Hydrazyl hydroxycoumarins as new potential conquerors towards Pseudomonas aeruginosa

A class of unique hydrazyl hydroxycoumarins (HHs) as novel structural scaffold was developed to combat dreadful bacterial infections. Some HHs could effectively suppress bacterial growth at low concentrations, especially, pyridyl HH 7 exhibited a good inhibition against Pseudomonas aeruginosa 27853 with a low MIC value of 0.5 μg/mL, which was 8-fold more active than norfloxacin. Furthermore, pyridyl HH 7 with low hemolytic activity and low cytotoxicity towards NCM460 cells showed much lower trend to induce the drug-resistant development than norfloxacin. Preliminarily mechanism exploration indicated that pyridyl HH 7 could eradicate the integrity of bacterial membrane, result in the leakage of intracellular proteins, and interact with bacterial DNA gyrase via non-covalent binding, and ADME analysis manifested that compound 7 gave good pharmacokinetic properties. These results suggested that the newly developed hydrazyl hydroxycoumarins as potential multitargeting antibacterial agents should be worthy of further investigation for combating bacterial infection.

Synthesis, Antimicrobial Evaluation, and Interaction of Emodin Alkyl Azoles with DNA and HSA

OBJECTIVE

This study aimed to overcome the growing antibiotic resistance. Moreover, the new series of emodin alkyl azoles were synthesized.

METHOD

The novel emodin alkyl azoles were synthesized using commercial emodin and azoles by alkylation. The NMR and HRMS spectra were employed to confirm the structures of novel prepared compounds. The in vitro antibacterial and antifungal activities of the prepared emodin compounds were studied by the 96-well plate method. The binding behavior between emodin 4-nitro imidazole compound 3c and S. aureus DNA was researched using an ultraviolet-visible spectrophotometer. Furthermore, fluorescence spectrometry was used to explore the interaction with human serum albumin (HSA).

RESULTS

The in vitro antimicrobial results displayed that compound 3c gave relatively strong activities with MIC values of 4-16 μg/mL. Notably, this compound exhibited 2-fold more potent activity against S. aureus (MIC = 4 μg/mL) and E. coli (MIC = 8 μg/mL) strains than clinical drug Chloromycin (MIC = 8 and 16 μg/mL). The UV-vis absorption spectroscopy showed that 4-nitro imidazole emodin 3c could form the 3c-DNA complex by intercalating into S. aureus DNA, inhibiting antimicrobial activities. The simulation results displayed that the emodin 3c and DNA complex were formed by hydrogen bonds. The spectral experiment demonstrated that compound 3c could be transported by human serum albumin (HSA) via hydrogen bonds. The molecular simulation found that the hydroxyl group and the nitroimidazole ring of the emodin compound showed an important role in transportation behavior.

CONCLUSION

This work may supply useful directions for the exploration of novel antimicrobial agents.

Comprehensive Insights into Medicinal Research on Imidazole-Based Supramolecular Complexes

The electron-rich five-membered aromatic aza-heterocyclic imidazole, which contains two nitrogen atoms, is an important functional fragment widely present in a large number of biomolecules and medicinal drugs; its unique structure is beneficial to easily bind with various inorganic or organic ions and molecules through noncovalent interactions to form a variety of supramolecular complexes with broad medicinal potential, which is being paid an increasing amount of attention regarding more and more contributions to imidazole-based supramolecular complexes for possible medicinal application. This work gives systematical and comprehensive insights into medicinal research on imidazole-based supramolecular complexes, including anticancer, antibacterial, antifungal, antiparasitic, antidiabetic, antihypertensive, and anti-inflammatory aspects as well as ion receptors, imaging agents, and pathologic probes. The new trend of the foreseeable research in the near future toward imidazole-based supramolecular medicinal chemistry is also prospected. It is hoped that this work provides beneficial help for the rational design of imidazole-based drug molecules and supramolecular medicinal agents and more effective diagnostic agents and pathological probes.

