Synthesis and Urease Inhibitory Properties of Some New N4-Substituted 5-Nitroisatin-3-thiosemicarbazones

Synthesis, Theoretical, in Silico and in Vitro Biological Evaluation Studies of New Thiosemicarbazones as Enzyme Inhibitors

Eleven new thiosemicarbazone derivatives (1-11) were designed from nine different biologically and pharmacologically important isothiocyanate derivatives containing functional groups such as fluorine, chlorine, methoxy, methyl, and nitro at various positions of the phenyl ring, in addition to the benzyl unit in the molecular skeletal structure. First, their substituted-thiosemicarbazide derivatives were synthesized from the treatment of isothiocyanate with hydrazine to synthesize the designed compounds. Through a one-step easy synthesis and an eco-friendly process, the designed compounds were synthesized with yields of up to 95 % from the treatment of the thiosemicarbazides with aldehyde derivatives having methoxy and hydroxy groups. The structures of the synthesized molecules were elucidated with elemental analysis and FT-IR, 1 H-NMR, and 13 C-NMR spectroscopic methods. The electronic and spectroscopic properties of the compounds were determined by the DFT calculations performed at the B3LYP/6-311++G(2d,2p) level of theory, and the experimental findings were supported. The effects of some global reactivity parameters and nucleophilic-electrophilic attack abilities of the compounds on the enzyme inhibition properties were also investigated. They exhibited a highly potent inhibition effect on acetylcholinesterase (AChE) and carbonic anhydrases (hCAs) (KI values are in the range of 23.54±4.34 to 185.90±26.16 nM, 103.90±23.49 to 325.90±77.99 nM, and 86.15±18.58 to 287.70±43.09 nM for AChE, hCA I, and hCA II, respectively). Furthermore, molecular docking simulations were performed to explain each enzyme-ligand complex's interaction.

Enzyme inhibition, molecular docking, and density functional theory studies of new thiosemicarbazones incorporating the 4-hydroxy-3,5-dimethoxy benzaldehyde motif

New Schiff base-bearing thiosemicarbazones (1-13) were obtained from 4-hydroxy-3,5-dimethoxy benzaldehyde and various isocyanates. The structures of the synthesized molecules were elucidated in detail. Density functional theory calculations were also performed to determine the spectroscopic properties of the compounds. Moreover, the enzyme inhibition activities of these compounds were investigated. They showed highly potent inhibition effects on acetylcholinesterase (AChE) and human carbonic anhydrases (hCAs) (K_I values are in the range of 51.11 ± 6.01 to 278.10 ± 40.55 nM, 60.32 ± 9.78 to 300.00 ± 77.41 nM, and 64.21 ± 9.99 to 307.70 ± 61.35 nM for AChE, hCA I, and hCA II, respectively). In addition, molecular docking studies were performed, confirmed by binding affinities studies of the most potent derivatives.

Enhancement of Schiff base biological efficacy by metal coordination and introduction of metallic compounds as anticovid candidates: a simple overview

In the prevailing apocalyptic times of coronavirus disease (COVID-19), the whole scientific community is busy in designing anticovid drug or vaccine. Under such a fascination, Schiff bases or azomethine compounds are continuously interrogated for antimicrobial properties. These compounds represent interesting molecular scaffolds of huge medicinal and industrial relevance. In order to update the current literature support of such facts this article introduces the synthetic chemistry, mechanism of formation of a Schiff base, followed by biological efficacy and finally a suitable discussion on the mechanism of respective bioactivity. In most of the studies revealing the biological evaluation of azomethine functionalized frameworks, fascinated results have been recorded in case of azomethine-metal complexes as compared with the free ligands. Also, the CH=N or C=N form of organic ligands have indicated marvellous results. Therefore, in connection with the biological relevance and microbicidal implications of such metallic compounds, this works reviews the current update of microorganism fighting efficacy of azomethine metal complexes along with the introduction of some metallodrugs as excellent candidates having COVID-19 defending potentiality.

