Investigation of the effect of structure modification of furamidine on the DNA minor groove binding and antiprotozoal activity.

New analogs of the antiprotozoal agent Furamidine were prepared utilizing Stille coupling reactions and amidation of the bisnitrile intermediate using lithium bis-trimethylsilylamide. Both the phenyl groups and the furan moiety of furamidine were replaced by heterocycles including thiophene, selenophene, indole or benzimidazole. Based upon the ΔTm and the CD results, the new compounds showed strong binding to the DNA minor groove. The new analogues are also more active both in vitro and in vivo than furamidine. Compounds 7a, 7b, and 7f showed the highest activity in vivo by curing 75% of animals, and this merits further evaluation.

Synthesis and Evaluation of Novel DNA Minor Groove Binders as Antiamoebic Agents.

The free-living amoeba Acanthamoeba castellanii is responsible for the central nervous infection granulomatous amoebic encephalitis and sight-threatening infection Acanthamoeba keratitis. Moreover, no effective treatment is currently present, and a combination drug therapy is used. In this study, twelve DNA minor groove binders (MGBs) were synthesized and tested for their antiamoebic activity via amoebicidal, encystation, excystation, and cytopathogenicity assays. It was found that the compounds MGB3, MGB6, MGB22, MGB24, and MGB16 significantly reduce amoeba viability to 76.20%, 59.45%, 66.5%, 39.32%, and 43.21%, respectively, in amoebicidal assays. Moreover, the compounds MGB6, MGB20, MGB22, MGB28, MGB30, MGB32, and MGB16 significantly inhibit Acanthamoeba cysts, leading to the development of only 46.3%, 39%, 30.3%, 29.6%, 27.8%, 41.5%, and 45.6% cysts. Additionally, the compounds MGB3, MGB4, MGB6, MGB22, MGB24, MGB28, MGB32, and MGB16 significantly reduce the re-emergence of cysts to trophozoites, with viable trophozoites being only 64.3%, 47.3%, 41.4%, 52.9%, 55.4%, 40.6%, 62.1%, and 51.7%. Moreover, the compounds MGB3, MGB4, and MGB6 exhibited the greatest reduction in amoeba-mediated host-cell death, with cell death reduced to 41.5%, 49.4%, and 49.5%. With the following determined, future in vivo studies can be carried out to understand the effect of the compounds on animal models such as mice.

Triaryl dicationic DNA minor-groove binders with antioxidant activity display cytotoxicity and induce apoptosis in breast cancer.

Despite advances in cancer treatment modalities, DNA still stands as one of the targets for anticancer agents. DNA minor groove binders (MGBs) represent an important investigational chemotherapeutic class with promising cytotoxic capacity. Herein this study reports the potent cytotoxic effect of a series of repurposed flexible bis-imidamides 1-4, triaryl bis-guanidine 5 and bis-N-substituted guanidines 6,7 having a 1,4-diphenoxybenzene scaffold backbone on MCF-7 and MDA-MB-231 breast cancer cell lines. Of these compounds, imidamide 4 was chosen for further in-vitro, in-vivo and molecular dynamics (MD) studies owing to its promising anti-tumor activity, with IC50 values on MCF-7 and MDA-MB-231 breast cancer cell lines of 1.9 and 2.08 µM, respectively. Annexin V/propidium iodide apoptosis assay revealed apoptosis induction on imidamide 4 treated MCF-7 cells. RT-PCR assay results demonstrated the proapoptotic effect of compound 4 through increase of mRNA levels of the pro-apoptotic genes; p53, PUMA, and Bax, and inhibiting the anti-apoptotic Bcl-2 gene expression in MCF-7 cells. Moreover, compound 4 induced a G0/G1 cell-cycle arrest in MCF-7 in a dose-dependent manner. Corroborating in-vivo experiments on Ehrlich ascites carcinoma (EAC)-bearing mice, reflected the anticancer strength of derivative 4. For further target validation, molecular dynamics (MD) studies demonstrated an energetically favorable binding of imidamide 4 with the DNA minor groove AT rich site. In effect, imidamide 4 can be viewed as a promising hit dicationic compound with good cytotoxic and apoptotic inducing activity against breast cancer that can be adopted for future optimization.

Sulfated Ceria Catalyzed Synthesis of Imidazopyridines and Their Implementation as DNA Minor Groove Binders.