A Comprehensive Review of Recent Advances in the Biological Activities of Quinazolines

Quinazoline heterocycles are critical in the development of medications. Quinazoline derivatives have been intensively researched, providing a wide range of compounds with diverse biological roles. The quinazoline nucleus has garnered a lot of attention in medical chemistry in recent years. It was assumed to be a pharmacophore component in the development of physiologically interesting drugs. This review is an attempt to increase the potential of quinazoline by highlighting a wide range of advancements demonstrated by numerous derivatives of the quinazoline moiety, as well as focusing on diverse pharmacological actions of the quinazoline moiety. This review compiles recent studies on the quinazoline moiety described in the literature by researchers.

Green Process for the Synthesis of 3-Amino-2-methyl-quinazolin-4(3H)-one Synthones and Amides Thereof:DNA Photo-Disruptive and Molecular Docking Studies

Eleven 3-amino-2-methyl-quinazolin-4(3H)-ones have been synthesized, in good to excellent yields, via their corresponding benzoxazinones using an efficient tandem microwave-assisted green process. Representative acetamides have been thermally derived from their functional free 3-amino group, whereas for the synthesis of various arylamides, a novel green microwave-assisted protocol has been developed, which involved the attack of hydrazides on benzoxazinones. Eight out of the eleven 3-amino-2-methyl-quinazolin-4(3H)-ones were found photo-active towards plasmid DNA under UVB, and four under UVA irradiation. Amongst all acetamides, only the 6-nitro derivative retained activity both under UVB and UVA irradiation, whereas the 6-bromo-substituted one was active only under UVB. 3-arylamido-6-bromo derivatives exhibited dramatically decreased photo-activity; however, all 3-arylamido-6-nitro compounds developed extraordinary activity, even at concentrations as low as 1μM, which was enhanced compared to their parent 3-amino-2-methyl-6-nitro-quinazolinone. Molecular docking studies were indicative of satisfactory binding to DNA and correlated to the presented photo-activity. Since quinazolinones are known “privileged” pharmacophores for anticancer and antimicrobial activities, the present study gives information on turning “on” and “off” photosensitization on various derivatives which are often used as synthones for drug development, when chromophores and auxochromes are incorporated or being functionalized. Thus, certain compounds may lead to the development of novel photo-chemo or photodynamic therapeutics.

Identification of Unique Quinazolone Thiazoles as Novel Structural Scaffolds for Potential Gram-Negative Bacterial Conquerors

A class of quinazolone thiazoles was identified as new structural scaffolds for potential antibacterial conquerors to tackle dreadful resistance. Some prepared compounds exhibited favorable bacteriostatic efficiencies on tested bacteria, and the most representative 5j featuring the 4-trifluoromethylphenyl group possessed superior performances against Escherichia coli and Pseudomonas aeruginosa to norfloxacin. Further studies revealed that 5j with inappreciable hemolysis could hinder the formation of bacterial biofilms and trigger reactive oxygen species generation, which could take responsibility for emerging low resistance. Subsequent paralleled exploration discovered that 5j not only disintegrated outer and inner membranes to induce leakage of cytoplasmic contents but also broke the metabolism by suppressing dehydrogenase. Meanwhile, derivative 5j could intercalate into DNA to exert powerful antibacterial properties. Moreover, compound 5j gave synergistic effects against some Gram-negative bacteria in combination with norfloxacin. These findings indicated that this novel structural type of quinazolone thiazoles showed therapeutic foreground in struggling with Gram-negative bacterial infections.

6-Nitro-Quinazolin-4(3H)-one Exhibits Photodynamic Effects and Photodegrades Human Melanoma Cell Lines. A Study on the Photoreactivity of Simple Quinazolin-4(3H)-ones

Photochemo and photodynamic therapies are minimally invasive approaches for the treatment of cancers and powerful weapons for competing bacterial resistance to antibiotics. Synthetic and naturally occurring quinazolinones are considered privileged anticancer and antibacterial agents, with several of them to have emerged as commercially available drugs. In the present study, applying a single-step green microwave irradiation mediated protocol we have synthesized eleven quinazolinon-4(3H)-ones, from cheap readily available anthranilic acids, in very good yields and purity. These products were irradiated in the presence of pBR322 plasmid DNA under UVB, UVA and visible light. Four of the compounds proved to be very effective DNA photocleavers, at low concentrations, being time and concentration dependent as well as pH independent. Participation of reactive oxygen species was related to the substitution of quinazolinone derivatives. 6-Nitro-quinazolinone in combination with UVA irradiation was found to be in vitro photodestructive for three cell lines; glioblastoma (U87MG and T98G) and mainly melanoma (A-375). Thus, certain appropriately substituted quinazolinones may serve as new lead photosensitizers for the development of promising biotechnological applications and as novel photochemo and photodynamic therapeutics.

