Synthesis and Anticancer Evaluation of 1,4-Naphthoquinone Derivatives Containing a Phenylaminosulfanyl Moiety

Synthesis and biochemical characterization of naphthoquinone derivatives targeting bacterial histidine kinases

Waldiomycin is an inhibitor of histidine kinases (HKs). Although most HK inhibitors target the ATP-binding region, waldiomycin binds to the intracellular dimerization domain (DHp domain) with its naphthoquinone moiety presumed to interact with the conserved H-box region. To further develop inhibitors targeting the H-box, various 2-aminonaphthoquinones with cyclic, aliphatic, or aromatic amino groups and naphtho [2,3-d] isoxazole-4,9-diones were synthesized. These compounds were tested for their inhibitory activity (IC50) against WalK, an essential HK for Bacillus subtilis growth, and their minimum inhibitory concentrations (MIC) against B. subtilis. As a result, 11 novel HK inhibitors were obtained as naphthoquinone derivatives (IC50: 12.6-305 µM, MIC: 0.5-128 µg ml-1). The effect of representative compounds on the expression of WalK/WalR regulated genes in B. subtilis was investigated. Four naphthoquinone derivatives induced the expression of iseA (formerly yoeB), whose expression is negatively regulated by the WalK/WalR system. This suggests that these compounds inhibit WalK in B. subtilis cells, resulting in antibacterial activity. Affinity selection/mass spectrometry analysis was performed to identify whether these naphthoquinone derivatives interact with WalK in a manner similar to waldiomycin. Three compounds were found to competitively inhibit the binding of waldiomycin to WalK, suggesting that they bind to the H-box region conserved in HKs and inhibit HK activity.

2,3-Dichloronaphthoquinone derivatives: Synthesis, antimicrobial activity, molecular modelling and ADMET studies

In the present study, an intermediate namely 2-(3-bromopropylamino)-3-chloronaphthalene-1,4-dione was initially synthesized via the nucleophilic addition-elimination reaction between 2,3-dichloro-1,4-naphthoquinone and 3-bromo-1-aminopropane. Then a coupling reaction between the intermediate and piperazine derivatives yielded a number of 1,4-naphthoquinone derivatives. Spectroscopic analysis successfully characterized the products that were obtained in good yields. In vitro antibacterial properties of the compounds were examined against different bacterial strains. In vitro antibacterial properties of the compounds were examined against the bacterial strains S. Aureus, E. Faecalis, E. Coli and P. Aeruginosa. While compound 9 was found to be effective against all bacterial strains used, compound 12 was active against three strains and compounds 10 and 11 were effective against the two. None of the compounds are effective against C. albicans strain. In silico molecular docking studies revealed that all compounds had docking scores comparable to the antibacterial drugs ciprofloxacin and gentamicin and might be considered as DNA gyrase B inhibitors. Molecular dynamics simulations were also conducted for a better understanding of the stability and the selected docked complexes. Additionally, the drug similarity of the synthesized compounds and ADMET characteristics were examined in conjunction with the antibiotic ciprofloxacin, and drug potentials were then evaluated. Compatible predictions were found with the drug similarity and ADMET parameters.

Strong intramolecular charge-transfer effect strengthening naphthoquinone-based chemosensor: Experimental and theoretical evaluation

An aminophenol-linked naphthoquinone-based fluorometric and colorimetric chemosensor 2-chloro-3-((3-hydroxyphenyl) amino) naphthalene-1,4-dione (2CAN-Dione) was synthesized for selective detection of Sn2+ ion in aqueous solution. The amine and conversion of carbonyl into carboxyl groups play a vital role in the sensing mechanism when Sn2+ is added to 2CAN-Dione. Comprehensive characterization of the sensor was carried out using standard spectral and analytical approaches. Because of the intramolecular charge transfer (ICT) effect and the turn-on sensing mode, the strong fluorometric emission towards Sn2+ was observed at about 435 nm. The chemosensor exhibited good selectivity for Sn2+ in the presence of coexisting metal ions. An improved linear connection was established with a low limit of detection (0.167 μM). FT-IR, 1H NMR, 13C NMR, and quantum chemistry methods were performed to verify the binding coordination mechanism. The chemosensing probe 2CAN-Dione was successfully employed in bioimaging investigations, demonstrating that it is a reliable fluorescent marker for Sn2+ in human cancer cells.

Unlocking the potential of 1,4-naphthoquinones: A comprehensive review of their anticancer properties

Cancer encompasses a group of pathologies with common characteristics, high incidence, and prevalence in all countries. Although there are treatments available for this disease, they are not always effective or safe, often failing to achieve the desired results. This is why it is necessary to continue the search for new therapies. One of the strategies for obtaining new antitumor drugs is the use of 1,4-naphthoquinone as a scaffold in synthetic or natural products with antitumor activity. This review focuses on compiling studies related to the antitumor activity of 1,4-naphthoquinone and its natural and synthetic derivatives over the last 10 years. The work describes the main natural naphthoquinones with antitumor activity and classifies the synthetic naphthoquinones based on the structural modifications made to the scaffold. Additionally, the formation of metal complexes using naphthoquinones as a ligand is considered. After a thorough review, 197 synthetic compounds with potent biological activity against cancer have been classified according to their chemical structures and their mechanisms of action have been described.

The Progress of Small Molecule Targeting BCR-ABL in the Treatment of Chronic Myeloid Leukemia

Chronic myelogenous leukemia (CML) is a malignant myeloproliferative disease. According to the American Cancer Society's 2021 cancer data report, new cases of CML account for about 15% of all leukemias. CML is generally divided into three stages: chronic phase, accelerated phase, and blast phase. Nearly 90% of patients are diagnosed as a chronic phase. Allogeneic stem cell transplantation and chemotherapeutic drugs, such as interferon IFN-α were used as the earliest treatments for CML. However, they could generate obvious side effects, and scientists had to seek new treatments for CML. A new era of targeted therapy for CML began with the introduction of imatinib, the first-generation BCR-ABL kinase inhibitor. However, the ensuing drug resistance and mutant strains led by T315I limited the further use of imatinib. With the continuous advancement of research, tyrosine kinase inhibitors (TKI) and BCR-ABL protein degraders with novel structures and therapeutic mechanisms have been discovered. From biological macromolecules to classical target protein inhibitors, a growing number of compounds are being developed to treat chronic myelogenous leukemia. In this review, we focus on summarizing the current situation of a series of candidate small-molecule drugs in CML therapy, including TKIs and BCR-ABL protein degrader. The examples provided herein describe the pharmacology activity of small-molecule drugs. These drugs will provide new enlightenment for future treatment directions.