Synthesis, Crystal Structure, Biological Evaluation and in Silico Studies on Novel (E)-1-(Substituted Benzylidene)-4-(3-isopropylphenyl)thiosemicarbazone Derivatives

A series of (E)-1-(substituted benzylidene)-4-(3-isopropylphenyl)thiosemicarbazone derivatives were synthesized and characterized by FT-IR spectrum, elemental analysis, NMR spectrum, HR-MS spectrum, and X-ray single crystal diffraction technology. The crystal structures and packing of (E)-1-(4-fluorobenzylidene)-4-(3-isopropylphenyl)thiosemicarbazone and (E)-1-(3-fluorobenzylidene)-4-(3-isopropylphenyl)thiosemicarbazone were maintained through the intramolecular hydrogen bond (N3-H6⋅⋅⋅N1) and intermolecular hydrogen bonds (N2-H4⋅⋅⋅S1, C14-H14⋅⋅⋅F1 and C7-H7⋅⋅⋅S1). The results obtained by employing the DPPH free radicals scavenging assay indicated that (E)-1-(4-methoxylbenzylidene)-4-(3-isopropylphenyl)thiosemicarbazone had a more significant antioxidant activity compared with other compounds. The results measured by adopting the disc diffusion method elucidated that (E)-1-(4-trifluoromethylbenzylidene)-4-(3-isopropylphenyl)thiosemicarbazone possessed a more prominent antifungal activity than other compounds. Molecular docking showed that (E)-1-(4-chlorobenzylidene)-4-(3-isopropylphenyl)thiosemicarbazone had the highest affinity with receptor protein (1NMT). Moreover, the drug-likeness characteristic, physicochemical properties, pharmacokinetic profiles, and bioactivity scores of all the compounds were predicted through in silico studies. The results illustrated that (E)-1-(4-fluorobenzylidene)-4-(3-isopropylphenyl)thiosemicarbazone had the drug-likeness characteristic and all the compounds were considered as moderately biological active molecules.

Benzylidine indane-1,3-diones: As novel urease inhibitors; synthesis, in vitro, and in silico studies

Current study deals with the evaluation of indane-1,3-dione based compounds as new class of urease inhibitors. For that purpose, benzylidine indane-1,3-diones (1-30) were synthesized and fully characterized by different spectroscopic techniques including EI-MS, HREI-MS, ¹H, and ¹³C NMR. All synthetic molecules 1-30 were evaluated for urease inhibitory activity and showed good to moderate inhibitory potential within the range of (IC₅₀ = 11.60 ± 0.3-257.05 ± 0.7 µM) as compared to the standard acetohydroxamic acid (IC₅₀ = 27.0 ± 0.5 µM). Compound 1 (IC₅₀ = 11.60 ± 0.3 µM) was found to be most potent inhibitor amongst all derivatives. The key binding interactions of most active compounds within the enzyme pocket were evaluated through in silico studies.

1-[(4'-Chlorophenyl) carbonyl-4-(aryl) thiosemicarbazide derivatives as potent urease inhibitors: Synthesis, in vitro and in silico studies

A series of 1-[(4'-chlorophenyl)carbonyl-4-(aryl)thiosemicarbazide derivatives 1-25 was synthesized and characterized by spectroscopic techniques such as EI-MS and ¹H NMR. All compounds were screened for urease inhibitory activity in vitro and demonstrated excellent inhibitory activity in the range of IC₅₀ = 0.32 ± 0.01-25.13 ± 0.13 μM as compared to the standard thiourea (IC₅₀ = 21.25 ± 0.13 μM). Amongst the potent analogs, compounds 3 (IC₅₀ = 2.31 ± 0.01 μM), 6 (IC₅₀ = 2.14 ± 0.04 μM), 10 (IC₅₀ = 1.14 ± 0.06 μM), 20 (IC₅₀ = 2.15 ± 0.05 μM), and 25 (IC₅₀ = 0.32 ± 0.01 μM) are many folds more active than the standard. Structure-activity relationship (SAR) was rationalized by looking at the effect of diversely substituted aryl ring on inhibitory potential which predicted that regardless of the nature of substituents, their positions on aryl ring is worth important for the potent activity. Furthermore, to verify these interpretations, in silico study was performed on all compounds and a good correlation was perceived between the biological evaluation and docking study of compounds.

