A glucose/mannose binding lectin from litchi (Litchi chinensis) seeds: Biochemical and biophysical characterizations

BackgroundLectins are highly important biomolecules to study several biological processes. A novel α-D-glucose/mannose specific lectin was isolated from the seeds of litchi fruits (Litchi chinensis) and its various biophysical and biochemical properties were studied.MethodsPurification was done by successive Sephadex G 100 and Con A-Sepharose 4B affinity chromatography. SDS-PAGE, Surface Plasmon Resonance (SPR), steady state absorbance, fluorescence, time-correlated single-photon counting, circular dichroism and antibiofilm activity by measuring total protein estimation and azocasein degradation assay have been performed.ResultsThe purified lectin is a homodimer of molecular mass ~ 54 kDa. The amount of lectin required for hemagglutination of normal human O erythrocytes was 6.72 µg/ml. Among the saccharides tested, Man-α-(1,6)-Man was found to be the most potent inhibitor (0.01 mM) determined by hemagglutination inhibition assay. Steady state and time resolved fluorescence measurements revealed that litchi lectin formed ground state complex with maltose (K_a=4.9 (±0.2)×10⁴ M^?1), which indicated static quenching (Stern-Volmer (SV) constant K_sv=4.6 (±0.2)×10⁴ M^?1). CD measurements demonstrated that litchi lectin showed no overall conformational change during the binding process with maltose. The lectin showed antibiofilm activity against Pseudomonus aeruginosa.ConclusionsA novel homodimeric lectin has been purified from the seeds of litchi fruits (Litchi chinensis) having specificity for α-d-glucose/mannose. The thermodynamics and conformational aspects of its interaction with maltose have been studied in detail. The antibiofilm activity of this lectin towards Pseudomonus aeruginosa has been explored.General significanceThe newly identified litchi lectin is highly specific for α-d-glucose/mannose with an important antibiofilm activity towards Pseudomonus aeruginosa.     

DNA binding acridine–thiazolidinone agents affecting intracellular glutathione

Three new acridine–thiazolidinone derivatives (2a–2c) have been synthesized and their interactions with calf thymus DNA and a number of cell lines (leukemic cells HL-60 and L1210 and human epithelial ovarian cancer cell lines A2780) were studied. The compounds 2a–2c possessed high affinity to calf thymus DNA and their binding constants determined by spectrofluorimetry were in the range of 1.37 × 10⁶–5.89 × 10⁶ M^?1. All of the tested derivatives displayed strong cytotoxic activity in vitro, the highest activity in cytotoxic tests was found for 2c with IC₅₀ = 1.3 ± 0.2 μM (HL-60), 3.1 ± 0.4 μM (L1210), and 7.7 ± 0.5 μM (A2780) after 72 h incubation. The cancer cells accumulated acridine derivatives very fast and the changes of the glutathione level were confirmed. The compounds inhibited proliferation of the cells and induced an arrest of the cell cycle and cell death. Their influence upon cells was associated with their reactivity towards thiols and DNA binding activity.     

Design,synthesis, and DNA binding characteristics of a group of orthogonally positioned diamino,N-formamido,pyrrole- and imidazole-containing polyamides

