Novel rhodanine derivatives are selective algicides against <Emphasis Type="Italic">Microcystis aeruginosa</Emphasis>

In this study, a series of rhodanine derivatives containing various substituents was synthesized and tested for in vitro algicidal activity. Among the tested substituent groups, phenyl substituents with halogen groups showed good inhibitory potency. Furthermore, the compound with chlorine at the C2 position of the phenyl ring exhibited a higher algicidal effect than the compound with chlorine at the C3 position of the phenyl ring. Among the various rhodanine derivatives tested, 5-(2,4-dichlorobenzylidene)- rhodanine (compound 20) was the most potent inhibitor against M. aeruginosa with a lethal concentration 50 (LC₅₀) value of 0.65 μM and Selenastrum capricornutum with an LC₅₀ value of 0.82 μM. To verify the feasibility of their use in ecosystems, 25 h of acute ecotoxicity tests were carried out for three derivatives against Danio rerio and Daphnia magna. No mortality was observed in groups exposed to 2.0 μM of compound 20 after 100 h of exposure. Moreover, a survival rate of 100% was observed in D. magna exposed to 2 μM of compound 20 for 100 h. Overall, the results show that rhodanine derivatives are a possible method for controlling and inhibiting harmful algal blooms.     

Rhodanine derivatives as novel inhibitors of PDE4

The discovery, synthesis and in vitro activity of a novel series of rhodanine based phosphodiesterase-4 (PDE4) inhibitors is described. Structure-activity relationship studies directed toward improving potency led to the development of submicromolar inhibitors 2n and 3i (IC(50)=0.89 & 0.74 microM). The replacement of rhodanine with structurally related heterocycles was also investigated and led to the synthesis of pseudothiohydantoin 7 (IC(50)=0.31 microM).     

5-benzylidenerhodanine and 5-benzylidene-2-4-thiazolidinedione based antibacterials

Herein we outline the antibacterial activity of amino acid containing thiazolidinediones and rhodanines against Gram-positive bacteria Staphylococcus aureus ATCC 31890, Staphylococcus epidermidis and Bacillus subtilis ATCC 6633. The rhodanine derivatives were generally more active than the analogous thiazolidinediones. Compounds of series 5 showed some selectivity for Bacillus subtilis ATCC 6633, the extent of which is enhanced by the inclusion of a non-polar amino acid at the 5-position of the core thiazolidinediones and rhodanines scaffolds. SAR data of series 8 demonstrated improved activity against the clinically more significant Staphylococci with selectivity over Bacillus subtilis ATCC 6633 induced by introduction of a bulky aryl substituent at the 5-position of the core scaffolds.     

Discovery and development of novel rhodanine derivatives targeting enoyl-acyl carrier protein reductase

A series of rhodanine derivatives RB1–RB23 were synthesized through a two-round screening. Their Mycobacterial tuberculosis (Mtb) InhA inhibitory activity and Mtb growth blocking capability were evaluated. The most potent hit compound RB23 indicated comparable InhA inhibiton (IC₅₀?=?2.55?μM) with the positive control Triclosan (IC₅₀?=?6.14?μM) and Isoniazid (IC₅₀?=?8.29?μM). Its improved growth-blocking effect on Mtb and low toxicity were attractive for further development. The docking simulation revealed the possible binding pattern of this series and picked the key interacted residues as Ser20, Phe149, Lys165 and Thr196. The 3D-QSAR model visualized the SAR discussion and hinted new information. Modifying the surroundings near rhodanine moiety might be promising attempts in later investigations.     

