Novel arylhydrazone derivatives bearing a rhodanine moiety: synthesis and evaluation of their antibacterial activities

Synthesis and Antibacterial evaluation of Rhodanine and Its related heterocyclic compounds against S. aureus and A. baumannii

Antimicrobial resistance is a serious challenge to modern medicine. Besides imposing high financial burden, multidrug resistant infections are directly responsible for high morbidity and mortality. Even though a number of antibiotics are currently available to treat infections caused by ESKAPE organisms, more and more bacterial strains are becoming resistant to these drugs. In these circumstances, there is an urgent unmet need for development of newer antimicrobials to treat the infections caused due to MDR organisms. Rhodanine and structurally related 5-membered heterocycles possess wide range of pharmacological activities. A number of these derivatives have shown good to potent inhibition against the various microorganisms. They are reported to alter the functions of DNA gyrase B, metallo-β-lactamases, pencilline binding protein (PBP), Mur ligases, RNA polymerase, Enoyl ACP reductases, 1-deoxy-d-xylulose-5-phosphate reductoisomerase. etc which are vital molecular targets involved in bacterial growth, survival and replication. In this study, we have generated a library of Rhodanine and related 5 membered heterocyclic derivatives and screened them against a panel of pathogens. Among all the compounds, 2a-i, 3a-b, 3g, 4, 6b-c, 6e, 6g, 12a-b and 14b-c have demonstrated good to moderate inhibition against S. aureus (MIC 0.125-8 µ g/mL). Further, compound 17b demonstrated moderate activity against A. baumannii (MIC 8 µ g/mL). In addition, compounds 2a, 2e, 4, 6c, 6g and 14b have shown good to mild inhibition against MDR S. aureus including VRSA (MIC 0.5-16 µ g/mL) with good selectivity index 20-1600. In addition, compound 2e has inhibited growth gradually after 6 h in time kill kinetic studies and not antagonized with the tested FDA approved drugs.

A New Synthesis Strategy for Rhodanine and Its Derivatives

Rhodanine and its derivatives have been known as privileged structures in pharmacological research because of their wide spectrum of biological activities, but the synthesis method of rhodanine skeleton is limited. In this paper, not only rhodanine skeleton, but also N-aryl rhodanines can be directly prepared via the reaction of thioureas and thioglycolic acid in one step catalyzed by protic acid, which provides a new approach of the synthesis of rhodanine and its derivatives. The developed strategy is straightforward, efficient, atom economical, and convenient in good yields.

Design, synthesis and application in biological imaging of a novel red fluorescent dye based on a rhodanine derivative

A novel acceptor–donor–acceptor type molecule, namely 2-triphenylamine-1,3-dia[2-(3-ethyl-4-oxo-thiazolidin-2-ylidene)-malononitrile] (2RDNTPA), is designed and synthesized. 2RDNTPA exhibits a large Stokes shift of 244 nm and red fluorescence emission of 629 nm with a decent photoluminescence quantum yield of 13%. Furthermore, as a potential red fluorescent dye, 2RDNTPA can be applied in fluorescence imaging of living cancer cells (HepG2) with negligible cytotoxicity and a half maximal inhibitory concentration much more than 100 μM.

2RDNTPA can be applied in fluorescence imaging of living cancer cells (HepG2) with red emission of 620 nm and negligible cytotoxicity with a half maximal inhibitory concentration much more than 100 μM.

Synthesis, Characterization, Antibacterial and Antioxidant Potency of NSubstituted- 2-Sulfanylidene-1,3-Thiazolidin-4-one Derivatives and QSAR Study

BACKGROUND

Rhodanine is known for its potential and important role in the medicinal chemistry since its derivatives exhibit a wide range of pharmacological activities such as antibacterial, antifungal, antidiabetic, antitubercular, anti-HIV, antiparasitic, antioxidant, anticancer, antiproliferative and anthelmintic agents.

