A review on the recent advances of interaction studies of anticancer metal-based drugs with therapeutic targets, DNA and RNAs.

Metal-based drugs hold promise as potent anticancer agents owing to their unique interactions with cellular targets. This review discusses recent advances in our understanding of the intricate molecular interactions of metal-based anticancer compounds with specific therapeutic targets in cancer cells. Advanced computational and experimental methodologies delineate the binding mechanisms, structural dynamics and functional outcomes of these interactions. In addition, the review sheds light on the precise modes of action of these drugs, their efficacy and the potential avenues for further optimization in cancer-treatment strategies and the development of targeted and effective metal-based therapies for combating various forms of cancer.

Quercetin-phenylalanine 3d-transition metal-based {Co(II), Ni(II) & Cu(II)} intercalative therapeutic agents: DNA & BSA interaction studies in vitro and cleavage activity.

New Quercetin-phenylalanine metal-based therapeutic agents of the formulation [Qu(Phe)M(II).(H2O)2].NO3 where M(II) = Co(II) and Ni(II) and [Qu(Phe)Cu(II).(H2O)2] were synthesized and their structure was predicted by IR, UV-vis, EPR and ESI-MS spectroscopic techniques. The bio-molecular interaction studies of the Quercetin-phenylalanine complexes, 1-3 with ct-DNA and BSA were performed using a battery of complimentary biophysical techniques. The corroborative results of these experiments revealed strong binding propensity via electrostatic interactions probably through minor grove binding towards ct-DNA, therapeutic target. The binding affinity of Quercetin-phenylalanine complexes 1-3 was quantified by determining binding constants values, Kb, Ksv, and the magnitude of binding propensity followed the order 3 > 1 > 2, implicating the preferential binding of Cu(II) complex 3 with ct-DNA. The cleavage studies were performed with complexes using gel electrophoretic mobility assay. The complexes 1-3 demonstrated efficient cleaving ability by the hydrolytic cleavage pathway involving hydroxyl (OH) radicals. BSA binding profile of Quercetin-phenylalanine metal therapeutics 1-3 was studied in order to understand the drug carrier potential of these compounds and found that complex 3 was capable of binding preferentially with BSA as compared to other complexes.

Advances in anticancer alkaloid-derived metallo-chemotherapeutic agents in the last decade: Mechanism of action and future prospects.

Metal-based complexes have occupied a pioneering niche in the treatment of many chronic diseases, including various types of cancers. Despite the phenomenal success of cisplatin for the treatment of many solid malignancies, a limited number of metallo-drugs are in clinical use against cancer chemotherapy till date. While many other prominent platinum and non­platinum- based metallo-drugs (e.g. NAMI-A, KP1019, carboplatin, oxaliplatin, titanocene dichloride, casiopeinas® etc) have entered clinical trials, many have failed at later stages of R&D due to deleterious toxic effects, intrinsic resistance and poor pharmacokinetic response and low therapeutic efficacy. Nonetheless, research in the area of medicinal inorganic chemistry has been increasing exponentially over the years, employing novel target based drug design strategies aimed at improving pharmacological outcomes and at the same time mitigating the side-effects of these drug entities. Over the last few decades, natural products became one of the key structural motifs in the anticancer drug development. Many eminent researchers in the area of medicinal chemistry are devoted to develop new 3d-transition metal-based anticancer drugs/repurpose the existing bioactive compounds derived from myriad pharmacophores such as coumarins, flavonoids, chromones, alkaloids etc. Metal complexes of natural alkaloids and their analogs such as luotonin A, jatrorrhizine, berberine, oxoaporphine, 8-oxychinoline etc. have gained prominence in the anticancer drug development process as the naturally occurring alkaloids can be anti-proliferative, induce apoptosis and exhibit inhibition of angiogenesis with better healing effect. While some of them are inhibitors of ERK signal-regulated kinases, others show activity based on cyclooxygenases-2 (COX-2) and telomerase inhibition. However, the targets of these alkaloid complexes are still unclear, though it is well-established that they demonstrate anticancer potency by interfering with multiple pathways of tumorigenesis and tumor progression both in vitro and in vivo. Over the last decade, many significant advances have been made towards the development of natural alkaloid-based metallo-drug therapeutics for intervention in cancer chemotherapy that have been summarized below and reviewed in this article.

Unique iminotetrahydroberberine-corbelled metronidazoles as potential membrane active broad-spectrum antibacterial agents.