Structural Optimization of Antimycobacterial Azaaurones Towards Improved Solubility and Metabolic Stability

While N-acetyl azaaurones have already been disclosed for their potential against tuberculosis (TB), their low metabolic stability remains an unaddressed liability. We now report a study designed to improve the metabolic stability and solubility of the azaaurone scaffold and to identify the structural requirements for antimycobacterial activity. Replacing the N-acetyl moiety for a N-carbamoyl group led to analogues with sub- and nanomolar potencies against M. tuberculosis H37Rv, as well as equipotent against drug-susceptible and drug-resistant M. tuberculosis isolates. The new N-carbamoyl azaaurones exhibited improved microsomal stability, compared to their N-acetylated counterparts, with several compounds displaying moderate to high kinetic solubility. The frequency of spontaneous resistance to azaaurones was observed to be in the range of 10-8 , a value that is comparable to current TB drugs in the market. Overall, these results reveal that azaaurones are amenable to structural modifications to improve metabolic and solubility liabilities, and highlight their potential as antimycobacterial agents.

A New Cu/Fe Layer Double Hydroxide Nanocomposite Exerts Anticancer Effects against PC-3 Cells by Inducing Cell Cycle Arrest and Apoptosis

Prostate cancer treatment poses significant challenges due to its varying aggressiveness, potential for metastasis, and the complexity of treatment options. Balancing the effectiveness of therapies, minimizing side effects, and personalizing treatment strategies are ongoing challenges in managing this disease. Significant advances in the use of nanotechnology for the treatment of prostate cancer with high specificity, sensitivity, and efficacy have recently been made. This study aimed to synthesize and characterize a novel Cu/Fe layer double hydroxide (LDH) nanocomposite for use as an anticancer agent to treat prostate cancer. Cu/Fe LDH nanocomposites with a molar ratio of 5:1 were developed using a simple co-precipitation approach. FT-IR, XRD, SEM, TEM, TGA, and zeta potential analyses confirmed the nanocomposite. Moreover, the MTT cell viability assay, scratch assay, and flow cytometry were utilized to examine the prospective anticancer potential of Cu/Fe LDH on a prostate cancer (PC-3) cell line. We found that Cu/Fe LDH reduced cell viability, inhibited cell migration, induced G1/S phase cell cycle arrest, and triggered apoptotic effect in prostate cancer cells. The findings also indicated that generating reactive oxygen species (ROS) formation could improve the biological activity of Cu/Fe LDH. Additionally, Cu/Fe LDH showed a good safety impact on the normal lung fibroblast cell line (WI-38). Collectively, these findings demonstrate that the Cu/Fe LDH nanocomposite exhibited significant anticancer activities against PC-3 cells and, hence, could be used as a promising strategy in prostate cancer treatment.

Functionalized Cyclopentenones with Low Electrophilic Character as Anticancer Agents

In this study were synthesized non-Michael acceptor cyclopentenones (CP) from biomass derivative furfural as anticancer agents. Cyclic enones, both from natural sources and synthetic analogues, have been described as cytotoxic agents. Most of these agents were unsuccessful in becoming valuable therapeutic agents due to toxicity problems derived from unselective critical biomacromolecule alkylation. This may be caused by Michael addition to the enone system. Ab initio studies revealed that 2,4-substituted CPs are less prone to Michael additions, and as such were tested three families of those derivatives. We prepare the new CPs from furfural through a tandem furan ring opening/Nazarov electrocyclization and further functionalization. Experimentally the 2,4-substituted CPs exhibited no reactivity towards sulphur nucleophiles, while maintaining cytotoxicity against HT-29, MCF-7, NCI-H460, HCT-116 and MDA-MB 231 cells lines. Moreover, the selected CP are non-toxic against healthy HEK 293T cell lines and present proper calculated drug-like properties.

Zeolite Nanoparticles Loaded with 2-Methoxystradiol as a Novel Drug Delivery System for the Prostate Cancer Therapy

The estrogen metabolite 2-methoxyestradiol (2ME) is a promissory anticancer drug mainly because of its pro-apoptotic properties in cancer cells. However, the therapeutic use of 2ME has been hampered due to its low solubility and bioavailability. Thus, it is necessary to find new ways of administration for 2ME. Zeolites are inorganic aluminosilicates with a porous structure and are considered good adsorbents and sieves in the pharmaceutical field. Here, mordenite-type zeolite nanoparticles were loaded with 2ME to assess its efficiency as a delivery system for prostate cancer treatment. The 2ME-loaded zeolite nanoparticles showed an irregular morphology with a mean hydrodynamic diameter of 250.9 ± 11.4 nm, polydispersity index of 0.36 ± 0.04, and a net negative surface charge of -34 ± 1.73 meV. Spectroscopy with UV-vis and Attenuated Total Reflectance Infrared Fourier-Transform was used to elucidate the interaction between the 2ME molecules and the zeolite framework showing the formation of a 2ME-zeolite conjugate in the nanocomposite. The studies of adsorption and liberation determined that zeolite nanoparticles incorporated 40% of 2ME while the liberation of 2ME reached 90% at pH 7.4 after 7 days. The 2ME-loaded zeolite nanoparticles also decreased the viability and increased the mRNA of the 2ME-target gene F-spondin, encoded by SPON1, in the human prostate cancer cell line LNCaP. Finally, the 2ME-loaded nanoparticles also decreased the viability of primary cultures from mouse prostate cancer. These results show the development of 2ME-loaded zeolite nanoparticles with physicochemical and biological properties compatible with anticancer activity on the human prostate and highlight that zeolite nanoparticles can be a good carrier system for 2ME.

