Synthesis of Schiff bases of naphtha[1,2-d]thiazol-2-amine and metal complexes of 2-(2'-hydroxy)benzylideneaminonaphthothiazole as potential antimicrobial agents

Synthetic and Medicinal Perspective of Fused-Thiazoles as Anticancer Agents

BACKGROUND

Cancer is second leading disease after cardiovascular disease. Presently, Chemotherapy, Radiotherapy and use of chemicals are some treatments available these days. Thiazole and its hybrid compounds extensively used scaffolds in drug designing and development of novel anticancer agents due to their wide pharmacological profiles. Fused thiazole scaffold containing drugs are available in market as a promising group of anticancer agents.

METHODS

The detailed study has been done using different database that focused on potent thiazole hybrid compounds with anticancer activity. The literature included in this review is focused on novel fused thiazole derivatives exhibiting anticancer potency in last decade.

RESULTS

Literature suggested that thiazoles and its fused and linked congener serve excellent pharmacological profile as an anticancer agent. Various synthetic strategies for fused thiazole are also summarized in this article. Novel thiazole and its fused congener showed anticancer activity against various cancer cell lines.

INTERPRETATION

Thiazole is a promising scaffold reported in literature with broad range of biological activities. This article covers the thiazole compounds fused with other carbocyclic/heterocycle including benzene, imidazole, pyridine, pyrimidine, quinoline, phenothiazine, thiopyrano, steroids, pyrrole etc. with anticancer activity from last decades. Several inhibitors for breast cancer, colon cancer, melanoma cancer, ovarian cancer, tubulin cancer etc. were reported in this review. Thus, this review will definitely aid to develop a lead for the new selective anticancer agents in future.

Bivalent Ni(II), Co(II) and Cu(II) complexes of [(E)-[(2-methyl-1,3-thiazol-5-yl)methylidene]amino]thiourea: synthesis, spectral characterization, DNA and in-vitro anti-bacterial studies

The present work describes the preparation of bivalent Ni(II), Co(II) and Cu(II) complexes of [(E)-[(2-methyl-1,3-thiazol-5-yl)methylidene]amino]thiourea (MTHC) by mixing in 1:2 ratio of corresponding metal salt and Schiff base ligand in ethanolic medium. The prepared ligand and its complexes are confirmed using elemental analysis, magnetic moments, FT-IR, NMR, electronic and ESR spectroscopy techniques. The spectroscopic data reveals that metal complexes are in square planar in nature. In DNA binding studies, the higher intrinsic binding constants (K_b) of Ni(II), Co(II) and Cu(II) complexes are 2.713 × 10⁶ M⁻¹, 5.529 × 10⁶ M⁻¹ and 2.950 × 10⁶ M⁻¹ respectively, evident that complexes are avid binder with DNA base pairs. The moderate anti-bacterial activity (in-vitro) against staphylococcus epidermidis, Bacillus subtilis, Pseudomonas aeruginosa and Escherichia coli bacterial culture may be due to the high electron density of ligand which prevents the charge reduction of metal ion. In the presence and absence of H₂O_2, it is notified that there is no appreciable DNA cleavage activity of Ni(II) and Co(II) complexes except Cu(II) complex which is due to aprotonation in the medium.

Synthesis, X-ray Crystal Structure and Antimicrobial Activity of Unexpected Trinuclear Cu(II) Complex from s-Triazine-Based Di-Compartmental Ligand via Self-Assembly

