Design, Synthesis, and Biological Evaluation of 1,5-Diaryl-1,2,4-triazole Derivatives as Selective Cyclooxygenase-2 Inhibitors

Structural and Energetic Properties of Weak Noncovalent Interactions in Two Closely Related 3,6-Disubstituted-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole Derivatives: In Vitro Cyclooxygenase Activity, Crystallography, and Computational Investigations

Two 3,6-disubstituted-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole derivatives, namely, 3-(adamantan-1-yl)-6-(2-chloro-6-fluorophenyl)-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole 1 and 6-(2-chloro-6-fluorophenyl)-3-phenyl-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole 2, were prepared, and the detailed analysis of the weak intermolecular interactions responsible for the supramolecular self-assembly was performed using X-ray diffraction and theoretical tools. Analyses of Hirshfeld surface and 2D fingerprint plot demonstrated the effect of adamant-1-yl/phenyl moieties on intermolecular interactions in solid-state structures. The effect of these substituents on H···H/Cl/N contacts was more specific. The CLP-PIXEL and density functional theory methods provide information on the energetics of molecular dimers observed in these compounds. The crystal structure of compound 1 stabilizes with a variety of weak intermolecular interactions, including C–H···N, C–H···π, and C–H···Cl hydrogen bonds, a directional C–S···π chalcogen bond, and unconventional short F···C/N contacts. The crystal structure of compound 2 is stabilized by π-stacking interactions, C–H···N, C–H···π, and C–H···Cl hydrogen bonds, and highly directional attractive σ–hole interactions such as the C–Cl···N halogen bond and the C–S···N chalcogen bond. In addition, S(lp)···C(π) and short N···N contacts play a supportive role in the stabilization of certain molecular dimers. The final supramolecular architectures resulting from the combination of different intermolecular interactions are observed in both the crystal packing. The molecular electrostatic potential map reveals complementary electrostatic potentials of the interacting atoms. The quantum theory of atoms in molecules approach was used to delineate the nature and strength of different intermolecular interactions present in different dimers of compounds 1 and 2. The in vitro experiments suggest that both compounds showed selectivity against COX-2 targets rather than COX-1. Molecular docking analysis showed the binding pose of the compounds at the active sites of COX-1/2 enzymes.

Design and Synthesis of Novel 1,3,4-Oxadiazole and 1,2,4-Triazole Derivatives as Cyclooxygenase-2 Inhibitors with Anti-inflammatory and Antioxidant activity in LPS-stimulated RAW264.7 Macrophages

In an attempt to obtain new candidates with potential anti-inflammatory activity, two series of 1,3,4-oxadiazole based derivatives (8a-g) and 1,2,4-triazole based derivatives (10a,b and 11a-g) were synthesized and evaluated for their COX-1/COX-2 inhibitory activity. In vitro assays showed potent COX-2 inhibitory activity and selectivity of the novel designed compounds (IC50 = 0.04 - 0.16 μM, SI = 60.71 - 337.5) compared to celecoxib (IC50 = 0.045 μM, SI = 326.67). The anti-inflammatory and antioxidant activity of the synthesized compounds was investigated via testing their ability to inhibit pro-inflammatory [tumour necrosis factor (TNF-α) and interleukin-6 (IL-6)] and oxidative stress [nitric oxide (NO) and reactive oxygen species (ROS)] markers production in lipopolysaccharide (LPS)-activated RAW 264.7 macrophages. Most of the novel compounds exhibited potent anti-inflammatory and antioxidant activity. In particular, the novel compounds showed excellent IL-6 inhibitory activity (IC50 = 0.96 - 11.14 μM) when compared to celecoxib (IC50 = 13.04 μM) and diclofenac sodium (IC50 = 22.97 μM). Moreover, the most potent and selective COX-2 inhibitor 11c (IC50 = 0.04 μM, SI = 337.5) displayed significantly higher activity against NO and ROS production compared to celecoxib (IC50 = 2.60 and 3.01 μM vs. 16.47 and 14.30 μM, respectively). Molecular modelling studies of the novel designed molecules into COX-2 active sites analysed their binding affinity. In-silico simulation studies indicated their acceptable physicochemical properties and pharmacokinetic profiles. This study suggests that the novel synthesized COX-2 inhibitors exert potent anti-inflammatory and antioxidant activity, highlighting their potential as promising therapeutic agents for the treatment of inflammation and oxidative stress-related diseases.