OBJECTIVES

Since N-substituted rhodanine synthons are rarely commercially available, it is desirable to develop a straightforward synthetic approach for the synthesis of these key building blocks. The objective was to synthesize a series of rhodanine derivatives and to investigate their antimicrobial and antioxidant activity. Also, in order to obtain an insight into their structure-activity relationship, QSAR studies on the antioxidant activity were performed.

METHODS

1H and 13C FTNMR spectra were recorded on Bruker Avance 600 MHz NMR Spectrometer, mass analysis was carried out on ESI+ mode by LC-MS/MS API 2000. 2,2-Diphenyl-1- picrylhydrazyl radical scavenging activity (% DPPH) was determined in dimethylsulfoxide (DMSO) as a solvent. The antibacterial activity was assessed against Bacillus subtilis, Staphylococcus aureus (Gram positive) and Escherichia coli, Pseudomonas aeruginosa (Gram negative) bacteria in terms of the minimum inhibitory concentrations (MICs) by a modified broth microdilution method.

RESULTS

A series of N-substituted-2-sulfanylidene-1,3-thiazolidin-4-ones were synthesized and characterized by 1H NMR, 13C NMR, FTIR, GC MS, LCMS/MS and C,H,N,S elemental analysis. Most of the synthesized compounds showed moderate to excellent antibacterial activity (MIC values from 125 μg/ml to 15.62 μg/mL) and DPPH scavenging activity (from 3.60% to 94.40%). Compound 2-thioxo-3- (4-(trifluoromethyl)-phenyl)thiazolidin-4-one showed the most potent activity against Escherichia coli (3.125 μg/mL), equivalent to antibiotic Amikacin sulphate and against Staphylococcus aureus (0.097 μg/ml), 100 times superior then antibiotic Amikacin sulphate. It has also shown a potent antioxidant activity (95% DPPH scavenging). Two best QSAR models, obtained by GETAWAY descriptor R7p+, Balabans molecular connectivity topological index and Narumi harmonic topological index (HNar), suggest that the enhanced antioxidant activity is related to the presence of pairs of atoms higher polarizability at the topological distance 7, substituted benzene ring and longer saturated aliphatic chain in N-substituents.

CONCLUSION

A series of novel N-substituted-2-thioxothiazolidin-4-one derivatives were designed, synthesized, characterized and evaluated for their antibacterial and antioxidant activity in vitro. Majority of the compounds showed excellent antibacterial activity compared to ampicillin and few of them have an excellent activity as compared to Chloramphenicol standard antibacterial drug. The QSAR study has clarified the importance of presenting a pairs of atoms higher polarizability, such as Cl and S at the specific distance, as well as the substituted benzene ring and a long saturated aliphatic chain in N-substituents for the enhanced antioxidant activity of 2-sulfanylidene-1,3- thiazolidin-4-one derivatives.

Drug screening of rhodanine derivatives for antibacterial activity

Introduction: Bacteriological infections are a major risk to human health. These include all hospital and public-acquired infections. In drug discovery, rhodanines are privileged heterocyclic frameworks. Their derivatives possess strong anti-bacterial activity and some of them have shown potent activity against multidrug-resistant pathogens, both under in vitro and in vivo conditions. To treat multi-drug resistant pathogens, the development of novel potent drugs, with superior anti-bacterial efficacy, is paramount. One avenue which shows promise is the design and development of novel rhodanines.Areas covered: This review summarizes the status on rhodanine-based derivatives and their anti-bacterial activity, based on published research over the past six years. Furthermore, to facilitate the design of novel derivatives with improved functions, their structure-activity relationships are assessed with reference to their efficacy as anti-bacterial agents and their toxicity.Expert opinion: The pharmacological activity of molecules bearing a rhodanine scaffold needs to be very critically assessed in spite of considerable information available from various biological evaluations. Although, some data on structure-activity relationship frameworks is available, information is not adequate to optimize the efficacy of rhodanine derivatives for different applications.