Synthesis and Cytotoxic Activity of Combretastatin A-4 and 2,3-Diphenyl-2H-indazole Hybrids

Cancer is the second leading cause of death, after cardiovascular diseases. Different strategies have been developed to treat cancer; however, chemotherapy with cytotoxic agents is still the most widely used treatment approach. Nevertheless, drug resistance to available chemotherapeutic agents is still a serious problem, and the development of new active compounds remains a constant need. Taking advantage of the molecular hybridization approach, in the present work we designed, synthesized, and tested the cytotoxic activity of two hybrid compounds and seven derivatives based on the structure of combretastatin A-4 and 2,3-diphenyl-2H-indazole. Practical modifications of reported synthetic protocols for 2-pheny-2H-indazole and 2,3-dipheny-2H-indazole derivatives under microwave irradiation were implemented. The cytotoxicity assays showed that our designed hybrid compounds possess strong activity, especially compound 5, which resulted even better than the reference drug cisplatin against HeLa and SK-LU-1 cells (IC₅₀ of 0.16 and 6.63 µM, respectively), and it had similar potency to the reference drug imatinib against K562 cells. Additionally, in silico and in vitro studies strongly suggest tubulin as the molecular target for hybrid compound 5.

The giardicidal activity of lobendazole, fabomotizole, tenatoprazole and ipriflavone: A ligand-based virtual screening and in vitro study

A ligand-based virtual screening study to search for giardicidal compounds on a 6551 ChEMBL drugs database was carried out using molecular similarity. Three fingerprints implemented in MayaChemTools with different design and validated by ROC curves, were used. Twelve compounds were retrieved from this screening, from which, four representative compounds were selected to carry out biological assays. Whereas two compounds were commercially available, the additional two compounds were synthesized during the development of this work. The biological assays revealed that the compounds possess in vitro activity against five strains of Giardia intestinalis, each with different susceptibility/resistance rates to metronidazole, albendazole and nitazoxanide. Particularly, tenatoprazole showed the best effect against the WB and IMSS strains. Furthermore, fabomotizole, tenatoprazole and ipriflavone showed a higher activity against resistant strains than the reference drugs: metronidazole, albendazole and nitazoxanide.

Pharmacokinetics and Pharmacodynamics of (S)-Ketoprofen Co-Administered with Caffeine: A Preclinical Study in Arthritic Rats

The purpose of the present study was to determine whether caffeine modifies the pharmacokinetics and pharmacodynamics of (S)-ketoprofen following oral administration in a gout-type pain model. 3.2 mg/kg of (S)-ketoprofen alone and combined with 17.8 mg/kg of caffeine were administered to Wistar rats and plasma levels were determined between 0.5 and 24.0 h. Additionally, antinociception was evaluated based on the protocol of the PIFIR (pain-induced functional impairment in the rat) model before blood sampling between 0.5 and 4.0 h. Significant differences in C_max, AUC_0-24, and AUC_0-∞ values were observed with caffeine administration (p < 0.05). Also, significant differences in E_max, T_max, and AUC_0-4 values were determined when comparing the treatments with and without caffeine (p < 0.05). By relating the pharmacokinetic and pharmacodynamic data, a counter-clockwise hysteresis loop was observed regardless of the administration of caffeine. When the relationship between AUCe and AUCp was fitted to the sigmoidal E_max model, a satisfactory correlation was found (R² > 0.99) as well as significant differences in E_max and EC₅₀ values (p < 0.05). With caffeine, E_max and EC₅₀ values changed by 489.5% and 695.4%, respectively. The combination studied represents a convenient alternative for the treatment of pain when considering the advantages offered by using drugs with different mechanisms of action.

Activity cliffs and activity cliff generators based on chemotype-related activity landscapes

Activity cliffs have large impact in drug discovery; therefore, their detection and quantification are of major importance. This work introduces the metric activity cliff enrichment factor and expands the previously reported activity cliff generator concept by adding chemotype information to representations of the activity landscape. To exemplify these concepts, three molecular databases with multiple biological activities were characterized. Compounds in each database were grouped into chemotype classes. Then, pairwise comparisons of structure similarities and activity differences were calculated for each compound and used to construct chemotype-based structure-activity similarity (SAS) maps. Different landscape distributions among four major regions of the SAS maps were observed for different subsets of molecules grouped in chemotypes. Based on this observation, the activity cliff enrichment factor was calculated to numerically detect chemotypes enriched in activity cliffs. Several chemotype classes were detected having major proportion of activity cliffs than the entire database. In addition, some chemotype classes comprising compounds with smooth structure activity relationships (SAR) were detected. Finally, the activity cliff generator concept was applied to compounds grouped in chemotypes to extract valuable SAR information.

