Synthesis of 2-methoxybenzoylhydrazone and evaluation of their antileishmanial activity

Synthesis of symmetrical bis-Schiff base-disulfide hybrids as highly effective anti-leishmanial agents

Leishmaniasis has affected a wider part of population around the globe. Most often, the existing regiments to battle against leishmaniasis are inadequate and limited. In our ongoing efforts to develop new leishmanicidal agents, we have synthesized a series of novel and symmetrical bis-Schiff base-disulfide hybrids 1-27. Intermediate disulfide was synthesized from corresponding 2-aminothiol followed by reacting the coupled adduct with various aromatic aldehydes. All these compounds showed outstanding inhibition when compared with standard (Table 1). Out of twenty seven analogues, twenty two analogues i.e. 1-5, 7-13, 17-21, 23-27 analogues showed excellent inhibitory potential with EC₅₀ values ranging from 0.010 ± 0.00 to 0.096 ± 0.01 μM while five compounds i.e. 6, 14-16, and 22 showed good inhibitory potential with EC₅₀ values ranging from 0.10 ± 0.00 to 0.137 ± 0.01 μM when compared with the standard Amphotericin B. Structure-activity relationship has been established while molecular docking studies were performed to pin the binding interaction of active molecules. This study will help to develop new antileishmanial lead compounds.

Synthesis, characterization, quantum chemical calculations and anticancer activity of a Schiff base NNOO chelate ligand and Pd(II) complex

This paper reports the synthesis, characterization, anticancer screening and quantum chemical calculation of a tetradentate Schiff base 2,2'-((1E,1'E)-((2,2-dimethylpropane-1,3-diyl)bis- (azanylylidene))bis(methanylylidene))bis(4-fluorophenol) (L2F) and its Pd (II) complex (PdL2F). The compounds were characterized via UV-Visible, NMR, IR spectroscopy and single crystal x-ray diffraction. Density Functional Theory (DFT) and time-dependent DFT calculations in gas and solvent phases were carried out using B3LYP, B3P86, CAM-B3LYP and PBE0 hybrid functionals combined with LanL2DZ basis set. Complexation of L2F to form PdL2F was observed to cause a bathochromic shift of the maximum absorption bands of n-π* from 327 to 410 nm; an upfield shift for δ (HC = N) from 8.30 to 7.96 ppm and a decreased wavenumber for ν(C = N) from 1637 to 1616 cm-1. Overall, the UV-Vis, NMR and IR spectral data are relatively well reproduced through DFT and TD-DFT methods. L2F and PdL2F showed IC50 of 90.00 and 4.10 μg/mL, respectively, against human colorectal carcinoma (HCT116) cell lines, signifying increased anticancer activity upon complexation with Pd (II).

Synthesis of 4-substituted ethers of benzophenone and their antileishmanial activities

Leishmaniasis is a vector-borne protozoan disease; it mainly originates from the bite of sandfly and initiated when parasite is transmitted to human at metacyclic flagellated promastigote form. In the current study, a synthesis of a series of 4-substituted benzophenone ethers 1-20 was carried out in good yields and their in vitro antileishmanial activities were also screened. Among synthetic derivatives, 15 compounds 1, 3, 5-12, 15 and 17-20 showed antileishmanial activities against promastigotes of Leishmania major with IC50 values in the range of 1.19-82.30 µg ml-1, and the values were compared with those of the standard pentamidine (IC50 = 5.09 ± 0.09 µg ml-1). Our study identified a series of new antileishmanial molecules as potential leads. Structures of these synthetic compounds were deduced by different spectroscopic techniques, such as 1H and 13C nuclear magnetic resonance, electron impact and high-resolution electron impact mass spectrometry and IR.

Hydrazone Derivatives Enhance Antileishmanial Activity of Thiochroman-4-ones

Cutaneous leishmaniasis (CL) is a neglected tropical disease, which causes severe skin lesions. Due to the lack of effective vaccines, and toxicity or reduced effectiveness of available drugs in addition to complex and prolonged treatments, there is an urgent need to develop alternatives for the treatment for CL with different mechanisms of action. In our effort to search for new promising hits against Leishmania parasites we prepared 18 acyl hydrazone derivatives of thiochroman-4-ones. Compounds were evaluated for their in vitro antileishmanial activity against the intracellular amastigote form of Leishmania panamensis and cytotoxic activity against human monocytes (U-937 ATCC CRL-1593.2). Our results show that derivatization of the thiochroman-4-ones with acyl hydrazones significantly enhances the antileishmanial activity. Among the compounds tested semicarbazone and thiosemicarbazone derivatives of thioflavanone 19 and 20 displayed the highest antileishmanial activities, with EC50 values of 5.4 and 5.1 µM and low cytotoxicities (100.2 and 50.1 µM respectively), resulting in higher indexes of selectivity (IS).