Biological Activity of Naphthoquinones Derivatives in the Search of Anticancer Lead Compounds

Naphthoquinones are a valuable source of secondary metabolites that are well known for their dye properties since ancient times. A wide range of biological activities have been described highlighting their cytotoxic activity, gaining the attention of researchers in recent years. In addition, it is also worth mentioning that many anticancer drugs possess a naphthoquinone backbone in their structure. Considering this background, the work described herein reports the evaluation of the cytotoxicity of different acyl and alkyl derivatives from juglone and lawsone that showed the best activity results from a etiolated wheat coleoptile bioassay. This bioassay is rapid, highly sensitive to a wide spectrum of activities, and is a powerful tool for detecting biologically active natural products. A preliminary cell viability bioassay was performed on cervix carcinoma (HeLa) cells for 24 h. The most promising compounds were further tested for apoptosis on different tumoral (IGROV-1 and SK-MEL-28) and non-tumoral (HEK-293) cell lines by flow cytometry. Results reveal that derivatives from lawsone (particularly derivative 4) were more cytotoxic on tumoral than in non-tumoral cells, showing similar results to those obtained with of etoposide, which is used as a positive control for apoptotic cell death. These findings encourage further studies on the development of new anticancer drugs for more directed therapies and reduced side effects with naphthoquinone skeleton.

1,4-Naphthoquinone Induces FcRn Protein Expression and Albumin Recycling in Human THP-1 Cells

The neonatal Fc receptor (FcRn) has been established as a major factor in regulating the metabolism of albumin and IgG in humans by protecting them from intracellular degradation after they are endocytosed into cells. We assume that increasing the levels of endogenous FcRn proteins in cells would be beneficial to enhance the recycling of these molecules. In this study, we identify the compound 1,4-naphthoquinone as an efficient stimulator of FcRn protein expression in human THP-1 monocytic cells with potency at the submicromolar range. Also, the compound increased the subcellular localization of FcRn to the endocytic recycling compartment and enhanced human serum albumin recycling in the PMA-induced THP-1 cells. These results suggest that 1,4-naphthoquinone stimulates FcRn expression and activity in human monocytic cells in vitro and it could open a new avenue for designing cotreatment agents to enhance the efficacy of biological treatments such as albumin-conjugated drugs in vivo.

Novel pyrrolidine-aminophenyl-1,4-naphthoquinones: structure-related mechanisms of leukemia cell death

Novel derivatives of aminophenyl-1,4-naphthoquinones, in which a pyrrolidine group was added to the naphthoquinone ring, were synthesized and investigated for the mechanisms of leukemic cell killing. The novel compounds, TW-85 and TW-96, differ in the functional (methyl or hydroxyl) group at the para-position of the aminophenyl moiety. TW-85 and TW-96 were found to induce concentration- and time-dependent apoptotic and/or necrotic cell death in human U937 promonocytic leukemia cells but only TW-96 could also kill K562 chronic myeloid leukemia cells and CCRF-CEM lymphoblastic leukemia cells. Normal peripheral blood mononuclear cells were noticeably less responsive to both compounds than leukemia cells. At low micromolar concentrations used, TW-85 killed U937 cells mainly by inducing apoptosis. TW-96 was a weaker apoptotic agent in U937 cells but proved to be cytotoxic and a stronger inducer of necrosis in all three leukemic cell lines tested. Both compounds induced mitochondrial permeability transition pore opening, cytochrome c release, and caspase activation in U937 cells. Cytotoxicity induced by TW-96, but not by TW-85, was associated with the elevation of the cytosolic levels of reactive oxygen species (ROS). The latter was attenuated by diphenyleneiodonium, indicating that NADPH oxidase was likely to be the source of ROS generation. Activation of p38 MAPK by the two agents appeared to prevent necrosis but differentially affected apoptotic cell death in U937 cells. These results further expand our understanding of the structure-activity relationship of aminophenyl-1,4-naphthoquinones as potential anti-leukemic agents with distinct modes of action.

Docetaxel Loaded in Copaiba Oil-Nanostructured Lipid Carriers as a Promising DDS for Breast Cancer Treatment

Breast cancer is the neoplasia of highest incidence in women worldwide. Docetaxel (DTX), a taxoid used to treat breast cancer, is a BCS-class-IV compound (low oral bioavailability, solubility and intestinal permeability). Nanotechnological strategies can improve chemotherapy effectiveness by promoting sustained release and reducing systemic toxicity. Nanostructured lipid carriers (NLC) encapsulate hydrophobic drugs in their blend-of-lipids matrix, and imperfections prevent drug expulsion during storage. This work describes the preparation, by design of experiments (2³ factorial design) of a novel NLC formulation containing copaiba oil (CO) as a functional excipient. The optimized formulation (NLC_DTX) showed approximately 100% DTX encapsulation efficiency and was characterized by different techniques (DLS, NTA, TEM/FE-SEM, DSC and XRD) and was stable for 12 months of storage, at 25 °C. Incorporation into the NLC prolonged drug release for 54 h, compared to commercial DTX (10 h). In vitro cytotoxicity tests revealed the antiproliferative effect of CO and NLC_DTX, by reducing the cell viability of breast cancer (4T1/MCF-7) and healthy (NIH-3T3) cells more than commercial DTX. NLC_DTX thus emerges as a promising drug delivery system of remarkable anticancer effect, (strengthened by CO) and sustained release that, in clinics, may decrease systemic toxicity at lower DTX doses.

Benzochromenopyrimidines: Synthesis, Antiproliferative Activity against Colorectal Cancer and Physicochemical Properties

Ten new differently substituted 3-benzyl-5-aryl-3,5-dihydro-4H-benzo[6,7]chromeno[2,3-d]pyrimidin-4,6,11-triones 3 were synthesized by a simple and cost-efficient procedure in a one-pot, three-component reaction from readily available ethyl 2-amino-4-aryl-5,10-dioxo-5,10-dihydro-4H-benzo[g]chromene-3-carboxylates, benzylamine and triethyl orthoformate under solvent- and catalyst-free conditions. All the new compounds were screened for their antiproliferative activity against two colorectal-cancer-cell lines. The results showed that the compounds 3-benzyl-5-phenyl-3,5-dihydro-4H-benzo[6,7]chromeno[2,3-d]pyrimidine-4,6,11-trione (3a) and 3-benzyl-5-(3-hydroxyphenyl)-3,5-dihydro-4H-benzo[6,7]chromeno[2,3-d]pyrimidine-4,6,11-trione (3g) exhibited the most potent balanced inhibitory activity against human LoVo and HCT-116 cancer cells.

