Synthesis and Biological Evaluation of Salicylic Acid Analogues of Celecoxib as a New Class of Selective Cyclooxygenase-1 Inhibitor.

A series of salicylic acid analogues of celecoxib where the phenylsulfonamide moiety in the structure of celecoxib is replaced by salicylic acid moiety was synthesized and tested for in vitro cyclooxygenase (COX)-1 and COX-2 enzyme inhibition. Among the series, 5-substituted-2-hydroxy-benzoic acid analogues (7a-7h) generally showed better inhibitory activities on both enzymes than 4-substituted-2-hydroxy-benzoic acid analogues (12a-12h). In particular, the chloro analogue 7f which had the highest inhibitory effect (IC50 = 0.0057 µM) to COX-1 with excellent COX-1 selectivity (SI = 768) can be classified as a new potent and selective COX-1 inhibitor. The high inhibitory potency of 7f was rationalized through the docking simulation of this analogue in the active site of COX-1 enzyme.

Synthesis, in-vitro, in-vivo anti-inflammatory activities and molecular docking studies of acyl and salicylic acid hydrazide derivatives.

Over the course of time several drugs have been synthesized and are available in market for the treatment of inflammation. However, they were unable to cure effectively and associated with side effects. To effectively deal with such diseases, heterocycles and their derivatives have gained their special position. For this reason 1,3,4-oxadiazole (15-16), 1,2,4-triazole (17-18), Schiff base (19-24) and 3,5-disubstituted pyrazole (25) derivatives were synthesized starting from salicylic acid and acyl acid hydrazides (12-14) as COX-1 and COX-2 inhibitors. In vivo anti-inflammatory activities were also tested by carrageenan-induced mice paw edema against albino mice of any sex. Structures of all the synthesized compounds were confirmed by FT-IR and 1H NMR analysis. Schiff base derivative of 4-amiontirazole (24) with IC50 value of 1.76 ± 0.05 (COX-2) and 117.8 ± 2.59 emerged as potent COX-2 inhibitor. Furthermore, we also performed in-vivo anti-inflammatory investigations by using carrageenan induced paw edema test. From in-vivo anti-inflammatory activities, it was found that after 1 h the maximum percentage inhibition 15.8% was observed by compound 14 which is comparable with that of the standard drug followed by the compound 18 with percentage inhibition of 10.5%. After 3 h, the maximum percentage inhibition was observed by compound 18 with 22.2% and compound 14 with 16.7%. After 5 h the maximum percentage inhibition was observed by compound 18 with 29.4% followed by compound 16 with 23.5%. We further explore the mechanism of the inhibition by using docking simulations. Docking studies revealed that the selective COX-2 inhibitors established interactions with additional COX-2 enzyme pocket residues.

Synthesis and biological evaluation of novel 5,6,7-trimethoxy flavonoid salicylate derivatives as potential anti-tumor agents.

5,6,7-Trimethoxy flavonoid salicylate derivatives were designed by the joining of three important pharmacophores (TMP, flavonoid, and SA) according to the combination principle. A series of novel trimethoxy flavonoid salicylate derivatives were synthesized and their in vitro anti-tumor activities were evaluated. Among these derivatives, compound 7f exhibited excellent antiproliferative activity against HGC-27 cells and MGC-803 cells with IC50 values of 10.26 ± 6.94 µM and 17.17 ± 3.03 µM, respectively. Subsequently, the effects on cell colony formation (clonogenic survival assay), cell migration (wound healing assay), cell cycle distribution (PI staining assay), cell apoptosis (Hoechst 33258 staining assay and annexin V-FITC/PI dual staining assay), lactate level (lactate measurement), microtubules disarrangement (immunofluorescence staining analysis) and docking posture (molecular docking simulation) were determined. Further western blot analysis confirmed that compound 7f could effectively down-regulate the expression of glycolysis-related proteins HIF-1α, PFKM and PKM2 and tumor angiogenesis-related proteins VEGF. Overall, these studies suggested that compound 7f, as the representative compound of those, might be a promising candidate for the treatment of gastric cancer and deserved the further studies.

Synthesis of NSC 106084 and NSC 14778 and evaluation of their DNMT inhibitory activity.

