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Pteridine reductase-1 (PTR1) is a promising drug target for the treatment of trypanosomiasis. We investigated the potential of a previously identified class of thiadiazole inhibitors of Leishmania major PTR1 for activity against Trypanosoma brucei (Tb). We solved crystal structures of several TbPTR1-inhibitor complexes to guide the structure-based design of new thiadiazole derivatives. Subsequent synthesis and enzyme- and cell-based assays confirm new, mid-micromolar inhibitors of TbPTR1 with low toxicity. In particular, compound 4m, a biphenyl-thiadiazole-2,5-diamine with IC50 = 16 μM, was able to potentiate the antitrypanosomal activity of the dihydrofolate reductase inhibitor methotrexate (MTX) with a 4.1-fold decrease of the EC50 value. In addition, the antiparasitic activity of the combination of 4m and MTX was reversed by addition of folic acid. By adopting an efficient hit discovery platform, we demonstrate, using the 2-amino-1,3,4-thiadiazole scaffold, how a promising tool for the development of anti-T. brucei agents can be obtained.

Bacterial resistance represents a worldwide emergency threatening the efficacy of all available antibiotics. Among the several resistance mechanisms developed by bacteria, β-lactamase enzymes (BLs), which are able to inactivate most β-lactam core antibiotics, represent a key target to block, thus prolonging antibiotics half-life. Several approaches aimed at inhibiting β-lactamases have been so far undertaken, mainly involving β-lactam-like or covalent inhibitors. Applying a structure-based de novo design approach, we recently discovered a novel, non-covalent and competitive inhibitor of AmpC β-lactamase: lead 1. It has a K i of 1 µM, a ligand efficiency of 0.38 kcal mol−1 and lead-like physical properties. Moreover, it reverts resistance to ceftazidime in bacterial pathogens expressing AmpC and does not up-regulate β-lactamases expression in cell culture. Its features make it a good candidate for chemical optimization: starting from lead 1 crystallographic complex with AmpC, 11 analogs were designed to complement additional AmpC sites, then synthesized and tested against clinically resistant pathogens. While the new inhibitors maintain similar in vitro activity as the starting lead, some of them, in biological assays, extert a higher potency showing improved synergic activity with ceftazidime in resistant clinically isolated strains.

Folate analogue inhibitors of Leishmania major pteridine reductase (PTR1) are potential antiparasitic drug candidates for combined therapy with dihydrofolate reductase (DHFR) inhibitors. To identify new molecules with specificity for PTR1, we carried out a virtual screening of the Available Chemicals Directory (ACD) database to select compounds that could interact with L. major PTR1 but not with human DHFR. Through two rounds of drug discovery, we successfully identified eighteen drug-like molecules with low micromolar affinities and high in vitro specificity profiles. Their efficacy against Leishmania species was studied in cultured cells of the promastigote stage, using the compounds both alone and in combination with 1 (pyrimethamine; 5-(4-chlorophenyl)-6-ethylpyrimidine-2,4-diamine). Six compounds showed efficacy only in combination. In toxicity tests against human fibroblasts, several compounds showed low toxicity. One compound, 5c (riluzole; 6-(trifluoromethoxy)-1,3-benzothiazol-2-ylamine), a known drug approved for CNS pathologies, was active in combination and is suitable for early preclinical evaluation of its potential for label extension as a PTR1 inhibitor and antiparasitic drug candidate.

The Fe3+ chelating ability of some curcumin glucosyl derivatives (Glc-H; Glc-OH; Glc-OCH3) is tested by means of UV and NMR study. The pK a values of the ligands and the overall stability constants of Fe3+ and Ga3+ complexes are evaluated from UV spectra. The only metal binding site of the ligand is the β-diketo moiety in the keto-enolic form; the glucosyl moiety does not interact with metal ion but it contributes to the stability of metal/ligand 1:2 complexes by means of hydrophilic interactions. These glucosyl derivatives are able to bind Fe3+ in a wide pH rage, forming complex species thermodynamically more stable than those of other ligands commonly used in the treatment of iron deficiency. In addition they demonstrate to have a poor affinity for competitive biological metal ions such as Ca2+. All ligands and their iron complexes have a good lypophilicity (log P > −0.7) suggesting an efficient gastrointestinal absorption in view of their possible use as iron supplements in oral therapy. The ligand molecules are also tested for their antioxidant properties in “ex vivo” biological system.

