Lucas L. Franco

Evaluation of 8-Hydroxyquinoline Derivatives as Hits for Antifungal Drug Design

Abstract Clioquinol is an 8‐hydroxyquinoline derivative that was widely used from the 1950s to 1970s as an oral antiparasitic agent. In 1970, the oral forms were withdrawn from the market due to reports of toxicity, but topical formulations for antifungal treatment remained available. Thus, the purpose of this study was to evaluate the toxicity, anti‐Candida and antidermatophyte activity and to determine pharmacodynamic characteristics of clioquinol and other 8‐hydroxyquinoline derivatives (8‐hydroxy‐5‐quinolinesulfonic acid and 8‐hydroxy‐7‐iodo‐5‐quinolinesulfonic acid). Antifungal activity was tested by broth microdilution and the fungicidal or fungistatic effect was checked by a time‐kill assay. Permeation and histopathological evaluation were performed in Franz diffusion cells with ear skin of pigs and examined under light microscopy. An HET‐CAM test was used to determine the potential irritancy. The three compounds were active against all isolates showing anti‐Candida and antidermatophyte activity, with MIC ranges of 0.031‐2 &mgr;g/ml, 1‐512 &mgr;g/ml, and 2‐1024 &mgr;g/ml for clioquinol, 8‐hydroxy‐5‐quinolinesulfonic acid, and 8‐hydroxy‐7‐iodo‐5‐quinolinesulfonic acid, respectively. All compounds showed fungistatic effect for Candida, 8‐hydroxy‐5‐quinolinesulfonic acid, and 8‐hydroxy‐7‐iodo‐5‐quinolinesulfonic acid showed a fungicidal effect for M. canis and T. mentagrophytes, and clioquinol showed a fungicidal effect only for T. mentagrophytes. Furthermore, they presented a fungicidal effect depending on the time and concentration. The absence of lesions was observed in histopathological evaluation and no compound was irritating. Moreover, clioquinol and 8‐hydroxy‐5‐quinolinesulfonic acid accumulated in the epithelial tissue, and 8‐hydroxy‐7‐iodo‐5‐quinolinesulfonic acid had a high degree of permeation. In conclusion, 8‐hydroxyquinoline derivatives showed antifungal activity and 8‐hydroxy‐5‐quinolinesulfonic acid demonstrated the potential for antifungal drug design.

Schiff bases and their metal complexes as urease inhibitors – A brief review

Graphical abstract

SÍNTESE DE N-GLICOSILSULFONAMIDAS DERIVADAS DE D-GLICOSE E N-ACETILGLICOSAMINA

Herein, we report the synthesis of β-N-glycosylsulfonamides derivatives of D-glucose and N-acetylglucosamine using conventional methods. We also describe a procedure that allows the preparation of these compounds in good yields without the anomerization of the intermediate glycosylamines. This method includes the intermediates obtained from the less reactive 1- and 2-naphthalenesulfonyl chlorides.

Annonalide and derivatives: Semisynthesis, cytotoxic activities and studies on interaction of annonalide with DNA

The cytotoxic activity of the pimarane diterpene annonalide (1) and nine of its semisynthetic derivatives (2-10) was investigated against the human tumor cell lines HL-60 (leukemia), PC-3 (prostate adenocarcinoma), HepG2 (hepatocellular carcinoma), SF-295 (glioblastoma) and HCT-116 (colon cancer), and normal mouse fibroblast (L929) cells. The preparation of 2-10 involved derivatization of the side chain of 1 at C-13. Except for 2, all derivatives are being reported for the first time. Most of the tested compounds presented IC50s below 4.0 μM, being considered potential antitumor agents. The structures of all new compounds were elucidated by spectroscopic analyses including 2D NMR and HRMS. Additionally, the interaction of annonalide (1) with ctDNA was evaluated using spectroscopic techniques, and the formation of a supramolecular complex with the macromolecule was confirmed. Competition assays with fluorescent probes (Hoechst and ethidium bromide) and theoretical studies confirmed that 1 interacts preferentially via DNA intercalation with stoichiometric ratio of 1:1 (1:ctDNA). The ΔG value was calculated as -28.24 kJ mol-1, and indicated that the interaction process occurs spontaneously. Docking studies revealed that van der Walls is the most important interaction in 1-DNA and EB-DNA complexes, and that both ligands (1 and EB) interact with the same DNA residues (DA6, DA17 and DT19).