Metronidazole-conjugates: A comprehensive review of recent developments towards synthesis and medicinal perspective

Nitroimidazoles based compounds remain a hot topic of research in medicinal chemistry due to their numerous biological activities. Moreover, many clinical candidates based on this chemical core have been reported to be valuable in the treatment of human diseases. Metronidazole (MTZ) derived conjugates demonstrated a potential application in medicinal chemistry research over the last decade. In this review, we summarize the synthesis, key structure-activity-relationship (SAR) and associated biological activities such as antimicrobial, anticancer, antidiabetic, anti-inflammatory, anti-HIV and anti-parasitic (Anti-trichomonas, antileishmanial, antiamoebic and anti-giardial) of explored MTZ-conjugates. The molecular docking analysis is also presented simultaneously, which will assist in developing an understanding towards designing of new MTZ-conjugates for target-based drug discovery against multiple disease areas.

1,2,4-Triazole hybrids with potential antibacterial activity against methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) has developed numerous mechanisms of virulence and strategies to evade the human immune system, and it can be transmitted between humans, animals, and the environment. Thus, MRSA is an important cause of morbidity and mortality in both hospitals and in the community, creating an urgent demand for the development of novel anti-MRSA candidates. The 1,2,4-triazole nucleus is a bioisostere of amide, ester, and carboxylic acid, and the 1,2,4-triazole ring is found in many compounds with diverse biological effects. 1,2,4-Triazole derivatives could exert their antibacterial activity through inhibition of efflux pumps, filamentous temperature-sensitive protein Z, penicillin-binding protein, DNA gyrase, and topoisomerase IV, and they play an important role in the discovery of novel antibacterial agents. Among them, 1,2,4-triazole hybrids, which have the potential to exert dual/multiple mechanisms of action, possess a promising broad-spectrum antibacterial activity against a panel of clinically important drug-resistant pathogens including MRSA. This review outlines the recent developments of 1,2,4-triazole hybrids with a potential anti-MRSA activity, covering articles published between 2010 and 2020. The mechanisms of action, critical aspects of their design, and structure-activity relationships are also discussed.

Nitroimidazole-containing compounds and their antibacterial and antitubercular activities

Infections especially tuberculosis caused by various bacteria including mycobacteria result in millions of lives every year, but the control of bacterial infections is challenged by the limitation of effective pharmaceuticals against drug-resistant pathogens. Nitroimidazoles belong to a group of nitroheterocyclic compounds that have broad-spectrum activity against a series of organisms such as mycobacteria, anaerobic Gram-positive and Gram-negative bacteria, and some of them have already been used in clinics or under clinical trials for the treatment of infectious diseases. In this review, we made an overview of the recent advances in nitroimidazole-containing compounds with antibacterial and antitubercular activity in the recent 20 years.

4(3H)-Quinazolinone derivatives: Promising antibacterial drug leads

Emergence of drug resistance has created unmet medical need for the development of new classes of antibiotics. Discovery of new antibacterial agents with new mode of action remains a high priority universally. 4(3H)-quinazolinone, a fused nitrogen heterocyclic compound has emerged as a biologically privileged structure, possessing a wide range of biological properties viz. anticancer, antibacterial, antitubercular, antifungal, anti-HIV, anticonvulsant, anti-inflammatory and analgesic activities. Promising antibacterial properties of quinazolinones have enthused the medicinal chemists to explore and develop this fused heterocyclic system for new antibacterial agents. Utilization of quinazolinone core for the design and synthesis of new antibacterial agents has recently gained momentum. This review aims to provide an overview of the structures and antibacterial activity of various 4(3H)-quinazolinone derivatives covering various aspects of in vitro and in vivo pharmacological activities and structure activity relationships (SARs).