The synthesis and X-ray crystal structure of the trinuclear [Cu3(HL)(Cl)2(NO3)(H2O)5](NO3)2 complex of the s-triazine-based di-compartmental ligand, 2-methoxy-4,6-bis(2-(pyridin-2-ylmsethylene)hydrazinyl)-1,3,5-triazine (H2L), are presented. The Cu1 and Cu2 are penta-coordinated with CuN3ClO coordination environment, distorted square pyramidal coordination geometry while Cu3 is hexa-coordinated with CuN2O4 coordination sphere, and distorted octahedral geometry. The complex crystallized in the primitive P-1 triclinic crystal system with two molecular units per unit cell. Its packing is dominated by the O–H (35.5%) and Cl–H (8.8%) hydrogen bonding interactions as well as the π–π stacking (2.3%) and anion–π-stacking interactions (3.7%). The different coordination interactions were analyzed using atoms in molecules (AIM) theory, and the number of charge transferences from the ligand group to Cu(II) were determined using natural bond orbital calculations. The effect of the free ligand and its Cu(II) complex on the tested pathogenic microbes (Staphylococcus aureus, S. epidermidis, Enterococcus faecalis, Escherichia coli, Salmonella typhi and Pseudomonas aeruginosa) and one fungal isolate (Candida albicans) is presented. Both have wide spectrum antimicrobial activity against the selected microorganism. It is observed that the free ligand at 180 µg/mL was more effective than its Cu(II) complex and showed close results compared to the positive control gentamicin. At higher concentrations (1 mg/mL), the Cu(II) complex was found to be more active against S. epidermidis, E. coli and C. albicans than the lower concentration. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values are also lower for the Cu(II) complex than the free ligand.

Metal complexes driven from Schiff bases and semicarbazones for biomedical and allied applications: a review

Schiff bases are versatile organic compounds which are widely used and synthesized by condensation reaction of different amino compound with aldehydes or ketones known as imine. Schiff base ligands are considered as privileged ligands as they are simply synthesized by condensation. They show broad range of application in medicine, pharmacy, coordination chemistry, biological activities, industries, food packages, dyes, and polymer and also used as an O2 detector. Semicarbazone is an imine derivative which is derived from condensation of semicarbazide and suitable aldehyde and ketone. Imine ligand-containing transition metal complexes such as copper, zinc, and cadmium have shown to be excellent precursors for synthesis of metal or metal chalcogenide nanoparticles. In recent years, the researchers have attracted enormous attention toward Schiff bases, semicarbazones, thiosemicarbazones, and their metal complexes owing to numerous applications in pharmacology such as antiviral, antifungal, antimicrobial, antimalarial, antituberculosis, anticancer, anti-HIV, catalytic application in oxidation of organic compounds, and nanotechnology. In this review, we summarize the synthesis, structural, biological, and catalytic application of Schiff bases as well as their metal complexes.

Metal complexes driven from Schiff bases and semicarbazones for biomedical and allied applications: a review

Schiff bases are versatile organic compounds which are widely used and synthesized by condensation reaction of different amino compound with aldehydes or ketones known as imine. Schiff base ligands are considered as privileged ligands as they are simply synthesized by condensation. They show broad range of application in medicine, pharmacy, coordination chemistry, biological activities, industries, food packages, dyes, and polymer and also used as an O₂ detector. Semicarbazone is an imine derivative which is derived from condensation of semicarbazide and suitable aldehyde and ketone. Imine ligand-containing transition metal complexes such as copper, zinc, and cadmium have shown to be excellent precursors for synthesis of metal or metal chalcogenide nanoparticles. In recent years, the researchers have attracted enormous attention toward Schiff bases, semicarbazones, thiosemicarbazones, and their metal complexes owing to numerous applications in pharmacology such as antiviral, antifungal, antimicrobial, antimalarial, antituberculosis, anticancer, anti-HIV, catalytic application in oxidation of organic compounds, and nanotechnology. In this review, we summarize the synthesis, structural, biological, and catalytic application of Schiff bases as well as their metal complexes.

Synthesis, characterization, spectroscopic studies and biological evaluation of Schiff bases derived from 1-hydroxy-2-acetonapthanone