Neutron activation of In(III) complexes with thiosemicarbazones leads to the production of potential radiopharmaceuticals for the treatment of breast cancer

In(III) complexes [In(2Ac4oClPh)2]NO3 (1) and [In(2Ac4pFPh)2]NO3·1.5H2O (2) were obtained with N(4)-ortho-chlorophenyl-2-acetylpyridine thiosemicarbazone (H2Ac4oClPh) and N(4)-para-fluorophenyl-2-acetylpyridine thiosemicarbazone (H2Ac4pFPh). Neutron activation of complexes (1) and (2), and of previously prepared [In(2Ac4oClPh)Cl2(MeOH)] (3) and [In(2Ac4pFPh)Cl2(MeOH)] (4) resulted in the formation of 114mIn/115mIn analogues (*1–*4). The cytotoxic activities of the compounds under study were investigated on MCF-7 breast cancer cells as well as against non-malignant MRC-5 fibroblast cells. Upon coordination to In(III) the cytotoxicity against MCF-7 cells significantly increased in complexes (1–4), suggesting that complexation was a good strategy to improve the cytotoxic effect. While both non-radioactive and radioactive In(III) salts were inactive against MCF-7 cells, the radioactive complexes (*1–*4) proved to be 102 to 104 times more potent than the non-radioactive analogues (1–4). For the non-radioactive In(III) complexes (1–4) the selectivity indexes (SI), defined as IC50 MRC-5/IC50 MCF-7, were SI = 0.07–0.36, while high values of SI were found for the radioactive In(III) analogues (*1–*4), SI = 46–4716, indicating that irradiation represented an interesting strategy for increasing the selectivity. Since cytotoxicity was evaluated following 48 h of treatment and 72 h after neutron activation, the observed cytotoxic effects were attributed mainly to 114mIn, the contribution of the 115mIn (t1/2 = 4.5 h) isomer being considered irrelevant. Complexes (*1–*4) induced higher levels of intracellular ROS in MCF-7 cells in comparison to the parent compounds. The results suggest that 114mIn complexes with thiosemicarbazones might show potential for application as radiopharmaceuticals for the treatment of breast cancer.

Glycotriazole-peptides derived from the peptide HSP1: synergistic effect of triazole and saccharide rings on the antifungal activity

This work proposes a strategy that uses solid-phase peptide synthesis associated with copper(I)-catalyzed azide alkyne cycloaddition reaction to promote the glycosylation of an antimicrobial peptide (HSP1) containing a carboxyamidated C-terminus (HSP1-NH2). Two glycotriazole-peptides, namely [p-Glc-trz-G1]HSP1-NH2 and [p-GlcNAc-trz-G1]HSP1-NH2, were prepared using per-O-acetylated azide derivatives of glucose and N-acetylglucosamine in the presence of copper(II) sulfate pentahydrate (CuSO4·5H2O) and sodium ascorbate as a reducing agent. In order to investigate the synergistic action of the carbohydrate motif linked to the triazole-peptide structure, a triazole derivative [trz-G1]HSP1-NH2 was also prepared. A set of biophysical approaches such as DLS, Zeta Potential, SPR and carboxyfluorescein leakage from phospholipid vesicles confirmed higher membrane disruption and lytic activities as well as stronger peptide-LUVs interactions for the glycotriazole-peptides when compared to HSP1-NH2 and to its triazole derivative, which is in accordance with the performed biological assays: whereas HSP1-NH2 presents relatively low and [trz-G1]HSP1-NH2 just moderate fungicidal activity, the glycotriazole-peptides are significantly more effective antifungal agents. In addition, the glycotriazole-peptides and the triazole derivative present strong inhibition effects on ergosterol biosynthesis in Candida albicans, when compared to HSP1-NH2 alone. In conclusion, the increased fungicidal activity of the glycotriazole-peptides seems to be the result of (A) more pronounced membrane-disruptive properties, which is related to the presence of a saccharide ring, together with (B) the inhibition of ergosterol biosynthesis, which seems to be related to the presence of both the monosaccharide and the triazole rings.

