Novel class of benzimidazole-thiazole hybrids: The privileged scaffolds of potent anti-inflammatory activity with dual inhibition of cyclooxygenase and 15-lipoxygenase enzymes.

The present study includes design and synthesis of new molecular hybrids of 2-methylthiobenzimidazole linked to various anti-inflammatory pharmacophores through 2-aminothiazole linker, to investigate the effect of such molecular variation on cyclooxygenase (COX) and 15-lipoxygenase (15-LOX) enzymes inhibition as well as in vivo anti-inflammatory activity. The chemical structures of new hybrids were confirmed using different spectroscopic tools and elemental analyses. Benzimidazole-thiazole hybrids linked to acetyl moiety 13, phenyl thiosemicarbazone 14, 1,3-thiazolines 15a-c and 4-thiazolidinone 16 exhibited significant COX-2 inhibition (IC50 = 0.045-0.075 µM) with significant COX-2 selectivity indices (SI = 142-294). All hybrids revealed potent 15-LOX inhibitory activity (IC50 = 1.67-6.56 µM). Benzimidazole-thiazole hybrid 15b was the most potent dual COX-2 (IC50 = 0.045 µM, SI = 294) inhibitor approximate to celecoxib (COX-2; IC50 = 0.045 µM, SI = 327), with double inhibitory activity versus 15-LOX enzyme (IC50 = 1.67 µM) relative to quercetin (IC50 = 3.34 µM). Three hybrids (14, 15b &16) were selected for in vivo screening using carrageenan-induced paw edema method. Benzimidazole-thiazole hybrid linked to 4-thiazolidinone 16 showed the maximum edema inhibition at both 3 h and 4 h intervals as well (~119% and 102% relative to indomethacin, respectively). The gastric ulcerogenic effect of benzimidazole-thiazole hybrid 16 was estimated compared with indomethacin showing superior gastrointestinal safety profile. In bases of molecular modeling; all new active hybrids were subjected to docking simulation into active sites of COX-2 and 15-LOX enzymes to study the binding mode of these novel potent dual COX-2/15-LOX inhibitors.

Further insight into the dual COX-2 and 15-LOX anti-inflammatory activity of 1,3,4-thiadiazole-thiazolidinone hybrids: The contribution of the substituents at 5th positions is size dependent.

Herin we report the design, synthesis, full characterization and biological investigation of new 15-LOX/COX dual inhibitors based on 1,3-thiazolidin-4-one (15-lipoxygenase pharmacophore) and 1,3,4-thiadiazole (COX pharmacophore) scaffolds. This series of molecular modifications is an extension of a previously reported series to further explore the structural activity relationship. Compounds 3a, 4e, 4n, 4q, 7 and 8 capable of inhibiting 15-LOX at (2.74, 4.2, 3.41, 10.21, 3.71 and 3.36 µM, respectively) and COX-2 at (0.32, 0.28, 0.28, 0.1, 0.28 and 0.27 µM, respectively). The results revealed that binding to 15-LOX and COX is sensitive to the bulkiness of the substituents at the 5 positions. 15-LOX bind better with small substituents, while COXs bind better with bulky substituents. Compounds 3a, 4r and 4q showed comparable in vivo anti-inflammatory activity to the reference drug (celecoxib). The ulcer liability test showed no sign of ulceration which ensures the safe gastric profile. Docking study was performed to explore the possible mode of interaction of the new compounds with the active site of human 15-LOX and COX-2. This study discloses some structural features for binding to 15-LOX and COX, thus pave the way to design anti-inflammatory agents with balanced dual inhibition of these enzymes.

Synthesis and anti-HSV activity of tricyclic penciclovir and hydroxybutylguanine derivatives.

A series of tricyclic penciclovir (PCV) and hydroxybutylguanine (HBG) derivatives have been prepared with enhanced lipophilicity following an efficient synthetic route. All the novel tricyclic derivatives were evaluated for inhibitory activity against herpes simplex virus 1 and 2 (HSV-1, HSV-2) and thymidine kinase deficient (ACV resistant) HSV-1. The tricyclic HBG derivatives were devoid of inhibitory activity however several of the tricyclic PCV derivatives showed promising antiviral activity, in particular 9g (R = 4-MeO-C6H4) displayed good inhibitory activity (HSV-1 EC50 1.5 µM, HSV-2 EC50 0.8 µM) and retained inhibitory activity in HSV-1 TK- cells (EC50 0.8 µM). Computational docking experiments supported the biological data observed and this preliminary study provides useful data for further development of tricyclic acyclic nucleoside derivatives with improved lipophilicity and retention of activity in HSV-1 TK deficient strains. Also, the new tricyclic derivatives were evaluated against a broad range of other DNA and RNA viruses, but were found to be inactive at subtoxic concentrations. In addition, weak to moderate cytostatic effect was observed for the new compounds.