In an effort for fighting with dreadful drug resistance, iminotetraberberine was hybridized with metronidazole to construct a unique type of potential broad-spectrum antibacterial iminotetrahydroberberine-corbelled metronidazoles. Some prepared hybrids exerted promising inhibitory effects against the tested microorganisms in comparison to the natural berberine, clinical metronidazole and norfloxacin. Noticeably, phenyl oxime derivative 8e displayed a broad antibacterial spectrum with a quite low MIC value of 0.024 mM against P. aeruginosa, being 63-, 62- and 2-fold to berberine, metronidazole and norfloxacin, respectively. The active compound 8e with low cytotoxicity under effective bacteriostatic concentration could decrease biofilm viability and show much lower trend to induce the resistant development than norfloxacin in the tested period. Mechanism investigation showed that compound 8e could disturb the bacterial membrane to lead to the leakage of cellular contents, thus exerting potent antibacterial potency. It was also revealed that compound 8e could interact with penicillin binding protein via multi-site non-covalent binding in docking simulation. The above results manifested that iminotetrahydroberberine-corbelled metronidazoles might bring hope for the exploitation of new broad-spectrum antibacterial agents with a membrane-destruction mechanism.

Natural Berberine-Hybridized Benzimidazoles as Novel Unique Bactericides against Staphylococcus aureus.

Natural berberine-hybridized benzimidazoles as potential antibacterial agents were constructed to treat Staphylococcus aureus infection in the livestock industry. Bioassay showed that some new berberine-benzimidazole hybrids exhibited potent antibacterial efficacies, especially, the 2,4-dichlorobenzyl derivative 7d not only showed strong activity against S. aureus ATCC 29213 with the MIC value of 0.006 mM but also effectively eradicated bacterial biofilm and exhibited low toxicity toward mammalian cells. The drug combination experiments showed that compound 7d together with norfloxacin could enhance the antibacterial efficacy. Moreover, the 2,4-dichlorobenzyl derivative 7d did not show obvious propensity to develop bacterial resistance. Preliminary mechanism studies revealed that the active molecule 7d could damage the membrane integrity, stimulate ROS generation, and bind with DNA as well as S. aureus sortase A, thus exerting powerful antibacterial ability. In light of these facts, berberine-benzimidazole hybrid 7d showed a large potentiality as a new bactericide for treating S. aureus in the livestock industry.

Novel chalcone-conjugated, multi-flexible end-group coumarin thiazole hybrids as potential antibacterial repressors against methicillin-resistant Staphylococcus aureus.

The increasing resistance of methicillin-resistant Staphylococcus aureus (MRSA) to antibiotics has led to a growing effort to design and synthesize novel structural candidates of chalcone-conjugated, multi-flexible end-group coumarin thiazole hybrids with outstanding bacteriostatic potential. Bioactivity screening showed that hybrid 5i, which was modified with methoxybenzene, exerted a significant inhibitory activity against MRSA (MIC = 0.004 mM), which was 6 times better than the anti-MRSA activity of the reference drug norfloxacin (MIC = 0.025 mM). Compound 5i neither conferred apparent resistance onto MRSA strains even after multiple passages nor triggered evident toxicity to human hepatocyte LO2 cells and normal mammalian cells (RAW 264.7). Molecular docking showed that highly active molecule 5i might bind to DNA gyrase by forming stable hydrogen bonds. In addition, molecular electrostatic potential surfaces were developed to explain the high antibacterial activity of the target compounds. Furthermore, preliminary mechanism studies suggested that hybrid 5i could disrupt the bacterial membrane of MRSA and insert itself into MRSA DNA to impede its replication, thus possibly becoming a potential antibacterial repressor against MRSA.

Molecular design and preparation of 2-aminothiazole sulfanilamide oximes as membrane active antibacterial agents for drug resistant Acinetobacter baumannii.

A series of 2-aminothiazole sulfanilamide oximes were developed as new membrane active antibacterial agents to conquer the microbial infection. Benzoyl derivative 10c was preponderant for the treatment of drug-resistant A. baumannii infection in contrast to norfloxacin and exerted excellent biocompatibility against mammalian cells including erythrocyte and LO2 cell line. Meanwhile, it had ability to eradicate established biofilm to alleviate the resistance burden. Mechanism investigation elucidated that compound 10c was able to disturb the membrane effectively and inhibit lactic dehydrogenase, which led to cytoplasmic content leakage. The cellular redox homeostasis was interfered via the production of reactive oxygen and nitrogen species (RONS), which further contributed to respiratory pathway inactivation and reduction of GSH activity. This work indicated that 2-aminothiazole sulfanilamide oximes could be a promising start for the exploitation of novel antibacterial agents against pathogens.

