dimethoxyphenyl)-3-[4-(morpholin-4-yl)phenyl]prop-2-en-1-one with arylhydrazine hydrochloride derivatives in acetic acid. Their inhibitory effects on acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) were determined using a modification of Ellman’s spectrophotometric method. In silico docking and Absorption, Distribution, Metabolism and Excretion (ADME) studies were performed using Schrödinger’s Maestro molecular modeling package.

Results:

In general, piperidine derivatives were found to be more effective than morpholine derivatives on cholinesterases (ChEs). 1-Phenyl-5-[4-(piperidin-1-yl)phenyl]-3-(3,4-dimethoxyphenyl)- 4,5-dihydro-1H-pyrazole (1) and 1-(4-cyanophenyl)-5-[4-(piperidin-1-yl)phenyl]-3-(3,4- dimethoxyphenyl)-4,5-dihydro-1H-pyrazole (7) were identified as the most effective AChE inhibitors in this series with 40.92% and 38.98%, respectively. Compounds 1 and 7 were docked into the active site of human AChE (PDB code: 4EY7). Both the compounds were found to be capable of forming π-π stacking interactions with Trp286. Based on in silico ADME studies, these compounds are expected to have reasonable oral bioavailability.

Conclusion:

In the view of this work, the structural modification of the identified agents is going on for the generation of new anticholinesterase agents with enhanced efficacy.

Steroidal pyrazolines as a promising scaffold in drug discovery

Steroidal pyrazolines constitute an interesting and promising scaffold for drug discovery as they display diverse chemical reactivity and a wide range of biological activities. Literature reports indicate potent anticancer potential of steroidal pyrazolines along with broad-spectrum antimicrobial activities. Strong neuroprotective effects with steroids possessing pyrazoline moiety have also been observed. Among all the therapeutically active steroidal pyrazolines, D-ring-substituted derivatives are highly potent and the least toxic. The current and futuristic research approaches in this area are focused towards the exploration of this promising scaffold to develop molecules with widespread pharmacological activities. This review article mainly covers the synthetic and pharmacological aspects of steroidal pyrazolines, which will assist the medicinal chemists working in this area in their scientific endeavors.

Opportunities and challenges of using five-membered ring compounds as promising antitubercular agents

Tuberculosis (TB), a chronic infectious disease, is one of the greatest risks to human beings and 10 million people were diagnosed with TB and 1.6 million died from this disease in 2017. In addition, with the emergence of multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB), the TB situation has become even worse, which has aggravated the mortality and spread of this disease. To overcome this problem, research into novel antituberculosis agents with enhanced activities against MDR-TB, reduced toxicity, and shortened duration of therapy is of great importance. Fortunately, many novel potential anti-TB drug candidates with five-membered rings, which are most likely to be effective against sensitive and resistant strains, have recently entered clinical trials. Different five-membered rings such as furans, pyranoses, thiazoles, pyrazolines, imidazoles, oxazolidinone, thiazolidins, isoxazoles, triazoles, oxadiazoles, thiadiazoles, and tetrazoles have been designed, prepared, and evaluated for their antimycobacterial activity against Mycobacterium tuberculosis. In this article, we highlight the recent advances made in the discovery of novel five-membered ring compounds and focus on their antitubercular activities, toxicity, structure-activity relationships, and mechanisms of action.

A Suitable Functionalization of Nitroindazoles with Triazolyl and Pyrazolyl Moieties via Cycloaddition Reactions

The alkylation of a series of nitroindazole derivatives with 1,2-dibromoethane afforded the corresponding N-(2-bromoethyl)- and N-vinyl-nitro-1H-indazoles. The Cu(I)-catalysed azide- alkyne 1,3-dipolar cycloaddition was selected to substitute the nitroindazole core with 1,4-disubstituted triazole units after converting one of the N-(2-bromoethyl)nitroindazoles into the corresponding azide. The reactivity in 1,3-dipolar cycloaddition reactions with nitrile imines generated in situ from ethyl hydrazono-α-bromoglyoxylates was studied with nitroindazoles bearing a vinyl unit. The corresponding nitroindazole-pyrazoline derivatives were obtained in good to excellent yields.

Overview of recent developments of pyrazole derivatives as an anticancer agent in different cell line

Pyrazole is a five-membered aromatic heterocyclic ring with two adjacent nitrogen atoms C₃H₃N₂H.The presence of this nucleus in pharmacological agents of various therapeutic categories gifts a broad spectrum of biological activities and pharmaceuticals that contain pyrazole like celecoxib (anti-inflammatory), CDPPB (antipsychotic), Rimonabant (anti-obesity), Difenamizole, (Analgesic), Betazole (H2 receptor agonist), Fezolamide (Antidepressant), etc… The pharmacological potential of the pyrazole fraction is proved in many publication where they synthesized and evaluated pyrazoles against several biological agents. The aim of this article review is to survey recent works linking pyrazole structures to anticancer activities corresponding to 9 different type of cancer.