DNA methylation is an epigenetic modification that is performed by DNA methyltransferases (DNMTs) and that leads to the transfer of a methyl group from S-adenosylmethionine (SAM) to the C5 position of cytosine. This transformation results in hypermethylation and silencing of genes such as tumor suppressor genes. Aberrant DNA methylation has been associated with the development of many diseases, including cancer. Inhibition of DNMTs promotes the demethylation and reactivation of epigenetically silenced genes. NSC 106084 and 14778 have been reported to inhibit DNMTs in the micromolar range. We report herein the synthesis of NSC 106084 and 14778 and the evaluation of their DNMT inhibitory activity. Our results indicate that while commercial NSC 14778 is moderately active against DNMT1, 3A/3L and 3B/3L, resynthesized NSC 14778 is inactive under our assay conditions. Resynthesized 106084 was also found to be inactive.

A New Series of Salicylic Acid Derivatives as Non-saccharide α-Glucosidase Inhibitors and Antioxidants.

In this study, a series of salicylic acid derivatives were designed and synthesized as novel non-saccharide α-glucosidase inhibitors. Biological evaluation indicated that when compared to acarbose, compounds T9, T10, and T32 exhibited a higher potency of α-glucosidase inhibitory activity with IC50 values of 0.15 ± 0.01, 0.086 ± 0.01 and 0.32 ± 0.02 mM, respectively. Evaluation of the inhibition kinetics indicated that T9, T10, T32, and acarbose interacted with α-glucosidase in a mixed non-competitive inhibitory manner. Moreover, T9, T10, and T32 statically quenched the fluorescence of α-glucosidase by formation of an inhibitor-α-glucosidase complex. The docking results showed that hydrogen bonds were generated between the test compounds and α-glucosidase. The antioxidant study revealed that compound T10 exhibited a higher antioxidant activity via scavenging 1,1-diphenyl-2-picrylhydrazyl free radical (DPPH), thereby inhibiting lipid peroxidation and the total reduction capacity. In brief, the salicylic acid derivatives identified in this study were promising candidates for development as novel non-saccharide α-glucosidase inhibitors.

Unified total synthesis of amorfrutins A and C via the Claisen rearrangement.

A concise, unified total synthesis of the two prenylated aromatic polyketides amorfrutins A and C, which exhibit various medicinally important biological profiles such as antimicrobial, PPARγ modulating and quorum sensing inhibitory activities, has been achieved from commercially available 3,5-dimethoxybenzaldehyde in 38% and 10% overall yields through nine and ten steps, respectively. The key transformation for the synthesis of amorfrutin A was the Claisen rearrangement of a mono-O-(1,1-dimethylallyl)resorcinol derivative to install the C3-prenyl substituent, while that for the synthesis of amorfrutin C was the double Claisen rearrangement of a di-O-(1,1-dimethylallyl)resorcinol derivative to introduce the two prenyl groups at the C3 and C5 positions all at once.

Synthesis of some novel orsellinates and lecanoric acid related depsides as α-glucosidase inhibitors.

Sixteen novel orsellinic esters (6a-l, 7a-d) along with four lecanoric acid related depsides (3a-c, 4) were synthesized and confirmed their structures by spectroscopic data (1H, 13C & HRMS). The synthesized compounds were evaluated for their in vitro α-glucosidase (Saccharomyces cerevisiae) inhibitory potential. Among the tested compounds, 3c (IC50: 140.9 µM) and 6c (IC50: 203.9 µM) displayed potent α-glucosidase inhibitory activity and found more active than the standard drug acarbose (IC50: 686.6 µM). Both the test compounds were subjected to in vivo antihyperglycemic activity using sucrose loaded model in Wistar rats and found compound 3c exhibited significant reduction in glucose levels.

Intramolecular Proton and Charge Transfer of Pyrene-based trans-Stilbene Salicylic Acids Applied to Detection of Aggregated Proteins.