Orthogonally positioned diamino/dicationic polyamides (PAs) have good water solubility and enhanced binding affinity, whilst retaining DNA minor groove and sequence specificity compared to their monoamino/monocationic counterparts. The synthesis and DNA binding properties of the following diamino PAs: f-IPI (3a), f-IPP (4), f-PIP (5), and f-PPP (6) are described. P denotes the site where a 1-propylamino group is attached to the N1-position of the heterocycle. Binding of the diamino PAs to DNA was assessed by DNase I footprinting, thermal denaturation, circular dichroism titration, biosensor surface plasmon resonance (SPR), and isothermal titration calorimetry (ITC) studies. According to SPR studies, f-IPI (3a) bound more strongly (K_eq = 2.4 × 10⁸ M^?1) and with comparable sequence selectivity to its cognate sequence 5′-ACGCGT-3′ when compared to its monoamino analog f-IPI (1). The binding of f-IPI (3a) to 5′-ACGCGT-3′ via the stacked dimer motif was balanced between enthalpy and entropy, and that was quite different from the enthalpy-driven binding of its monoamino parent f-IPI (1). f-IPP (4) also bound more strongly to its cognate sequence 5′-ATGCAT-3′ (K_eq = 7.4 × 10⁶ M^?1) via the side-by-side stacked motif than its monoamino analog f-IPP (2a). Although f-PPP (6) bound via a 1:1 motif, it bound strongly to its cognate sequence 5′-AAATTT-3′ (K_eq = 4.8 × 10⁷ M^?1), 15-times higher than the binding of its monoamino analog f-PPP (2c), albeit f-PPP bound via the stacked motif. Finally, f-PIP (5) bound to its target sequence 5′-ATCGAT-3′ as a stacked dimer and it has the lowest affinity among the diamino PAs tested (K_eq <1 × 10⁵ M^?1). This was about two times lower in affinity than the binding of its monoamino analog f-PIP (2b). The results further demonstrated that the ‘core rules’ of DNA recognition by monoamino PAs also apply to their diamino analogs. Specifically, PAs that contain a stacked IP core structure bind most strongly (highest binding constants) to their cognate GC doublet, followed by the binding of PAs with a stacked PP structure to two degenerate AT base pairs, and finally the binding of PAs with a PI core to their cognate CG doublet.     

Triazolopyridyl ketones as a novel class of antileishmanial agents. DNA binding and BSA interaction

A new series of triazolopyridyl pyridyl ketones has been synthetized by regioselective lithiation of the corresponding [1,2,3]triazolo[1,5-a]pyridine at 7 position followed by reaction with different electrophiles. The in vitro antileishmanial activity of these compounds was evaluated against Leishmania infantum, Leishmania braziliensis, Leishmania guyanensis and Leishmania amazonensis. Compounds 6 and 7 were found to be the most active leishmanicidal agents. Both of them showed activities at micromolar concentration against cultured promastigotes of Leishmania spp. (IC₅₀ = 99.8–26.8 μM), without cytotoxicity on J774 macrophage cells. These two compounds were also tested in vivo in a murine model of acute infection by L. infantum. The triazolopyridine derivative 6 was effective against both spleen and liver parasites forms, while 7 was inactive against liver parasites. Mechanistic aspects of the antileishmanial activity were investigated by means of DNA binding studies (UV-titration and viscosimetry). Results have revealed that these active ligands are able to interact strongly with DNA [K_b = 1.14 × 10⁵ M⁻¹ (6) and 3.26 × 10⁵ M⁻¹ (7)]. Moreover, a DNA groove binding has been proposed for both 6 and 7. To provide more insight on the mode of action of compounds 6 and 7 under biological conditions, their interaction with bovine serum albumin (BSA) was monitored by fluorescence titrations and UV–visible spectroscopy. The quenching constants and binding parameters were determined. Triazolopyridine ketones 6 and 7 have exhibited significant affinity towards BSA [K_b = 2.5 × 10⁴ M⁻¹ (6) and 1.9 × 10⁴ M⁻¹ (7)]. Finally, to identify the binding location of compounds 6 and 7 on the BSA, competitive binding experiments were carried out, using warfarin, a characteristic marker for site I, and ibuprofen as one for site II. Results derived from these studies have indicated that both compounds interact at BSA site I and, to a lesser extent, at site II.     