5-Nitroimidazole-derived Schiff bases and their copper(II) complexes exhibit potent antimicrobial activity against pathogenic anaerobic bacteria

In the present work a family of novel secnidazole-derived Schiff base compounds and their copper(II) complexes were synthesized. The antimicrobial activities of the compounds were evaluated against clinically important anaerobic bacterial strains. The compounds exhibited in vitro antibacterial activity against Bacteroides fragilis, Bacteroides thetaiotaomicron, Bacteroides vulgatus, Bacteroides ovatus, Parabacteroides distasonis and Fusubacterium nucleatum pathogenic anaerobic bacteria. Upon coordination to copper(II) the antibacterial activity significantly increased in several cases. Some derivatives were even more active than the antimicrobial drugs secnidazole and metronidazole. Therefore, the compounds under study are suitable for in vivo evaluation and the microorganisms should be classified as susceptible to them. Electrochemical studies on the reduction of the nitro group revealed that the compounds show comparable reduction potentials, which are in the same range of the bio-reducible drugs secnidazole and benznidazole. The nitro group reduction potential is more favorable for the copper(II) complexes than for the starting ligands. Hence, the antimicrobial activities of the compounds under study might in part be related to intracellular bio-reduction activation. Considering the increasing resistance rates of anaerobic bacteria against a wide range of antimicrobial drugs, the present work constitutes an important contribution to the development of new antibacterial drug candidates.

Two Novel Donepezil-Lipoic Acid Hybrids: Synthesis, Anticholinesterase and Antioxidant Activities and Theoretical Studies

Alzheimer disease (AD) is a complex disease related to multiple pathogenic mechanisms. A strategy to develop effective drugs is based on the so-called multi-target directed ligands (MTDL) by using hybrid compounds. So, in the present study, we have designed and synthesized two hybrids, containing the indanone-piperidine moiety of donepezil, a drug approved for the treatment of AD, and the lipoic acid scaffold, an antioxidant compound endowed with neuroprotective effects. One hybrid was synthesized in four steps with 42% global yield, and the other hybrid in six steps with 19% global yield. The latter hybrid displayed moderate inhibitory activity against human acetylcholinesterase (hAChE) and greater activity against human butyrylcholinesterases (hBuChE). The selectivity for hBuChE was further rationalized by theoretical study. Importantly, the second hybrid showed a good antioxidant activity, exhibiting better ability in scavenging 2,2-diphenyl1-picrylhydrazyl (DPPH) radicals than lipoic acid.

ESTUDO DA GLICOSILAÇÃO DO CICLO-HEXANOL COM DIFERENTES DERIVADOS DE D-GLICOSAMINA E PROMOTORES DE GLICOSILAÇÃO PELO MÉTODO DE KOENIGS-KNORR

We report herein a study on the glycosylation of cyclohexanol with four D-glucosamine-based peracetylated glycosyl chlorides bearing different substituents at C-2 and three glycosylation promoters, silver carbonate, silver triflate and mercury II chloride/mercury II oxide, by the Koenigs-Knorr method. Under the conditions studied, glycosylation was successful only when 3,4,6-tri-O -acetyl-2-deoxy-2-phthalimido-α-D-glucopyranosyl chloride was used as the glycosyl donor, with silver carbonate proving the best promoter. In order to investigate the influence of the nature of the halogen at C-1, we also carried out the glycosylation of cyclohexanol with 3,4,6-tri-O -acetyl-2-deoxy-2-phthalimido-α-D-glucopyranosyl bromide, a more reactive glycosyl donor. As expected, the yield with the bromide derivative was higher with the three promoters and, again, silver carbonate was the most efficient promoter. Finally, to illustrate the well-known efficient procedure for conversion of the phtalimido group at C-2 to the corresponding acetamido group, cyclohexyl 3,4,6-tri-O -acetyl-2-deoxy-2-phtalimido-β-D-glucopyranoside was converted into cyclohexyl 2-deoxy-2-acetamido-β-D-glucopyranoside in two steps, namely, hydrazinolysis of the phtalimido group followed by chemoselective acetylation of the free amino group by treatment with acetic anhydride in methanol, at 77% overall yield.

SYNTHESIS OF D-GLUCOSE- ANDN-ACETYLGLUCOSAMINE-BASEDN-GLYCOSYLSULFONAMIDES

Herein, we report the synthesis of β-N-glycosylsulfonamides derivatives of D-glucose and N-acetylglucosamine using conventional methods. We also describe a procedure that allows the preparation of these compounds in good yields without the anomerization of the intermediate glycosylamines. This method includes the intermediates obtained from the less reactive 1- and 2-naphthalenesulfonyl chlorides.