Synthesis and antiprotozoal activity of nitazoxanide-N-methylbenzimidazole hybrids

A series of a novel hybrid compounds between nitazoxanide and N-methylbenzimidazole were synthesized starting from the corresponding N-methyl-2-nitroanilines. The new hybrid compounds (1-13) were evaluated in vitro against Giardia intestinalis, Entamoeba histolytica, Trichomonas vaginalis. NTZ, MTZ and ABZ were used as drug standards. Experimental evaluations revealed all of the new compounds (1-13) were active and showed strong activity against the three protozoa, particularly with E. histolytica where the IC50 values ranged between 3 and 69 nM. Overall, compounds 2, 5, 7, 8, 9, 11 and 12 stood out with values lower than 87 nM for all three protozoa, comparatively better than the reference drugs.

CASE plots for the chemotype-based activity and selectivity analysis: a CASE study of cyclooxygenase inhibitors

Structure-activity characterization of molecular databases plays a central role in drug discovery. However, the characterization of large databases containing structurally diverse molecules with several end-points represents a major challenge. For this purpose, the use of chemoinformatic methods plays an important role to elucidate structure-activity relationships. Herein, a general methodology, namely Chemotype Activity and Selectivity Enrichment plots, is presented. Chemotype Activity and Selectivity Enrichment plots provide graphical information concerning the activity and selectivity patterns of particular chemotypes contained in structurally diverse databases. As a case study, we analyzed a set of 658 compounds screened against cyclooxygenase-1 and cyclooxygenase-2. Chemotype Activity and Selectivity Enrichment plots analysis highlighted chemotypes enriched with active and selective molecules against cyclooxygenase-2; all this in a simple 2D graphical representation. Additionally, the most active and selective chemotypes detected in Chemotype Activity and Selectivity Enrichment plots were analyzed separately using the previously reported dual activity-difference maps. These findings indicate that Chemotype Activity and Selectivity Enrichment plots and dual activity-difference maps are complementary chemoinformatic tools to explore the structure-activity relationships of structurally diverse databases screened against two biological end-points.

Synthesis and biological activity of 2-(trifluoromethyl)-1H-benzimidazole derivatives against some protozoa and Trichinella spiralis

A series of 2-(trifluoromethyl)-1H-benzimidazole derivatives (1a-1i) were synthesized via Phillips cyclocondensation of a substituted 1,2-phenylenediamine and trifluoroacetic acid. The synthesized compounds were evaluated in vitro against various protozoan parasites: Giardia intestinalis, Entamoeba histolytica, Trichomonas vaginalis and Leishmania mexicana, and they showed nanomolar activities against the first three protozoa tested. The compounds were also tested in vitro and in vivo against the nematode Trichinella spiralis. Compounds 1b, 1c and 1e had the most desirable in vitro antiparasitic profile against all parasites studied. In the in vivo model against T. spiralis, compounds 1b and 1e showed good activity against the adult phase at 75 mg/Kg. However, against the muscle larvae stage, only compound 1f exhibited in vivo antiparasitic efficacy.

Anthelmintic activity of benzimidazole derivatives against Toxocara canis second-stage larvae and Hymenolepis nana adults

The anthelmintic activity of 11 benzimidazole derivatives (A1-A11) and 2 thioureides N,N'-disubstituted (B1-B2) was determined. Each compound and albendazole was tested in vitro against Toxocara canis larvae and in vivo against Hymenolepis nana adult. Compounds A1-A6 and B1-B2 were designed as albendazole prodrugs. Compounds A8-A11 were designed as direct analogues of A7, which had previously proved to be an effective agent against Fasciola hepatica. Results of the in vitro screening showed that A6 was more active than albendazole at 0.18 microM (relative mobility 40% and 80%, respectively). Whereas that the in vivo evaluation against H. nana, compounds A7-A11 demonstrated significant activity in terms of removing cestode adults in the range of 88-97%, displaying better efficacy than albendazole (83%).