Synthesis,X-ray crystal structure,DNA/protein binding and cytotoxicity studies of five α-aminophosphonate N-derivatives

Five new α-aminophosphonates are synthesized and characterized by EA, FT-IR, ¹H NMR, ¹³C NMR, ³¹P NMR, ESI-MS and X-ray crystallography. The X-ray analyses reveal that the crystal structures of 1–5 are monoclinic or triclinic system with the space group P 21/c, P − 1, P − 1, P2(1)/c and P − 1, respectively. All P atoms of 1–5 have tetrahedral geometries involving two O-ethyl groups, one C_α atom, and a double bond O atom. The binding interaction of five new α-aminophosphonate N-derivatives (1–5) with calf thymus(CT)-DNA have been investigated by UV–visible and fluorescence emission spectrometry. The apparent binding constant (Kapp) values follows the order: 1 (3.38 × 10⁵ M⁻¹) > 2 (3.04 × 10⁵ M⁻¹) > 4 (2.52 × 10⁵ M⁻¹) > 5 (2.32 × 10⁵ M⁻¹) > 3 (2.10 × 10⁵ M⁻¹), suggesting moderate intercalative binding mode between the compounds and DNA. In addition, fluorescence spectrometry of bovine serum albumin (BSA) with the compounds 1–5 showed that the quenching mechanism might be a static quenching procedure. For the compounds 1–5, the number of binding sites were about one for BSA and the binding constants follow the order: 1 (2.72 × 10⁴ M⁻¹) > 2 (2.27 × 10⁴ M⁻¹) > 4 (2.08 × 10⁴ M⁻¹) > 5 (1.79 × 10⁴ M⁻¹) > 3 (1.17 × 10⁴ M⁻¹). Moreover, the DNA cleavage abilities of 1 exhibit remarkable changes and the in vitro cytotoxicity of 1 on tumor cells lines (MCF-7, HepG2 and HT29) have been examined by MTT and shown antitumor effect on the tested cells.     

Investigations into specificity of azepinomycin for inhibition of guanase: Discrimination between the natural heterocyclic inhibitor and its synthetic nucleoside analogues

In our long and broad program to explore structure–activity relationships of the natural product azepinomycin and its analogues for inhibition of guanase, an important enzyme of purine salvage pathway of nucleic acid metabolism, it became necessary to investigate if the nucleoside analogues of the heterocycle azepinomycin, which are likely to be formed in vivo, would be more or less potent than the parent heterocycle. To this end, we have resynthesized both azepinomycin (1) and its two diastereomeric nucleoside analogues (2 and 3), employing a modified, more efficient procedure, and have biochemically screened all three compounds against a mammalian guanase. Our results indicate that the natural product is at least 200 times more potent toward inhibition of guanase as compared with its nucleoside analogues, with the observed K_i of azepinomycin (1) against the rabbit liver guanase = 2.5 (±0.6) × 10^?6 M, while K_i of Compound 2 = 1.19 (±0.02) × 10^?4 M and that of Compound 3 = 1.29 (±0.03) × 10^?4 M. It is also to be noted that while IC₅₀ value of azepinomycin against guanase in cell culture has long been reported, no inhibition studies nor K_i against a pure mammalian enzyme have ever been documented. In addition, we have, for the first time, determined the absolute stereochemistry of the 6-OH group of 2 and 3 using conformational analysis coupled with 2-D ¹H NMR NOESY     

Effect of methyl substitution in a ligand on the selectivity and binding affinity for a nucleobase: A case study with isoxanthopterin and its derivatives

Isoxanthopterin (IX) has two edges with hydrogen bond-forming sites suitable for binding to thymine (T) and cytosine (C). The binding affinity of IX for T or C is stronger than for adenine (A) and guanine (G), whereas the base selectivity of IX for T over C (and vice versa) is moderate. In order to improve both the binding affinity and base selectivity for T over C or C over T, a methyl group is introduced respectively at the N-3 or N-8 position of IX. This leads to the known ligands 3-methyl isoxanthopterin (3-MIX) and 8-methyl isoxanthopterin (8-MIX), and the binding affinity for C or T is expected to be tuned and improved by methyl substitution. Indeed, 3-MIX selectively binds to T more strongly than IX with a binding constant of 1.5 × 10⁶ M^?1 and it loses its binding affinity for C. In contrast, 8-MIX selectively binds to C over T with a binding constant of 1.0 × 10⁶ M^?1 and the binding affinity is greatly improved compared to the parent ligand IX. The thermodynamics of the ligand–nucleotide interaction is analyzed by isothermal calorimetric titrations, and the results show that the interaction follows a 1:1 stoichiometry and is enthalpy-driven. The introduction of methyl groups at both N-3 and N-8 positions results in an increase in enthalpy of the ligand–nucleotide interaction, which leads to the improved binding affinity.     