Two analogues to the fluorescent amyloid probe 2,5-bis(4'-hydroxy-3'-carboxy-styryl)benzene (X-34) were synthesized based on the trans-stilbene pyrene scaffold (Py1SA and Py2SA). The compounds show strikingly different emission spectra when bound to preformed Aß1-42 fibrils. This remarkable emission difference is retained when bound to amyloid fibrils of four distinct proteins, suggesting a common binding configuration for each molecule. Density functional theory calculations show that Py1SA is twisted, while Py2SA is more planar. Still, an analysis of the highest occupied molecular orbitals (HOMOs) and lowest unoccupied molecular orbitals (LUMOs) of the two compounds indicates that the degree of electronic coupling between the pyrene and salicylic acid (SA) moieties is larger in Py1SA than in Py2SA. Excited state intramolecular proton transfer (ESIPT) coupled-charge transfer (ICT) was observed for the anionic form in polar solvents. We conclude that ICT properties of trans-stilbene derivatives can be utilized for amyloid probe design with large changes in emission spectra and decay times from analogous chemical structures depending on the detailed physical nature of the binding site.

Synthesis and Biological Evaluation of Cajaninstilbene Acid and Amorfrutins A and B as Inhibitors of the Pseudomonas aeruginosa Quorum Sensing System.

The quorum sensing (QS) system inhibitors of Pseudomonas aeruginosa are thought to attenuate bacterial pathogenicity and drug resistance by inhibiting biofilm formation and the production of virulence factors. In this study, a synthetic approach to the natural products cajaninstilbene acid (1) and amorfrutins A (2) and B (3) has been developed and was characterized by the Heck reaction, which was used to obtain the stilbene core and a Pinick oxidation to give the O-hydroxybenzoic acid. The biological activities of these compounds against the P. aeruginosa quorum sensing systems were evaluated. Amorfrutin B (3) showed promising antibiofilm activity against P. aeruginosa PAO1 with a biofilm inhibition ratio of 50.3 ± 2.7. Three lacZ reporter strains were constructed to identify the effects of compound 3 on different QS systems. Suppression efficacy of compound 3 on the expression of lasB-lacZ and pqsA-lacZ as well as on the production of their corresponding virulence factors elastase and pyocyanin was observed.

A photoredox-neutral Smiles rearrangement of 2-aryloxybenzoic acids.

We report on the use of visible light photoredox catalysis for the radical Smiles rearrangement of 2-aryloxybenzoic acids to obtain aryl salicylates. The method is free of noble metals and operationally simple and the reaction can be run under mild batch or flow conditions. Being a redox neutral process, no stoichiometric oxidants or reductants are needed.

Design, synthesis, and evaluation of salicyladimine derivatives as multitarget-directed ligands against Alzheimer's disease.

A series of salicyladimine derivatives were designed, synthesized and evaluated as multi-target-directed ligands for the treatment of Alzheimer's disease (AD). Biological activity results demonstrated that some derivatives possessed significant inhibitory activities against amyloid-ß (Aß) aggregation and human monoamine oxidase B (hMAO-B) as well as remarkable antioxidant effects and low cell toxicity. The optimal compound, 5, exhibited excellent potency for inhibition of self-induced Aß1-42 aggregation (91.3±2.1%, 25µM), inhibition of hMAO-B (IC50, 1.73±0.39µM), antioxidant effects (43.4±2.6µM of IC50 by DPPH method, 0.67±0.06 trolox equivalent by ABTS method), metal chelation and BBB penetration. Furthermore, compound 5 had neuroprotective effects against ROS generation, H2O2-induced apoptosis, 6-OHDA-induced cell injury, and a significant in vitro anti-inflammatory activity. Collectively, these findings highlighted that compound 5 was a potential balanced multifunctional neuroprotective agent for the development of anti-AD drugs.

Synthesis and activity of the salicylic acid ester of bakuchiol in psoriasis-surrogate keratinocytes and skin substitutes.

