Synthesis and Biological Evaluation of Novel Amino and Amido Substituted Pentacyclic Benzimidazole Derivatives as Antiproliferative Agents.

Newly designed pentacyclic benzimidazole derivatives featuring amino or amido side chains were synthesized to assess their in vitro antiproliferative activity. Additionally, we investigated their direct interaction with nucleic acids, aiming to uncover potential mechanisms of biological action. These compounds were prepared using conventional organic synthesis methodologies alongside photochemical and microwave-assisted reactions. Upon synthesis, the newly derived compounds underwent in vitro testing for their antiproliferative effects on various human cancer cell lines. Notably, derivatives 6 and 9 exhibited significant antiproliferative activity within the submicromolar concentration range. The biological activity was strongly influenced by the N atom's position on the quinoline moiety and the position and nature of the side chain on the pentacyclic skeleton. Findings from fluorescence, circular dichroism spectroscopy, and thermal melting assays pointed toward a mixed binding mode-comprising intercalation and the binding of aggregated compounds along the polynucleotide backbone-of these pentacyclic benzimidazoles with DNA and RNA.

Synthesis and Biological Activity of 2-Benzo[b]thienyl and 2-Bithienyl Amidino-Substituted Benzothiazole and Benzimidazole Derivatives.

Novel benzo[b]thienyl- and 2,2'-bithienyl-derived benzothiazoles and benzimidazoles were synthesized to study their antiproliferative and antitrypanosomal activities in vitro. Specifically, we assessed the impact that amidine group substitutions and the type of thiophene backbone have on biological activity. In general, the benzothiazole derivatives were more active than their benzimidazole analogs as both antiproliferative and antitrypanosomal agents. The 2,2'-bithienyl-substituted benzothiazoles with unsubstituted and 2-imidazolinyl amidine showed the most potent antitrypanosomal activity, and the greatest selectivity was observed for the benzimidazole derivatives bearing isopropyl, unsubstituted and 2-imidazolinyl amidine. The 2,2'-bithiophene derivatives showed most selective antiproliferative activity. Whereas the all 2,2'-bithienyl-substituted benzothiazoles were selectively active against lung carcinoma, the benzimidazoles were selective against cervical carcinoma cells. The compounds with an unsubstituted amidine group also produced strong antiproliferative effects. The more pronounced antiproliferative activity of the benzothiazole derivatives was attributed to different cytotoxicity mechanisms. Cell cycle analysis, and DNA binding experiments provide evidence that the benzimidazoles target DNA, whereas the benzothiazoles have a different cellular target because they are localized in the cytoplasm and do not interact with DNA.

Biological Activity of Newly Synthesized Benzimidazole and Benzothizole 2,5-Disubstituted Furane Derivatives.

Newly designed and synthesized cyano, amidino and acrylonitrile 2,5-disubstituted furane derivatives with either benzimidazole/benzothiazole nuclei have been evaluated for antitumor and antimicrobial activity. For potential antitumor activity, the compounds were tested in 2D and 3D cell culture methods on three human lung cancer cell lines, A549, HCC827 and NCI-H358, with MTS cytotoxicity and BrdU proliferation assays in vitro. Compounds 5, 6, 8, 9 and 15 have been proven to be compounds with potential antitumor activity with high potential to stop the proliferation of cells. In general, benzothiazole derivatives were more active in comparison to benzimidazole derivatives. Antimicrobial activity was evaluated with Broth microdilution testing (according to CLSI (Clinical Laboratory Standards Institute) guidelines) on Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. Additionally, Saccharomyces cerevisiae was included in testing as a eukaryotic model organism. Compounds 5, 6, 8, 9 and 15 showed the most promising antibacterial activity. In general, the compounds showed antitumor activity, higher in 2D assays in comparison with 3D assays, on all three cell lines in both assays. In natural conditions, compounds with such an activity profile (less toxic but still effective against tumor growth) could be promising new antitumor drugs. Some of the tested compounds showed antimicrobial activity. In contrast to ctDNA, the presence of nitro group or chlorine in selected furane-benzothiazole structures did not influence the binding mode with AT-DNA. All compounds dominantly bound inside the minor groove of AT-DNA either in form of monomers or dimer and higher-order aggregates.

Novel amino substituted tetracyclic imidazo[4,5-b]pyridine derivatives: Design, synthesis, antiproliferative activity and DNA/RNA binding study.