Cyclic ferrocenylnaphthalene diimide derivative as a new class of G-quadruplex DNA binding ligand

To identify an effective ligand that binds to a G-quadruplex structure but not a double-stranded DNA (dsDNA), a set of biophysical and biochemical experiments were carried out using newly synthesized cyclic ferrocenylnaphthalene diimide (cFNDI, 1) or the non-cyclic derivative (2) with various structures of G-quadruplex DNAs and dsDNA. Compound 1 bound strongly to G-quadruplexes DNAs (10⁶ M^?1 order) with diminished binding to dsDNA (10⁴ M^?1 order) in 100 mM AcOH-AcOK buffer (pH 5.5) containing 100 mM KCl. Interestingly, 1 showed an approximately 50-fold higher selectivity to mixed hybrid-type telomeric G-quadruplex DNA (K = 3.4 × 10⁶ M^?1 and a 2:1 stoichiometry) than dsDNA (K = 7.5 × 10⁴ M^?1) did. Furthermore, 1 showed higher thermal stability to G-quadruplex DNAs than it did to dsDNA with a preference for c-kit and c-myc G-quadruplex DNAs over telomeric and thrombin binding aptamers. Additionally, 1 exhibited telomerase inhibitory activity with a half-maximal inhibitory concentration (IC₅₀) of 0.4 μM. Compound 2 showed a preference for G-quadruplex; however, the binding affinity magnitude and preference were improved in 1 because the former had a cyclic structure.     

Targeting the ICB2 site of the topoisomerase IIα promoter with a formamido-pyrrole–imidazole–pyrrole H-pin polyamide

The synthesis, DNA binding characteristics and biological activity of an N-formamido pyrrole- and imidazole-containing H-pin polyamide (f-PIP H-pin, 2) designed to selectively target the ICB2 site on the topoIIα promoter, is reported herein. Thermal denaturation, circular dichroism, isothermal titration calorimetry, surface plasmon resonance and DNase I footprinting studies demonstrated that 2 maintained the selectivity of the unlinked parent monomer f-PIP (1) and with a slight enhancement in binding affinity (K_eq = 5 × 10⁵ M^?1) to the cognate site (5′-TACGAT-3′). H-pin 2 also exhibited comparable ability to inhibit NF-Y binding to 1, as demonstrated by gel shift studies. However, in stark contrast to monomer 1, the H-pin did not affect the up-regulation of topoisomerase IIα (topoIIα) in cells (Western blot), suggesting that the H-pin does not enter the nucleus. This study is the first to the authors’ knowledge that reports such a markedly different cellular response between two compounds of almost identical binding characteristics.     

DNA binding and photocleavage properties and apoptosis-inducing activities of a ruthenium porphyrin complex [(Py-3′)TPP-Ru(phen)2Cl]Cl and its heterometallic derivatives

