Analysis of Quinolinequinone Analogs with Promising Cytotoxic Activity against Breast Cancer.

It is quite challenging to find out bioactive molecules in the vast chemical universe. Quinone moiety is a unique structure with a variety of biological properties, particularly in the treatment of cancer. In an effort to develop potent and secure antiproliferative lead compounds, five quinolinequinones (AQQ1-5) described previously have been selected and submitted to the National Cancer Institute (NCI) of Bethesda to envisage their antiproliferative profile based on the NCI Developmental Therapeutics Program. According to the preliminary in vitro single-dose anticancer screening, four of five quinolinequinones (AQQ2-5) were selected for five-dose screening and they displayed promising antiproliferative effects against several cancer types. All AQQs showed a excellent anticancer profile with low micromolar GI50 and TGI values against all leukemia cell lines, some non-small cell lung and ovarian cancer, most colon, melanoma, and renal cancer, and in addition to some breast cancer cell lines. AQQ2-5 reduced the proliferation of all leukemia cell lines at a single dose and five additional doses, as well as some non-small cell lung and ovarian cancer, the majority of colon cancer, melanoma and renal cancer, and some breast cancer cell lines. This motivated us to use in vitro, in silico, and in vivo technologies to further investigate their mode of action. We investigated the in vitro cytotoxic activities of the most promising compounds, AQQ2 and AQQ3, in HCT-116 colon cancer, MCF7 and T-47D breast cancer, and DU-145 prostate cancer cell lines, and HaCaT human keratinocytes. Concomitantly, IC50 values of AQQ2 and AAQ3 against MCF7 and T-47D cell lines of breast cancer, DU-145 cell lines of prostate cancer, HCT-116 cell lines of colon cancer, and HaCaT human keratinocytes were determined. AQQ2 exhibited anticancer activity through the induction of apoptosis and caused alterations in the cell cycle. In silico pharmacokinetic studies of all analogs have been carried out against ATR, CHK1, WEE1, CDK1, and CDK2. In addition to this, in vitro ADME and in vivo pharmacokinetic profiling for the most effective AAQ (AAQ2) have been studied.

Discovery of quinolinequinones with N-phenylpiperazine by conversion of hydroxyquinoline as a new class of antimicrobial agents targeting resistant pathogenic microorganisms.

The development of new antimicrobial agents is necessary to overcome the emerging antimicrobial resistance among infectious microbial pathogens. Herein, we successfully designed and synthesized quinolinequinones (QQs) with N-phenylpiperazine (QQ1-7) containing strong or weak EDG in the amino moiety by converting hydroxyquinoline (HQ) to the dichloroquinolinequinone (QQ) via chlorooxidation. We performed an extensive antimicrobial activity assessment of the QQs with N-phenylpiperazine (QQ1-7). Among the seven quinolinequinones (QQs) with N-phenylpiperazine tested, QQ3 and QQ4 were the most active molecules against Staphylococcus aureus (ATCC® 29213) with a MIC value of 1.22 µg/mL. In addition to this, while QQ4 was more than six (6) times more effective towards Enterococcus faecalis (ATCC® 29212), QQ3 was twenty-six (26) times more effective against same strain. Furthermore, the evaluation of antimicrobial activity indicated that six of seven synthesized QQs (QQ1-4, QQ6, and QQ7) exhibited superior biological potency, eight (8) times for five of them (QQ1-4 and QQ6) and two (2) times for QQ7, against Staphylococcus epidermidis (ATCC® 12228). Besides, all QQs except QQ5 displayed excellent antifungal activity against the fungi Candida albicans (ATCC® 10231). Among these, the two QQs (QQ3 and QQ4), which showed the lowest values against gram-positive bacterial strains (Staphylococcus aureus (ATCC® 29213), Staphylococcus epidermidis (ATCC® 12228), and Enterococcus faecalis (ATCC® 29212)) as well as fungal strains (Candida albicans (ATCC® 10231) and Candida parapsilosis (ATCC® 22019)), were further evaluated for their biofilm inhibition properties and their mode of action with in vitro potential antimicrobial activity against each of 20 clinically obtained resistant strains of gram-positive bacteria, and bactericidal activity using time-kill curve assay. In this study, we investigated the bactericidal effects of QQ3 against methicillin-resistant Staphylococcus aureus (MRSA) and Candida albicans strains. The findings of this study suggest that a significant bactericidal effect was seen with all tested 1 × MIC and 4 × MIC concentrations used within 24 h. Our findings present significant implications for an antimicrobial drug candidate for treating infections, especially those caused by clinically resistant MRSA isolates.