A novel series of tetracyclic imidazo[4,5-b]pyridine derivatives was designed and synthesized as potential antiproliferative agents. Their antiproliferative activity against human cancer cells was influenced by the introduction of chosen amino side chains on the different positions on the tetracyclic skeleton and particularly, by the position of N atom in the pyridine nuclei. Thus, the majority of compounds showed improved activity in comparison to standard drug etoposide. Several compounds showed pronounced cytostatic effect in the submicromolar range, especially on HCT116 and MCF-7 cancer cells. The obtained results have confirmed the significant impact of the position of N nitrogen in the pyridine ring on the enhancement of antiproliferative activity, especially for derivatives bearing amino side chains on position 2. Thus, regioisomers 6, 7 and 9 showed noticeable enhancement of activity in comparison to their counterparts 10, 11 and 13 with IC50 values in a nanomolar range of concentration (0.3-0.9 µM). Interactions with DNA (including G-quadruplex structure) and RNA were influenced by the position of amino side chains on the tetracyclic core of imidazo[4,5-b]pyridine derivatives and the ligand charge. Moderate to high binding affinities (logKs = 5-7) obtained for selected imidazo[4,5-b]pyridine derivatives suggest that DNA/RNA are potential cell targets.

Design, synthesis, antitrypanosomal activity, DNA/RNA binding and in vitro ADME profiling of novel imidazoline-substituted 2-arylbenzimidazoles.

Novel imidazoline benzimidazole derivatives containing diversely substituted phenoxy moieties were synthesized with the aim of evaluating their antitrypanosomal activity, DNA/RNA binding affinity and in vitro ADME properties. The presence of the diethylaminoethyl subunit in 18a-18c led to enhanced antitrypanosomal potency, particularly for 18a and 18c, which contain unsubstituted and methoxy-substituted phenoxy moieties. They were found to be > 2-fold more potent against African trypanosomes than nifurtimox. Fluorescence and CD spectroscopy, thermal denaturation assays and computational analysis indicated a preference of 18a-18c toward AT-rich DNA and their minor groove binding mode. Replacement of the amidine group with less basic and ionisable nitrogen-containing moieties failed to improve membrane permeability of the investigated compounds. Due to structural diversification, the compounds displayed a range of physico-chemical features resulting in variable in vitro ADME properties, leaving space for further optimization of the biological profiles.

Synthesis, DNA/RNA-interaction and biological activity of benzo[k,l]xanthene lignans.

Interactions of two newly synthesized and six previously reported benzoxanthene lignans (BXLs), analogues of rare natural products, with DNA/RNA, G-quadruplex and HSA were evaluated by a set of spectrophotometric methods. Presence/absence of methoxy and hydroxy groups on the benzoxanthene core and minor modifications at C-1/C-2 side pendants - presence/absence of phenyl ring and presence/absence of methoxy and hydroxy groups on phenyl ring - influenced the fluorescence changes and the binding strength to double-stranded (ds-) and G-quadruplex structures. In general, compounds without phenyl ring showed stronger fluorescence changes upon binding than phenyl-substituted BXLs. On the other hand, BXLs with an unsubstituted phenyl ring showed the best stabilization effects of G-quadruplex. Circular dichroism spectroscopy results suggest mixed binding mode, groove binding and partial intercalation, to ds-DNA/RNA and end-stacking to top or bottom G-tetrads as the main binding modes of BXLs to those targets. All compounds exhibited micromolar binding affinities toward HSA and an increased protein thermal stability. Moderate to strong antiradical scavenging activity was observed for all BXLs with hydroxy groups at C-6, C-9 and C-10 positions of the benzoxanthene core, except for derivative bearing methoxy groups at these positions. BXLs with unsubstituted or low-substituted phenyl ring and one derivative without phenyl ring showed strong growth inhibition of Gram-positive Staphylococcus aureus. All compounds showed moderate to strong tumor cell growth-inhibitory activity and cytotoxicity.

Synthesis, antiproliferative activity and DNA/RNA-binding properties of mono- and bis-(1,2,3-triazolyl)-appended benzimidazo[1,2-a]quinoline derivatives.