Discovery of novel purinylthiazolylethanone derivatives as anti-Candida albicans agents through possible multifaceted mechanisms.

An unprecedented amount of fungal and fungal-like infections has recently brought about some of the most severe die-offs and extinctions due to fungal drug resistance. Aimed to alleviate the situation, new effort was made to develop novel purinylthiazolylethanone derivatives, which were expected to combat the fungal drug resistance. Some prepared purinylthiazolylethanone derivatives possessed satisfactory inhibitory action towards the tested fungi, among which compound 8c gave a MIC value of 1 µg/mL against C. albicans. The active molecule 8c was able to kill C. albicans with undetectable resistance as well as low hematotoxicity and cytotoxicity. Furthermore, it could hinder the growth of C. albicans biofilm, thus avoiding the occurrence of drug resistance. Mechanism research manifested that purinylthiazolylethanone derivative 8c led to damage of cell wall and membrane disruption, so protein leakage and the cytoplasmic membrane depolarization were observed. On this account, the activity of fungal lactate dehydrogenase was reduced and metabolism was impeded. Meanwhile, the increased levels of reactive oxygen species (ROS) and reactive nitrogen species (RNS) disordered redox equilibrium, giving rise to oxidative damage to fungal cells and fungicidal effect.

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.

Novel carbazole-oxadiazoles as potential Staphylococcus aureus germicides.

Staphylococcus aureus resistance poses nonnegligible threats to the livestock industry. In light of this, carbazole-oxadiazoles were designed and synthesized for treating S. aureus infection. Bioassay discovered that 3,6-dibromocarbazole derivative 13a had effective inhibitory activities to several Gram-positive bacteria, in particular to S. aureus, S. aureus ATCC 29213, MRSA and S. aureus ATCC 25923 (MICs = 0.6-4.6 nmol/mL), which was more active than norfloxacin (MICs = 6-40 nmol/mL). Subsequent studies showed that 3,6-dibromocarbazole derivative 13a acted rapidly on S. aureus ATCC 29213 and possessed no obvious tendency to induce bacterial resistance. Further evaluations indicated that 3,6-dibromocarbazole derivative 13a showed strong abilities to disrupt bacterial biofilm and interfere with DNA, which might be the power sources of antibacterial performances. Moreover, 3,6-dibromocarbazole derivative 13a also exhibited slight cell lethality toward Hek 293 T and LO2 cells and low hemolytic toxicity to red blood cells. The above results implied that the active molecule 13a could be studied in the future development of agricultural available antibiotics.

Aloe-emodin derived azoles as a new structural type of potential antibacterial agents: design, synthesis, and evaluation of the action on membrane, DNA, and MRSA DNA isomerase.

As serious global drug resistance motivated the exploration of new structural drugs, we developed a type of novel structural aloe-emodin azoles as potential antibacterial agents in this work. Some target aloe-emodin azoles displayed effective activity against the tested strains, especially tetrazolyl aloe-emodin 4b showed a low MIC value of 2 µg mL-1 towards MRSA, being more efficient than the reference drug norfloxacin (MIC = 8 µg mL-1). Also, the active molecule 4b exhibited low cytotoxicity against LO2 cells with no distinct tendency to induce the concerned resistance towards MRSA. The tetrazolyl derivative 4b was preliminarily investigated for the possible mechanism; it was revealed that tetrazolyl derivative 4b could both disrupt the integrity of MRSA membrane and form 4b-DNA supramolecular complex by intercalating into DNA. Moreover, tetrazolyl aloe-emodin 4b could bind with MRSA DNA isomerase at multiple sites through hydrogen bonds in molecular simulation.

Pyrimidinetrione-imidazoles as a Unique Structural Type of Potential Agents towards Candida Albicans: Design, Synthesis and Biological Evaluation.

Substantial morbidity and mortality of fungal infections have aroused concerns all over the world, and common Candida spp. currently bring about severe systemic infections. A series of pyrimidinetrione-imidazole conjugates as potentially antifungal agents were developed. Bioassays manifested that 4-fluobenzyl pyrimidinetrione imidazole 5 f exerted favorable inhibition towards C. albicans (MIC=0.002 mM), being 6.5 folds more active than clinical antifungal drug fluconazole (MIC=0.013 mM). Preliminary mechanism research indicated that compound 5 f could not only depolarize membrane potential but also permeabilize the membrane of C. albicans. Molecular docking was operated to simulate the interaction mode between molecule 5 f and CYP51. In addition, hybrid 5 f might form 5 f-DNA supramolecular complex via intercalating into DNA. The interference of membrane and DNA might contribute to its fungicidal capacity with no obvious tendency to induce the resistance against C. albicans. Conjugate 5 f endowed good blood compatibility as well as low cytotoxicity towards HeLa and HEK-293T cells.