Synthesis, crystal structure, molecular docking studies and bio-evaluation of some N4-benzyl-substituted isatin- 3-thiosemicarbazones as urease and glycation inhibitors

Fifteen N4-benzyl-substituted isatin-3-thiosemicarbazones 5a–o were synthesized and evaluated for their urease and glycation inhibitory potential. Lemna aequinocitalis growth and Artemia salina assays were also done to determine their phytotoxic and toxic effects. All compounds are potent inhibitors of the urease enzyme, displaying inhibition [half maximal inhibitory concentration (IC50)=1.08±0.12–11.23±0.19 μm] superior to that of the reference inhibitor thiourea (IC50=22.3±1.12 μm). Compounds 5c, 5d, 5h, 5j,k are potent antiglycating agents, showing glycation inhibitory activity better than that of the reference inhibitor rutin (IC50 values 209.87±0.37–231.70±6.71 vs. 294.5±1.5 μm). In the phytotoxicity assay, 11 thiosemicarbazones 5a–d, 5g, 5h, 5j–l, 5n,o are active, demonstrating 5–100% growth inhibition of L. aequinocitalis at the highest tested concentrations (1000 or 500 μg/mL). In the brine shrimp (A. salina) lethality bioassay, three derivatives 5b, 5j and 5o are active with median lethal dose (LD50) values of 3.63×10−5, 2.90×10−5 and 2.31×10−4 m, respectively.

A newly synthesized nickel chelate can selectively target and overcome multidrug resistance in cancer through redox imbalance both in vivo and in vitro

Induction of undesired toxicity and emergence of multidrug resistance (MDR) are the major obstacles for cancer treatment. Moreover, aggressive cancers are less sensitive towards existing chemotherapeutics. Therefore, selective targeting of cancers without inducing undesired side effects and designing proper strategies to overcome MDR has utmost importance in modern chemotherapy. Previously we revealed the anticancer properties of some transition metal chelates of Schiff base, but the effectiveness of nickel complex is still unrevealed. Herein, we synthesized and characterized a Schiff base nickel chelate, nickel-(II) N-(2-hydroxyacetophenone) glycinate (NiNG), through different spectroscopic means. NiNG proves to be a broad spectrum anticancer agent with considerable efficacy to overcome MDR in cancer. Antiproliferative effects of NiNG was evaluated using drug-resistant (CEM/ADR5000; NIH-MDR-G185; EAC/Dox), drug-sensitive aggressive (Hct116; CCRF-CEM; EAC/S) and normal (NIH-3T3) cells that reveal the selective nature of NiNG towards drug resistant and sensitive cancer cells without inducing any significant toxicity in normal cells. Moreover, NiNG involves reactive oxygen species (ROS)-mediated redox imbalance for induction of caspase 3-dependent apoptosis in aggressive drug-sensitive Hct116 and drug-resistant NIH-MDR-G185 cells through disruption of mitochondrial membrane potential. Moreover, intraperitoneal (i.p.) application of NiNG at non-toxic doses caused significant increase in the life-span of Swiss albino mice bearing sensitive and doxorubicin-resistant subline of Ehrlich ascites carcinoma cells. It is noteworthy that, in vitro NiNG can only overcome P-glycoprotein-mediated MDR while in vivo NiNG can overcome MRP1-mediated MDR in cancer. Therefore, NiNG has therapeutic potential to target and overcome MDR in cancer.

Synthesis, biological evaluation and docking studies of some novel isatin-3-hydrazonothiazolines

The putative binding mode of compound 6i in the active site of Jack bean urease.