"Azole" as privileged heterocycle for targeting the inducible cyclooxygenase enzyme

An over-expression of COX-2 isoenzyme belonging to the Cyclooxygenase Enzyme Family triggers the overproduction of pro-inflammatory prostaglandins that instigate the development of chronic inflammation and related disorders. Hence, the rationally designed drugs for mitigating over-activity of COX-2 isoenzyme play a regulatory role toward the alleviation of the progression of these disorders. However, a selective COX-2 inhibition chemotherapy prompts several side effects that necessitate the identification of novel molecular scaffolds for deliberating state-of-the-art drug designing strategies. The heterocyclic "azole" scaffold, being polar and hydrophilic, possesses remarkable physicochemical advantages for designing physiologically active molecules capable of interacting with a wide range of biological components, including enzymes, peptides, and metabolites. The substituted derivatives of azole nuclei enable a comprehensive SAR analysis for the appraisal of bioactive profile of the deliberated molecules for obtaining the rationally designed compounds with prominent activities. The comprehensive SAR analysis readily prompted the identification of Y-shaped molecules and the eminence of bulkier group for COX-2 selective inhibition. This review presents an epigrammatic collation of the pharmacophore-profile of the chemotherapeutics based on azole motif for a selective targeting of the COX-2 isoenzyme.

Prediction of the Antiinflammatory Activity of New S-alkyl Derivatives of 1,2,4-triazol-3-thiones Using the PASS Computer Program and Molecular Docking

The strategy of rational approaches to the search for selective COX-2 inhibitors as potential antiinflammatory agents has been proposed and elaborated. It is based on the use of PASS-prediction and molecular docking. The choice of the basic structure of 4-amino-3-thio-1,2,4-triazole as a promising object of chemical modification has been substantiated. Using a modification of the primary molecule, a virtual library of S-derivatives of 5-substituted 4-amino(pyrrol)3-thio-4H-1,2,4-triazoles in the amount of 100 compounds (ten groups) has been obtained by introducing various pharmacophore fragments. Based on the analysis of the results of the PASS-prediction and molecular docking, six of the ten planned groups of compounds have been selected for the synthesis as promising selective COX-2 inhibitors. The reliability of the prediction results has already been confirmed for one of the promising group 4-amino-5-(pyridine-4-yl)-1,2,4-triazole (4?)-3-yl-thioacetamides.

Exploring the Chemistry and Therapeutic Potential of Triazoles: A Comprehensive Literature Review

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Triazole is a valuable platform in medicinal chemistry, possessing assorted pharmacological properties, which could play a major role in the common mechanisms associated with various disorders like cancer, infections, inflammation, convulsions, oxidative stress and neurodegeneration. Structural modification of this scaffold could be helpful in the generation of new therapeutically useful agents. Although research endeavors are moving towards the growth of synthetic analogs of triazole, there is still a lot of scope to achieve drug discovery break-through in this area. Upcoming therapeutic prospective of this moiety has captured the attention of medicinal chemists to synthesize novel triazole derivatives. The authors amalgamated the chemistry, synthetic strategies and detailed pharmacological activities of the triazole nucleus in the present review. Information regarding the marketed triazole derivatives has also been incorporated. The objective of the review is to provide insights to designing and synthesizing novel triazole derivatives with advanced and unexplored pharmacological implications.

Design, synthesis, evaluation and molecular modelling studies of some novel 5,6-diphenyl-1,2,4-triazin-3(2H)-ones bearing five-member heterocyclic moieties as potential COX-2 inhibitors: A hybrid pharmacophore approach

A series of novel hybrids comprising of 1,3,4-oxadiazole/thiadiazole and 1,2,4-triazole tethered to 5,6-diphenyl-1,2,4-triazin-3(2H)-one were designed, synthesised and evaluated as COX-2 inhibitors for the treatment of inflammation. The synthesised hybrids were characterised using FT-IR, 1H NMR, 13C NMR, elemental (C,H,N) analyses and assessed for their anti-inflammatory potential by in vitro albumin denaturation assay. Compounds exhibiting activity comparable to indomethacin and celecoxib were further evaluated for in vivo anti-inflammatory activity. Oral administration of promising compounds 3c-3e and 4c-4e did not evoke significant gastric, hepatic and renal toxicity in rats. These potential compounds exhibited reduced malondialdehyde (MDA) content on the gastric mucosa suggesting their protective effects by inhibition of lipid peroxidation. Based on the outcome of in vitro COX assay, compounds 3c-3e and 4c-4e (IC₅₀ 0.60-1.11μM) elicited an interesting profile as competitive selective COX-2 inhibitors. Further, selected compounds 3e and 4c were found devoid of cardiotoxicity post evaluation on myocardial infarcted rats. The in silico binding mode of the potential compounds into the COX-2 active site through docking and molecular dynamics exemplified their consensual interaction and subsequent COX-2 inhibition with significant implications for structure-based drug design.

Hybrid molecules: The privileged scaffolds for various pharmaceuticals

The practice of polypharmacology is not a new concept but the approaches which are being adopted for administering the two or more drugs together are varied from time to time. Taking two or more drugs simultaneously, co-formulation of two or more active agents in a single tablet and development of hybrid molecular entities capable to modulate multiple targets are the three popular approaches for multidrug therapy. The simultaneous use of more than one drug for the chemotherapy of a single disease demands a lot of patient compliance. Hence the present form of polypharmacology is gaining popularity in the form of hybrid molecules (multiple ligand approach). From the last 1-2 decades, the synthesis of hybrid molecules by the combination of different biologically relevant moieties has been under constant escalation along with their evaluation as diverse range of pharmacological agents and as potent drugs. This review is focused on the biological potential of hybrid molecules with particular mention of those exhibiting anti-fungal, anti-tuberculosis, anti-malarial, anti-inflammatory and anti-cancer activities. A comparison of the drug potency of the hybrid molecules with their individual counterparts is discussed for quantifying the significance of the concept of molecular hybridisation.