Active Quinolinequinones against Methicillin-Resistant Staphylococcus spp.

Serious bacterial infections could be caused by Gram-positive microorganisms, in particular methicillin-resistant Staphylococcus aureus and Staphylococcus epidermidis. Aiming to address this challenging issue by developing the potent and selective antimicrobial lead structures against methicillin-resistant Staphylococcus spp., herein, we report in vitro evaluation of quinolinequinones (QQ1-QQ10) against the Gram-negative and Gram-positive strains using the broth microdilution technique. The design principle of the quinolinequinones was based on the variation of the structures attached to the 1,4-quinone moiety and substituent(s) within amino phenyl moiety. A series of ten quinolinequinones displayed activity mainly against the Gram-positive strains with a minimal inhibitory concentration (MIC=1.22-1250 mg/L) within the Clinical and Laboratory Standards Institute (CLSI) levels. Interestingly, QQ3, QQ5, and QQ6 displayed equal antibacterial inhibitory activity against S. aureus (MIC=1.22 mg/L), respectively, to the standard positive control Cefuroxime-Na. QQ2, QQ3, and QQ5 had the best inhibitory activity with the MIC value of 1.22 mg/L (4-fold more potent compared reference standard Cefuroxime) against S. epidermidis. On the other hand, QQ3 was the most effective quinolinequinone against fungi, in particular C. albicans. The identified lead quinolinequinones (QQ3 and QQ5) with a comprehensive analysis of structure-activity relationships and further studies showed high activity against methicillin-resistant Staphylococcus spp. It is worth noting that the isopropyl group has importance for excellent bioactivity. Remarkably, the in vitro antibiofilm and bactericidal activities (each of 32 clinically obtained strains of Gram-positive bacteria) of the selected two quinolinequinones (QQ3 and QQ5) have been evaluated for the mode of action in addition to the time-kill curve study.

Discovery and structure-activity relationships of the quinolinequinones: Promising antimicrobial agents and mode of action evaluation.

In our pursuit of developing the novel, potent, and selective antimicrobial agents, we managed to obtain the quinolinequinone for their antimicrobial profile with minimal inhibitory concentrations (MICs) determined against a panel of seven bacterial strains (three gram-positive and four gram-negative bacteria) and three fungi. The structure-activity relationship (SAR) for the quinolinequinone class of antimicrobials was determined. Interestingly, QQ1, QQ4, QQ6-9, QQ12, and QQ13 displayed equal antibacterial potential against S. aureus (MIC = 1.22 mg/L), respectively, to the standard positive control Cefuroxime-Na. QQ10 had the best inhibitory activity with the MIC value of 1.22 mg/L (fourfold more potent compared to reference standard Clotrimazole) against Candida albicans. On the other hand, while QQ10 is not too effective against gram-positive bacteria as much as the other analogs, QQ10 was the most effective quinolinequinones against fungi. Selected quinolinequinones were further evaluated for the mode of action, using in vitro antibiofilm activity, bactericidal activity by using time-kill curve assay, antibiofilm activity, and potential antimicrobial activity against each of 32 clinically obtained resistant strains of Gram-positive Bacteria. The results also revealed that the QQ14 had specific antifungal activity against fungi in particular C. albicans. Our results clearly showed that quinolinequinones are much more active in the inhibition of the biofilm attachment process than the inhibition of mature biofilm formation. Thus, as treatment options are narrowing for Methicillin-resistant Staphylococcus spp., Vancomycin-resistant Staphylococcus spp. daily, the quinolinequinones reported herein display promise as the lead candidates for further clinical applications against serious infections.

Highly Active Small Aminated Quinolinequinones against Drug-Resistant Staphylococcus aureus and Candida albicans.