Molecular hybridization conceded exceptionally potent quinolinyl-oxadiazole hybrids through phenyl linked thiosemicarbazide antileishmanial scaffolds: In silico validation and SAR studies

The high potential of quinoline containing natural products and their derivatives in medicinal chemistry led us to discover a novel series of compounds 6-23 based on the concept of molecular hybridization. Most of the synthesized analogues exhibited potent leishmanicidal potential. The most potent compound (23, IC₅₀=0.10±0.001μM) among the series was found ∼70 times more lethal than the standard drug. The current series 6-23 conceded in the development of fourteen (14) extraordinarily active compounds against leishmaniasis. In silico analysis were also performed to probe the mode of action while all the compounds structure were established by NMR and Mass spectral analysis.

Synthesis and molecular modelling studies of phenyl linked oxadiazole-phenylhydrazone hybrids as potent antileishmanial agents

Molecular hybridization yielded phenyl linked oxadiazole-benzohydrazones hybrids 6-35 and were evaluated for their antileishmanial potentials. Compound 10, a 3,4-dihydroxy analog with IC₅₀ value of 0.95 ± 0.01 μM, was found to be the most potent antileishmanial agent (7 times more active) than the standard drug pentamidine (IC₅₀ = 7.02 ± 0.09 μM). The current series 6-35 conceded in the identification of thirteen (13) potent antileishmanial compounds with the IC₅₀ values ranging between 0.95 ± 0.01-78.6 ± 1.78 μM. Molecular docking analysis against pteridine reductase (PTR1) were also performed to probe the mode of action. Selectivity index showed that compounds with higher number of hydroxyl groups have low selectivity index. Theoretical stereochemical assignment was also done for certain derivatives by using density functional calculations.

Acylhydrazone derivatives as potential anticancer agents: Synthesis, bio-evaluation and mechanism of action

A series of novel acylhydrazone derivatives were designed, synthesized and evaluated for their potential cytotoxic effects against human cancer cell lines. The preliminary results indicated that some of the obtained compounds (such as 8b, 13c) exhibited good to moderate cytotoxic activities against human HepG2, Huh-7, and BCG-823 cell lines. Especially, compounds 8c and 8e presented obviously selective cytotoxic activities against Huh-7 in vitro (8c, IC50=7.74±2.18μg/mL; 8e, IC50=4.46±1.05μg/mL) compared to 5-FU (IC50=10.41±3.41μg/mL). The highly potential compounds to induce apoptosis in HepG2 cells were analyzed by flow cytometry, and the apoptotic effects of compounds 8b and 13c were further evaluated using Annexin V-FITC/propidium iodide dual staining assay.

Synthesis of novel derivatives of oxindole, their urease inhibition and molecular docking studies

We synthesized a series of novel 5-24 derivatives of oxindole. The synthesis started from 5-chlorooxindole, which was condensed with methyl 4-carboxybezoate and result in the formation of benzolyester derivatives of oxindole which was then treated with hydrazine hydrate. The oxindole benzoylhydrazide was treated with aryl acetophenones and aldehydes to get target compounds 5-24. The synthesized compounds were evaluated for urease inhibition; the compound 5 (IC50 = 13.00 ± 0.35 μM) and 11 (IC50 = 19.20 ± 0.50 μM) showed potent activity as compared to the standard drug thiourea (IC50 = 21.00 ± 0.01 μM). Other compounds showed moderate to weak activity. All synthetic compounds were characterized by different spectroscopic techniques including (1)H NMR, (13)C NMR, IR and EI MS. The molecular interactions of the active compounds within the binding site of urease enzyme were studied through molecular docking simulations.

Schiff's bases of quinazolinone derivatives: Synthesis and SAR studies of a novel series of potential anti-inflammatory and antioxidants

A series of quinazolinone derived Schiff base derivatives 7-28 were synthesized and characterized as novel antioxidants and anti-inflammatory agents. The in vitro antioxidant activities of these compounds were evaluated and compared with commercial antioxidants ascorbic acid (AA), gallic acid (GA), butylatedhydroxytoluene (BHT), butylatedhydroxyanisole (BHA) employing 1,1-diphenyl-2-picryl-hydrazyl (DPPH) assay, 2,2-azinobis-(3-ethylbenzothiazoline-6-sufonic acid) (ABTS) assay and N,N-dimethyl-p-phenylenediamine dihydrochloride (DMPD) assay. The results revealed that IC50 of 17, 18, 23, 24, 25, 27 and 28 were lower than the IC50 of standards in all the three performed antioxidant assays indicating good activities of these compounds. In addition, in vitro anti-inflammatory activity of the synthesized compounds were evaluated and the results demonstrate that the compounds 9-12 exhibited excellent anti-inflammatory activity. Preliminary structure-activity relationship revealed that the compounds 17, 18, 23, 24, 25, 27 and 28 with electron donating moiety (OH, OCH3) were found to be excellent antioxidants and compounds 9, 10, 11 and 12 with electron withdrawing moiety (Cl, NO2) were found to be excellent anti-inflammatory agents.