The four Schiff bases (I - IV) were synthesized by the condensation reaction of 1(1-hydroxynaphthalen-2-yl)ethanone, 1-(4-chloro-1hydroxynaphthalen-2-yl)ethanone and 1-(4-bromo-1-hydroxynaphthalen-2-yl)ethanone with propane-1,3-diamine and pentane-1,3-diamine. The structural analysis is done by UVvis., FT-IR, 1H NMR, 13C NMR, LCMS and elemental analyses. These compounds were assayed for antibacterial (Escherichia coli and Salmonella Typhi) activity and antioxidant (2,2-Diphenyl-1-Picryl Hydrazyl(DPPH) and Hydroxyl radical scavenging method) activity. The antibacterial and antioxidant activities of synthesized Schiff bases exhibited better degrees of inhibitory effects. Among these, Schiff base 2,2'-((propane-1,3-diylbis(azanylylidene))bis(ethan-1-yl-1-ylidene))bis(4-chloronaphthalen-1-ol) (II) exhibited excellent antibacterial activity with MICs of 0.12, 0.25, 0.5 and 1 mg/ml against E. coli and Salmonella Typhi. Furthermore, two Schiff bases such as, 2,2'-((propane-1,3-diylbis(azanylylidene))bis(ethan-1-yl-1-ylidene))bis(naphthalen-1-ol) (I) and 2,2'-((pentane-1,3-diylbis(azanylylidene))bis(ethan-1-yl-1-ylidene))bis(4-bromonaphthalen-1-ol) (IV) exhibited promising antioxidant activity.

Synthesis of new 1,3-thiazol derivatives of maleopimaric acid as anticancer, antibacterial and antifungal agents

A series of new 1,3-thiazole derivatives of maleopimaric acid 6a-f, 7a-f were synthesized and evaluated for anticancer, antibacterial and antifungal activities. Evaluation of cytotoxic activity against human embryonic kidney 293 cells (HEK293), human neuroblastoma cell line (SH-SY5Y), hepatocellular carcinoma cell line (HepG2) and human T-cell lymphoblast-like line (Jurkat), showed that introduction of the aminothiazole fragment at position 6 of the diterpenoid molecule leads to decrease of cell viability. Substance 3 was found to be the most active against all tested cell lines, inhibiting cell viability with IC₅₀ values in the range of 2-24 μM. The structure-activity relationship of these compounds was studied and the results show that the compounds 6c and 7e exhibited in vitro antifungal activity against Candida albicans and also possessed antibacterial profile against Enterobacter aerogenes, Klebsiella pneumoniae, Staphylococcus aureus, Streptococcus pyogenes, Escherichia coli and Proteus vulgaris.

Crystal structure of bis[(((4-fluorophenyl)amino)methyl)triphenylphosphonium] tetrachloridocobaltate(II), C50H44Cl4CoF2N2P2

C50H44Cl4CoF2N2P2, orthorhombic, Pbca (no. 61), a = 18.4662(6) Å, b = 15.2888(5) Å, c = 33.2661(10) Å, V = 9391.9(5) Å3, Z = 8, R gt(F) = 0.0403, wR ref(F 2) = 0.1005, T = 180.0(5) K.

Naphthalene, a versatile platform in medicinal chemistry: Sky-high perspective

Naphthalene, a cytotoxic moiety, is an extensively explored aromatic conjugated system with applications in various pathophysiological conditions viz. anticancer, antimicrobial, anti-inflammatory, antiviral, antitubercular, antihypertensive, antidiabetic, anti-neurodegenerative, antipsychotic, anticonvulsant, antidepressant. Naphthalene epoxides and naphthoquinones are most reactive metabolites of naphthalene and are responsible for the covalent interaction with cysteine amino acid of cellular proteins for cytotoxic nature. Many naphthalene derived bioactive phytoconstituents are present in nature including podophyllotoxins (Etoposide, teniposide), bis-ANS 82, Rifampicin, Justiprocumin A, B, Patentiflorin A. The naphthalene-based molecules, viz. Naphyrone, tolnaftate, naftifine, nafcillin, terbinafine, propranolol, nabumetone, nafimidone, naproxen, duloxetine, lasofoxifene, bedaquiline etc. have also been approved by FDA and are being marketed as therapeutics. Thus, the naphthalene scaffold emerges as an important building block in drug discovery owing to its broad spectrum of biological activities through varying structural modifications. This review incorporates the pharmacological aspects of different types of chemically modified naphthalene-based molecules along with their activity profile. This compiled information may serve as a benchmark for the alteration of existing ligands to design novel potent molecules with lesser side effects.