Discovery of potential anti-inflammatory drugs: diaryl-1,2,4-triazoles bearing N-hydroxyurea moiety as dual inhibitors of cyclooxygenase-2 and 5-lipoxygenase

A series of hybrids from diaryl-1,2,4-triazole and hydroxamic acid or N-hydroxyurea were synthesized and evaluated as novel anti-inflammatory agents. The biological data showed that (i) all the compounds showed dual COX-2/5-LOX inhibitory activities in vitro, and 15e showed optimal inhibitory activities (COX-2: IC50 = 0.15 μM, 5-LOX: IC50 = 0.85 μM), (ii) 15e selectively inhibited COX-2 relative to COX-1 with selectivity index (SI = 0.012) comparable to celecoxib (SI = 0.015), (iii) 15e exhibited potent anti-inflammatory activity (inhibition: 54.1%) which was comparable to the reference drug celecoxib (inhibition: 46.7%) in a xylene-induced ear edema assay, and (iv) 15e displayed promising analgesic activity in acetic acid-induced writhing response and hot-plate assay. Finally, a molecular modeling study revealed the binding interactions of 15e with COX-2 and 5-LOX. Our findings suggest that 15e may be a promising anti-inflammatory agent for further evaluation.

Synthesis of some new s-alkylated 1,2,4-triazoles, their mannich bases and their biological activities

A series of 1-(4-methoxyphenyl)-2-[5-{(biphenyl-4-yloxy)methyl}4-(substituted phenyl)-3-mercapto-(4H)-1,2,4-triazol-3-ylthio)] ethanones (6a-6s) and 4-(substituted phenyl)-3-(morpholin/pyrrolidin-4-ylmethylthio)-5-(4-phenylphenoxymethyl)-4H-1,2,4-triazoles (7a-7e) were synthesized in order to obtain new compounds with potent anti-inflammatory and analgesic activity with insignificant ulceration. Among the synthesized compounds, (6c), (6e), (6g) and (6l) from triazole series and (7b) and (7e) from Mannich base series were found to exhibit significant anti-inflammatory activity with 59.69, 59.69, 64.69, 79.84, 54.54, 79.69% and 52.55, 57.50, 72.52, 83.03, 60.06, 84.08% inhibition of paw edema at 3 h and 5 h respectively, in comparison to the standard drug ibuprofen (78.93 and 82.58% at 3 h and 5 h). The active compounds were further tested for their analgesic activity and gastric ulceration study. Compounds 6g, 7b and 7e exhibited significant analgesic activity with reaction time (3.60, 3.22, 3.88 s) respectively at 60 min. without causing any gastric irritation. These compounds were also screened for their in vitro antimicrobial activity, Compounds 6f, 6g, 6h, 6l, 6o, 6p, 7a, 7b and 7c showed significant zone of inhibition against various antimicrobial stains. It is concluded that the compounds 6g, 7b and 7e possess a good spectrum of activities. Compound 7e may be considered potent for development of better anti-inflammatory agent. The antimicrobial activity revealed that most of the compounds showed moderate to significant activity. Compounds containing nitro, chloro, bromo and fluoro group showing better activity. All the compounds from 7a, 7b and 7e were active against gram positive bacteria (S. aureus).

Cyclooxygenase-2 inhibitors: a literature and patent review (2009 - 2010)

INTRODUCTION

COXs catalyze the complex conversion of arachidonic acid to prostaglandins and thromboxanes, which trigger as autacoids with autocrine and paracrine biological effects many physiological and pathophysiological responses. The structural similarities of the COX-1 and -2 enzymes make the search for selective inhibitors for COX-2 versus -1 a formidable challenge.

AREAS COVERED

The present review provides a survey of the development of novel COX-2 inhibitors covering literature and patents between 2009 and 2010. The presence of a central, typically 1,2-diaryl substituted, heterocycle or carbocycle as a characteristic structural motif in many selective COX-2 inhibitors represents the basis of their classification in this review. The classification in this review includes COX-2 inhibitors based on five- and six-membered heterocycles, benzoheterocycles (e.g., benzopyrans, benzopyranones, indoles and quinolines), quinones, chalcones, natural products and miscellaneous. When available, COX-2 inhibitors are presented with their related COX-2 inhibitory potency and selectivity.

EXPERT OPINION

The availability of detailed information on the crystal structure of the COX-2 enzyme with various substrates, cofactors and inhibitors, and the recently reported increased risk of cardiovascular events associated with selective COX-2 inhibitors will further stimulate development of COX-2 inhibitors with favorable COX-2 inhibition profiles without adverse effects to the cardiovascular system.