In Vitro Cytotoxicity Evaluation of Plastoquinone Analogues against Colorectal and Breast Cancers along with In Silico Insights

Colorectal cancer (CRC) and breast cancer are leading causes of death globally, due to significant challenges in detection and management. The late-stage diagnosis and treatment failures require the discovery of potential anticancer agents to achieve a satisfactory therapeutic effect. We have previously reported a series of plastoquinone analogues to understand their cytotoxic profile. Among these derivatives, three of them (AQ-11, AQ-12, and AQ-15) were selected by the National Cancer Institute (NCI) to evaluate their in vitro antiproliferative activity against a panel of 60 human tumor cell lines. AQ-12 exhibited significant antiproliferative activity against HCT-116 CRC and MCF-7 breast cancer cells at a single dose and further five doses. MTT assay was also performed for AQ-12 at different concentrations against these two cells, implying that AQ-12 exerted notable cytotoxicity toward HCT-116 (IC₅₀ = 5.11 ± 2.14 μM) and MCF-7 (IC₅₀ = 6.06 ± 3.09 μM) cells in comparison with cisplatin (IC₅₀ = 23.68 ± 6.81 μM and 19.67 ± 5.94 μM, respectively). This compound also augmented apoptosis in HCT-116 (62.30%) and MCF-7 (64.60%) cells comparable to cisplatin (67.30% and 78.80%, respectively). Molecular docking studies showed that AQ-12 bound to DNA, forming hydrogen bonding through the quinone scaffold. In silico pharmacokinetic determinants indicated that AQ-12 demonstrated drug-likeness with a remarkable pharmacokinetic profile for future mechanistic anti-CRC and anti-breast cancer activity studies.

Exploring the Anticancer Effects of Brominated Plastoquinone Analogs with Promising Cytotoxic Activity in MCF-7 Breast Cancer Cells via Cell Cycle Arrest and Oxidative Stress Induction

Plastoquinone analogs are privileged structures among the known antiproliferative natural product-based compound families. Exploiting one of these analogs as a lead structure, we report the investigation of the brominated PQ analogs (BrPQ) in collaboration with the National Cancer Institute of Bethesda within the Developmental Therapeutics Program (DTP). These analogs exhibited growth inhibition in the micromolar range across leukemia, non-small cell lung cancer (EKVX, HOP-92, and NCI-H522), colon cancer (HCT-116, HOP-92), melanoma (LOX IMVI), and ovarian cancer (OVCAR-4) cell lines. One brominated PQ analog (BrPQ5) was selected for a full panel five-dose in vitro assay by the NCI’s Development Therapeutic Program (DTP) division to determine GI50, TGI, and LC50 parameters. The brominated PQ analog (BrPQ5) displayed remarkable activity against most tested cell lines, with GI50 values ranging from 1.55 to 4.41 µM. The designed molecules (BrPQ analogs) obeyed drug-likeness rules, displayed a favorable predictive Absorption, Distribution, Metabolism, and Excretion (ADME) profile, and an in silico simulation predicted a possible BrPQ5 interaction with proteasome catalytic subunits. Furthermore, the in vitro cytotoxic activity of BrPQ5 was assessed, and IC50 values for U-251 glioma, MCF-7 and MDA-MB-231 breast cancers, DU145 prostate cancer, HCT-116 colon cancer, and VHF93 fibroblast cell lines were evaluated using an MTT assay. MCF-7 was the most affected cell line, and the effects of BrPQ5 on cell proliferation, cell cycle, oxidative stress, apoptosis/necrosis induction, and proteasome activity were further investigated in MCF-7 cells. The in vitro assay results showed that BrPQ5 caused cytotoxicity in MCF-7 breast cancer cells via cell cycle arrest and oxidative stress induction. However, BrPQ5 did not inhibit the catalytic activity of the proteasome. These results provide valuable insights for further discovery of novel antiproliferative agents.

Discovery of Anilino-1,4-naphthoquinones as Potent EGFR Tyrosine Kinase Inhibitors: Synthesis, Biological Evaluation, and Comprehensive Molecular Modeling

Epidermal growth factor receptor (EGFR) has been recognized as one of the attractive targets for anticancer drug development. Herein, a set of anilino-1,4-naphthoquinone derivatives (3-18) was synthesized and investigated for their anticancer and EGFR inhibitory potentials. Among all tested compounds, three derivatives (3, 8, and 10) were selected for studying EGFR inhibitory activity (in vitro and in silico) due to their most potent cytotoxic activities against six tested cancer cell lines (i.e., HuCCA-1, HepG2, A549, MOLT-3, MDA-MB-231, and T47D; IC50 values = 1.75-27.91 μM), high selectivity index (>20), and good predicted drug-like properties. The experimental results showed that these three promising compounds are potent EGFR inhibitors with nanomolar IC50 values (3.96-18.64 nM). Interestingly, the most potent compound 3 bearing 4-methyl substituent on the phenyl ring displayed 4-fold higher potency than the known EGFR inhibitor, erlotinib. Molecular docking, molecular dynamics simulation, and MM/GBSA-based free energy calculation revealed that van der Waals force played a major role in the accommodations of compound 3 within the ATP-binding pocket of EGFR. Additionally, the 4-CH3 moiety of the compound was noted to be a key chemical feature contributing to the highly potent EGFR inhibitory activity via its formations of alkyl interactions with A743, K745, M766, and L788 residues as well as additional interactions with M766 and T790.

Promising Antibacterial and Antifungal Agents Based on Thiolated Vitamin K3 Analogs: Synthesis, Bioevaluation, Molecular Docking

In the present study, we designed and synthesized thiolated VK3 analogs (VK3a–g) along with an extensive antimicrobial study. After the evaluation of the antibacterial and antifungal activity against various bacterial and fungal strains, we presented an initial structure–activity relationship study on these VK3 analogs. In particular, four thiolated VK3 analogs exhibited superior biological potency against some Gram-positive bacterial strains, including Staphylococcus aureus (ATCC^® 29213) and Enterococcus faecalis (ATCC^® 29212). Next, all thiolated VK3 analogs were evaluated for their potential of cell growth inhibition on the NCI-60 cancer cell lines panel. This screening underlined that the thiolated VK3 analogs have no visible cytotoxicity on different cancer cell lines. The selected two thiolated VK3 analogs (VK3a and VK3b), having minimal hemolytic activity, which also have the lowest MIC values on S. aureus and E. faecalis, were further evaluated for their inhibition capacities on biofilm formation after evaluating their potential in vitro antimicrobial activity against each of the 20 clinically obtained resistant strains of Staphylococcus aureus. VK3b showed excellent antimicrobial activity against clinically resistant S. aureus isolates. Furthermore, the tested molecules showed nearly two log₁₀ reduction in the viable cell count at six hours according to the time kill curve studies. Although these molecules decreased biofilm attachment about 50%, when sub-MIC concentrations were used these molecules increased the percentage of biofilm formation. The molecular docking of VK3a and VK3b in S. aureus thymidylate kinase was conducted in order to predict their molecular interactions. VK3a and VK3b exhibited excellent lead-likeness properties and pharmacokinetic profiles that qualify them for further optimization and development. In conclusion, since investigating efficient novel antimicrobial molecules is quite difficult, these studies are of high importance, especially in the present era of antimicrobial resistance.