Microplate assay for screening the antibacterial activity of Schiff bases derived from substituted benzopyran-4-one

Schiff bases (SB(1)-SB(3)) were synthesized from the condensation of 6-formyl-7-hydroxy-5-methoxy-2-methylbenzopyran-4-one with 2-aminopyridine (SB(1)), p-phenylenediamine (SB(2)) and o-phenylenediamine (SB(3)), while Schiff bases (SB(4)-SB(6)) were synthesized by condensation of 5,7-dihydroxy-6-formyl-2-methylbenzopyran-4-one with 2-aminopyridine (SB(4)), p-phenylenediamine (SB(5)) and o-phenylenediamine (SB(6)). Schiff bases were characterized using elemental analysis, IR, UV-Vis, (1)H NMR, (13)C NMR and mass spectroscopy. These compounds were screened for antibacterial activities by micro-plate assay technique. Escherichia coli and Staphylococcus capitis were exposed to different concentrations of the Schiff bases. Results showed that the antibacterial effect of these Schiff bases on Gram-negative bacteria were higher than that on Gram-positive bacteria moreover, the Schiff bases containing substituent OCH(3) on position five have higher antibacterial activity than that containing hydroxy group on the same position.

Synthesis of New VO(II), Co(II), Ni(II) and Cu(II) Complexes with Isatin-3-Chloro-4-Floroaniline and 2-Pyridinecarboxylidene-4-Aminoantipyrine and their Antimicrobial Studies

The complexes of tailor made ligands with life essential metal ions may be an emerging area to answer the problems of multi drug resistance. The coordination complexes of VO(II), Co(II), Ni(II) and Cu(II) with the Schiff bases derived from isatin with 3-chloro-4-floroaniline and 2-pyridinecarboxaldehyde with 4-aminoantipyrine have been synthesized by conventional as well as microwave methods. These compounds have been characterized by elemental analysis, molar conductance, electronic spectra, FT-IR, FAB mass and magnetic susceptibility measurements. FAB mass data show degradation of complexes. Both the ligands behave as bidentate and tridentate coordinating through O and N donor. The complexes exhibit coordination number 4, 5 or 6. The Schiff base and metal complexes show a good activity against the bacteria; Staphylococcus aureus, Escherichia coli and Streptococcus fecalis and fungi Aspergillus niger, Trichoderma polysporum, Candida albicans and Aspergillus flavus. The antimicrobial results also indicate that the metal complexes are better antimicrobial agents as compared to the Schiff bases. The minimum inhibitory concentrations of the metal complexes were found in the range 10~40 µg/mL.

Neuroprotective effect of naphtha[1,2-d]thiazol-2-amine in an animal model of Parkinson's disease

Increased oxidative stress has been implicated in the pathogenesis of dopaminergic neurodegeneration leading to the development of Parkinson's disease. In this study, we investigated whether naphtha[1,2-d]thiazol-2-amine (NTA) may ameliorate haloperidol-induced catalepsy and oxidative damage in mice brain. Haloperidol-induced catalepsy was measured with the standard bar test. The extent of oxidative stress has been evaluated by measuring levels of MDA, GSH and activities of antioxidant enzymes (SOD and GSH-Px) from brain homogenate. Haloperidol treatment significantly induced the catalepsy as observed from increased descent time measured in the bar test. Pretreatment with NTA significantly reduced the catalepsy induced by haloperidol in a dose-dependent manner. The elevated level of MDA in haloperidol-treated mice was significantly decreased by NTA pretreatment. The decreased level of GSH as well as SOD and GSH-Px activities in haloperidol-treated mice were significantly increased by NTA pretreatment. NTA reduces the oxidative stress allowing recovery of detoxifying enzyme activities and controlling free radical production, suggesting a potential role of the drug as an alternative/adjuvant drug in preventing and treating the neurodegenerative diseases, such as Parkinson's disease.

(E)-2-[1-(3-Amino-4-chloro-phenyl-imino)eth-yl]-4-bromo-phenol

The title Schiff base compound, C₁₄H₁₂BrClN₂O, exists in an E configuration with respect to the central C=N double bond. The amino group adopts a pyramidal configuration. The dihedral angle between the two benzene rings is 76.88 (10)° and an intra­molecular O—H⋯N hydrogen bond forms a six-membered ring, generating an S(6) ring motif. In the crystal structure, mol­ecules are linked into chains along [010] via N—H⋯O hydrogen bonds. The presence of π–π inter­actions [centroid–centroid distance = 3.6244 (12) Å] further stabilizes the crystal structure.