Design, synthesis and evaluation of carbazole derivatives as PPAR alpha/gamma dual agonists and antioxidants

A new insight into the treatment of diabetes by means of pan PPAR agonists

PPARs stand for 'peroxisome proliferator-activated receptors' and are ligand-activated transcription factors of nuclear hormone receptor superfamily. A list of the most commonly used single receptor PPAR agonists, that is α (alpha) PPAR agonists, β/δ(beta/delta) PPAR agonists, γ(gamma) PPAR agonists, along with pan PPAR agents, that are being researched on, are marketed, are in clinical trials or are being studied for further derivative findings, has been listed. Type 2 diabetes constitutes about 90% of total diabetes cases. Pan PPAR ligands could very well pave the foundation for a new class of agents, that can act on all 3 PPAR receptors, and produce better effects in general, than the individual receptor-acting ligands or dual combination ligands (α/ γ). In this review paper, we have detailed various pan PPAR agonists that can be used to treat type 2 diabetes, which can generate potential derivatives as well.

Direct ortho-Selective Amination of 2-Naphthol and Its Analogues with Hydrazines

Described herein is a regioselective ortho-amination of 2-naphthol and its analogues with substituted hydrazines. It provides a direct methodology for the synthesis of N-arylaminated naphthol derivatives without the formation of related 1,1'-biaryl-2,2'-diamine or carbazole byproducts. Specifically, using N, N-disubstituted hydrazine precursors, N-unsubstituted ortho-aminated derivatives and related secondary amines can be formed in ethylene glycol in moderate to excellent yields. Variation of substrates to N, N'-diarylhydrazines and N-methyl- N, N'-diarylhydrazines led to N-aryl-1-amino-2-naphthol compounds. It is noted that biologically interesting indazole motifs can be facilely created by the reaction of N, N'-dialkylhydrazines with 2-naphthols. These ortho-amination reactions have the advantage of one-pot operation without the use of transition metal catalysts.

Investigations on Binding Pattern of Kinase Inhibitors with PPARγ: Molecular Docking, Molecular Dynamic Simulations, and Free Energy Calculation Studies

Peroxisome proliferator-activated receptor gamma (PPARγ) is a potential target for the treatment of several disorders. In view of several FDA approved kinase inhibitors, in the current study, we have investigated the interaction of selected kinase inhibitors with PPARγ using computational modeling, docking, and molecular dynamics simulations (MDS). The docked conformations and MDS studies suggest that the selected KIs interact with PPARγ in the ligand binding domain (LBD) with high positive predictive values. Hence, we have for the first time shown the plausible binding of KIs in the PPARγ ligand binding site. The results obtained from these in silico investigations warrant further evaluation of kinase inhibitors as PPARγ ligands in vitro and in vivo.

TFAA/H3PO4 mediated unprecedented N-acylation of carbazoles leading to small molecules possessing anti-proliferative activities against cancer cells

For the first time TFAA/H3PO4 has facilitated the direct and metal-free N-acylation of carbazoles leading to a number of N-acylated derivatives. Several of these compounds were found to be promising when tested for their anti-proliferative properties against oral cancer cell lines.

Pro-oxidant effects of phenothiazine and phenoxazine on erythrocytes in the presence of peroxyl radical

Phenothiazine (PtzNH) and phenoxazine (PozNH) can protect human erythrocytes against hemolysis induced by 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH), a peroxyl radical supplier. However, an antioxidant may be a pro-oxidant to accelerate the oxidation in the presence of radicals. The aim of this work is to assess whether PtzNH and PozNH have the potential to be pro-oxidants in AAPH-induced hemolysis of human erythrocytes. It has been found that high concentrations of PtzNH and PozNH employed were able to initiate hemolysis even in the absence of AAPH. In the presence of AAPH, the period of PtzNH and PozNH to lag hemolysis (t(lag)) decreased with the increase in the concentrations of PtzNH and PozNH, implicating that high concentration of PtzNH and PozNH accelerated hemolysis. So, PtzNH and PozNH played pro-oxidants' role in this case. Furthermore, high concentrations of AAPH employed made the pro-oxidant effect of PtzNH more remarkable. On the contrary, PozNH played a pro-oxidant role if only low concentration of AAPH was employed.

Palladium-catalyzed method for the synthesis of carbazoles via tandem C-H functionalization and C-N bond formation

The development of a new method for the assembly of unsymmetrical carbazoles is reported. The strategy involves the selective intramolecular functionalization of an arene C-H bond and the formation of a new arene C-N bond. The substitution pattern of the carbazole product can be controlled by the design of the biaryl amide substrate, and the method is compatible with a variety of functional groups. The utility of the new protocol was demonstrated by the concise synthesis of three natural products from commercially available materials.