Influence of the diversified structural variations at the imine functionality of 4-bromophenylacetic acid derived hydrazones on alkaline phosphatase inhibition: synthesis and molecular modelling studies

Putative binding mode of 4g inside the active pocket of h-PLAP.

Antileishmanial drug discovery: comprehensive review of the last 10 years

This review covers the current aspects of leishmaniasis including marketed drugs, new antileishmanial agents, and possible drug targets of antileishmanial agents.

(E)-3-Chloro-N'-(2-fluoro-benzyl-idene)thio-phene-2-carbohydrazide

The title compound, C₁₂H₈ClFN₂OS, is a hydrazide derivative adopting an E conformation with an azomethine N=C double bond length of 1.272 (2) Å. The mol­ecular skeleton is approximately planar; the terminal five- and six-membered rings form a dihedral angle of 5.47 (9)°. In the crystal, mol­ecules are linked by N—H⋯O and C—H⋯O hydrogen bonds into zigzag chains propagating in [100].

Phenoxyacetohydrazide Schiff bases: β-glucuronidase inhibitors

Phenoxyacetohydrazide Schiff base analogs 1–28 have been synthesized and their in vitroβ-glucouoronidase inhibition potential studied. Compounds 1 (IC₅₀ = 9.20 ± 0.32 µM), 5 (IC₅₀ = 9.47 ± 0.16 µM), 7 (IC₅₀ = 14.7 ± 0.19 µM), 8 (IC₅₀ = 15.4 ± 1.56 µM), 11 (IC₅₀ = 19.6 ± 0.62 µM), 12 (IC₅₀ = 30.7 ± 1.49 µM), 15 (IC₅₀ = 12.0 ± 0.16 µM), 21 (IC₅₀ = 13.7 ± 0.40 µM) and 22 (IC₅₀ = 22.0 ± 0.14 µM) showed promising β-glucuronidase inhibition activity, better than the standard (D-saccharic acid-1,4-lactone, IC₅₀ = 48.4 ± 1.25 µM).

Synthesis, crystal structure, DFT studies and evaluation of the antioxidant activity of 3,4-dimethoxybenzenamine schiff bases

Schiff bases of 3,4-dimethoxybenzenamine 1-25 were synthesized and evaluated for their antioxidant activity. All the synthesized compounds were characterized by various spectroscopic techniques. In addition, the characterizations of compounds 13, 15 and 16 were supported by crystal X-ray determinations and their geometrical parameters were compared with theoretical DFT calculations at the B3LYP level of theory. Furthermore, the X-ray crystal data of two non-crystalline compounds 8 and 18 were theoretically calculated and compared with the practical values of compounds 13, 15, 16 and found a good agreement. The compounds showed good DPPH scavenging activity ranging from 10.12 to 84.34 μM where compounds 1-4 and 6 showed stronger activity than the standard n-propyl gallate. For the superoxide anion radical assay, compounds 1-3 showed better activity than the standard.

A Quantum Chemical and Statistical Study of Phenolic Schiff Bases with Antioxidant Activity against DPPH Free Radical

Phenolic Schiff bases are known as powerful antioxidants. To select the electronic, 2D and 3D descriptors responsible for the free radical scavenging ability of a series of 30 phenolic Schiff bases, a set of molecular descriptors were calculated by using B3P86 (Becke's three parameter hybrid functional with Perdew 86 correlation functional) combined with 6-31 + G(d,p) basis set (i.e., at the B3P86/6-31 + G(d,p) level of theory). The chemometric methods, simple and multiple linear regressions (SLR and MLR), principal component analysis (PCA) and hierarchical cluster analysis (HCA) were employed to reduce the dimensionality and to investigate the relationship between the calculated descriptors and the antioxidant activity. The results showed that the antioxidant activity mainly depends on the first and second bond dissociation enthalpies of phenolic hydroxyl groups, the dipole moment and the hydrophobicity descriptors. The antioxidant activity is inversely proportional to the main descriptors. The selected descriptors discriminate the Schiff bases into active and inactive antioxidants.