Two subseries of aminated quinolinequinones (AQQs, AQQ1-16) containing electron-withdrawing group (EWG) or electron-donating group (EDG) in aryl amine moiety were successfully synthesized. Antimicrobial activity assessment indicates that some of the AQQs (AQQ8-10 and AQQ12-14) with an EDG in aryl amine exhibited strong antibacterial activity against Gram-positive bacterial strains, including Staphylococcus aureus (ATCC® 29213) and Enterococcus faecalis (ATCC® 29212). In contrast, AQQ4 with an EWG in aryl amine displayed excellent antifungal activity against fungi Candida albicans (ATCC® 10231) with a MIC value of 1.22 µg/mL. To explore the mode of action, the selected AQQs (AQQ4 and AQQ9) were further evaluated in vitro to determine their antimicrobial activity against each of 20 clinically obtained resistant strains of Gram-positive bacteria by performing antibiofilm activity assay and time-kill curve assay. In addition, in silico studies were carried out to determine the possible mechanism of action observed in vitro. The data obtained from these experiments suggests that these molecules could be used to target pathogens in different modes of growth, such as planktonic and biofilm.

In Vitro and In Silico Study of Analogs of Plant Product Plastoquinone to Be Effective in Colorectal Cancer Treatment.

Plants have paved the way for the attainment of molecules with a wide-range of biological activities. However, plant products occasionally show low biological activities and/or poor pharmacokinetic properties. In that case, development of their derivatives as drugs from the plant world has been actively performed. As plant products, plastoquinones (PQs) have been of high importance in anticancer drug design and discovery; we have previously evaluated and reported the potential cytotoxic effects of a series of PQ analogs. Among these analogs, PQ2, PQ3 and PQ10 were selected for National Cancer Institute (NCI) for in vitro screening of anticancer activity against a wide range of cancer cell lines. The apparent superior anticancer potency of PQ2 on the HCT-116 colorectal cancer cell line than that of PQ3 and PQ10 compared to other tested cell lines has encouraged us to perform further mechanistic studies to enlighten the mode of anti-colorectal cancer action of PQ2. For this purpose, its apoptotic effects on the HCT-116 cell line, DNA binding capacity and several crucial pharmacokinetic properties were investigated. Initially, MTT assay was conducted for PQ2 at different concentrations against HCT-116 cells. Results indicated that PQ2 exhibited significant cytotoxicity in HCT-116 cells with an IC50 value of 4.97 ± 1.93 µM compared to cisplatin (IC50 = 26.65 ± 7.85 µM). Moreover, apoptotic effects of PQ2 on HCT-116 cells were investigated by the annexin V/ethidium homodimer III staining method and PQ2 significantly induced apoptosis in HCT-116 cells compared to cisplatin. Based on the potent DNA cleavage capacity of PQ2, molecular docking studies were conducted in the minor groove of the double helix of DNA and PQ2 presented a key hydrogen bonding through its methoxy moiety. Overall, both in vitro and in silico studies indicated that effective, orally bioavailable drug-like PQ2 attracted attention for colorectal cancer treatment. The most important point to emerge from this study is that appropriate derivatization of a plant product leads to unique biologically active compounds.

Studies on 1,4-Quinone Derivatives Exhibiting Anti-Leukemic Activity along with Anti-Colorectal and Anti-Breast Cancer Effects.

Colorectal cancer (CRC), breast cancer, and chronic myeloid leukemia (CML) are life-threatening malignancies worldwide. Although potent therapeutic and screening strategies have been developed so far, these cancer types are still major public health problems. Therefore, the exploration of more potent and selective new agents is urgently required for the treatment of these cancers. Quinones represent one of the most important structures in anticancer drug discovery. We have previously identified a series of quinone-based compounds (ABQ-1-17) as anti-CML agents. In the current work, ABQ-3 was taken to the National Cancer Institute (NCI) for screening to determine its in vitro antiproliferative effects against a large panel of human tumor cell lines at five doses. ABQ-3 revealed significant growth inhibition against HCT-116 CRC and MCF-7 breast cancer cells with 2.00 µM and 2.35 µM GI50 values, respectively. The MTT test also showed that ABQ-3 possessed anticancer effects towards HCT-116 and MCF-7 cells with IC50 values of 5.22 ± 2.41 µM and 7.46 ± 2.76 µM, respectively. Further experiments indicated that ABQ-3 induced apoptosis in both cell lines, and molecular docking studies explicitly suggested that ABQ-3 exhibited DNA binding in a similar fashion to previously reported compounds. Based on in silico pharmacokinetic prediction, ABQ-3 might display drug-like features enabling this compound to become a lead molecule for future studies.