Metal-/catalyst-free one-pot three-component thioamination of 1,4-naphthoquinone in a sustainable solvent

A metal-/catalyst-free protocol for the direct thioamination of 1,4-naphthoquinone with thiophenols and amines using air as an oxidant in a green solvent has been developed. This environmentally friendly strategy was...

An ultrasound-assisted solvent and catalyst-free synthesis of structurally diverse pyrazole centered 1,5-disubstituted tetrazoles via one-pot four-component reaction

Abstract:

1,5-Disubstituted tetrazoles are vital drug-like scaffold usually encountered as valuable bioisosteres of cis-amide bond. In this article, we reported synthesis of some novel medicinally relevant pyrazole centered 1,5-disubstituted tetrazoles using ultrasound irradiation via a one-pot 4-C reaction from various pyrazole originated aldehyde, amine, isocyanide, and sodium azide. All the synthesized derivatives were characterized by IR, 1H NMR, 13C NMR, spectroscopic techniques, and mass analysis. This ultrasound-assisted green protocol has several advantages like mild reaction condition, high yield, catalyst and solvent-free reaction protocol, 15 minutes reaction time and easy workup.

Anticancer agents based on Plastoquinone analogs with N-phenylpiperazine: Structure-activity relationship and mechanism of action in breast cancer cells

2,3-Dimethyl-1,4-benzoquinones named as Plastoquinone (PQ) analogs have antiproliferative activity and are promising new members of molecules that can be used to cope with cancer. In an attempt to develop effective and potentially safe antiproliferative agents, previously reported twelve Plastoquinone analogs (PQ1-12) have been obtained to understand their antiproliferative profile. All PQ analogs have been selected by the National Cancer Institute (NCI) of Bethesda based on the NCI Developmental Therapeutics Program and tested against the panel of 60 cancer cell lines. Based on those studies, the cytotoxicity of the selected PQ analogs (PQ8, PQ9, PQ11, and PQ12) was determined using four breast cancer cell lines (MCF7, UACC-2087, MDA-MB-231, and MDA-MB-435) and a normal cell line (HaCaT). For better understanding, apoptosis induction, changes in cell proliferation, cell migration, and reactive oxygen species (ROS) generation were investigated for the selected PQ analog (PQ11) on MCF7 and UACC-2087 cell lines. According to the study results, PQ11 showed the most promising anticancer activity against MCF7 cell line through increased oxidative stress and apoptosis and suppression of cell proliferation. Based on the biological activity profile, we hypothesize that PQ11 could be a modulator of the cannabinoid 2 (CB2) receptor. Accordingly, we analyzed molecular level interaction of PQ11 with CB2 receptor through molecular docking simulation and it was also predicted to have a favorable ADMET profile. Overall, our findings suggest that integration of the N-phenylpiperazine moiety can be a good strategy for the structural optimization of PQ analogs as anticancer agents, especially in breast cancer.

Insight into Factors Influencing Wound Healing Using Phosphorylated Cellulose-Filled-Chitosan Nanocomposite Films

Marine polysaccharides are believed to be promising wound-dressing nanomaterials because of their biocompatibility, antibacterial and hemostatic activity, and ability to easily shape into transparent films, hydrogels, and porous foams that can provide a moist micro-environment and adsorb exudates. Current efforts are firmly focused on the preparation of novel polysaccharide-derived nanomaterials functionalized with chemical objects to meet the mechanical and biological requirements of ideal wound healing systems. In this contribution, we investigated the characteristics of six different cellulose-filled chitosan transparent films as potential factors that could help to accelerate wound healing. Both microcrystalline and nano-sized cellulose, as well as native and phosphorylated cellulose, were used as fillers to simultaneously elucidate the roles of size and functionalization. The assessment of their influences on hemostatic properties indicated that the tested nanocomposites shorten clotting times by affecting both the extrinsic and intrinsic pathways of the blood coagulation system. We also showed that all biocomposites have antioxidant capacity. Moreover, the cytotoxicity and genotoxicity of the materials against two cell lines, human BJ fibroblasts and human KERTr keratinocytes, was investigated. The nature of the cellulose used as a filler was found to influence their cytotoxicity at a relatively low level. Potential mechanisms of cytotoxicity were also investigated; only one (phosphorylated microcellulose-filled chitosan films) of the compounds tested produced reactive oxygen species (ROS) to a small extent, and some films reduced the level of ROS, probably due to their antioxidant properties. The transmembrane mitochondrial potential was very slightly lowered. These biocompatible films showed no genotoxicity, and very importantly for wound healing, most of them significantly accelerated migration of both fibroblasts and keratinocytes.

Exploration of brominated Plastoquinone analogs: Discovery and structure-activity relationships of small antimicrobial lead molecules

In the fight with the antimicrobial resistance, our continuous effort to find quinone analogs with higher inhibitory activity has previously led us to the promising Plastoquinone analogs. The 1,4-quinone moiety substituted with alkoxy substituent(s) plays an important role in the field of antimicrobial and anticancer drug discovery and development. Thus, an extensive series of 1,4-quinones, substituted in different positions with a variety of alkoxy substituents, has been designed, synthesized, and evaluated for their antimicrobial activity. Here, we describe the synthesis of brominated Plastoquinone analogs (BrPQ1-15) based on the dimethyl-1,4-quinone scaffold by employing two different paths. We also present here the in vitro antimicrobial activity of these analogs (BrPQ1-15) against a panel of pathogenic organisms. These studies resulted in several new selective antibacterial inhibitors and gave valuable insights into the structure-activity relationships. Among all the analogs studied, two analogs BrPQ1 with a methoxy substituent and BrPQ14 with a cyclic dioxy stand out as the most promising antibacterial molecules against Staphylococcus aureus and Staphylococcus epidermidis. Afterwards, two analogs were selected for a further investigation for biofilm evaluation. Finally, molecular docking studies for BrPQ1 and BrPQ14 with probable target S. aureus PNPase (5XEX) and predictive ADMET studies were also carried out.