The three series of 5-mono- and 2,5-bis-1,2,3-triazolyl-substituted benzimidazo[1,2-a]quinolines as potential antitumor agents were synthesized. Their growth-inhibitory activity is influenced by the introduction of fluorine at C-2 and the mono-triazolyl nuclei at C-5 of the tetracyclic skeleton, particularly if the 1,2,3-triazole moiety contains a short aliphatic side-chain. Thus, the chloropropyl side-chain in all three series had the highest impact on the inhibitory effect. 1,2,3-Triazolyl-2-fluorobenzimidazo[1,2-a]quinoline conjugates 8a and 8b with 3-chloropropyl and 2-hydroxyethyl substituents, respectively, exhibited the most pronounced cytostatic effect on colon cancer (HCT116) cells in the submicromolar range. The compound 8a emerged as the most promising candidate because of its higher potency and some selectivity in the non-tumor aneuploid immortal keratinocyte (HaCaT) cells. Fluorescence and CD spectroscopy, as well as the thermal denaturation assays, revealed moderate to high DNA/RNA binding affinities of the selected compounds and identified intercalation as a dominant binding mode to both polynucleotides. However, results of intracellular distribution assay in human lung carcinoma (H460) cells suggest that both 8a and 8b do not target nuclear DNA and that their non-specific cytotoxic effect may be attributed to the damage of intercellular membranes.

DNA/RNA recognition controlled by the glycine linker and the guanidine moiety of phenanthridine peptides.

The binding of four phenanthridine-guanidine peptides to DNA/RNA was evaluated via spectrophotometric/microcalorimetric methods and computations. The minor structural modifications-the type of the guanidine group (pyrrole guanidine (GCP) and arginine) and the linker length (presence or absence of glycine)-greatly affected the conformation of compounds and consequently the binding to double- (ds-) and single-stranded (ss-) polynucleotides. GCP peptide with shorter linker was able to distinguish between RNA (A-helix) and DNA (B-helix) by different circular dichroism response at 295 nm and thus can be used as a chiral probe. Opposed to the dominant stretched conformation of GCP peptide with shorter linker, the more flexible and longer linker of its analogue enabled the molecule to adopt the intramolecularly stacked form which resulted in weaker yet selective binding to DNA. Beside efficient organization of ss-polynucleotide structures, GCP peptide with shorter linker bound stronger to ss-DNA/RNA compared to arginine peptides which emphasize the importance of GCP unit.

Specific and highly efficient condensation of GC and IC DNA by polyaza pyridinophane derivatives.

Two bis-polyaza pyridinophane derivatives and their monomeric reference compounds revealed strong interactions with ds-DNA and RNA. The bis-derivatives show a specific condensation of GC- and IC-DNA, which is almost two orders of magnitude more efficient than the well-known condensation agent spermine. The type of condensed DNA was identified as ψ-DNA, characterized by the exceptionally strong CD signals. At variance to the almost silent AT(U) polynucleotides, these strong CD signals allow the determination of GC-condensates at nanomolar nucleobase concentrations. Detailed thermodynamic characterisation by ITC reveals significant differences between the DNA binding of the bis-derivative compounds (enthalpy driven) and that of spermine and of their monomeric counterparts (entropy driven). Atomic force microscopy confirmed GC-DNA compaction by the bis-derivatives and the formation of toroid- and rod-like structures responsible for the ψ-type pattern in the CD spectra.

1-ethyl-3-(6-methylphenanthridine-8-il) urea modulates TLR3/9 activation and induces selective pro-inflammatory cytokine expression in vitro.

We have previously demonstrated the nucleic acid binding capacity of phenanthridine derivatives (PHTs). Because nucleic acids are potent inducers of innate immune response through Toll-like receptors (TLRs), and because PTHs bear a structural resemblance to commonly used synthetic ligands for TLR7/8, we hypothesized that PHTs could modulate/activate immune response. We found that compound M199 induces secretion of IL-6, IL-8 and TNFα in human PBMCs and inhibits TLR3/9 activation in different cellular systems (PBMCs, HEK293 and THP-1 cell lines).

Discovery of 'click' 1,2,3-triazolium salts as potential anticancer drugs.

BACKGROUND: In order to increase the effectiveness of cancer treatment, new compounds with potential anticancer activities are synthesized and screened. Here we present the screening of a new class of compounds, 1-(2-picolyl)-, 4-(2-picolyl)-, 1-(2-pyridyl)-, and 4-(2-pyridyl)-3-methyl-1,2,3-triazolium salts and 'parent' 1,2,3-triazole precursors. METHODS: Cytotoxic activity of new compounds was determined by spectrophotometric MTT assay on several tumour and one normal cell line. Effect of the selected compound to bind double stranded DNA (ds DNA) was examined by testing its influence on thermal stability of calf thymus DNA while its influence on cell cycle was determined by flow cytometric analysis. Generation of reactive oxygen species (ROS) was determined by addition of specific substrate 5-(and-6)-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate, acetyl ester (CM-H2DCFDA). RESULTS: Parent triazoles were largely inactive, while some of the triazolium salts were highly cytotoxic for HeLa cells. Triazolium salts exhibited high cell-type dependent cytotoxicity against different tumour cells. Selected compound (4-(4-methoxyphenyl)-3-methyl-1-(2-picolyl)-1H-1,2,3-triazolium hexafluorophosphate(V) (2b) was significantly more cytotoxic against tumour cells than to normal cells, with very high therapeutic index 7.69 for large cell lung carcinoma H460 cells. Additionally, this compound was similarly cytotoxic against parent laryngeal carcinoma HEp-2 cells and their drug resistant 7T subline, suggesting the potential of this compound in treatment of drug resistant cancers. Compound 2b arrested cells in the G1 phase of the cell cycle. It did not bind ds DNA, but induced ROS in treated cells, which further triggered cell death. CONCLUSIONS: Our results suggest that the 'click' triazolium salts are worthy of further investigation as anti-cancer agents.