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.

Design, synthesis and investigation of the mechanism of action underlying anti-leukemic effects of the quinolinequinones as LY83583 analogs.

Literature conclusively shows that one of the quinolinequinone analogs (6-anilino-5,8-quinolinequinone), referred to as LY83583 hereafter, an inhibitor of guanylyl cyclase, was used as the inhibitor of the cell proliferation in cancer cells. In the present work, a series of analogs of the LY83583 containing alkoxy group(s) in aminophenyl ring (AQQ1-15) were designed and synthesized via a two-step route and evaluated for their in vitro cytotoxic activity against four different cancer cell lines (K562, Jurkat, MT-2, and HeLa) and human peripheral blood mononuclear cells (PBMCs) by MTT assay. The analog (AQQ13) was identified to possess the most potent cytotoxic activity against K562 human chronic myelogenous (CML) cell line (IC50 = 0.59 ± 0.07 µM) with significant selectivity (SI = 4.51) compared to imatinib (IC50 = 5.46 ± 0.85 µM; SI = 4.60). Based on its superior cytotoxic activity, the analog AQQ13 was selected for further mechanistic studies including determination of its apoptotic effects on K562 cell line via annexin V/ethidium homodimer III staining potency, ABL1 kinase inhibitory activity, and DNA cleaving capacity. Results ascertained that the analog AQQ13 induced apoptosis in K562 cell line with notable DNA-cleaving activity. However, AQQ13 demonstrated weak ABL1 inhibition indicating the correlation between anti-K562 and anti-ABL1 activities. In continuance, respectively conducted in silico molecular docking and Absorption, Distribution, Metabolism, and Excretion (ADME) studies drew attention to enhanced binding interactions of AQQ13 towards DNA and its high compatibility with the potential limits of specified pharmacokinetic parameters making it as a potential anti-leukemic drug candidate. Our findings may provide a new insight for further development of novel quinolinequinone-based anticancer analogs against CML.

Design, synthesis, and biological activity of Plastoquinone analogs as a new class of anticancer agents.

In this paper, based on Plastoquinone (PQ) analogs possessing substituted aniline containing alkoxy group(s), new 2,3-dimethyl-5-amino-1,4-benzoquinones (PQ1-15) were designed and synthesized in either two steps or one-pot reaction. Specifically, the substituted amino moiety containing mono or poly alkoxy group(s) with various positions and groups were mainly explored to understand the structure-activity relationships for the cytotoxic activity against three human cancer cell lines (K562, Jurkat, and MT-2) and human peripheral blood mononuclear cells (PBMC). PQ2 was found to be most effective anticancer compound on K562 and Jurkat cell lines with IC50 values of 6.40 ±â€¯1.73 µM and 7.72 ±â€¯1.49 µM, respectively. Interestingly, the compound was non-cytotoxic to normal PBMC and also MT-2 cancer cells. PQ2 which showed significant selectivity in MTT assay was chosen for apoptotic/necrotic evaluation and results exhibited that it induced apoptosis in K562 cell line after 6 h of treatment. PQ2 showed anti-Abelson kinase 1 (Abl1) activity with different inhibitory profile than Imatinib in the panel of eight kinases. The binding mode of PQ2 into Abl ATP binding pocket was predicted in silico showing the formation of some key interactions. In addition, PQ2 induced Bcr-Abl1 mediated ERK pathway in human chronic myelogenous leukemia (CML) cells. Furthermore, DNA-cleaving capability of PQ2 was clearly enhanced by iron (II) complex system. Afterward, a further in silico ADMET prediction revealed that PQ2 possesses desirable drug-like properties and favorable safety profile. These results indicated that PQ2 has multiple mechanism of action and two of them are anti-Bcr-Abl1 and DNA-cleaving activity. This study suggests that Plastoquinone analogs could be potential candidates for multi-target anticancer therapy.

Discovery and structure-activity relationship of plastoquinone analogs as anticancer agents against chronic myelogenous leukemia cells.