The interactions of a ruthenium porphyrin complex [(Py-3′)TPP-Ru(phen)₂Cl]Cl (phen = 1,10-phenanthroline, (Py-3′)TPP = 5-(3′-pyridyl-10,15,20-triphenylporphyrin) (1) and its heterometallic derivatives, [Ni(Py-3′)TPP-Ru(phen)₂Cl][PF₆] (2) and [Cu(Py-3′)TPP-Ru(phen)₂Cl][PF₆] (3), with calf thymus DNA have been investigated by spectroscopic and viscosity measurements in this study. The results showed that these synthetic complexes can bind to double strand helix DNA in groove binding mode, and the intrinsic binding constants of complexes 1, 2 and 3, as calculated according to the decay of the Soret absorption, are (1.35 ± 0.5) ×10⁵ M^?1 (s = 4.2), (1.29 ± 0.5) × 10⁵ M^?1 (s = 5.6) and (1.22 ± 0.5) × 10⁵ M^?1 (s = 6.2) (s is the binding-site size), respectively, which are consistent with those obtained from ethidium bromide-quenching experiments. Further investigations on the photocleavage properties of these complexes on plasmid pBR 322 DNA showed that complexes 1, 2 and 3 could cleave single chain DNA and convert DNA molecules from supercoiled form to the nicked form. As determined by MTT assay, the complexes were also identified as potent antiproliferative agents against A375 human melanoma cells, MCF-7 human breast adrenocarcinoma cells, Colo201 human colon adenocarcinoma cells and HepG2 human liver cancer cells. Complex 1 inhibits the growth of A375 cells through induction of apoptotic cell death and G0/G1 cell cycle arrest. Further investigation on intracellular mechanisms indicated that Complex 1 induced depletion of mitochondrial membrane potential (ΔΨ_m) in A375 cells through regulating the expression of pro-survival and pro-apoptotic Bcl-2 family members. Our results suggest that ruthenium porphyrin complexes could be candidates for further evaluation as chemopreventive and chemotherapeutic agents for human cancers.     

A Kazal-type serine proteinase inhibitor from chicken liver (clTI-1): Purification,primary structure,and inhibitory properties

Low-molecular-mass trypsin inhibitor (clTI-1; chicken liver Trypsin Inhibitor-1) was purified from chicken liver by extraction with perchloric acid, ammonium sulfate precipitation, a combination of ethanol-acetone fractionation followed by gel filtration, ion-exchange chromatography and RP-HPLC on a C18 column. The inhibitor occurs in two isoforms with molecular masses of 5938.56 and 6026.29 Da (determined by MALDI TOFF mass spectrometry). The complete amino acid sequences of both isoforms were determined (UniProtKB/Swiss-Prot P85000; ISK1L_CHICK). The inhibitor shows a high homology to Kazal-type family inhibitors, especially to trypsin/acrosin inhibitors and pancreatic secretory trypsin inhibitors. clTI-1 inhibits both bovine and porcine trypsin (K_a = 1.1 × 10⁹ M^?1 and 2.5 × 10⁹ M^?1, respectively). Significant differences were shown in the inhibition of the anionic and cationic forms of chicken trypsin (K_a = 4.5 × 10⁸ M^?1 and 1.2 × 10¹⁰ M^?1). Weak interaction with human plasmin (K_a = 1.2 × 10⁷ M^?1) was also revealed.     

Cytotoxicity and DNA binding property of phenanthrene imidazole with polyglycol side chains

A series of phenanthrene imidazole with polyglycol side chain (2a–2c and 3a–3c) were synthesized and characterized by IR, NMR and MS. The cytotoxicity of 2a–2c and 3a–3c against cancer cell lines (HL-60, BGC-823, Bel-7402 and KB) in vitro were measured using MTT method. The DNA binding properties of 3a–3c were investigated by UV, fluorescence, CD spectroscopies and thermal denaturation. The results indicate that 2a exhibits higher cytotoxicity than cisplatin against BGC-823 and Bel-7402 cell lines, 3b and 3c exhibit higher cytotoxicity than 2b and 2c against BGC-823, Bel-7402 and KB cell lines. The cytotoxic effect of 2a–2c decrease with the increase of side chains length, the cytotoxic effect of 3a–3c increased with the increasing length of side chains against BGC-823, Bel-7402 and KB cell lines. Compounds 3a–3c intercalated DNA with a vertical orientation in the intercalation pocket. The binding constants of 3a–3c with Ct-DNA are 1.68 × 10⁶, 1.51 × 10⁶ and 0.709 × 10⁶ M^?1, respectively. The binding affinity of 3a–3c with Ct-DNA trended to decrease with the increasing length of polyglycol side chains.     