Synthesis and biological evaluation of rhodanine derivatives bearing a quinoline moiety as potent antimicrobial agents

Three series of rhodanine derivatives bearing a quinoline moiety (6a–h, 7a–g, and 8a–e) have been synthesized, characterized, and evaluated as antibacterial agents. The majority of these compounds showed potent antibacterial activities against several different strains of Gram-positive bacteria, including multidrug-resistant clinical isolates. Of the compounds tested, 6g and 8c were identified as the most effective with minimum inhibitory concentration (MIC) values of 1 μg/mL against multidrug-resistant Gram-positive organisms, including methicillin-resistant and quinolone-resistant Staphylococcus aureus (MRSA and QRSA, respectively). None of the compounds exhibited any activity against the Gram-negative bacteria Escherichia coli 1356 at 64 μg/mL. The cytotoxic activity assay showed that compounds 6g, 7g and 8e exhibited in vitro antibacterial activity at non-cytotoxic concentrations. Thus, these studies suggest that rhodanine derivatives bearing a quinoline moiety are interesting scaffolds for the development of novel Gram-positive antibacterial agents.     

Evaluation of dihydropyrimidin-(2H)-one analogues and rhodanine derivatives as tyrosinase inhibitors

A series of dihydropyrimidin-(2H)-one analogues and rhodanine derivatives were synthesized and their inhibitory effects on the diphenolase activity of mushroom tyrosinase were evaluated. The results showed that some of the synthesized compounds exhibited significant inhibitory activities. Especially, compound 15 bearing a hydroxyethoxyl group at position-4 of phenyl ring exhibited most potent tyrosinase inhibitory activity with IC₅₀ value of 0.56 mM. The inhibition mechanism analysis of compound 15 demonstrated that the inhibitory effect of the compound on the tyrosinase was irreversible. These results suggested that such compounds might be served as lead compounds for further designing new potential tyrosinase inhibitors.     

Synthesis and antimicrobial properties of novel silver/polyrhodanine nanofibers

Silver nanoparticle-embedded polyrhodanine nanofibers were synthesized by chemical oxidation polymerization. Silver ions were reduced to silver nanoparticles by oxidizing rhodanine monomer and simultaneously complexed with the rhodanine due to coordinative interactions, resulting in the formation of silver nanoparticle-embedded polyrhodanine nanofibers. The synthesized silver/polyrhodanine nanofiber was found to have the excellent antimicrobial activity against gram-negative Escherichia coli, gram-positive Staphylococcus aureus, and Candida albicans. The modified Kirby-Bauer test demonstrated that the silver/polyrhodanine nanofiber had better antimicrobial efficacy than silver sulfadiazine.     

Determination of gallotannin with rhodanine

A reliable method for quantitative analysis of gallotannin in plants has been devised. Gallotannin is hydrolyzed with acid, and gallic acid in the hydrolysate is then assayed using rhodanine. This method is very specific; no interferences from other plant phenolics, including ellagic acid and condensed tannin, have been observed. The rhodanine assay has a sensitivity of 0.01 mg of gallic acid and a precision of 2.2% (relative standard deviation).     

Selective small molecule inhibitors of the potential breast cancer marker,human arylamine N-acetyltransferase 1, and its murine homologue,mouse arylamine N-acetyltransferase 2

The identification, synthesis and evaluation of a series of rhodanine and thiazolidin-2,4-dione derivatives as selective inhibitors of human arylamine N-acetyltransferase 1 and mouse arylamine N-acetyltransferase 2 is described. The most potent inhibitors identified have submicromolar activity and inhibit both the recombinant proteins and human NAT1 in ZR-75 cell lysates in a competitive manner. ¹H NMR studies on purified mouse Nat2 demonstrate that the inhibitors bind within the putative active site of the enzyme.     

Rhodanine resistance and dependence of echovirus 12: a possible consequence of capsid flexibility.

Recombinant viruses of echovirus 12 carrying mutations of a rhodanine-resistant or -dependent variant, were investigated, and five single mutations each inducing a rhodanine-resistant or -dependent phenotype were defined. Four mutations are localized in the capsid protein VP1, and the fifth exchange is in VP4. All original and recombinant viruses were shown to be stabilized by the antiviral drug rhodanine against heat inactivation. Hence, resistant and dependent variants still seem able to bind rhodanine, and apparently none of the exchanges affects the putative drug binding site. We hypothesize that drug resistance and dependence are consequences of an increased flexibility of the virus capsid.     