Two series of amino-1,4-benzoquinones (AQ1-18) based on the structural analogs of plastoquinones were synthesized and the structure-activity relationship against chronic myelogenous leukemia activity was examined. All of the synthesized compounds were tested for their cytotoxic effects on different leukemic cell lines. Of interest, AQ15 exhibited a better selectivity than the reference drug imatinib on cancer cells. Owing to this, AQ15 was selected for a further apoptosis/necrosis evaluation where AQ15-treated K562 cells demonstrated similar apoptotic effects like imatinib-treated cells at their IC50 values. The inhibitory effects of AQ15 and the other three compounds with various activities against eight tyrosine kinases, including ABL1, were investigated. AQ15 showed weak activity against ABL1, and a correlation was observed between the anti-K562 and anti-ABL1 activities. The binding mode of AQ15 into the ATP binding pocket of ABL1 kinase was predicted in silico, showing the formation of some key interactions. In addition, AQ15 was shown to suppress the downstream signaling of BCR-ABL in K562 cells. Finally, AQ15 obviously cleaved DNA in the presence of an iron(II) complex system, indicating that this can be the major mechanism of its antiproliferative action, whereas the mild inhibition of ABL kinase is just in-part mechanism of its overall outstanding cellular activity.

Discovery of a new family of heterocyclic amine linked plastoquinone analogs for antimicrobial evaluation.

A series of aminobenzoquinones, denoted as PQ analogs (PQ1-13), were synthesized by employing a green methodology approach using water as solvent developed by Tandon et al. Subsequently, in vitro antimicrobial potential of all PQ analogs was evaluated in a panel of seven bacterial strains (three gram positive and four gram negative bacteria) and three fungi. The antifungal profile of all PQ analogs indicated that four analogs (while PQ2, PQ9, and PQ10 were effective against Candida tropicalis, PQ11 is effective against Candida albicans) have potent antifungal activity. The results revealed that PQ9 showed similar antibacterial activity against Staphylococcus epidermidis compared clinically prevalent antibacterial drugs cefuroxime. PQ11 exhibited the highest antibacterial activity against S. epidermidis, which was about fourfold better than that of cefuroxime. Owing to their outstanding activities, PQ9 and PQ11 were chosen for a further investigation for biofilm and cytotoxicity evaluation. Based on the tests performed, there was a significant positive correlation between inhibition of the biofilm attachment and time. In addition, PQ9 and PQ11 showed cytotoxic effects at high concentrations on Balb/3T3, HaCaT, HUVEC, and NRK-52E cells (>24 and >18 µg/mL, respectively). Thus, two analogs (PQ9 and PQ11) were identified as the hits with the strong antibacterial efficiency against the S. epidermidis with low MIC values.

Prospects for Prostate Cancer Chemotherapy: Cytotoxic Evaluation and Mechanistic Insights of Quinolinequinones with ADME/PK Profile.

The evaluation of in vitro biological activity of several previously reported quinolinequinones (AQQ1-5) against 60 human cancer cell lines (NCI-60) used by the National Cancer Institute's Developmental Therapeutics Program (DTP) contributed to our earlier research on possible anticancer and/or antibacterial agents. Of interest, NCI-60 screening revealed that two quinolinequinones (AQQ1 and AQQ2) significantly reduced the proliferation of several cancer genotypes. Following the administration of a single dose and five additional doses, all quinolinequinones demonstrated a significant inhibitory effect on the growth of leukemia and other cancer cell lines. Hence, a series of subsequent in vitro biological assessments were performed to further understand the mechanistic impact of the compounds. In MTT assays, it was found that AQQ1 and AQQ2 exhibited higher efficacy against DU-145 cells (IC50 4.18 µM and 4.17 µM, respectively) compared to MDA-MB-231 (IC50 8.27 and 13.33 µM, respectively) and HCT-116 cells (IC50 5.83 and 9.18 µM, respectively). Additionally, AQQ1 demonstrated greater activity in this context. Further investigations revealed that AQQ1 inhibited DU-145 cell growth and migration dose-dependently. Remarkably, arrest of the DU-145 cell cycle at G0/G1 phase and ROS elevation were observed. Pharmacokinetic (PK) studies revealed that AQQ1 has better PK parameters than AQQ2 with %F of 9.83 in rat. Considering the data obtained with human liver microsomal stability studies, AQQ1 should have a better PK profile in human subjects. In silico studies (molecular dynamics) with three kinases (CDK2, CDK4, and MAPK) leading to cell cycle arrest at G0/G1 identified MAPK as a probable target for AQQ1. Taken together, our results showed that AQQ1 could be a potential chemotherapeutic lead molecule for prostate cancer.