A ratiometric fluorescent detection of Zn(II) in aqueous solutions using pyrene-appended histidine

A fluorescent chemosensor, Py-His, based on histidine was easily synthesized in solid phase synthesis. Py-His displayed a highly sensitive ratiometric response to Zn(II) with potent binding affinity (K_a = 1.17 × 10¹³ M^?2) in aqueous solutions. The detection limit of Py-His for Zn(II) was calculated as 80.8 nM. Moreover, Py-His distinguished Zn(II) and Hg(II) by different ratiometric response type; the chemosensor showed a more enhanced increase of excimer emission intensity to Zn(II) than Hg(II). Upon addition of Ag(I) and Cu(II), Py-His showed a turn-off response mainly due to the quenching effect of these metal ions. The binding stoichiometry (2:1 or 1:1) of Py-His to target metal ions played a critical role in the fluorescent response type (ratiometric and turn off response) to target metal ions. The role of imidazole group of Py-His for ratiometric detection of Zn(II) was proposed by pH titration experiments.     

Cationic porphyrin–quinoxaline conjugate as a photochemically triggered novel cytotoxic agent

A novel cationic porphyrin–quinoxaline conjugate 8 was prepared in good yield by the coupling of activated quinoxaline carboxylic acid 5 with an appropriate aminoporphyrin. The UV–vis spectra of conjugate 8 with the addition of ctDNA shows substantial hypochromicity (39%) and a red shift (12 nm) in the Soret band indicating intercalation and self stacking along the surface. The binding constant of conjugate 8 with ctDNA was determined to be 1.26 × 10⁶ M^?1. The porphyrin–quinoxaline conjugate 8 displayed enhanced photocytotoxicity (IC₅₀ = 0.06 μM) when compared to TMPyP against A549 cancer cells.     

Design of a new fluorescent probe: Pyrrole/imidazole hairpin polyamides with pyrene conjugation at their γ-turn

Fluorophores that are conjugated with N-methylpyrrole-N-methylimidazole (Py–Im) polyamides postulates versatile applications in biological and physicochemical studies. Here, we show the design and synthesis of new types of pyrene-conjugated hairpin Py–Im polyamides (1–5). We evaluated the steady state fluorescence of the synthesized conjugates (1–5) in the presence and absence of oligodeoxynucleotides 5′-CGTATGGACTCGG-3′ (ODN 1) and 5′-CCGAGTCCATACG-3′ (ODN 2) and observed a distinct increase in emission at 386 nm with conjugates 4 and 5. Notably, conjugate 5 that contains a β-alanine linker had a stronger binding affinity (K_D = 1.73 × 10^?8 M) than that of conjugate 4 (K_D = 1.74 × 10^?6 M). Our data suggests that Py–Im polyamides containing pyrene fluorophore with a β-alanine linker at the γ-turn NH₂ position can be developed as the competent fluorescent DNA-binding probes.     

A novel fluorogenic substrate for dinuclear Zn(II)-containing metallo-β-lactamases

In an effort to prepare a fluorogenic substrate to be used in activity assays with metallo-β-lactamases, (6R,7R)-8-oxo-7-(2-oxo-2H-chromene-3-carboxamido)-3-((4-(2-oxo-2H-chromene-3-carboxamido)-phenylthio)methyl)-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid (CA) was synthesized and characterized. CA exhibited a fluorescence quantum yield (φ) of 0.0059, two fluorescence lifetimes of 3.63 × 10^?10 and 5.38 × 10^?9 s, and fluorescence intensity that is concentration-dependent. Steady-state kinetic assays revealed that CA is a substrate for metallo-β-lactamases (MβLs) L1 and CcrA, exhibiting K_m and k_cat values of 18 μM and 5 s^?1 and 11 μM and 17 s^?1, respectively.     