A simple synthetic pathway to obtain glycosilated β-diketo derivatives is proposed. These compounds show a good iron(III) affinity therefore we may suggest the use of their Fe 3+ -complexes as oral iron supplements in the treatment of anaemia. The glycosilated compounds (6-GlcH, 6-GlcOH and 6-GlcOCH 3 ) are characterized by means of spectroscopic (UV, 1 H and 13 C NMR) and potentiometric techniques; they have a good water solubility, are kinetically stable in physiological condition ( t 1/2 > 100 h) and show a low cytotoxicity also in high concentrations (IC 50 > 400 μM). They are able to bind Fe 3+ ion in acid condition (pH ∼ 2) forming complex species thermodynamically more stable than those of other ligands commonly used in the treatment of iron deficiency. The iron complexes show also a good kinetic stability both in acidic and physiological pH and have a good lypophilicity (log P > −0.7) that suggests an efficient gastrointestinal absorption in view of their possible use in oral therapy. In addition they demonstrate a poor affinity for competitive biological metal ion such as Ca 2+ , and in particular 6-GlcOCH 3 is able to inhibit lipid peroxidation.

The NMR study on the interaction of Pt(II) with Amadori compounds is performed. The Amadori compounds are derived from the reaction of β- d -glucose with l -cystine leading to N,N′-di-(1-deoxy-β-fructos-1-yl)- l -cystine [FruCyscys], and with l -methionine leading to N-(1-deoxy-β-fructos-1-yl)- l -methionine [FruMet]. The great instability of 2-(1,2,3,4,5-pentahydroxypentyl)-1,3-thiazolidine-4-carboxylic acid [GlcCys], formed by the condensation reaction of β- d -glucose and l -cysteine, prevents the formation of its Pt(II) complexes. Differently, FruMet well reacts with K2PtCl4 in 1:1 M/L molar ratio leading to the formation of [Pt(FruMet-N,S)Cl2], in which the Amadori compound coordinates the metal ion through nitrogen and sulphur atoms. FruMet originates also a solid trans complex [Pt(FruMet-N,S)2]Cl2. Its NMR solution study allowed to identify two isomers with respect to nitrogen and sulphur atoms: R,R and S,S. In [Pt2FruCyscysCl4] species, FruCyscys molecule links two Pt(II) ions giving rise to two pentaatomic N,S-chelate rings.

Here we report the first evidence of Pt(II) interaction with Amadori compound [N-(1-deoxy- d -Fructos-1-yl)glycine (Fru-Hgly)]. The 1H and 195Pt NMR results show that complexation of Pt(II) by Fru-Hgly is strongly dependent on pH and reaction molar ratio. In 1/1 Pt/Fru-Hgly molar ratio, at acidic pH, the first coordination site is the carboxylic oxygen, while at physiological pH the anchoring group is the aminic one, in both cases the system slowly evolves towards an N,O chelating mode. In 1/2 Pt/Fru-Hgly molar ratio the only coordination site is nitrogen atom while the carboxylic oxygen is not involved in metal coordination.

Here we report the synthesis, the characterization and a theoretical study on new glycosylated phenyl substituted β-diketones; two classes of compounds are obtained according to the condensation reaction: central and side derivatives. Their iron(III) chelating ability is tested by means of UV–visible (UV–vis), potentiometric and NMR techniques. The conformation of central derivatives does not allow any metal chelation, while side derivatives bind iron(III) through the β-dioxo moiety. The glycosyl moiety does not interact with metal ion but it helps to stabilize metal/ligand (1/3) complexes by means of hydrophylic interactions. The pKa of the ligands and the stability constants of their Fe(III) complexes are evaluated by means of UV–vis spectroscopy and potentiometry. A comparison with other iron-chelating agents, on the basis of lipophilicity and the pFe(III), is finally reported.

To identify specific bacterial thymidylate synthase (TS) inhibitors, we exploited phenolphthalein (PTH), which inhibits both bacterial and human enzymes. The X-ray crystal structure of Lactobacillus casei TS (LcTS) that binds PTH showed multiple binding modes of the inhibitor, which prevented a classical structure-based drug design approach. To overcome this issue, we synthesized two phthalimidic libraries that were tested against TS enzymes and then we performed X-ray crystallographic screening of the active compounds. Compounds 6A, 8A, and 12A showed 40-fold higher affinity for bacterial TS than human TS. The X-ray crystallographic screening characterized the binding mode of six inhibitors in complexes with LcTS. Of these, 20A, 23A, and 24A showed a common unique binding mode, whereas 8A showed a different, unique binding mode. A comparative analysis of the LcTS X-ray complexes that were obtained with the pathogenic TS enabled the selection of compounds 8A and 23A as specific compounds and starting points to be exploited for the specific inhibition of pathogen enzymes.

In the present study, we investigate the structures of glucosylated curcumin derivatives with DFT at B3LYP/6-31G* level. A conformational analysis is performed in order to determine the conformational minimum (GS) and rotational transition state (TS) of curcumin derivatives and then their electronic features are evaluated. HOMO and LUMO frontier orbitals and maps of electron density potential (MEPs) are plotted and compared. In order to correlate their predicted spectroscopic properties with IR, UV–vis and NMR experimental data we extended the theoretical study on electronic properties to different solvents (H2O, MeOH, ACN, DMSO). The main finding is that the curcuminic core maintains the same geometrical and electronic structures in all compounds miming the metal coordination capability showed by curcumin. Therefore, we may confirm that the presence of glucose does not affect the electronic properties of the derivatives. Copyright © 2010 John Wiley & Sons, Ltd.