BACKGROUND: Topical retinoids are effective in retarding skin ageing and restoring homeostasis in skin conditions such as psoriasis. However their adverse effects (AEs), which include irritation (retinoid dermatitis), photosensitivity and teratogenicity, limit their use and patient compliance. Development of retinoid analogues with minimal AEs would allow a broader and more compliant use. AIM: To synthesise a novel molecule, bakuchiol salicylate (bakusylan), with a modulatory gene expression profile similar to retinoids, using as reference three prescription retinoids: tretinoin, tazarotene and adapalene. METHODS: We hypothesized that because bakuchiol salicylate has a structure entirely different from existing retinoids, there would be at least a partial uncoupling of AEs from the skin-normalizing activity of this retinoid. This hypothesis was tested at the transcriptional level in psoriatic cytokine-treated cultures of keratinocytes and organotypic skin substitutes, using DNA microarrays and custom PCR arrays. RESULTS: Evaluation of the gene expression profile of bakuchiol salicylate revealed elimination of several components of the retinoid-like proinflammatory response and teratogenic signature, without a substantial loss of normalizing potential. A possible mechanism of action, consisting of keratinocyte desensitization to psoriatic cytokine signalling through inhibition of the signal transducer and regulator of transcription (STAT)1/3/interferon inflammatory signal transduction axis was also identified. CONCLUSION: Bipartite materials obtained by merging two skin-active entities with specific, complementary bioactivities, such as bakuchiol and salicylic acid, may yield a new class of functional retinoids.

Synthesis and Bioactivity Evaluation of Novel 2-Salicyloylbenzofurans as Antibacterial Agents.

In order to discover new antibacterial agents, series of 2-salicyloylbenzofuran derivatives were designed, synthesized and evaluated for their antibacterial activities against three Gram-(+) strains (methicillin-sensitive Staphylococcus aureus (MSSA) ATCC 29213, methicillin-resistant Staphylococcus aureus (MRSA) ATCC 43300, and Streptococcus faecalis (S. faecalis) ATCC 29212) and one Gram-(-) strain (Escherichia coli (E. coli) ATCC 25922). The 2-salicyloylbenzofuran heterocycles were generated by Rap-Stoermer condensation of salicylaldehydes with phenacyl bromides and then converted to diverse O-ether derivatives by Williamson synthesis. The targeted products were screened for in vitro qualitative (zone of inhibition) and quantitative (MIC) antibacterial activities by agar well diffusion assay and agar dilution method. Amongst the compounds, those bearing carboxylic acid functional group were found to exhibit reasonable activity against Gram-(+) bacterial strains including S. faecalis, MSSA and MRSA with the most potent antibacterial agent 8h (MICs = 0.06-0.12 mM). Besides, the 2-salicyloylbenzofurans partly displayed inhibitory activity against MRSA with the best MICs = 0.14 mM (8f) and 0.12 mM (8h). Finally, the antibacterial results preliminarily suggested that the substituent bearing carboxylic acid group at salicyloyl-C2 and the bromine atoms on the benzofuran moiety seem to be the functionality necessary for antibacterial activities.

Carboxylation of Phenols with CO2 at Atmospheric Pressure.

A convenient and efficient method for the ortho-carboxylation of phenols under atmospheric CO2 pressure has been developed. This method provides an alternative to the previously reported Kolbe-Schmitt method, which requires very high pressures of CO2 . The addition of a trisubstituted phenol has proved essential for the successful carboxylation of phenols with CO2 at standard atmospheric pressure, allowing the efficient preparation of a broad variety of salicylic acids.

Synthesis, Characterization, and Anti-Inflammatory Activities of Methyl Salicylate Derivatives Bearing Piperazine Moiety.

In this study, a new series of 16 methyl salicylate derivatives bearing a piperazine moiety were synthesized and characterized. The in vivo anti-inflammatory activities of target compounds were investigated against xylol-induced ear edema and carrageenan-induced paw edema in mice. The results showed that all synthesized compounds exhibited potent anti-inflammatory activities. Especially, the anti-inflammatory activities of compounds M15 and M16 were higher than that of aspirin and even equal to that of indomethacin at the same dose. In addition, the in vitro cytotoxicity activities and anti-inflammatory activities of four target compounds were performed in RAW264.7 macrophages, and compound M16 was found to significantly inhibit the release of lipopolysaccharide (LPS)-induced interleukin (IL)-6 and tumor necrosis factor (TNF)-α in a dose-dependent manner. In addition, compound M16 was found to attenuate LPS induced cyclooxygenase (COX)-2 up-regulation. The current preliminary study may provide information for the development of new and safe anti-inflammatory agents.