Discovery of Benzimidazole-Quinolone Hybrids as New Cleaving Agents toward Drug-Resistant Pseudomonas aeruginosa DNA

A series of benzimidazole-quinolone hybrids as new potential antimicrobial agents were designed and synthesized. Bioactive assays indicated that some of the prepared compounds exhibited potent antibacterial and antifungal activities. Notably, 2-fluorobenzyl derivative 5 b (ethyl 7-chloro-6-fluoro-1-[[1-[(2-fluorophenyl)methyl]benzimidazol-2-yl]methyl]-4-oxo-quinoline-3-carboxylate) showed remarkable antimicrobial activity against resistant Pseudomonas aeruginosa and Candida tropicalis isolated from infected patients. Active molecule 5 b could not only rapidly kill the tested strains, but also exhibit low toxicity toward Hep-2 cells. It was more difficult to trigger the development of bacterial resistance of P. aeruginosa against 5 b than that against norfloxacin. Molecular docking demonstrated that 5 b could effectively bind with topoisomerase IV-DNA complexes, and quantum chemical studies theoretically elucidated the good antimicrobial activity of compound 5 b. Preliminary experimental reaction mechanism exploration suggested that derivative 5 b could not intercalate into DNA isolated from drug-resistant P. aeruginosa, but was able to cleave DNA effectively, which might further block DNA replication to exert powerful bioactivities. In addition, compound 5 b is a promising antibacterial agent with membrane disruption abilities.

Novel naphthalimide nitroimidazoles as multitargeting antibacterial agents against resistant Acinetobacter baumannii

Aim: The increasing emergence of resistant bacteria imposed an urgent request to discover novel antibacterial agents. This work was to develop naphthalimide nitroimidazoles as potentially antibacterial agents. Results/methodology: Compound 9e showed the strong antibacterial activity (minimal inhibitory concentration = 0.013 μmol/ml) against resistant Acinetobacter baumannii (A. baumannii) with rapid killing effect and no obvious triggering of the development of resistance. Its combination use with chloromycin, norfloxacin or clinafloxacin improved the antibacterial potency. It could not only effectively permeate membrane of resistant A. baumannii bacteria, but also intercalate into resistant A. baumannii DNA to form 9e–DNA complex. The interaction with bacterial DNA gyrase B was driven by hydrogen bonds. Conclusion: Compound 9e should be a potentially multitargeting antibacterial agent against resistant A. baumannii.

Novel Naphthalimide Aminothiazoles as Potential Multitargeting Antimicrobial Agents

A series of novel naphthalimide aminothiazoles were developed for the first time and evaluated for their antimicrobial activity. Some prepared compounds possessed good inhibitory activity against the tested bacteria and fungi. Noticeably, the piperazine derivative 4d displayed superior antibacterial activity against MRSA and Escherichia coli with MIC values of 4 and 8 μg/mL, respectively, to reference drugs. The most active compound 4d showed low toxicity against mammalian cells with no obvious triggering of the development of bacterial resistance, and it also possessed rapid bactericidal efficacy and efficient membrane permeability. Preliminarily investigations revealed that compound 4d could not only bind with gyrase-DNA complex through hydrogen bonds but could effectively intercalate into MRSA DNA to form 4d-DNA supramolecular complex, which might be responsible for the powerful bioactivity. Further transportation behavior evaluation indicated that molecule 4d could be effectively stored and carried by human serum albumin, and the hydrophobic interactions and hydrogen bonds played important roles in the binding process.