Unique para-aminobenzenesulfonyl oxadiazoles as novel structural potential membrane active antibacterial agents towards drug-resistant methicillin resistant Staphylococcus aureus.

A class of structurally unique para-aminobenzenesulfonyl oxadiazoles as new potential antimicrobial agents was designed and synthesized from acetanilide. Some target para-aminobenzenesulfonyl oxadiazoles showed antibacterial potency. Noticeably, hexyl derivative 8b (MIC = 1 µg/mL) was more active than norfloxacin against drug resistant MRSA. Compound 8b was able to disturb the membrane effectively and intercalate into deoxyribonucleic acid (DNA) to form a steady 8b-DNA complex, which might be responsible for bacterial metabolic inactivation. Molecular docking indicated that 8b could interact with DNA topoisomerase IV through noncovalent interactions to form a supramolecular complex and hinder the function of this enzyme. These results indicated that hexyl derivative 8b deserved further investigation as a new lead compound.

Membrane active 7-thiazoxime quinolones as novel DNA binding agents to decrease the genes expression and exert potent anti-methicillin-resistant Staphylococcus aureus activity.

A novel class of 7-thiazoxime quinolones was developed as potential antimicrobial agents for the sake of bypassing resistance of quinolones. Biological assays revealed that some constructed 7-thiazoxime quinolones possessed effective antibacterial efficiency. Methyl acetate oxime derivative 6l exhibited 32-fold more active than ciprofloxacin against MRSA, which also possessed rapidly bactericidal ability and low toxicity towards mammalian cells. The combination use of 7-thiazoxime quinolone 6l and ciprofloxacin was able to improve antibacterial potency and effectively alleviate bacterial resistance. The preliminarily mechanism exploration revealed that compound 6l could destroy the cell membrane and insert into MRSA DNA to bind with DNA gyrase, then decrease the expression of gyrB and femB genes. The above results strongly suggested that methyl acetate oxime derivative 6l held a promise for combating MRSA infection.

Novel Schiff base-bridged multi-component sulfonamide imidazole hybrids as potentially highly selective DNA-targeting membrane active repressors against methicillin-resistant Staphylococcus aureus.

A new type of Schiff base-bridged multi-component sulfonamide imidazole hybrids with antimicrobial potential was developed. Some target compounds showed significant antibacterial potency. Observably, butylene hybrids 4h exhibited remarkable inhibitory efficacy against clinical MRSA (MIC = 1 µg/mL), but had no significant toxic effect on normal mammalian cells (RAW 264.7). The highly active molecule 4h was revealed by molecular modeling study that it could insert into the base-pairs of DNA hexamer duplex and bind with the ASN-62 residue of human carbonic anhydrase isozyme II through hydrogen bonding. Furthermore, further preliminary antibacterial mechanism experiments confirmed that compound 4h could effectively interfere with MRSA membrane and insert into bacterial DNA isolated from clinical MRSA strains through non-covalent bonding to produce a supramolecular complex, thus exerting its strong antibacterial efficacy by impeding DNA replication. These findings strongly implied that the highly active hybrid 4h could be used as a potential DNA-targeting template for the development of valuable antimicrobial agent.

An unexpected discovery toward novel membrane active sulfonyl thiazoles as potential MRSA DNA intercalators.

Aim: With the increasing emergence of drug-resistant bacteria, the need for new antimicrobial agents has become extremely urgent. This work was to develop sulfonyl thiazoles as potential antibacterial agents. Results & methodology: Novel hybrids of sulfonyl thiazoles were developed from commercial acetanilide and acetylthiazole. Hybrids 6e and 6f displayed excellent inhibitory efficacy against clinical methicillin-resistant Staphylococcus aureus (MRSA) (minimum inhibitory concentration = 1 µg/ml) without obvious toxicity toward normal mammalian cells (RAW 264.7). The combination uses were found to improve the antimicrobial ability. Further preliminary antibacterial mechanism experiments showed that the active molecule 6f could effectively interfere with MRSA membrane and insert into MRSA DNA. Conclusion: Compounds 6e and 6f could serve as potential DNA-targeting templates toward the development of promising antimicrobial agents.