Synthesis, cytotoxic and urease inhibitory activities of some novel isatin-derived bis-Schiff bases and their copper(ii) complexes

The putative binding mode of the most active compound 3b in the active site of Jack bean urease.

Anticancer activity and DNA-binding investigations of the Cu(II) and Ni(II) complexes with coumarin derivative

Two new copper(II) (2) and nickel(II) (3) complexes with a new coumarin derivative have been synthesized and structurally characterized. The DNA-binding activities of the two complexes have been investigated by spectrometric titrations, ethidium bromide displacement experiments, CD (circular dichroism) spectral analysis, and viscosity measurements. The results indicate that the two complexes, especially the complex 2, can strongly bind to calf-thymus DNA (CT--DNA). The intrinsic binding constants Kb of the complexes with CT-DNA are 2.99 × 10(5) and 0.61 × 10(5) for 2 and 3, respectively. Comparative cytotoxic activities of the two complexes are also determined by MTT assay. The results show that the drugs designed here have significant cytotoxic activity against the human hepatic (HepG2), human promyelocytic leukemia (HL60), and human prostate (PC3) cell lines. Cell apoptosis was detected by Annexin V/PI flow cytometry, and the results show that the two copper complexes can induce apoptosis of the three human tumor cells. In conclusions, the two complexes show considerable cytotoxic activity against the three human cancer and induce apoptosis of the threes.

1-(2-Oxoindolin-3-yl-idene)-4-[2-(tri-fluoro-meth-yl)phen-yl]thio-semicarbazide

In the title compound, C₁₆H₁₁F₃N₄OS, the dihedral angle between the aromatic ring systems is 69.15 (10)°. Intra­molecular N—H⋯N and N—H⋯O hydrogen bonds generate S(5) and S(6) rings, respectively. A short N—H⋯F contact also occurs. In the crystal, inversion dimers linked by pairs of N—H⋯O hydrogen bonds generate R₂²(8) loops. The dimers are linked by N—H⋯F hydrogen bonds, forming polymeric chains propagating in [100]. π–π inter­actions also exist between the centroids of the benzene rings of the 2-oxoindoline group at a distance of 3.543 (3) Å and a short C=O⋯π contact occurs. Two F atoms of the trifluoro­methyl group are disordered over two sets of sites in a 0.517 (8):0.483 (8) ratio.

1-[2-Oxo-5-(trifluoro-meth-oxy)indolin-3-yl-idene]-4-[4-(trifluoro-methyl)-phen-yl]thio-semicarbazide

In the title compound, C₁₇H₁₀F₆N₄O₂S, an intra­molecular N—H⋯N hydrogen bonds forms an S(5) ring whereas N—H⋯O and C—H⋯S inter­actions complete S(6) ring motifs. The dihedral angle between the fused ring system and the phenyl ring is 6.68 (8)°. In the crystal, the mol­ecules are dimerized due to N—H⋯O inter­actions. π–π inter­actions are present between the benzene rings [centroid–centroid distance = 3.6913 (15) Å] and between the five membered ring and the trifluoro­meth­yl)phenyl ring [centroids–centroid distance = 3.7827 (16) Å]. One of the trifluoro­meth­oxy F atoms is disordered over two sites with occupancy ratio of 0.76 (3):0.24 (3). The F atoms of the p-trifluoro­methyl substituent are disordered over three sets of sites with an occupancy ratio of 0.70 (2):0.152 (11):0.147 (13).

1-[1-(4-Bromo-phen-yl)ethyl-idene]-4-(2,4-dimeth-oxy-phen-yl)thio-semicarbazide

In the title compound, C(17)H(18)BrN(3)O(2)S, the dihedral angle between the aromatic rings is 9.15 (17)°. A bifurcated intra-molecular N-H⋯(N,O) hydrogen bond generates two S(5) rings and a weak intra-molecular C-H⋯S inter-action completes an S(6) ring motif. In the crystal, inversion dimers linked by pairs of N-H⋯S hydrogen bonds generate R(2) (2)(8) loops and weak C-H⋯S and C-H⋯π inter-actions are also present.

