Mária Balog

Synthesis of N-substituted 3,5-bis(arylidene)-4-piperidones with high antitumor and antioxidant activity.

A series of 3,5-bis(arylidene)-4-piperidone (DAP) compounds are considered as synthetic analogues of curcumin for anticancer properties. We performed structure-activity relationship studies by synthesizing a number of DAPs N-alkylated or acylated with nitroxides or their amine precursors as potent antioxidant moieties. Both subtituents on arylidene rings and on piperidone nitrogen (five- or six-membered, 2- or 3-substituted or 3,4-disubstituted isoindoline nitroxides) were varied. The anticancer efficacy of the new DAP compounds was tested by measuring their cytotoxicity to cancer cell lines A2780 and MCF-7 and to the H9c2 cell line. The results showed that all DAP compounds induced a significant loss of cell viability in the human cancer cell lines tested; however, only pyrroline appended nitroxides (5c (Selvendiran, K.; Tong, L.; Bratasz, A.; Kuppusamy, L. M.; Ahmed, S.; Ravi, Y.; Trigg, N. J.; Rivera, B. K.; Kálai, T.; Hideg, K.; Kuppusamy, P. Mol. Cancer Ther. 2010, 9, 1169-1179), 5e, 7, 9) showed limited toxicity toward noncancerous cell lines. Computer docking simulations support the biological activity tested. These results suggest that antioxidant-conjugated DAPs will be useful as a safe and effective anticancer agent for cancer therapy.

New Poly(ADP-ribose) Polymerase-1 Inhibitors with Antioxidant Activity Based on 4-Carboxamidobenzimidazole-2-ylpyrroline and -tetrahydropyridine Nitroxides and Their Precursors

4-Carboxamidobenzimidazoles were previously described as PARP inhibitor compounds. Here we report upon 4-carboxamido-1H-benzimidazoles substituted in the 2-position with nitroxides or their amine or hydroxylamine precursors. Among the new molecules, a highly active PARP inhibitor 4h (IC(50) = 14 nM) was identified with antioxidant/radical scavenger activity. We concluded that in most cases sterically hindered amines are better PARP inhibitors than their oxidized form and structural changes in the 2-substituted 4-carboxamido-1H-benzimidazoles (such as N-substitution or changing the position of the carboxamide group) were detrimental to PARP inhibition activity but not to antioxidant activity. These results indicate the advantages of combining an antioxidant nitroxide or nitroxide precursor with a PARP inhibitor molecule to decrease or eliminate the deleterious processes initiated by reactive oxygen and reactive nitrogen species (ROS and RNS). The radical scavenging capability of 4h was demonstrated by EPR study of urine collected after drug administration.

Synthesis and functional survey of new Tacrine analogs modified with nitroxides or their precursors

A series of new Tacrine analogs modified with nitroxides or pre-nitroxides on 9-amino group via methylene or piperazine spacers were synthesized; the nitroxide or its precursors were incorporated into the Tacrine scaffold. The new compounds were tested for their hydroxyl radical and peroxyl radical scavenging ability, acetylcholinesterase inhibitor activity and protection against Aβ-induced cytotoxicity. Based on these assays, we conclude that Tacrine analogs connected to five and six-membered nitroxides via piperazine spacers (9b, 9b/HCl and 12) exhibited the best activity, providing direction for further development of additional candidates with dual functionality (anti Alzheimers and antioxidant).

Induction of mitochondrial destabilization and necrotic cell death by apolar mitochondria-directed SOD mimetics.

In this paper, we present evidence, for the first time, that increasing the lipophilicity of mitochondria targeting SOD mimetics reverses their cytoprotective properties, destabilizing the mitochondrial membrane system and promoting cell death. A new mitochondria-directed apolar SOD mimetic, HO-3814, was found to provoke mitochondrial swelling and loss of mitochondrial membrane potential, and these effects were not inhibited by cyclosporine A. HO-3814-induced cell death was predominantly necrotic, caspase-independent, and not affected by mitochondrial permeability transition inhibitors or cyclophilin D-suppression, inhibitors of mitogen-activated protein kinases or Akt, or various antioxidants. In contrast, Bcl-2 overexpression diminished the effects of HO-3814.

Synthesis and biological evaluation of curcumin-nitroxide-based molecular hybrids as antioxidant and anti-proliferative agents

BACKGROUND Natural products and their derivatives are widely used to treat cancer and other diseases associated with ROS- and RNS-induced damages. METHODS A series of paramagnetic modified curcumin analogs and 3,5-diarylidene-piperidones (DAP) have been designed, synthesized, and characterized on their anti-proliferative and antioxidant activity. RESULTS Biological characterization of the new compounds supported the earlier results that incorporation of a nitroxide moiety or its precursor into curcumin or diarylidenylpiperidone (DAP) scaffolds resulted in anti-proliferative effect toward cancerous cell-lines in case of aryl hydroxy and/or methoxy substituent containing derivatives, suggesting their potential for targeted therapeutic applications. In case of basic side chain derivatives, nitroxide incorporation gave unambiguous results, however in tendency the more accessible DAP derivatives had stronger anti-proliferative effect. In most cases, the nitroxide incorporation increased the TEAC value (proton and electron donation capability) of DAP derivatives. CONCLUSIONS Among the compounds synthesized and investigated the spin-labeled curcumin and 3,5-bis(4-hydroxy-3-methoxybenzylidene)piperidin-4-one derivatives were the most effective antiproliferative and antioxidant derivatives.

Synthesis of New Pyrroline Nitroxides with Ethynyl Functional Group

Abstract 3-Substituted and 3,4-disubstituted pyrroline nitroxides containing an ethynyl group or two ethynyl groups were achieved by the reaction of a paramagnetic aldehydes with dimethyl (1-diazo-2-oxopropyl)phosphonate (Bestmann–Ohira reagent). The new compounds containing an ethynyl group were found to be useful building blocks in Sonogashira coupling, cyclization, and cycloaddition reactions producing potentially “azido-specific” cross-linking spin labels, paramagnetic ligands, and polyradical scaffolds. GRAPHICAL ABSTRACT