Curcumin, a phenolic compound from the plant Curcuma longa L., has shown a wide-spectrum of chemopreventive, antioxidant and antitumor properties. Although its promising chemotherapeutic activity, preclinical and clinical studies highlight Curcumin limited therapeutic application due to its instability in physiological conditions. To improve its stability and activity, many derivatives have been synthesized and studied, among which bis-DemethoxyCurcumin (bDMC) and diAcetylCurcumin (DAC). In this report, we show that both bDMC and DAC are more stable than Curcumin in physiological medium. To explore the mechanism of their chemotherapeutic effect, we studied their role in proliferation in the HCT116 human colon cancer cells. We correlated kinetic stability and cellular uptake data to their biological effects. Both bDMC and DAC impair correct spindles formation and induce a p53- and p21CIP1/WAF1-independent mitotic arrest, which is more stable and long-lasting for bDMC. A subsequent p53/p21CIP1/WAF1-dependent inhibition of G1 to S transition is triggered by Curcumin and DAC as a consequence of the mitotic slippage, preventing post-mitotic cells from re-entering the cell cycle. Conversely, the G1/S arrest induced by bDMC is a direct effect of the drug and concomitant to the mitotic block. Finally, we demonstrate that bDMC induces rapid DNA double-strand breaks, moving for its possible development in anti-cancer clinical applications.

Turmeric extracts, among which curcumin and bis-demethoxycurcumin, are by far known for their therapeutic activities. In this study we propose easy and low cost synthetic pathways in order to obtain glucosyl-curcuminoids, safe and water soluble potential drugs and dyes, which may be implied in different fields ranging from pharmacology to food chemistry. The complete (1)H and (13)C NMR characterization of naturally occurring curcumin, bis-demethoxycurcumin and new synthetic glucosyl-curcuminoids is reported.

The main target of this study is a high-level computational analysis of Curcumin, employing DFT approach with two different sets of basis functions (B3LYP/6-31G ∗ and B3LYP/6-311G ∗∗ ). Accurate quantum mechanical studies, both in vacuum and in methanol medium, are carried out with the aim to analyze the conformational equilibria, to find the most stable equilibrium structure and to define the nature of the molecular orbitals, fundamental to explain Curcumin binding characteristic. Our theoretical calculations, performed at B3LYP/6-31G ∗ and B3LYP/6-311G ∗∗ levels both in vacuum and in methanol medium, confirm that the keto-enolic forms are more stable than the di-keto one, whose extremely low population suggests that this structure should not influence Curcumin properties. Keto-enolic form C results the most stable, independently on calculation level and solvent (methanol) effect. HOMO and LUMO molecular orbitals are calculated for all the structures with the two sets of basis with very similar results. MEPs show that the negative charge is localized on the oxygen atoms, which, in the keto-enolic forms, point in the same direction enabling metal coordination. NMR, UV–vis and FT-IR experimental data are employed in the comparison with electronic and conformational properties of Curcumin resulting from theoretical calculations. The two different calculation levels (B3LYP/6-31G ∗ and B3LYP/6-311G ∗∗ ) give very similar results. Good linear correlations between the experimental 1 H and 13 C NMR chemical shifts ( δ exp ), in methanol- d 4 (MeOD) and DMSO- d 6 (DMSO), and calculated magnetic isotropic shielding tensors ( σ calc ) are found ( δ exp = a · σ calc + b ). A good prediction of UV–vis experimental maximum absorption ( λ max ) on the basis of conformer populations is obtained. A linear relation with a good correlation coefficient is observed plotting the FT-IR experimental wavenumbers vs . the calculated ones, allowing to predict FT-IR spectra.

A solution study on the ability of some derivatised sugars [glucuronic acid (GluA), galacturonic acid (GalA) and glucosaminic acid (GlNA)] to complex the Hg(II) ion is reported. The stability constants of the complex species were determined by potentiometric measurements while 1H NMR experiments allow to define the coordination sites of sugar molecules. GluA coordinates the metal ion through the carboxylic oxygen and the O-4 hydroxyl group and is found to form more stable complexes with respect to GalA in which metal ligation is from the carboxylic oxygen and the O-5 ring oxygen. GlNA forms stable complexes chelating Hg(II) ion through carboxylic oxygen and the α-amino group. The ternary 2,2′-bipyridine containing systems were also investigated by means of potentiometric studies. The ML2 complexes were also isolated in the solid state and characterised by IR spectroscopy.