A dual-channel colorimetric and ratiometric fluorescence chemosensor for detection of Hg2+ ion and its bioimaging applications

A new colorimetric and ratiometric fluorescence chemosensor 4-((3-(octadecylthio)-1,4-dioxo-1,4-dihydronaphthalen-2-yl)amino)benzenesulfonamide (4DBS) was synthesized and investigated for the selective detection of Hg²⁺ in DMSO-H₂O (9:1, v/v) solution. The chemosensor was efficiently synthesized in two steps via Michael-like addition and nucleophilic substitution reactions. The ratiometric fluorescence turn-on response was obtained towards Hg²⁺, and its fluorescence emission peak was red-shifted by 140 nm with an associated color change from light maroon to pale yellow due to the intramolecular charge transfer effect. The formed coordination metal complex was further evaluated by FT-IR, ¹H NMR, and quantum chemical analyses to confirm the binding mechanism. The detection process was sensitive/reversible, and the calculated limit of detection for Hg²⁺ was 0.451 µM. Furthermore, 4DBS was effectively utilized as a bioimaging agent for detection of Hg²⁺ in live cells and zebrafish larvae. Additionally, 4DBS showed distinguishing detection of Hg²⁺ in cancer cells in comparison with normal cells. Thus, 4DBS could be employed as an efficient bioimaging probe for discriminative identification of human cancer cells.

Mitochondria-targeted dual-channel colorimetric and fluorescence chemosensor for detection of Sn2+ ions in aqueous solution based on aggregation-induced emission and its bioimaging applications

Several fluorescence and colorimetric chemosensory for Sn²⁺ detection in an aqueous media have been reported, but applications remain limited for discriminative Sn²⁺ detection in live human cells and zebrafish larvae. Herein, a mitochondria-targeted Sn²⁺ "turn-on" colorimetric and fluorescence chemosensor, 2CTA, with an aggregation-induced emission (AIE) response was developed. The sensing of Sn²⁺ was enabled by a reduction-enabled binding pathway, with the conversion of -C˭O groups to -C-OH groups at the naphthoquinone moiety. The color changed from light maroon to milky white in a buffered aqueous solution. The chemosensor 2CTA possessed the excellent characteristics of good water solubility, fast response (less than 10 s), and high sensitivity (79 nM) and selectivity for Sn²⁺ over other metal ions, amino acids, and peptides. The proposed binding mechanism was experimentally verified by means of FT-IR and NMR studies. The chemosensor 2CTA was successfully employed to recognize Sn²⁺ in live human cells and in zebrafish larvae. In addition, a colocalization study proved that the chemosensor had the ability to target mitochondria and overlapped almost completely with MitoTracker Red. Furthermore, a bioimaging study of live cells demonstrated the discriminative detection of Sn²⁺ in human cancer cells and the practical applications of 2CTA in biological systems.

Growing Preferences towards Analog-based Drug Discovery

BACKGROUND

The major concern of today's time is the developing resistance in most of the clinically derived pathogenic micro-organisms for available drugs through several mechanisms. Therefore, there is a dire need to develop novel molecules with drug-like properties that can be effective against the otherwise resistant micro-organisms.

METHODS

New drugs can be developed using several methods like structure-based drug design, ligandbased drug design, or by developing analogs of the available drugs to further improve their effects. However, the smartness is to opt for the techniques that have comparatively less expenditure, lower failure rates, and faster discovery rates.

RESULTS

Analog-Based Drug Design (ABDD) is one such technique that researchers worldwide are opting to develop new drug-like molecules with comparatively lower market values. They start by first designing the analogs sharing structural and pharmacological similarities to the existing drugs. This method embarks on scaffold structures of available drugs already approved by the clinical trials, but are left ineffective because of resistance developed by the pathogens.

CONCLUSION

In this review, we have discussed some recent examples of anti-fungal and anti-bacterial (antimicrobial) drugs that were designed based on the ABDD technique. Also, we have tried to focus on the in silico tools and techniques that can contribute to the designing and computational screening of the analogs, so that these can be further considered for in vitro screening to validate their better biological activities against the pathogens with comparatively reduced rates of failure.

Naphthoquinone derivatives exhibit apoptosis-like effect and anti-trypanosomal activity against Trypanosoma evansi

Trypanosoma evansi is an extracellular flagellate blood protozoan parasite and an etiological agent of animal trypanosomosis. Presently, only a few drugs are registered and have been used for the treatment of animal trypanosomosis, but they show severe toxic effects and also face the problem of drug resistance. Naphthoquinones (NTQ) are considered as fortunate structures in the field of medicinal chemistry as they have been reported for their antitrypanosomal potential against other trypanosomes-T. brucei and T. cruzi. In the present study, six naphthoquinones (NTQ1-NTQ6) derivatives were evaluated for anti-trypanosomal activity by demonstrating their growth inhibitory effect against T. evansi. All NTQs significantly (p < 0.001) exhibited activity against parasite growth and multiplication with IC₅₀ values of 11.48 μM, 373.6 μM, 12.97 μM, 21.97 μM, 18.19 μM and 5.758 μM but NTQ1, NTQ3 and NTQ6 were selected based on their IC₅₀ value for further studies. The dose-and time-dependent morphological effect on parasite was evaluated including the measurement of reactive oxygen species (ROS) by spectrofluorometery and measurement of apoptosis by flow cytometry. The selected NTQs exhibited a significant production of ROS and displayed a significant AV⁺ and PI⁺ labelled cells in the axenic culture of T. evansi than quinapyramine methyl sulphate (QPS), as reference control. NTQs also showed more cytotoxic effect on horse peripheral blood mononuclear cells as compare to QPS. Therefore, we confirmed the antitrypanosomal activity and apoptotic-like mechanism of NTQs in an axenic culture of T. evansi.