Synthesis, biological evaluation and docking study of 1,3,4-thiadiazole-thiazolidinone hybrids as anti-inflammatory agents with dual inhibition of COX-2 and 15-LOX.

Selective inhibition of both cyclooxygenase-2 (COX-2) and 15-lipooxygenase (15-LOX) may provide good strategy for alleviation of inflammatory disorders while minimizing side effects associated with current anti-inflammatory drugs. The present study describes the synthesis, full characterization and biological evaluation of a series of thiadiazole-thiazolidinone hybrids bearing 5-alk/arylidene as dual inhibitors of these enzymes. Our design was based on merging pharmacophores that exhibit portent anti-inflammatory activities in one molecular frame. 5-(4-hydroxyphenyl)-1,3,4-thiadiazol-2-amine (3) was efficiently synthesized, chloroacetylated and cyclized to give the key 4-thiazolidinone (5). Knovenagel condensation of 5 with different aldehydes afforded the final compounds 6a-m, 7, 8 and 9. These compounds were subjected to in vitro COX-1/COX-2, 15-LOX inhibition assays. Compounds (6a, 6f, 6i, 6l, 6m and 9) with promising potency (IC50 = 70-100 nM) and selectivity index (SI = 220-55) were further tested for in vivo anti-inflammatory activity and effect on gastric mucosa. The most promising compound (6l) inhibits COX-2 enzyme at a nanomolar concentration (IC50 = 70 nM, SI = 220) with simultaneous inhibition of 15-LOX (IC50 = 11 µM). These results are comparable to the potency and selectivity of the standard drugs of both enzymes; celecoxib (COX-2 IC50 = 49 nM, SI = 308) and zileuton (15-LOX IC50 = 15 µM) in one construct. Interestingly three compounds (6a, 6l and 9) exhibited equivalent to or even higher than that of celecoxib in vivo anti-inflammatory activity at 3 h interval with good GIT safety profile. Molecular docking study conferred binding sites of these compounds on COX-2 and 15-LOX. Such type of compounds would represent valuable leads for further investigation and derivatization.

Design and synthesis of some substituted thiazolo[3,2-a]pyrimidine derivatives of potential biological activities.

In continuation to our previous work, thiazolopyrimidines 2a-x were synthesized through intramolecular cyclization of 2-phenacylthio-dihydropyrimidine hydrobromides 1a-x using polyphosphoric acid. On the other hand, thiazolo[3,2-a]pyrimidine-3-one 3 was coupled with aryldiazonium salts or condensed with isatin to afford compounds 4a-c or 5, respectively. Chemical structure of the target compounds was substantiated by IR, FT-IR, (1)H-, (13)C and DEPT-(13)C NMR, MS as well as microanalyses. Moreover, the lipophilicity of the target compounds is expressed as Clog P. The antimicrobial screening of the test compounds 2a-x, 4a-c and 5 revealed moderate activity in comparison to reference drugs. Compounds 2a-c, 2e, 2o and 2v showed a gradual increase in their anti-inflammatory activity reaching its maximum at 5 h compared to indomethacin. Furthermore, the analgesic activity of compounds 2a-c, 2e, 2o and 2v revealed a maximum activity after 5 h of injection compared to aspirin and the LD50 of compounds 2e and 2v was determined.

Design and synthesis of novel 5-aminosalicylate (5-ASA)-4-thiazolinone hybrid derivatives with promising antiproliferative activity.

Two privileged pharmacophores were assembled in one molecular frame involving 5-aminosalicylate and 4-thiazolinones that can be found in different stereochemical features. The compounds were fully characterized and evaluated for antiproliferative activity against four human cancer cell lines and some are equipotent to doxorubicin with lower cytotoxicity to normal cells. The most interesting finding relates to compound 10, which shows an IC50 value of 70nM against MCF-7 cells, while the IC50 against human fibroblasts is 10µM. The results of this study indicate that the new compounds are optimal anti-cancer leading compounds and merit further studies to optimize their structure, detect their biotargets and in vivo activity.

Design, synthesis and molecular docking of some new 1,2,4-triazolobenzimidazol-3-yl acetohydrazide derivatives with anti-inflammatory-analgesic activities.