Novel potentially antifungal hybrids of 5-flucytosine and fluconazole: Design, synthesis and bioactive evaluation

A series of novel potentially antifungal hybrids of 5-flucytosine and fluconazole were designed, synthesized and characterized by ¹H NMR, ¹³C NMR, IR and HRMS spectra. Bioactive assay manifested that some prepared compounds showed moderate to good antifungal activities in comparison with fluconazole and 5-flucytosine. Remarkably, the 3,4-dichlorobenzyl hybrid 7h could inhibit the growth of C. albicans ATCC 90023 and clinical resistant strain C. albicans with MIC values of 0.008 and 0.02 mM, respectively. The active molecule 7h could not only rapidly kill C. albicans but also efficiently permeate membrane of C. albicans. Molecular docking study revealed that compound 7h could interact with the active site of CACYP51 through hydrogen bond. Quantum chemical studies were also performed to explain the high antifungal activity. Further preliminary mechanism research suggested that molecule 7h could intercalate into calf thymus DNA to form a steady supramolecular complex, which might block DNA replication to exert the powerful bioactivities.

Discovery of potential antifungal triazoles: design, synthesis, biological evaluation, and preliminary antifungal mechanism exploration

A series of triazoles as miconazole analogues was designed, synthesized and characterized by IR, NMR, MS and HRMS. All the newly prepared compounds were screened for their antifungal activities against five kinds of fungi. The bioactive assay showed that most of the synthesized compounds exhibited good or even stronger antifungal activities in comparison with the reference drugs miconazole and fluconazole. In particular, the 3,4-dichlorobenzyl derivative 5b showed a comparable or superior activity against all the tested fungal strains to standard drugs, and formed a supramolecular complex with CYP51 via the hydrogen bond between the 4-nitrogen of the triazole nucleus and the histidine residue. Preliminary experiments revealed that both of the active molecules 5b and 9c could intercalate into calf thymus DNAs, which might block DNA replication to exhibit their powerful antifungal abilities. Further studies indicated that compound 5b might be stored and transported by human serum albumin through hydrophobic interactions, specific electrostatic interactions and hydrogen bonds. These results strongly suggested that compound 5b could serve as a promising antifungal candidate.

Interaction studies of copper complex containing food additive carmoisine dye with human serum albumin (HSA): Spectroscopic investigations

In this study, the interaction between human serum albumin (HSA) and a copper complex of carmoisine dye; [Cu(carmoisine)₂ (H₂ O)₂ ], was studied in vitro using multi-spectroscopic methods. It was found that the intrinsic fluorescence of HSA was quenched by the addition of the [Cu(carmoisine)₂ (H₂ O)₂ ] complex and the quenching mechanism was considered as static quenching by formation of a [Cu(carmoisine)₂ (H₂ O)₂ ]-HSA complex. The binding constant was about 10⁴  M^-1 at room temperature. The values of the calculated thermodynamic parameters (ΔH < 0 and ΔS > 0) suggested that both hydrogen bonds and the hydrophobic interactions were involved in the binding process. The site marker competitive experiments revealed that the binding of [Cu(carmoisine)₂ (H₂ O)₂ ] to HSA primarily occurred in subdomain IIIA (site II) of HSA. The results of circular dichroism (CD) and UV-vis spectroscopy showed that the micro-environment of amino acid residues and the conformation of HSA were changed after addition of the [Cu(carmoisine)₂ (H₂ O)₂ ] complex. Finally, the binding of the [Cu(carmoisine)₂ (H₂ O)₂ ] complex to HSA was modelled by a molecular docking method. Excellent agreement was obtained between the experimental and theoretical results with respect to the binding forces and binding constant.

Design, synthesis and biological evaluation of novel Schiff base-bridged tetrahydroprotoberberine triazoles as a new type of potential antimicrobial agents

A series of novel Schiff base-bridged tetrahydroprotoberberine (THPB) triazoles were designed, synthesized and characterized for the first time. Antimicrobial assay showed that some of the prepared compounds exerted stronger antibacterial and antifungal activities than the reference drugs. Especially, THPB triazole 7a gave low MIC values of 0.5, 1 and 2 μg mL^-1 against B. yeast, M. luteus and MRSA, respectively. Further experiments indicated that the highly active molecule 7a was able to rapidly kill the MRSA strain and did not trigger the development of bacterial resistance even after 14 passages. The preliminary exploration for the antimicrobial mechanism revealed that compound 7a could effectively intercalate into calf thymus DNA to form a 7a-DNA supramolecular complex, and its Zn²⁺ complex had the ability to directly cleave pUC19 DNA, which suggested that compound 7a might be a potentially dual-targeting antibacterial molecule. It was also found that compound 7a could be efficiently stored and carried by human serum albumin (HSA), and the hydrophobic interactions and hydrogen bonds played important roles in the transportation of HSA to the active molecule 7a.