Cytotoxic activity of quinolinequinones in cancer: In vitro studies, molecular docking, and ADME/PK profiling.

Lead molecules containing 1,4-quinone moiety are intriguing novel compounds that can be utilized to treat cancer owing to their antiproliferative activities. Nine previously reported quinolinequinones (AQQ1-9) were studied to better understand their inhibitory profile to produce potent and possibly safe lead molecules. The National Cancer Institute (NCI) of Bethesda chose all quinolinequinones (AQQ1-9) based on the NCI Developmental Therapeutics Program and tested them against a panel of 60 cancer cell lines. At a single dose and five further doses, AQQ7 significantly inhibited the proliferation of all leukemia cell lines and some breast cancer cell lines. We investigated the in vitro cytotoxic activities of the most promising compounds, AQQ2 and AQQ7, in MCF7 and T-47D breast cancer cells, DU-145 prostate cancer cells, HCT-116 and COLO 205 colon cancer cell lines, and HaCaT human keratinocytes using the MTT assay. AQQ7 showed particularly high cytotoxicity against MCF7 cells. Further analysis showed that AQQ7 exhibits anticancer activity through the induction of apoptosis without causing cell cycle arrest or oxidative stress. Molecular docking simulations for AQQ2 and AQQ7 were conducted against the COX, PTEN, and EGFR proteins, which are commonly overexpressed in breast, cervical, and prostate cancers. The in vitro ADME and in vivo PK profiling of these compounds have also been reported.

Exploring the Relationships between Structure and Antimicrobial Potency of Quinolinequinones.

Microorganisms are responsible for hospital infections, and methicillin-resistant Staphylococcus aureus is one of them. In looking for the most effective lead structures to cope with the rise of antimicrobial (antibiotic) resistance, we evaluated the antimicrobial profile of quinolinequinones for potential antimicrobial applications. 1,4-quinone molecules fused with heteroatom have been studied extensively for many years as a source of drugs and lead structures. The aims of this study were to evaluate the antimicrobial activity of quinolinequinones against bacterial and fungal strains, and to probe for potential lead structures. For this reason, the activity of these compounds against three different strains of Candida fungi (C. albicans, C. parapsilosis, and C. tropicalis) and Gram-positive and Gram-negative pathogenic bacteria were investigated, searching for potential lead compounds. Five of nine quinolinequinones showed activity mainly against the Gram-positive strains with a minimal inhibitory concentration within the Clinical and Laboratory Standards Institute (CLSI) levels. The results revealed that quinolinequinones have significant activity against bacteria including Staphylococcus aureus and Staphylococcus epidermidis, and fungi including Candida albicans and Candida parapsilosis. QQ1, QQ2, QQ3, QQ5, and QQ6 exhibited the highest growth inhibition against two essential species of the Gram-positive strains (Staphylococcus epidermidis and Staphylococcus aureus). Among these, four molecules (QQ2, QQ3, QQ5, and QQ6) were also active against Enterococcus faecalis, the other member of the Gram-positive strains. The antifungal profile of two quinolinequinones (QQ7 and QQ8) indicated that they were as effective as the reference drug Clotrimazole against Candida albicans. The same molecules also have potential inhibitory antifungal activity against Candida tropicalis. For better understanding, the most active two quinolinequinones (QQ2 and QQ6) were examined for biofilm inhibition and a time-kill kinetic study.

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.

Natural-product-inspired design and synthesis of thiolated coenzyme Q analogs as promising agents against Gram-positive bacterial strains: insights into structure-activity relationship, activity profile, mode of action, and molecular docking.