Evaluation of bisindole as potent β-glucuronidase inhibitors: synthesis and in silico based studies

Bisindole analogs 1-17 were synthesized and evaluated for their in vitro β-glucuronidase inhibitory potential. Out of seventeen compounds, the analog 1 (IC50=1.62±0.04 μM), 6 (IC50=1.86±0.05 μM), 10 (IC50=2.80±0.29 μM), 9 (IC50=3.10±0.28 μM), 14 (IC50=4.30±0.08 μM), 2 (IC50=18.40±0.09 μM), 19 (IC50=19.90±1.05 μM), 4 (IC50=20.90±0.62 μM), 7 (IC50=21.50±0.77 μM), and 3 (IC50=22.30±0.02 μM) showed superior β-glucuronidase inhibitory activity than the standard (d-saccharic acid 1,4-lactone, IC50=48.40±1.25 μM). In addition, molecular docking studies were performed to investigate the binding interactions of bisindole derivatives with the enzyme. This study has identified a new class of potent β-glucouronidase inhibitors.

2-{[2-(2-Hy-droxy-5-meth-oxy-benzyl-idene)hydrazin-1-yl-idene]meth-yl}-4-meth-oxy-phenol

The title phenyl­hydrazine derivative, C₁₆H₁₆N₂O₄, has a crystallographically imposed centre of symmetry. Except for the methyl group, all non-H atoms are almost coplanar (r.m.s. deviation = 0.0095 Å). Intra­molecular O—H⋯N hydrogen bonds are observed, generating S(6) graph-set ring motifs.

Synthesis of 4-methoxybenzoylhydrazones and evaluation of their antiglycation activity

A series of 4-methoxybenzoylhydrazones 1-30 was synthesized and the structures of the synthetic derivatives elucidated by spectroscopic methods. The compounds showed a varying degree of antiglycation activity, with IC50 values ranging between 216.52 and 748.71 µM, when compared to a rutin standard (IC50=294.46±1.50 µM). Compounds 1 (IC50=216.52±4.2 µM), 3 (IC50=289.58±2.64 µM), 6 (IC50=227.75±0.53 µM), 7 (IC50=242.53±6.1) and 11 (IC50=287.79±1.59) all showed more activity that the standard, and these compounds have the potential to serve as possible leads for drugs to inhibit protein glycation in diabetic patients. A preliminary SAR study was performed.

Synthesis, characterization and evaluation of the substituent effect on the amoebicide activity of new hydrazone derivatives

The electronic environment reflected in redox potential values of the hydrazone linkage and the nitro group plays a fundamental role in the amoebicidal activity.

Antioxidant properties of phenolic Schiff bases: structure-activity relationship and mechanism of action

Phenolic Schiff bases are known for their diverse biological activities and ability to scavenge free radicals. To elucidate (1) the structure-antioxidant activity relationship of a series of thirty synthetic derivatives of 2-methoxybezohydrazide phenolic Schiff bases and (2) to determine the major mechanism involved in free radical scavenging, we used density functional theory calculations (B3P86/6-31+(d,p)) within polarizable continuum model. The results showed the importance of the bond dissociation enthalpies (BDEs) related to the first and second (BDEd) hydrogen atom transfer (intrinsic parameters) for rationalizing the antioxidant activity. In addition to the number of OH groups, the presence of a bromine substituent plays an interesting role in modulating the antioxidant activity. Theoretical thermodynamic and kinetic studies demonstrated that the free radical scavenging by these Schiff bases mainly proceeds through proton-coupled electron transfer rather than sequential proton loss electron transfer, the latter mechanism being only feasible at relatively high pH.

Synthesis, evaluation of antioxidant activity and crystal structure of 2,4-dimethylbenzoylhydrazones

2,4-Dimethylbenzoylhydrazones 1-30 were synthesized by condensation reactions of 2,4-dimethylbenzoylhydrazide with various aromatic aldehydes and characterized. The assigned structures of compounds 10, 15 and 22 were further supported by single-crystal X-ray diffraction data. The synthesized compounds were evaluated for their in vitro DPPH radical scavenging activity. They exerted varying degree of scavenging activity toward DPPH radical with IC₅₀ values between 25.6-190 µM. Compounds 1, 4, 2, 3, 7, and 6 have IC₅₀ values of 25.6, 28.1, 29.3, 29.8, 30.0 and 30.1 µM respectively, showing better activity than an n-propyl gallate standard (IC₅₀ value = 30.30 µM). For super oxide anion scavenging activity compounds 1, 2 and 3 with IC₅₀ values of 98.3, 102.6, and 105.6, respectively, also showed better activity than the n-propyl gallate standard (IC₅₀ value = 106.34 µM).