Multi-targeting exploration of new 2-aminothiazolyl quinolones: Synthesis, antimicrobial evaluation, interaction with DNA, combination with topoisomerase IV and penetrability into cells

A series of new potentially multi-targeting antimicrobial 2-aminothiazolyl quinolones were designed, synthesized and characterized by ¹H NMR, ¹³C NMR, IR, MS and HRMS spectra. Bioactive assay manifested that some of the prepared compounds showed moderate to good antibacterial and antifungal activities. Noticeably, compound 10f could effectively inhibit the growth of B. typhi and MRSA with MIC values of 1 and 8 μg/mL, respectively. Experimental results revealed that compound 10f was membrane-active and had the ability to rapidly kill the tested strains and effectively prevent the development of bacterial resistance. Moreover, this compound also exhibited low toxicity against L929 cells. Molecular docking indicated that compound 10f could bind with topoisomerase IV-DNA complexes through hydrogen bonds and hydrophobic interactions. Quantum chemical studies were also performed on 10f to understand the structural features essential for activity. The preliminary mechanism research suggested that compound 10f could intercalate into calf thymus DNA to form a steady supramolecular complex which might block DNA replication to exert the powerful bioactivities.

Antifungal potential of Sideroxylon obtusifolium and Syzygium cumini and their mode of action against Candida albicans

Context The emergence of resistant pathogens and toxicity of antifungals have encouraged an active search for novel candidates to manage Candida biofilms. Objective In this study, the little known species Sideroxylon obtusifolium T.D. Penn (Sapotacea) and Syzygium cumini (L.) Skeels (Myrtaceae), from the Caatinga biome in Brazil were chemically characterized and explored for their antifungal potential against C. albicans. Materials and methods We determined the effects of hydroalcoholic extracts/fractions upon fungal growth (minimum inhibitory and fungicidal concentrations, MIC/MFC), biofilm morphology (scanning electron microscopy) and viability (confocal laser scanning microscopy), proposed their mode of action (sorbitol and ergosterol assays), and finally investigated their effects against macrophage and keratinocyte cells in a cell-based assay. Data were analysed using one-way analysis of variance with Tukey-Kramer post-test (α = 0.05). Results The n-butanol (Nb) fraction from S. obtusifolium and S. cumini extract (Sc) showed flavonoids (39.11 ± 6.62 mg/g) and saponins (820.35 ± 225.38 mg/g), respectively, in their chemical composition and demonstrated antifungal activity, with MICs of 62.5 and 125 μg/mL, respectively. Nb and Sc may complex with ergosterol as there was a 4-16-fold increase in MICs in the presence of exogenous ergosterol, leading to disrupted permeability of cell membrane. Deleterious effects were observed on morphology and viability of treated biofilms from concentrations as low as their MICs and higher. Sc was not toxic to macrophages and keratinocytes at these concentrations (p > 0.05), unlike Nb. Conclusions Nb and Sc demonstrated considerable antifungal activity and should be further investigated as potential alternative candidates to treat Candida biofilms.

Quinazolinone azolyl ethanols: potential lead antimicrobial agents with dual action modes targeting methicillin-resistant Staphylococcus aureus DNA

Aim: Due to bacterial drug resistance, a new series of quinazolinone azolyl ethanols were synthesized and evaluated. Results: In vitro antibacterial assay showed that triazolyl ethanol quinazolinone 3a was the most active compound, especially against methicillin-resistant Staphylococcus aureus (MRSA) with minimal inhibitory concentration value of 8 µg/ml, which was superior to chloromycin and comparable to norfloxacin. Molecular docking study displayed that compound 3a could interact with MRSA DNA by the formation of hydrogen bonds. Further interactions of quinazolinone 3a with MRSA DNA suggested that it could intercalate into MRSA DNA to form 3a–DNA complex. DNA cleavage properties of 3a–Cu2+ and 3a–Zn2+ complexes were confirmed by agarose gel electrophoresis experiments. Conclusion: Compound 3a should be a potential lead antibacterial molecule with dual action modes.