Structure activity relationship studies on rhodanines and derived enethiol inhibitors of metallo-β-lactamases

Metallo-β-lactamases (MBLs) enable bacterial resistance to almost all classes of β-lactam antibiotics. We report studies on enethiol containing MBL inhibitors, which were prepared by rhodanine hydrolysis. The enethiols inhibit MBLs from different subclasses. Crystallographic analyses reveal that the enethiol sulphur displaces the di-Zn(II) ion bridging ‘hydrolytic’ water. In some, but not all, cases biophysical analyses provide evidence that rhodanine/enethiol inhibition involves formation of a ternary MBL enethiol rhodanine complex. The results demonstrate how low molecular weight active site Zn(II) chelating compounds can inhibit a range of clinically relevant MBLs and provide additional evidence for the potential of rhodanines to be hydrolysed to potent inhibitors of MBL protein fold and, maybe, other metallo-enzymes, perhaps contributing to the complex biological effects of rhodanines. The results imply that any medicinal chemistry studies employing rhodanines (and related scaffolds) as inhibitors should as a matter of course include testing of their hydrolysis products.     

Infectious cDNA clones of echovirus 12 and a variant resistant against the uncoating inhibitor rhodanine differ in seven amino acids.

Determination of the complete sequences of echovirus 12 and a rhodanine-resistant variant revealed seven amino acid deviations and two additional exchanges not confirmed in all clones. In rhodanine sensitivity assays with infectious cDNAs, it was shown that the biological markers of the original viruses are maintained.     

Spectral analyses of absorption changes associated with nerve excitation in dye-stained crab nerve

Spectral characteristics of absorption changes associated with nerve excitation were studied with crab nerves stained with a homologous series of dyes, merocyanine-rhodanines and rhodanine oxonols. In these classes of dyes, the absorption changes which followed approximately the same time course as that of the action potential (fast responses) depended in a similar fashion on the wavelength and polarization of the incident light. In order to interpret those commonly observed dependencies, a mode of reorientation of the absorption oscillators of the dye molecules in the membrane matrix during nerve excitation was proposed. In addition to the fast changes mentioned above, slow responses which developed during and after the action potential were commonly observed with oxonols. The spectra of the slow changes differed from those of the fast ones, indicating a distinct mechanism on the response production. A possible mechanism of the production of fast responses was also discussed based on the proposed mode of reorientation of the absorption oscillators.     

Synthesis,Antimicrobial and Antitumor Properties of 5-Thiophen-2-ylmethylen-2-Thioxothiazolidin-4-one Derivatives

Russian Journal of Bioorganic Chemistry - By the reaction of thiophen-2-carbaldehyde with rhodanine derivatives, 5-thiophen-2-ylmethylene-2-thioxothiazolidin-4-ones have been synthesized. The...     

New hybrid molecules combining benzothiophene or benzofuran with rhodanine as dual COX-1/2 and 5-LOX inhibitors: Synthesis,biological evaluation and docking study

New molecular hybrids combining benzothiophene or its bioisostere benzofuran with rhodanine were synthesized as potential dual COX-2/5-LOX inhibitors. The benzothiophene or benzofuran scaffold was linked at position -2 with rhodanine which was further linked to various anti-inflammatory pharmacophores so as to investigate the effect of such molecular variation on the anti-inflammatory activity. The target compounds were evaluated for their in vitro COX/LOX inhibitory activity. The results revealed that, compound 5h exhibited significant COX-2 inhibition higher than celecoxib. Furthermore, compounds 5a, 5f and 5i showed COX-2 inhibitory activity comparable to celecoxib. Compound 5h showed selectivity index SI = 5.1 which was near to that of celecoxib (SI = 6.7). Compound 5h displayed LOX inhibitory activity twice than that of meclofenamate sodium. Moreover, compounds 5a, 5e and 5f showed significant LOX inhibitory activity higher than that of meclofenamate sodium. Compound 5h was screened for its in vivo anti-inflammatory activity using formalin-induced paw edema and gastric ulcerogenic activity tests. The results revealed that, it showed in vivo decrease in formalin-induced paw edema volume higher than celecoxib. It also displayed gastrointestinal safety profile as celecoxib. The biological results were also consistent with the docking studies at the active sites of the target enzymes COX-2 and 5-LOX. Also, compound 5h showed physicochemical, ADMET, and drug-like properties within those considered adequate for a drug candidate.     