In an attempt to develop effective and potentially active antibacterial and/or antifungal agents, we designed, synthesized, and characterized thiolated CoQ analogs (CoQ1-8) with an extensive antimicrobial study. The antimicrobial profile of these analogs was determined using four Gram-negative bacteria, three Gram-positive bacteria, and three fungi. Because of the fact that the thiolated CoQ analogs were quite effective on all tested Gram-positive bacterial strains, including Staphylococcus aureus (ATCC® 29213) and Enterococcus faecalis (ATCC® 29212), the first two thiolated CoQ analogs emerged as potentially the most desirable ones in this series. Importantly, after the evaluation of the antibacterial and antifungal activity, we presented an initial structure-activity relationship for these CoQ analogs. In addition, the most promising thiolated CoQ analogs (CoQ1 and CoQ2) having the lowest MIC values on all tested Gram-positive bacterial strains, were further evaluated for their inhibition capacities of biofilm formation after evaluating their in vitro potential antimicrobial activity against each of 20 clinically obtained resistant strains of Gram-positive bacteria. CoQ1 and CoQ2 exhibited potential molecular interactions with S. aureus DNA gyrase in addition to excellent pharmacokinetics and lead-likeness profiles. Our findings offer important implications for a potential antimicrobial drug candidate, in particular for the treatment of infections caused by clinically resistant MRSA isolates.

In Vitro and In Silico Study to Assess Toxic Mechanisms of Hybrid Molecules of Quinone-Benzocaine as Plastoquinone Analogues in Breast Cancer Cells.

We managed to obtain three different series of 2,3-dimethyl-1,4-benzoquinones, named nonhalogenated and halogenated (brominated and chlorinated) PQ analogues, via the molecular hybridization strategy. Sixteen of eighteen hybrid molecules were selected by the National Cancer Institute (NCI) of Bethesda for their in vitro antiproliferative potential against the full NCI 60 cell line panel. The hybrid molecules (BrPQ5, CIPQ1, and CIPQ3) showed good growth inhibition at 10 µM concentration, particularly against breast cancer cell lines. As per the results obtained from in vitro antiproliferative evaluation, cytotoxic activities of the hybrid molecules (BrPQ5, CIPQ1, and CIPQ3) were evaluated with an 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay in T47D and MCF7 breast cancer and human umbilical vein endothelial (HUVEC) cells. Molecules exhibited cytotoxic activity, and especially, CIPQ1 showed remarkable cytotoxic activity and good selectivity on T47D and MCF7 cells. Furthermore, CIPQ1 could inhibit cell proliferation, cause apoptotic cell death and disturb the cell cycle in T47D and MCF7 cells. Additionally, CIPQ1 caused oxidative stress induction in both cells, more so in T47D. In vitro study results indicated that the anticancer activity of CIPQ1 was more prominent in T47D cells than in MCF7 cells. The compound CIPQ1 showed a prominent binding with JNK3 in silico. Thus, the obtained hybrid molecules via the molecular hybridization strategy of two important pharmacophores could be useful in the discovery of novel antiproliferative agents, and CIPQ1 could be considered a promising drug candidate.

Aminated Quinolinequinones as Privileged Scaffolds for Antibacterial Agents: Synthesis, In Vitro Evaluation, and Putative Mode of Action.

Our previous studies have revealed that the aminated 1,4-quinone scaffold can be used for the development of novel antibacterial and/or antifungal agents. In this study, the aminated quinolinequinones (AQQ1-9) were designed, synthesized, and evaluated for their antimicrobial activity against a panel of seven bacterial strains (three Gram-positive and four Gram-negative bacteria) and three fungal strains. The structure-activity relationship (SAR) for the QQs was also summarized. The antibacterial activity results indicated that the two aminated QQs (AQQ6 and AQQ9) were active against Enterococcus faecalis (ATCC 29212) with a MIC value of 78.12 µg/mL. Besides, the two aminated QQs (AQQ8 and AQQ9) were active against Staphylococcus aureus (ATCC 29213) with MIC values of 4.88 and 2.44 µg/mL, respectively. The most potent aminated QQs (AQQ8 and AQQ9) were identified as promising lead molecules to further explore their mode of action. The selected QQs (AQQ8 and AQQ9) were further evaluated in vitro to assess their potential antimicrobial activity against each of 20 clinically obtained methicillin-resistant S. aureus isolates, antibiofilm activity, and bactericidal activity using time-kill curve assay. We found that the molecules prevented adhesion of over 50% of the cells in the biofilm. Molecular docking studies were performed to predict the predominant binding mode(s) of the ligands. We believe that the molecules need further investigation, especially against infections involving biofilm-forming microbes.

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.