Design and synthesis of 6-methyl-2-oxo-1,2,3,4-tetrahydro-pyrimidine-5-carboxylic acid derivatives as PPARγ activators

The design and synthesis of novel series of 6-methyl-2-oxo-1,2,3,4-tetrahydro-pyrimidine-5-carboxylic acid (pyrimidone) derivatives that are high affinity ligands for peroxisome proliferators activated receptor gamma have been reported as a potential substitute of 2,4-thiazolidinedione head group. The FlexX docking and radioligand binding affinity of some promising compounds of this series is comparable to that of thiazolidinedione based antidiabetic drugs currently in clinical use.

Synthesis and evaluation of N-acetyl-l-tyrosine based compounds as PPARα selective activators

The development of type 2 diabetes in obese individuals is linked to lipid accumulation in non-adipose tissues. A series of N-acetyl-L-tyrosine derivatives were synthesized and evaluated for PPAR transactivation. Compounds 4d and 4f were found to show better PPARalpha transactivation as compared to PPARgamma. Molecular docking analysis was carried out to study their important interactions with the active site of PPARalpha.

Free-radical-scavenging effect of carbazole derivatives on AAPH-induced hemolysis of human erythrocytes

Since the research on antioxidants provides theoretical information for the medicinal development, and supplies some in vitro methods for quick-optimizing drugs, it attracts more scientific attention from bioorganic and medicinal chemists. In addition to the traditional O-H bond-type antioxidant, carbazole and its related tricyclic amines (Ar2NHs), in which N-H bond functioned as the antioxidant, have attracted much research attention because Ar2NHs have always been the central structure in many currently used drugs. Thus, the investigation on the structure-activity relationship (SAR) between Ar2NHs and their free-radical-scavenging capacities in detail will benefit the development of novel radical-scavenging drugs containing Ar2NHs as the central structure. Therefore, carbazole (CazNH) and its structural analogues including phenoxazine (PozNH), phenothiazine (PtzNH), iminostilbene (IsbNH) together with diphenylamine (DpaNH) were applied to protect human erythrocytes against 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH)-induced hemolysis in vitro. By introducing the chemical kinetic formula related to free radical reaction, namely, the quantitative relationship between inhibition period (tinh) and the concentration of antioxidant (AH), tinh=(n/Ri)[AH], into AAPH-induced hemolysis, the values of stoichiometric factor (n) of Ar2NHs indicated that the free-radical-scavenging sequence of Ar2NHs is PozNH>DpaNH>CazNH>IsbNH>PtzNH >alpha-tocopherol (TocH). Another aim of this work was to investigate the antioxidative effect of Ar2NHs used together with other antioxidants including Trolox (TroH), VC, L-ascorbyl-6-laurate (VC-12), and TocH. The obtained data revealed that n value of PozNH when used together with all the other antioxidants decreases, whereas, n values of CazNH, DpaNH, IsbNH, and PtzNH when used in combination with TroH increase, demonstrating that two different interaction styles existed in the case of Ar(2)NHs used with other antioxidants. These findings may be useful for the development of agents for various ROS-mediated diseases in vivo.

Combining the rapid MTT formazan exocytosis assay and the MC65 protection assay led to the discovery of carbazole analogs as small molecule inhibitors of Abeta oligomer-induced cytotoxicity

The discovery of small molecule inhibitors of cytotoxicity induced by amyloid-beta (Abeta) oligomers, either applied extracellularly or accumulated intraneuronally, is an important goal of drug development for Alzheimer's disease (AD), but has been limited by the lack of efficient screening methods. Here we describe our approach using two cell-based methods. The first method takes advantage of the unique ability of extracellularly applied Abeta oligomers to rapidly induce the exocytosis of formazan formed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). We employed a short protocol to quantify this toxicity, and quickly identified two novel inhibitors, code-named CP2 and A5, from two compound libraries. A second independent screen of the same libraries using our previously published MC65 protection assay, which identifies inhibitors of toxicity related to intracellular Abeta oligomers, also selected the same two leads, suggesting that both assays select for the same anti-Abeta oligomer properties displayed by these compounds. We further demonstrated that A5 attenuated the progressive aggregation of existing Abeta oligomers, reduced the level of intracellular Abeta oligomers, and prevented the Abeta oligomer-induced death of primary cortical neurons, effects similar to those demonstrated by CP2. Our results suggest that, when combined, the two methods would generate fewer false results and give a high likelihood of identifying leads that show promises in ameliorating Abeta oligomer-induced toxicities within both intraneuronal and extracellular sites. Both assays are simple, suitable for rapid screening of a large number of medicinal libraries, and amenable for automation.