The small molecules that bind to DNA minor groove are considered as potential therapeutic agents to fight against many human diseases. They induce cell death by interfering with transcription, replication and progression of cell cycle. Herein, we report the synthesis of imidazopyridine-3-amines using sulfated ceria catalyst by employing Groebkee-Blackburne-Bienayme reaction. We evaluated the possible antiproliferative and antimycobacterial activity against A549 cells and Mycobacterium tuberculosis, respectively. Among the tested compounds, N-tert-butyl-2-(2-butyl-4-chloro-1H-imidazol-5-yl)-5,7-dimethylimidazo[1,2-a]pyridin-3-amine (4g) was identified as cytotoxic heterocycle and antimycobacterial agent. Molecular docking studies of the imidazopyridine derivatives revealed the consistent positioning in the minor groove with a tight shape fit between receptor and ligands. Therefore, we speculate that new imidazopyridines induce their pharmacological effect by targeting the minor groove of DNA.

Indole and Benzimidazole Bichalcophenes: Synthesis, DNA Binding and Antiparasitic Activity.

A novel series of indole and benzimidazole bichalcophene diamidine derivatives were prepared to study their antimicrobial activity against the tropical parasites causing African sleeping sickness and malaria. The dicyanoindoles needed to synthesize the target diamidines were obtained through Stille coupling reactions while the bis-cyanobenzimidazoles intermediates were made via condensation/cyclization reactions of different aldehydes with 4-cyano-1,2-diaminobenzene. Different amidine synthesis methodologies namely, lithium bis-trimethylsilylamide (LiN[Si(CH3)3]2) and Pinner methods were used to prepare the diamidines. Both types (indole and benzimidazole) derivatives of the new diamidines bind strongly with the DNA minor groove and generally show excellent in vitro antitrypanosomal activity. The diamidino-indole derivatives also showed excellent in vitro antimalarial activity while their benzimidazole counterparts were generally less active. Compound 7c was highly active in vivo and cured all mice infected with Trypanosoma brucei rhodesiense, a model that mimics the acute stage of African sleeping sickness, at a low dose of 4 × 5 mg/kg i.p. and hence 7c is more potent in vivo than pentamidine.

Exploration of DAPI analogues: Synthesis, antitrypanosomal activity, DNA binding and fluorescence properties.

The DAPI structure has been modified by replacing the phenyl group with substituted phenyl or heteroaryl rings. Twelve amidines were synthesized and their DNA binding, fluorescence properties, in vitro and in vivo activities were evaluated. These compounds are shown to bind in the DNA minor groove with high affinity, and exhibit superior in vitro antitrypanosomal activity to that of DAPI. Six new diamidines (5b, 5c, 5d, 5e, 5f and 5j) exhibit superior in vivo activity to that of DAPI and four of these compounds provide 100% animal cure at a low dose of 4 × 5 mg/kg i.p. in T. b. rhodesiense infected mice. Generally, the fluorescence properties of the new analogues are inferior to that of DAPI with the exception of compound 5i which shows a moderate increase in efficacy while compound 5k is comparable to DAPI.

Synthesis, DNA binding and antitrypanosomal activity of benzimidazole analogues of DAPI.

A series of novel benzimidazole diamidines were prepared from the corresponding dicyano analogues either by applying Pinner methodology (5a-c, 10 and 13a) or by making amidoximes intermediates that were reduced to the corresponding amidines (15a-c). The new amidines were evaluated in vitro against the protozoan parasite Trypanosoma brucei rhodesiense (T. b. r.). The thiophene analogue 5b and the N-methyl compound 15a showed superior antitrypanosomal activity compared to that of the parent I.

Isouronium and N-hydroxyguanidinium derivatives as Cell growth inhibitors: A comparative study.

Based on the results obtained from a computational study on the suitability of the isouronium and N-hydroxyguanidinium cations as hydrogen bond donors/acceptors, the DNA binding of a series of isouronium derivatives was assessed by DNA thermal denaturation experiments and compared to related N-hydroxyguanidines. Due to the poor DNA binding observed, the nature of the diaromatic linker was explored by preparing the corresponding amide-linked bis-isouronium derivative and measuring its DNA affinity. Next, the inhibitory effects of the isouronium derivatives on cell viability were evaluated in two different cancer cell lines providing IC50 values in the range of 36.9-57.4 µM (HL-60, leukemia), and 17.3-33.9 µM (Kelly, neuroblastoma). These values are comparable to those previously found for the N-hydroxyguanidine series. Compounds with the -S- linker (3, 6, and 10) proved to be considerably active in the HL-60 cells and even more active in the Kelly cell line. No correlation was found between DNA minor groove binding and cell growth inhibition; hence, activity may depend on different modes of action. Further studies into the apoptotic potential of these compounds indicated that, besides inhibiting cell viability and proliferation, derivatives 9 and 10, are significant apoptosis-inducers in both cell lines. Results obtained with HL-60 cells suggest that G2/M arrest and subsequent apoptosis induced by compound 10 are associated with microtubular depolymerisation, loss of mitochondrial membrane potential and activation of the caspase cascade. Moreover, the effects of compound 10 on cell viability and apoptosis in two non-cancereous cell lines (NIH3T3 and MCF-10A) indicate none or minimal toxicity.