Discovery of novel berberine imidazoles as safe antimicrobial agents by down regulating ROS generation

A series of novel berberine-based imidazole derivatives as new type of antimicrobial agents were developed and characterized. Most of them gave good antibacterial activity toward the Gram-positive and negative bacteria. Noticeably, imidazolyl berberine 3a exhibited low MIC value of 1μg/mL against Eberthella typhosa, which was even superior to reference drugs berberine, chloromycin and norfloxacin. The cell toxicity and ROS generation assay indicated that compound 3a showed low cell toxicity. The interactive investigation by UV-vis spectroscopic method revealed that compound 3a could effectively intercalate into calf thymus DNA to form 3a-DNA complex which might further block DNA replication to exert the powerful antimicrobial activities. The binding behavior of compound 3a to DNA topoisomerase IB revealed that hydrogen bonds and electrostatic interactions played important roles in the association of compound 3a with DNA topoisomerase IB.

Structure-activity relationship study between baicalein and wogonin by spectrometry, molecular docking and microcalorimetry

Flavones (e.g. baicalein and wogonin) extensively used worldwide in food preparation and traditional medicine. In this study, a systematically comparative study of their structure-activity relationships (SAR) on their interaction with BSA, antioxidant activity and antibacterial activity has been carried out by spectrometry, molecular docking and microcalorimetry. Our results show that the skeleton structure of flavones, the number of hydroxyl groups, the type of functional group, conjugated system and the steric hindrance may be responsible for their different biological activity. These findings not only would lay a scientific foundation for discovering and designing flavones-based food and drug, may also help us to understanding the structure-activity relationship between flavones at the molecular level.

Discovery of membrane active benzimidazole quinolones-based topoisomerase inhibitors as potential DNA-binding antimicrobial agents

A series of novel benzimidazole quinolones as potential antimicrobial agents were designed and synthesized. Most of the prepared compounds exhibited good or even stronger antimicrobial activities in comparison with reference drugs. The most potent compound 15m was membrane active and did not trigger the development of resistance in bacteria. It not only inhibited the formation of biofilms but also disrupted the established Staphylococcus aureus and Escherichia coli biofilms. It was able to inhibit the relaxation activity of E. coli topoisomerase IV at 10 μM concentration. Moreover, this compound also showed low toxicity against mammalian cells. Molecular modeling and experimental investigation of compound 15m with DNA suggested that this compound could effectively bind with DNA to form a steady 15m-DNA complex which might further block DNA replication to exert the powerful bioactivities.

Synthesis and biological evaluation of Schiff base-linked imidazolyl naphthalimides as novel potential anti-MRSA agents

Schiff base-linked imidazolyl naphthalimide 9i was a potential anti-MRSA agent, which could effectively inhibit the growth of MRSA.

Design, synthesis, and biological evaluation of novel carbazole aminothiazoles as potential DNA-targeting antimicrobial agents

Synthesis of a series of carbazole aminothiazoles as a new type of potential antimicrobial agents, and preliminary interactions with DNA indicated a possible intercalation mechanism.

Synthesis, characterization, and air stability study of pyrimido[4,5-g]quinazoline-4,9-dione-based polymers for organic thin film transistors

This study reports the synthesis of two novel π-conjugated pyrimido[4,5-g]quinazoline-4,9-dione (PQ) based polymers and reveals that the air stability of PQ based polymers is critically affected by the donor comonomer.

Interaction of flavones with DNA in vitro: structure–activity relationships

The structure–activity relationship of the different flavones has been investigated, which may meaningful for drug discovery, and novel drug design.

Understanding the structure–activity relationship between quercetin and naringenin: in vitro

The interactions of quercetin and naringenin with DNA have been studied at molecular level, which may throw light on their structure–activity relationships, helpful for the design of analogs flavonoids and their application in drug industries.