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Most of the FDA approved histone deacetylase inhibitors (HDACi) contain hydroxamate as the zinc binding group (ZBG). Hydroxamates form strong electrostatic metal chelation with divalent zinc present in HDAC. This strong zinc chelation leads to unwanted metabolic abnormalities. Therefore, the design of a non-hydroxamate moiety as a ZBG encourages medicinal chemistry researchers. Here, a series of nicotinamide derivatives have been designed and synthesized as HDACi. All compounds were tested for their inhibitory activities against pan HDACs (containing predominantly HDAC1 and HDAC2 isozymes) and against the HDAC3 isoform. Among these, compounds 6b and 6n showed comparable pan HDAC inhibitory activity (IC50 = 4.648 μM and IC50 = 5.481 μM, respectively) compared with BG45 (IC50 = 5.506 μM). Compound 6b exhibited the best potency against HDAC3 with IC50 = 0.694 μM. In addition, the anti-proliferative activity of the synthesized compounds 6a–s was evaluated against three different cancer cell lines including B16F10, MCF-7, and A549. Compound 6b displayed the highest anti-proliferative potency (IC50 = 4.66 μM in B16F10 cell lines) and compounds 6b, 6c, 6h, 6i, 6l, 6m, and 6n exhibited higher cytotoxicity against all cell lines compared with the reference BG45. The selected potent compounds also displayed significant selectivity against cancer cell lines over normal human embryonic kidney (HEK-293) cell lines. The molecular modelling study displayed possible interactions between the most potent inhibitor 6b and HDAC3 active sites. Furthermore, the predicted in silico studies of all target compounds revealed acceptable physicochemical properties and pharmacokinetic parameters.

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 (IC

A new set of ibuprofen-quinoline conjugates comprising quinolinyl heterocycle and ibuprofen moieties linked by an alkyl chain were synthesized in good yields utilizing an optimized reaction procedure in a molecular hybridization approach to overcome the drawbacks of the current non-steroidal anti-inflammatory drugs. The synthesized conjugates were screened for their anti-inflammatory, and ulcerogenic properties. Several conjugates were found to have significant anti-inflammatory properties in the carrageenan-induced rat paw edema test without showing any ulcerogenic liability. In addition, most conjugates showed promising peripheral analgesic activity in the acetic acid-induced writhing test as well as central analgesic properties in the in vivo hot plate test. The most promising conjugates were the unsubstituted and 6-substituted fluoro- and chloro-derivatives of 2-(trifluoromethyl)quinoline linked to ibuprofen by a propyl chain. Their anti-inflammatory activity was evaluated against LPS-stimulated inflammatory reactions in RAW264.7 mouse macrophages. In this regard, it was found that most of the conjugates were able to significantly reduce the release and production of nitric oxide in the LPS-stimulated macrophages. The secretion and expression of the pro-inflammatory cytokines IL-6, TNF-α, and inducible nitric oxide synthase (iNOS) were also significantly suppressed.

In an attempt to counteract bacterial pathogenicity, a set of novel imidazolidine-2,4-dione and 2-thioxoimidazolidin-4-one derivatives was synthesized and evaluated as inhibitors of bacterial virulence. The new compounds were characterized and screened for their effects on the expression of virulence factors of Pseudomonas aeruginosa, including protease, hemolysin, and pyocyanin. Imidazolidine-2,4-diones 4c, 4j, and 12a showed complete inhibition of the protease enzyme, and they almost completely inhibited the production of hemolysin at 1/4 MIC (1/4 minimum inhibitory concentration; 1, 0.5, and 0.5 mg/ml, respectively). 2-Thioxoimidazolidin-4-one derivative 7a exhibited the best inhibitory activity (96.4%) against pyocyanin production at 1 mg/ml (1/4 MIC). A docking study was preformed to explore the potential binding interactions with quorum-sensing receptors (LasR and RhlR), which are responsible for the expression of virulence genes.

Based on the observed pharmacophoric structural features for the reported dual COX/15-LOX inhibitors and inspired by the abundance of COX/LOX inhibitory activities reported for the 1,2,4-triazine and quinoline scaffolds, we designed and synthesized novel 1,2,4-triazine-quinoline hybrids (8a-n). The synthesized hybrids were evaluated in vitro as dual COXs/15-LOX inhibitors. The new triazine-quinoline hybrids (8a-n) exhibited potent COX-2 inhibitory profiles (IC50 = 0.047–0.32 μM, SI ∼ 20.6–265.9) compared to celecoxib (IC50 = 0.045 μM, SI ∼ 326). Moreover, they revealed potent inhibitory activities against 15-LOX enzyme compared to reference quercetin (IC50 = 1.81–3.60 vs. 3.34 μM). Hybrid 8e was the most potent and selective dual COX-2/15-LOX inhibitor (COX-2 IC50 = 0.047 μM, SI = 265.9, 15-LOX IC50 = 1.81 μM). These hybrids were further challenged by their ability to inhibit NO, ROS, TNF-α, IL-6 inflammatory mediators, and 15-LOX product, 15-HETE, production in LPS-activated RAW 264.7 macrophages cells. Compound 8e was the most potent hybrid in reducing ROS and 15-HETE levels showing IC50 values of 1.02 μM (11-fold more potent than that of celecoxib, IC50 = 11.75 μM) and 0.17 μM (about 43 times more potent than celecoxib, IC50 = 7.46 μM), respectively. Hybrid 8h exhibited an outstanding TNF-α inhibition with IC50 value of 0.40 μM which was about 25 times more potent than that of celecoxib and diclofenac (IC50 = 10.69 and 10.27 μM, respectively). Docking study of the synthesized hybrids into the active sites of COX-2 and 15-LOX enzymes ensures their favored binding affinity. To our knowledge, herein we reported the first 1,2,4-triazine-quinoline hybrids as dual COX/15-LOX inhibitors.

A method for regioselective alkylation of the 3-thiono-1,2,4-triazinone 10 at the sulfur atom is reported. Subsequent Claisen rearrangements, triggered either thermally or using a palladium catalyst, deliver N-alkylated products 13, while acid-catalysed rearrangements of examples where a tertiary carbenium ion can be generated, result in the formation of N-thioalkyl derivatives.

Carbenium ions generated from substituted benzhydryls using acid catalysis undergo smooth intramolecular trapping by pendant sulfonamide groups to provide excellent yields of 1-aryltetrahydroisoquinolines.