Synthesis and structure-activity studies of the V-ATPase inhibitor saliphenylhalamide (SaliPhe) and simplified analogs.

An efficient total synthesis of the potent V-ATPase inhibitor saliphenylhalamide (SaliPhe), a synthetic variant of the natural product salicylihalamide A (SaliA), has been accomplished aimed at facilitating the development of SaliPhe as an anticancer and antiviral agent. This new approach enabled facile access to derivatives for structure-activity relationship studies, leading to simplified analogs that maintain SaliPhe's biological properties. These studies will provide a solid foundation for the continued evaluation of SaliPhe and analogs as potential anticancer and antiviral agents.

Novel derivatives of nitro-substituted salicylic acids: Synthesis, antimicrobial activity and cytotoxicity.

Inspired by the high antituberculous activity of novel nitro-substituted derivatives and based on promising predicted ADMET properties we have synthesized a series of 33 salicylanilides containing nitro-group in their salicylic part and evaluated them for their in vitro antimycobacterial, antimicrobial and antifungal activities. The presence of nitro-group in position 4 of the salicylic acid was found to be beneficial and the resulting molecules exhibited minimum inhibitory concentrations (MICs) ranging from 2 to 32 µM against Mycobacterium tuberculosis. The best activity was found for 2-hydroxy-4-nitro-N-[4-(trifluoromethyl)phenyl]benzamide (MIC=2 µM). 4-Nitrosalicylanilides were also found to be active against all Staphylococcus species tested while for MRSA strain 2-hydroxy-4-nitro-N-[4-(trifluoromethyl)phenyl]benzamide's MIC was 0.98 µM. None of the nitrosalicylanilides was active against Enterococcus sp. J 14365/08 and no considerable activity was found against Gram-negative bacteria or fungi. The hepatotoxicity of all nitrosalicylanilides was found to be in the range of their MICs for HepG2 cells.

Design, synthesis and molecular docking of salicylic acid derivatives containing metronidazole as a new class of antimicrobial agents.

A series of novel salicylic acid derivatives containing metronidazole as Staphylococcus aureus Tyrosyl-tRNA synthetase (TyrRS) inhibitors have been synthesized and evaluated their biology activities as potential antibacterial agents. Among these compounds, compound 5r exhibited the most potent antibacterial activity against Gram-positive (S. aureus ATCC 6538 and Bacillus subtilis ATCC 6633) and Gram-negative (Escherichia coli ATCC 35218 and Pseudomonas aeruginosa ATCC 13525) with MICs of 0.39-1.57 µg/mL and showed the most potent S. aureus Tyrosyl-tRNA synthetase inhibitory with 2.3 µM. Docking simulation was performed to insert compound 5r into the crystal structure of S. aureus Tyrosyl-tRNA synthetase active site to determine the probable binding model. These results suggested that compound 5r may be a promising antibacterial agent.

General method for the synthesis of salicylic acids from phenols through palladium-catalyzed silanol-directed C-H carboxylation.

A silanol-directed, palladium-catalyzed C-H carboxylation reaction of phenols to give salicylic acids has been developed. This method features high efficiency and selectivity, and excellent functional-group tolerance. The generality of this method was demonstrated by the carboxylation of estrone and by the synthesis of an unsymmetrically o,o'-disubstituted phenolic compound through two sequential C-H functionalization processes.

Synthesis and biological evaluation of hybrids from farnesylthiosalicylic acid and hydroxylcinnamic acid with dual inhibitory activities of Ras-related signaling and phosphorylated NF-κB.

A series of hybrids (5a­r) of farnesylthiosalicylic acid (FTS) and hydroxylcinnamic acid were designed and synthesized. Most of the hybrids displayed potent antiproliferative activity against seven cancer cell lines in vitro, superior to FTS as well as sorafenib. The most potent compound 5f selectively inhibited cancer cells but not non-tumor liver cell proliferation in vitro, and significantly induced SMMC-7721 cell apoptosis. Interestingly, 5f could simultaneously inhibit not only Ras-related signaling but also phosphorylated NF-κB, which may synergetically contribute to the cell growth inhibition and apoptosis induction. Moreover, 5f showed low acute toxicity to mice and significantly inhibited the hepatoma tumor growth.