Synthesis of biological based hennotannic acid-based salts over porous bismuth coordination polymer with phosphorous acid tags

In this paper, a novel porous polymer capable of coordinating to bismuth (PCPs-Bi) was synthesized. The Bi-PCPs was then reacted with phosphorous acid to produce a novel polymer PCPs(Bi)N(CH2PO3H2)2 which is shown to act as an efficient and recyclable catalyst. The mentioned catalyst was applied for the efficient synthesis of new mono and bis naphthoquinone-based salts of piperidine and/or piperazine via the reaction of hennotannic acid with various aldehydes, piperidine and/or piperazine, respectively. The structure of the resulting mono and bis substituted piperazine or piperidine-based naphthoquinone salts was thoroughly characterized spectroscopically. The electrochemical behavior of the products was also investigated. The presented protocol has the advantages of excellent yields (82-95%), short reaction times (4-30 min) and simple work-up.

Design, synthesis, characterization, enzymatic inhibition evaluations, and docking study of novel quinazolinone derivatives

In this study, novel quinazolinone derivatives 7a-n were synthesized and evaluated against metabolic enzymes including α-glycosidase, acetylcholinesterase, butyrylcholinesterase, human carbonic anhydrase I, and II. These compounds exhibited high inhibitory activities in comparison to used standard inhibitors with K_i values in the range of 19.28-135.88 nM for α-glycosidase (K_i value for standard inhibitor = 187.71 nM), 0.68-23.01 nM for acetylcholinesterase (K_i value for standard inhibitor = 53.31 nM), 1.01-29.56 nM for butyrylcholinesterase (K_i value for standard inhibitor = 58.16 nM), 10.25-126.05 nM for human carbonic anhydrase I (K_i value for standard inhibitor = 248.18 nM), and 13.46-178.35 nM for human carbonic anhydrase II (K_i value for standard inhibitor = 323.72). Furthermore, the most potent compounds against each enzyme were selected in order to evaluate interaction modes of these compounds in the active site of the target enzyme. Cytotoxicity assay of the title compounds 7a-n against cancer cell lines MCF-7 and LNCaP demonstrated that these compounds do not show significant cytotoxic effects.

New 2-Acetyl-3-aminophenyl-1,4-naphthoquinones: Synthesis and In Vitro Antiproliferative Activities on Breast and Prostate Human Cancer Cells

The reaction of 2-acyl-1,4-naphthoquinones with N,N-dimethylaniline and 2,5-dimethoxyaniline, promoted by catalytic amounts of CeCl₃·7H₂O under “open-flask” conditions, produced a variety of 2-acyl-3-aminophenyl-1,4-naphthoquinones structurally related to the cytotoxic 2-acetyl-3-phenyl-1,4-naphthoquinone, an inhibitor of the heat shock chaperone protein Hsp90. The members of the 2-acyl-3-aminophenyl-1,4-naphthoquinone series were isolated in good yields (63-98%). The cyclic voltammograms of the 2-acyl-3-aminophenyl-1,4-naphthoquinone exhibit two one-electron reduction waves to the corresponding radical-anion and dianion and two quasireversible oxidation peaks. The first and second half-wave potential values (E_1/2) of the members of the series are sensitive to the push-pull electronic effects of the substituents in the naphthoquinone scaffold. Furthermore, the in vitro antiproliferative properties of these new quinones were evaluated on two human cancer cells DU-145 (prostate) and MCF-7 (mammary) and a nontumorigenic HEK-293 (kidney) cell line, using the MTT colorimetric method. Two members, within the series, exhibited interesting cytotoxic activities on human prostate and mammary cancer cells.

Synergistic Antibacterial Activity Between 1,4-Naphthoquinone and β-Lactam Antibiotics Against Methicillin-Resistant Staphylococcus aureus

Aims: Currently, limited antibiotics are available to treat methicillin-resistant Staphylococcus aureus (MRSA) infections. One approach is the use of adjuvants in antibiotic therapy. 1,4-Naphthoquinones are naturally occurring alkaloids shown to have antibacterial properties. The objective of this study is to investigate the synergy between 1,4-naphthoquinone and selected β-lactam antibiotics and to evaluate the potential use of 1,4-naphthoquinone as an adjuvant in antibiotic treatment against MRSA infections. Methods: The antibacterial activity of 1,4-naphthoquinone and plumbagin was tested against nine pathogenic bacterial strains using the microdilution broth method. The interactions between 1,4-naphthoquinone and three antibiotics (cefuroxime, cefotaxime, and imipenem) were estimated by calculating the fractional inhibitory concentration of the combination. Results: The compounds 1,4-naphthoquinone and plumbagin exhibited a broad range of bacteriostatic and bactericidal effects against both Gram-positive and Gram-negative bacteria. The interaction between 1,4-naphthoquinone and imipenem, cefuroxime, and cefotaxime was synergistic against methicillin-sensitive Staphylococcus aureus and MRSA clinical strains. Against ATCC-cultured MRSA, a synergistic effect was observed between 1,4-naphthoquinone and cefotaxime. However, combination with imipenem only produced an additive effect, and an antagonistic action was observed between 1,4-naphthoquinone and cefuroxime. Conclusions: Although individually less potent than common antibiotics, 1,4-naphthoquinone acts synergistically with imipenem, cefuroxime, and cefotaxime against MRSA clinical strains and could potentially be used in adjuvant-antibiotic therapy against multidrug resistant bacteria.

Synthesis and Biological Evaluation of New Naphthoquinones Derivatives

:

New substituted 1,4-naphthoquinones have been prepared in good overall yields through the naphthol route. The cytotoxicity of these compounds was tested in vitro on MCF-7 breast tumor cells. The most active compound 14 displayed an IC50 of 15μM.

Objective:

To investigate the cytotoxicity of new naphthoquinones derivatives on MCF-7 cells.

Methods:

Synthesis of new naphtoquinones derivatives and in vitro evaluation of their cytotoxicity on MCF-7 cells (rezasurin cell-based assay).

Results:

Starting from Ethyl 4-hydroxy-6,7-dimethoxy-2-naphthoate, four naphthoquinones were prepared and exhibited substantial cytotoxicity against MCF-7 cells.

Conclusion:

Preliminary studies of the structure-activity relationship have shown the influence of the structural parameters and, in particular, the nature of the naphthoquinone side chain.

