Synthesis and Cytotoxicity of Some Imidazo[4,5‐ b ]pyridine Derivatives and Their Regioselective N ‐Alkylation

Synthesis of some new 2-(substituted-phenyl)imidazo[4,5-c] and [4,5-b]pyridine derivatives and their antimicrobial activities

The synthesis of 5H-imidazo[4,5-c]pyridines analogues (1a - 1h) and 4H-imidazo[4,5-b]pyridines (3a - 3c) was achieved by reacting 3,4-diaminopyridine or 2,3-diaminopyridine with Na2S2O5 adduct of corresponding benzaldehydes (a1 - a8). Alkylation of compounds (1a - 1h) and (3a - 3c) using 4-chlorobenzyl and /or butyl bromide under basic conditions (K2CO3, DMF) predominantly resulted in the formation of N5 regioisomers (2a - 2l) and N4,3 regioisomers (4a - 4c1,2), respectively. The N5,4,3-regioisomeric structures were confirmed using 2D-NOESY (Nuclear Overhauser Effect Spectroscopy) and HMBC (Heteronuclear Multiple Bond Correlation) spectra. The antibacterial and antifungal activities of the synthesized compounds (2a - 2g, 4a - 5d) were evaluated in vitro against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Methicillin resistant S. aureus, Enterococcus faecalis and Candida albicans, Candida parapsilosis. Among the synthesized compounds, promising activities were observed with compounds 2g, 2h, 4a and 4b with lowest MIC values (4-8 µg/mL). The compounds 2i, 2j, 2k, 2l showed moderate activity. Additionally, a computational approach (ADMETlab 2.0) was used to evaluate the drug likeness properties of the compounds.

The evaluation of the anti-cancer effects of Anoectochilus roxburghii on hematological cancers in vitro

The cause of hematological cancers is the uncontrolled proliferation of hematopoietic and lymphoid tissues, and chemotherapy is used to treat cancer. However, adverse side effects of chemotherapy are common. Therefore, the use of plant extracts as a method for treating cancer is becoming increasingly popular. Anoectochilus roxburghii (wall.) Lindl. (A. roxburghii) is one of the original sources of the valuable medicinal plants known as the king medicine and the golden grass. This study investigated the potential anticancer effect of A. roxburghi (AR) on JURKAT, MM1S, THP1 and U266 cells. To test the cytotoxic and apoptotic effects of AR, hematological cancer cells were exposed to increasing doses of AR (0.1-0.5 µg/µl). The spectrophotometric MTT assay and the flow cytometric Annexin V staining were used to examine the viability and apoptosis of the cells, respectively. qRT-PCR was used to determine the expression levels of the apoptosis-related genes BAD, BAX, BIM and BCL-2. Our results show that AR treatment decreased cell viability and induced apoptosis in each cell line. Our RT-PCR data showed that AR significantly increased the expression levels of the pro-apoptotic BAX gene in JURKAT and MM1S cells, whereas it significantly increased the expression levels of both BAX and BIM in U266 cells. This is the first study to investigate how AR modulates apoptosis in hematological cancer cells. As a result, AR therapy may be a promising treatment modality for the treatment of cancer.

Exploring Antimicrobial Features for New Imidazo[4,5-b]pyridine Derivatives Based on Experimental and Theoretical Study

5-bromopyridine-2,3-diamine reacted with benzaldehyde to afford the corresponding 6-Bromo-2-phenyl-3H-imidazo[4,5-b]pyridine (1). The reaction of the latter compound (1) with a series of halogenated derivatives under conditions of phase transfer catalysis solid–liquid (CTP) allows the isolation of the expected regioisomers compounds (2–8). The alkylation reaction of (1) gives, each time, two regioisomers, N3 and N4; in the case of ethyl bromoactate, the reaction gives, at the same time, the three N1, N3 and N4 regioisomers. The structures of synthesized compounds were elucidated on the basis of different spectral data (1H NMR, 13C NMR), X-Ray diffraction and theoretical study using the DFT method, and confirmed for each compound. Hirshfeld surface analysis was used to determine the intermolecular interactions responsible for the stabilization of the molecule. Density functional theory was used to optimize the compounds, and the HOMO-LUMO energy gap was calculated, which was used to examine the inter/intra molecular charge transfer. The molecular electrostatic potential map was calculated to investigate the reactive sites that were present in the molecule. In order to determine the potential mode of interactions with DHFR active sites, the three N1, N3 and N4 regioisomers were further subjected to molecular docking study. The results confirmed that these analogs adopted numerous important interactions, with the amino acid of the enzyme being targeted. Thus, the most docking efficient molecules, 2 and 4, were tested in vitro for their antibacterial activity against Gram-positive bacteria (Bacillus cereus) and Gram-negative bacteria (Escherichia coli). Gram-positive bacteria were more sensitive to the action of these compounds compared to the Gram-negative, which were much more resistant.