Rhodanine-based PRL-3 inhibitors blocked the migration and invasion of metastatic cancer cells

PRL-3, phosphatase of regenerating liver-3, plays a role in cancer progression through its involvement in invasion, migration, metastasis, and angiogenesis. We synthesized rhodanine derivatives, CG-707 and BR-1, which inhibited PRL-3 enzymatic activity with IC₅₀ values of 0.8 μM and 1.1 μM, respectively. CG-707 and BR-1 strongly inhibited the migration and invasion of PRL-3 overexpressing colon cancer cells without exhibiting cytotoxicity. The specificity of the inhibitors on PRL-3 phosphatase activity was confirmed by the phosphorylation recovery of known PRL-3 substrates such as ezrin and cytokeratin 8. The compounds selectively inhibited PRL-3 in comparison with other phosphatases, and CG-707 regulated epithelial-to-mesenchymal transition (EMT) marker proteins. The results of the present study reveal that rhodanine is a specific PRL-3 inhibitor and a good lead molecule for obtaining a selective PRL-3 inhibitor.     

Design and synthesis of biaryloxazolidinone derivatives containing a rhodanine or thiohydantoin moiety as novel antibacterial agents against Gram-positive bacteria

Novel biaryloxazolidinone derivatives containing a rhodanine or thiohydantoin moiety were designed, synthesized and evaluated for their antibacterial activity. The key compounds 7 and 9 were synthesized by the knoevenagel condensation of intermediate aldehyde 5 with rhodanine derivatives 6a?6b. The preliminary study showed that compounds 7, 9 and 10e exhibited potent antibacterial activity with MIC values of 0.125?µg/mL against S. aureus, MRSA, MSSA, LREF and VRE pathogens, using linezolid and radezolid as the positive controls. The most promising compound 10e exhibited potent antibacterial activity against tested clinical isolates of MRSA, MSSA, VRE and LREF with MIC values in the range of 0.125–0.5?µg/mL, and the potency of 10e against clinical isolates of LREF was 64-fold higher than that of linezolid. Moreover, compound 10e was non-cytotoxic with an IC₅₀ value of 91.04?μM against HepG2 cell. Together, compound 10e might serve as a novel antibacterial agent for further investigation.     

Catechol–rhodanine derivatives: Specific and promiscuous inhibitors of Escherichia coli deoxyxylulose phosphate reductoisomerase (DXR)

To develop more effective inhibitors than fosmidomycin, a natural compound which inhibits the deoxyxylulose 5-phosphate reductoisomerase (DXR), the second enzyme of the MEP pathway, we designed molecules possessing on the one hand a catechol that is able to chelate the magnesium dication and on the other hand a group able to occupy the NADPH recognition site. Catechol–rhodanine derivatives (1–6) were synthesized and their potential inhibition was tested on the DXR of Escherichia coli. For the inhibitors 1 and 2, the presence of detergent in the enzymatic assays led to a dramatic decrease of the inhibition suggesting, that these compounds are rather promiscuous inhibitors. The compounds 4 and 5 kept their inhibition capacity in the presence of Triton X100 and could be considered as specific inhibitors of DXR. Compound 4 showed antimicrobial activity against Escherichia coli. The only partial protection of NADPH against the inhibition suggested that the catechol–rhodanine derivatives did not settle in the coenzyme binding site. This paper points out the necessity to include a detergent in the DXR enzymatic assays to avoid false positive when putative hydrophobic inhibitors are tested and especially when the IC₅₀, are in the micromolar range.