The Cellular and Molecular Determinants of Naphthoquinone-Dependent Activation of the Aryl Hydrocarbon Receptor

1,2-naphthoquinone (1,2-NQ) and 1,4-naphthoquinone (1,4-NQ) are clinically promising biologically active chemicals that have been shown to stimulate the aryl hydrocarbon receptor (AhR) signaling pathway, but whether they are direct or indirect ligands or activate the AhR in a ligand-independent manner is unknown. Given the structural diversity of AhR ligands, multiple mechanisms of AhR activation of gene expression, and species differences in AhR ligand binding and response, we examined the ability of 1,2-NQ and 1,4-NQ to bind to and activate the mouse and human AhRs using a series of in vitro AhR-specific bioassays and in silico modeling techniques. Both NQs induced AhR-dependent gene expression in mouse and human hepatoma cells, but were more potent and efficacious in human cells. 1,2-NQ and 1,4-NQ stimulated AhR transformation and DNA binding in vitro and was inhibited by AhR antagonists. Ligand binding analysis confirmed the ability of 1,2-NQ and 1,4-NQ to competitively bind to the AhR ligand binding cavity and the molecular determinants for interactions were predicted by molecular modeling methods. NQs were shown to bind distinctly differently from that of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and differences were also observed between species. Mutation of amino acid residues (F289, M334, and M342) involved in critical NQ:AhR binding interactions, decreased NQ- and AhR-dependent gene expression, consistent with a role for these residues in binding and activation of the AhR by NQs. These studies provide insights into the molecular mechanism of action of NQs and contribute to the development of emerging NQ-based therapeutics.

Chlorinated plastoquinone analogs that inhibit Staphylococcus epidermidis and Candida albicans growth

Infectious diseases are the significant global health problem because of drug resistance to most classes of antimicrobials. Interest is growing in the development of new antimicrobials in pharmaceutical discovery. For that reason, the urgency for scientists to find and/or develop new important molecules is needed. Many natural active molecules that exhibit various biological activities have been isolated from the nature. For the present research, a new selected set of aminobenzoquinones, denoted as plastoquinone analogs (PQ1-24), was employed for their in vitro antimicrobial potential in a panel of seven bacterial strains (three Gram-positive and four Gram-negative bacteria) and three fungi. The results revealed PQ analogs with specific activity against bacteria including Staphylococcus epidermidis and pathogenic fungi, including Candida albicans. PQ8 containing methoxy group at the ortho position on the phenylamino moiety exhibited the highest growth inhibition against S. epidermidis with a minimum inhibitory concentration of 9.76 μg/mL. The antifungal profile of all PQ analogs indicated that five analogs (while PQ1, PQ8, PQ9, PQ11, and PQ18 were effective against Candida albicans, PQ1 and PQ18 were effective against Candida tropicalis) have potent antifungal activity. Selected analogs, PQ1 and PQ18, were studied for biofilm evaluation and time-kill kinetic study for better understanding.

Pyrazolylphenanthroimidazole heterocycles: synthesis, biological and molecular docking studies

The synthesis of a series of novel pyrazolylphenanthroimidazoles 6a–6j has been accomplished utilizing a multi-step synthetic protocol, and characterized through physical and spectral techniques.

Simple Fluorescence Turn-On Chemosensor for Selective Detection of Ba2+ Ion and Its Live Cell Imaging

A phenoxazine-based fluorescence chemosensor 4PB [(4-(tert-butyl)-N-(4-((4-((5-oxo-5H-benzo[a]phenoxazin-6-yl)amino)phenyl)sulfonyl)phenyl)benzamide)] was designed and synthesized by a simple synthetic methods. The 4PB fluorescence chemosensor selectively detects Ba²⁺ in the existence of other alkaline metal ions. In addition, 4PB showed high selectivity and sensitivity for Ba²⁺ detection. The detection limit of 4PB was 0.282 μM and the binding constant was 1.0 × 10⁶ M^-1 in CH₃CN/H₂O (97.5:2.5 v/v, HEPES = 1.25 mM, pH 7.3) medium. This chemosensor functioned through the intramolecular charge transfer (ICT) mechanism, which was further confirmed by DFT studies. Live cell imaging in MCF-7 cells confirmed the cell permeability of 4PB and its capability for specific detection of Ba²⁺ in living cells.

Synthesis and Antimicrobial Evaluation of 1,4-Naphthoquinone Derivatives as Potential Antibacterial Agents

1,4-Naphthoquinones are an important class of compounds present in a number of natural products. In this study, a new series of 1,4-naphthoquinone derivatives were synthesized. All the synthesized compounds were tested for in vitro antimicrobial activity. In this present investigation, two Gram-positive and five Gram-negative bacterial strains and one pathogenic yeast strain were used to determine the antibacterial activity. Naphthoquinones tested for its antibacterial potencies, among seven of them displayed better antimicrobial activity against Staphylococcus aureus (S. aureus; 30-70 μg/mL). Some of the tested compounds showed moderate to low antimicrobial activity against Pseudomonas aeruginosa (P. aeruginosa) and Salmonella bongori (S. bongori; 70-150 μg/mL). In addition, most active compounds against S. aureus were evaluated for toxicity to human blood cells using a hemolysis assay. For better understanding, reactive oxygen species (ROS) generation, time-kill kinetic study, and apoptosis, necrosis responses were investigated for three representative compounds.

1,4-Naphthoquinone Analogues: Potent Antibacterial Agents and Mode of Action Evaluation

1,4-Naphthoquinones have antibacterial activity and are a promising new class of compound that can be used to treat bacterial infections. The goal was to improve effective antibacterial agents; therefore, we synthesized a new class of naphthoquinone hybrids, which contain phenylamino-phenylthio moieties as significant counterparts. Compound 4 was modified as a substituted aryl amide moiety, which enhanced the antibacterial activity of earlier compounds 3 and 4. In this study, five bacterial strains Staphylococcus aureus (S. aureus), Listeria monocytogenes (L. monocytogenes), Escherichia coli (E. coli), Pseudomonas aeruginosa (P. aeruginosa) and Klebsiella pneumoniae (K. pneumoniae) were used to evaluate the antibacterial potency of synthesized naphthoquinones using the minimal inhibitory concentration (MIC) method. Most of the studied naphthoquinones demonstrated major antibacterial activity with a MIC of 15.6 µg/mL–500 µg/mL. Selected compounds (5a, 5f and 5x) were studied for the mode of action, using intracellular ROS generation, determination of apoptosis by the Annexin V-FITC/PI assay, a bactericidal kinetic study and in silico molecular modelling. Additionally, the redox potentials of the specified compounds were confirmed by cyclic voltammetry (CV).