Cytotoxic activity of acridin-3,6-diyl dithiourea hydrochlorides in human leukemia line HL-60 and resistant subline HL-60/ADR

A series of acridin-3,6-diyl dithiourea hydrochloride derivatives (alkyl-AcrDTU) was prepared and tested against sensitive and drug resistant leukemia cell lines for their cytotoxic/cytostatic activity. The products (ethyl-, n-propyl-, n-butyl-, n-pentyl-AcrDTU) showed high DNA binding affinity via intercalation (K = 7.6 ? 2.9 × 10⁵ M^?1). All derivatives inhibited proliferation of HL-60 cells and its resistant subline HL-60/ADR, unexpectedly the resistant subline was more sensitive than the parental one (IC₅₀ = 3.5 μM, 48-treatment of HL-60/ADR with pentyl-AcrDTU). Cytotoxicity of tested compounds was associated with their DNA-binding properties and the level of intracellular thiols has been changed in the presence of AcrDTU.     

Enhanced estrogen receptor beta (ERβ) selectivity of fluorinated carborane-containing ER modulators

We previously showed that fluorination of the carborane-containing selective estrogen receptor modulator (SERM) BE360 altered the agonist/antagonist activity balance and the estrogen receptor (ER) α/β subtype selectivity. Here, we designed and synthesized a series of fluorinated carboranyl phenols as candidate ERβ-selective ligands. Introduction of a fluorine atom onto the carborane cage commonly reduced the binding affinity for ERα, to an extent that depended on the other substituents present. The B-fluorinated m-carboranyl phenol 4a showed fourfold more potent ERβ-binding affinity than the parent non-fluorinated compound 7. 1-Iodo-9-fluoro-m-carboranyl phenol 4f showed high ERβ-binding affinity with an ERβ/ERα selectivity ratio of 8.2. Among the compounds tested, 6 showed the highest ERβ selectivity (10.1-fold) and the highest ER-agonistic activity (EC₅₀: 5.1 × 10^?10 M) in MCF-7 cell proliferation assay.     

Curcumin-I Knoevenagel’s condensates and their Schiff’s bases as anticancer agents: Synthesis,pharmacological and simulation studies

Pyrazolealdehydes (4a–d), Knoevenagel’s condensates (5a–d) and Schiff’s bases (6a–d) of curcumin-I were synthesized, purified and characterized. Hemolysis assays, cell line activities, DNA bindings and docking studies were carried out. These compounds were lesser hemolytic than standard drug doxorubicin. Minimum cell viability (MCF-7; wild) observed was 59% (1.0 μg/mL) whereas the DNA binding constants ranged from 1.4 × 10³ to 8.1 × 10⁵ M^?1. The docking energies varied from ?7.30 to ?13.4 kcal/mol. It has been observed that DNA-compound adducts were stabilized by three governing forces (Van der Wall’s, H-bonding and electrostatic attractions). It has also been observed that compounds 4a–d preferred to enter minor groove while 5a–d and 6a–d interacted with major grooves of DNA. The anticancer activities of the reported compounds might be due to their interactions with DNA. These results indicated the bright future of the reported compounds as anticancer agents.     

Inhibition of acetylcholinesterase by chromophore-linked fluorophosphonates

Fluorophosphonate (FP) head groups were tethered to a variety of chromophores (C) via a triazole group and tested as FPC inhibitors of recombinant mouse (rMoAChE) and electric eel (EEAChE) acetylcholinesterase. The inhibitors showed bimolecular inhibition constants (k_i) ranging from 0.3 × 10⁵ M^?1 min^?1 to 10.4 × 10⁵ M^?1 min^?1. When tested against rMoAChE, the dansyl FPC was 12.5-fold more potent than the corresponding inhibitor bearing a Texas Red as chromophore, whereas the Lissamine and dabsyl chromophores led to better anti-EEAChE inhibitors. Most inhibitors were equal or better inhibitors of rMoAChE than EEAChE. 3-Azidopropyl fluorophosphonate, which served as one of the FP head groups, showed excellent inhibitory potency against both AChE’s (? 1 × 10⁷ M^?1 min^?1) indicating, in general, that addition of the chromophore reduced the overall anti-AChE activity. Covalent attachment of the dabsyl-FPC analog to rMoAChE was demonstrated using size exclusion chromatography and spectroscopic analysis, and visualized using molecular modeling.