Synthesis of metronidazole based thiazolidinone analogs as promising antiamoebic agents.

Metronidazole and its derivatives are widely used for the treatment of amoebiasis. However, metronidazole is considered as the standard drug but it has many side effects. The present study describes the synthesis of a series of metronidazole based thiazolidinone analogs via Knoevenagel condensation of 4-[2-(2-methyl-5-nitro-1H-imidazole-1-yl)ethoxy]benzaldehyde 1 with various thiazolidinone derivatives 2-14 to get the new scaffold (15-27) having better activity and lesser toxicity. Six compounds have shown better efficacy and lesser cytotoxicity than the standard drug metronidazole towards HM1: IMSS strain of Entamoeba histolytica. These compounds may combat the problem of drug resistance and might be effective in identifying potential alternatives for future drug discovery against EhOASS.

Design and biological evaluation of a novel type of potential multi-targeting antimicrobial sulfanilamide hybrids in combination of pyrimidine and azoles.

This work explored a novel type of potential multi-targeting antimicrobial three-component sulfanilamide hybrids in combination of pyrimidine and azoles. The hybridized target molecules were characterized by 1H NMR, 13C NMR and HRMS spectra. Some of the developed target compounds exerted promising antimicrobial activity in comparison with the reference drugs norfloxacin and fluconazole. Noticeably, sulfanilamide hybrid 5c with pyrimidine and indole could effectively inhibit the growth of E. faecalis with MIC value of 1 µg/mL. The active molecule 5c showed low cell toxicity and did not obviously trigger the development of resistance towards the tested bacteria strains. Mechanism exploration indicated that compound 5c could not only exert efficient membrane permeability, but also intercalate into DNA of resistant E. faecalis to form 5c-DNA supramolecular complex, which might be responsible for its antimicrobial action. The further investigation showed that this molecule could be effectively transported by human serum albumins through hydrogen bonds and van der Waals force.

Ethylenic conjugated coumarin thiazolidinediones as new efficient antimicrobial modulators against clinical methicillin-resistant Staphylococcus aureus.

In an effort for the development of novel antimicrobial agents, ethylenic conjugated coumarin thiazolidinediones as potential multi-targeting new antimicrobial compounds were synthesized through convenient procedures from commercially available resorcinol and were evaluated for their antimicrobial potency. Bioactive evaluation revealed that some of the prepared compounds showed strong antimicrobial activities towards the tested microorganisms including clinically drug-resistant strains. Especially, propargyl derivative 12b exhibited effective anti-MRSA potency with MIC value of 0.006 µmol/mL, which was highly advantageous over clinical antibacterial drug norfloxacin. Compound 12b showed rapid killing effect, low toxicity against hepatocyte LO2 cell line, and no obvious drug resistance development against MRSA. Preliminary exploration of action mechanism manifested that molecule 12b acted upon MRSA through forming stable supramolecular complex with bacterial DNA which might impede DNA replication. Molecular docking showed that compound 12b could bind with DNA-gyrase through hydrogen bonds.

A new exploration towards aminothiazolquinolone oximes as potentially multi-targeting antibacterial agents: Design, synthesis and evaluation acting on microbes, DNA, HSA and topoisomerase IV.

This work did a new exploration towards aminothiazolquinolone oximes as potentially multi-targeting antimicrobial agents. A class of novel hybrids of quinolone, aminothiazole, piperazine and oxime fragments were designed for the first time, conveniently synthesized as well as characterized by 1H NMR, 13C NMR and HRMS spectra. Biological activity showed that some of the synthesized compounds exhibited good antimicrobial activities in comparison with the reference drugs. Especially, O-methyl oxime derivative 10b displayed excellent inhibitory efficacy against MRSA and S. aureus 25923 with MIC values of 0.009 and 0.017 mM, respectively. Further studies indicated that the highly active compound 10b showed low toxicity toward BEAS-2B and A549 cell lines and no obvious propensity to trigger the development of bacterial resistance. Quantum chemical studies have also been conducted and rationally explained the structural features essential for activity. The preliminarily mechanism exploration revealed that compound 10b could not only exert efficient membrane permeability by interfering with the integrity of cells, bind with topoisomerase IV-DNA complex through hydrogen bonds and π-π stacking, but also form a steady biosupramolecular complex by intercalating into DNA to exert the efficient antibacterial activity. The supramolecular interaction between compound 10b and human serum albumin (HSA) was a static quenching, and the binding process was spontaneous, where hydrogen bonds and van der Waals force played vital roles in the supramolecular transportation of the active compound 10b by HSA.