Advances in Peptide-based DNA/RNA-Intercalators.

Interactions between DNA/RNA and huge variety of peptides are quite common in nature, controlling vast number of processes. Also, there are several naturally occurring small molecules which contain peptide and DNA intercalator in structure, whereby their biological activity is based on synergistic interactions of both components; for instance bis-intercalator echinomycin. Versatility of synthetic approaches to short peptides allowed their usage as simple recognition units within the DNA or RNA grooves or as backbone carriers for variety of bioactive substituents attached to amino acid side chains, one of very popular examples being PNAs. Such peptide-backbones were also used for synthesis of novel intercalators and poly-intercalators, many of them showing intriguing novel DNA/RNA interacting properties.

Molecular recognition of AT-DNA sequences by the induced CD pattern of dibenzotetraaza[14]annulene (DBTAA)-adenine derivatives.

An investigation of the interactions of two novel and several known DBTAA-adenine conjugates with double-stranded DNA and RNA has revealed the DNA/RNA groove as the dominant binding site, which is in contrast to the majority of previously studied DBTAA analogues (DNA/RNA intercalators). Only DBTAA-propyladenine conjugates revealed the molecular recognition of AT-DNA by an ICD band pattern > 300 nm, whereas significant ICD bands did not appear for other ds-DNA/RNA. A structure-activity relation for the studied series of compounds showed that the essential structural features for the ICD recognition are a) the presence of DNA-binding appendages (adenine side chain and positively charged side chain) on both DBTAA side chains, and b) the presence of a short propyl linker, which does not support intramolecular aromatic stacking between DBTAA and adenine. The observed AT-DNA-ICD pattern differs from previously reported ss-DNA (poly dT) ICD recognition by a strong negative ICD band at 350 nm, which allows for the dynamic differentiation between ss-DNA (poly dT) and coupled ds-AT-DNA.

Interactions with polynucleotides and antitumor activity of amidino and imidazolinyl substituted 2-phenylbenzothiazole mesylates.

Based on previously reported antiproliferative activity screening, four most promising disubstituted 2-phenylbenzothiazole hydrochlorides were chosen for detailed study. Water solubility, as well as liphophilicity/hydrophilicity balance of organic core were modified by conversion to mesylate salts. For purpose of structure/activity studies their structures were determined by X-ray structure analysis. Detailed analysis of interactions of new compounds with double stranded (ds-) DNA/RNA by UV/Vis and CD titrations, thermal melting and viscometry experiments revealed that most of studied compounds intercalate into ds-RNA but bind into minor groove of AT-DNA, and agglomerate along GC-DNA. Furthermore, compounds also interact with ss-RNA, but only amino-imidazolinyl 2-phenylbenzothiazole, 4b displayed well defined orientation and dominant binding mode (by induced CD signals) with poly A and poly G. Besides, in vitro investigations revealed moderate to high antiproliferative activity of benzothiazoles against seven human cancer cell lines, while in some cases (HTC 116, SW620, MIA PaCa-2) high correlation between the type of the amidino group and cytotoxic activity was observed.

The dicationic derivatives of DBTAA: Interactions with DNA/RNA and antiproliferative effects on human cell lines.

Three dibenzotetraaza[14]annulenes non-covalently interacted with double-stranded DNA and RNA by mixed minor groove and/or intercalative binding mode. Observed interactions were strongly dependent on the steric exposure of positive charges and the length of the linkers of studied compounds as well as on the secondary structure and basepair composition of DNA/RNA. Compound 2 showed pronounced selectivity toward dA-dT-rich sequences and binding mode switch from dominant minor groove binding to ds-DNA to dominant intercalation into ds-RNA. Antiproliferative effect of studied compounds on human tumor and normal cell lines was in good agreement with the strength of observed interactions with DNA/RNA.