4-(3-Iodo-phen-yl)-1-(2-oxoindolin-3-yl-idene)thio-semicarbazide

In the title compound, C₁₅H₁₁IN₄OS, intra­molecular N—H⋯N, N—H⋯O and C—H⋯S inter­actions generate one S(5) and two S(6) ring motifs. In the crystal, mol­ecules form centrosymmetric dimers via pairs of N—H⋯O inter­actions, generating R₂²(8) ring motifs. In addition a short inter­molecular I⋯S contact of 3.352 (3) Å is observed.

1-Acetyl-3-[2-(2,3,5,6-tetra-fluoro-phen-yl)hydrazin-1-yl-idene]indolin-2-one

In the title compound, C₁₆H₉F₄N₃O₂, the dihedral angle between the aromatic ring systems is 4.10 (14)° and a bifurcated intra­molecular N—H⋯(O,F) hydrogen bond generates an S(6) ring for the O-atom acceptor and an S(5) ring for the F-atom acceptor. A short C—H⋯O conact also occurs. In the crystal, mol­ecules are linked by C—H⋯O inter­actions.

4-(3-Methoxyphenyl)-1-(2-oxoindolin-3-ylidene)thiosemicarbazide

In the title compound, C₁₆H₁₄N₄O₂S, intra­molecular N—H⋯N hydrogen bonding forms an S(5) ring, whereas N—H⋯O and C—H⋯S inter­actions complete S(6) ring motifs. In the crystal, mol­ecules form inversion dimers due to N—H⋯O inter­actions. The dimers are inter­linked through N—H⋯S hydrogen bonds and π–π inter­actions occur with a centroid–centroid distance of 3.8422 (11) Å between the meth­oxy-containing benzene ring and the five-membered heterocyclic ring.

4-(5-Chloro-2-methyl-phen-yl)-1-[2-oxo-5-(trifluoro-meth-oxy)indolin-3-yl-idene]thio-semicarbazide

The asymmetric unit of the title compound, C₁₇H₁₂ClF₃N₄O₂S, contains two mol­ecules, which differ in their planarity and hydrogen bonding. In one mol­ecule, the 2-oxoindolin (C₈/N/O A), thio­semicarbazide (N₃/C/S B) and 5-chloro-2-methyl­phenyl (C₇/Cl C) units are planar with r.m.s. deviations of 0.0110, 0.0173 and 0.0259 Å, respectively. The dihedral angles A/B, B/C and A/C are 1.74 (15), 40.70 (13) and 41.00 (11)°, respectively. In the other mol­ecule the deviations are 0.0455, 0.0007 and 0.0143 Å, respectively, and the dihedral angles are 5.01 (14), 4.53 (16) and 3.38 (13)°, respectively. In both mol­ecules, intra­molecular N—H⋯N and N—H⋯O hydrogen bonds form S(5) and S(6) ring motifs, respectively and C—H⋯S interactions occur. In one of the molecules, an intramolecular C—H⋯F interaction is also present. In the crystal, the mol­ecules are linked by N—H⋯O, C—H⋯F, C—H⋯O and N—H⋯S hydrogen bonding, forming a polymeric network.

4-(2-Fluoro-phen-yl)-1-(2-oxoindolin-3-yl-idene)thio-semicarbazide

The title compound, C(15)H(11)FN(4)OS, is almost planar, the dihedral angle between the aromatic ring systems being 5.00 (13)°. The conformation is stabilized by intra-molecular N-H⋯N and N-H⋯O hydrogen bonds, which generate S(5) and S(6) rings, respectively. N-H⋯F and C-H⋯S inter-actions also occur. In the crystal, inversion dimers linked by pairs of N-H⋯O hydrogen bonds occur, generating R(2) (2)(8) loops.