The present work describes the synthesis and evaluation of some new acetohydrazones, 1,3,4-oxadiazoles and 1,2,4-triazoles of 1,2,4-triazolo[1,5-a]benzimidazole as anti-inflamm atory-analgesic agents. Structure elucidation of these compounds was confirmed by IR, (1)H NMR, and mass spectrometry along with elemental microanalyses. Most compounds exhibited significant anti-inflammatory activity in comparison to indomethacin. Further, some compounds were tested for their analgesic effects where two compounds showed results comparable to indomethacin at 4 h interval. The most active anti-inflammatory and analgesic compounds (4c and 11a) were examined on gastric mucosa and didn't show any gastric ulcerogenic effect compared with the reference indomethacin. Moreover, LD50 of compounds (4c and 11a) were determined in mice; they were found non toxic up to 240 and 300 mg/kg (i.p.). Also, docking simulation of some compounds into COX active sites was studied.

Synthesis and Antimicrobial Evaluation of Some New Thiazoline and Thiazolidinone Derivatives Incorporating [1,2,4]Triazolo[1,5-a]benzimidazole.

Two new series of 3-[2-(3,4-disubstituted-2,3-dihydrothiazol-2-ylidene)hydrazonopropylidenyl]-2-(methylthio)-3H-[1,2,4]triazolo[1,5-a]benzimidazole (6-29) and 3-[2-(3-substituted-4-oxothiazolidin-2-ylidene)hydrazonopropylidenyl]-2-(methylthio)-3H-[1,2,4]triazolo[1,5-a]benzimidazole (30-33) were synthesised starting from 1-[2-(methylthio)-3H-[1,2,4]triazolo[1,5-a]benzimidazol-3-yl] acetone N(4)-alkyl (aryl) thiosemicarbazones (2-5). Chemical structures of the compounds have been elucidated by different spectral data as well as elemental microanalysis. The newly synthesised compounds were tested for their in vitro antimicrobial activity using the standard agar cup diffusion method. Results revealed that most of the test compounds showed promising broad spectrum antibacterial and antifungal profiles against tested microorganisms, relative to references.

Synthesis of new 4,5-3(2H)pyridazinone derivatives and their cardiotonic, hypotensive, and platelet aggregation inhibition activities.

4,5-dihydro-3(2H)pyridazinones such as CI-914, CI-930 and pimobendan along with tetrahydropyridopyridazine (endralazine) and perhydropyridazinodiazepine (cilazopril) have been used as potent positive inotropes, antihypertensives as well as platelet aggregation inhibitors. Accordingly, the present work involves the synthesis of 24 target compounds; 4,5-dihydro-3(2H)pyridazinones in addition to seven reported intermediates. The chemical structures of the new compounds were assigned by microanalysis, IR, 1H-NMR spectral analysis and some representatives by mass spectrometry. The positive inotropic effect of the final compounds and the intermediates 12a-12d as well as the reported intermediate compound 10 was determined in-vitro on isolated rabbit heart in comparison to digoxin. Data obtained revealed that twelve of the test compounds exhibited higher effective response than digoxin, nine compounds elicited comparable effects to digoxin and eight compounds were less active than digoxin. In addition, four compounds approved marked significant hypotensive effect better than that of the previously reported compound 10. Moreover, two compounds induced complete platelet aggregation inhibition. The last two compounds were also subjected to determination of their LD50 and they showed no signs of toxicity up to the dose level 300 mg/kg (i.p.), while the reported oral LD50 of digoxin is 17.78 mg/kg. Correlation of cardiotonic and hypotensive activities with structures of compounds was tried and pharmacophore models were computed to get useful insight onto the essential structural features required for inhibiting phosphodiesterase-III in the heart muscles and blood vessels.

Synthesis and biological activities of new substituted thiazoline-quinoline derivatives.

5-Acyl-8-hydroxyquinoline-2-(3'-substituted-4'-aryl-2,3-dihydrothiazol-2'-ylidene)hydrazones, 5a-e to 10a-c, were prepared by the reaction of appropriate 5-acyl-8-hydroxyquinoline-4-substituted thiosemicarbazones 3a-e and phenacyl bromides 4a-e. Structures of the new compounds were verified on the basis of spectral and elemental analyses. Twenty-eight new compounds were tested for their possible antimicrobial activities. Most of the tested compounds showed weak to moderate antibacterial activity against most of the bacterial strains used in comparison with gatifloxacin as a reference drug. The test compounds showed weak to moderate antifungal activity against tested fungi in comparison with ketoconazole as a reference drug. On the other hand, the newly synthesized compounds were tested for their anti-inflammatory effects and most of them showed good to excellent anti-inflammatory activity compared to indomethacin. Moreover, ulcerogenicity and the median lethal dose (LD(50)) of the most active anti-inflammatory compounds 6b and 9e were determined in mice; they were non-toxic at doses up to 400 mg kg(-1) after i.p. administration.