Synthesis and biological evaluations of chalcones, flavones and chromenes as farnesoid x receptor (FXR) antagonists

Discovery of novel and selective farnesoid X receptor antagonists through structure-based virtual screening, preliminary structure-activity relationship study, and biological evaluation

Farnesoid X receptor (FXR) is a bile acids receptor and plays a crucial role in regulating bile acids, lipids, and glucose metabolism. Previous research suggests that inhibiting FXR activation can be beneficial in reducing cholesterol and low-density lipoprotein cholesterol (LDL-C) levels, offering potential treatment options for metabolic syndrome with lipid disorders. Herein, we report p-acetylaminobenzene sulfonate derivatives as a novel scaffold of FXR antagonists by multistage screening. Among these derivatives, compound F44-A13 exhibited a half-maximal inhibitory concentration of 1.1 μM. Furthermore, compound F44-A13 demonstrated effective inhibition of FXR activation in cellular assays and exhibited high selectivity over eleven other nuclear receptors. Besides, compound F44-A13 significantly suppressed the regulation of FXR target genes Shp, Besp, and Cyp7a1, while reducing cholesterol levels in human hepatoma HepG2 cells. Pharmacological studies conducted on C57BL/6 mice further confirmed that compound F44-A13 had beneficial effects in reducing cholesterol, triglycerides, and LDL-C levels. These findings highlight that F44-A13 is a highly selective FXR antagonist that might serve as a useful molecule for further FXR studies as well as the development of FXR antagonists for the potential treatment of metabolic diseases with lipid disorders.

4-Dimethylaminopyridine (DMAP), A Superior Mediator for Morita-Balylis-Hillman Reaction-Triggered Annulative Condensation of Salicylaldehydes and Acrylonitrile to Form 3-Cyano-2H-chromenes

We unveiled superior base mediators for the annulative condensation of salicylaldehydes and acrylonitrile to give 3-cyano-2H-chromenes, which has been mediated only by 1,4-diazabicyclo[2.2.2]octane (DABCO) over the past two decades. The reactions were most efficiently mediated by 4-dimethylaminopyridine (DMAP), which yielded 3-cyano-2H-chromenes in higher yields than DABCO in most cases. We also confirmed that the reaction remained high yielding in a decagram-scale experiment with a catalytic amount of DMAP. The utility of this reaction was also exemplified by derivatization of an obtained 3-cyano-2H-chromene into a known 2H-chromene-3-carboxylic acid, which was previously synthesized with a non-readily available reagent.

Chlorinated Naringenin Analogues as Potential Inhibitors of Transthyretin Amyloidogenesis

Misfolding and aggregation of transthyretin are implicated in the fatal systemic disease known as transthyretin amyloidosis. Here, we report the development of a naringenin derivative bearing two chlorine atoms that will be efficacious for preventing aggregation of transthyretin in the eye. The amyloid inhibitory activity of the naringenin derivative was as strong as that of tafamidis, which is the first therapeutic agent targeting transthyretin in the plasma. X-ray crystal structures of the compounds in complex with transthyretin demonstrated that the naringenin derivative with one chlorine bound to the thyroxine-binding site of transthyretin in the forward mode and that the derivative with two chlorines bound to it in the reverse mode. An ex vivo competitive binding assay showed that naringenin derivatives exhibited more potent binding than tafamidis in the plasma. Furthermore, an in vivo pharmacokinetic study demonstrated that the dichlorinated derivative was significantly delivered to the eye.

Structure Modification of FXR Antagonistic Chalcones and Their Inhibitory Effects on NSCLC Cell Proliferation and Metastasis

Although Farneosid X Receptor (FXR) has been regarded as a promising drug target for metabolic diseases as well as anti-inflammatory, antitumor and antiviral actions, the antagonism by FXR ligands are still underrepresented in the current FXR targeted therapy. In this study, we discovered selective FXR antagonists through the structure optimization from polyoxygenated chalcone scaffold. The selective antagonist 6p is not only inhibitory to non small cell lung cancer (NSCLC) cell proliferation in an FXR dependent way, but also active in metastasis models. Taken together, chalcone-based FXR antagonist is of potential to the targeted therapy for FXR highly expressed NSCLC.

Identification of inhibitors targeting polyketide synthase 13 of Mycobacterium tuberculosis as antituberculosis drug leads

Polyketide synthase 13 (Pks13) is an essential enzyme in the synthesis of mycolic acids in Mtb. Therefore, Pks13 is a promising drug target for tuberculosis treatment. We used a structure-guided approach to identify novel chemotype inhibitors of Pks13 and assessed them using a Pks13 enzymatic assay and surface plasmon resonance. The structure-activity relationships (SAR) results demonstrated that the substituents at the 2, 5, and 6 positions of the 4H-chromen-4-one scaffold are critical for maintaining the MIC. Compound 6e with 2-hydroxyphenyl at the 2 position of the 4H-chromen-4-one scaffold, exhibited potent activity against Mtb H37Rv (MIC = 0.45 μg/mL) and displayed good Pks13 affinity and inhibition (IC₅₀ = 14.3 μM). This study described here could provide an avenue to explore a novel inhibitor class for Pks13 and aid the further development of antituberculosis drugs.

Flavonoid-triazolyl hybrids as potential anti-hepatitis C virus agents: Synthesis and biological evaluation

A series of flavonoid-triazolyl hybrids were synthesized and evaluated as novel inhibitors of hepatitis C virus (HCV). The results of anti-HCV activity assays showed that most of the synthesized derivatives at a concentration of 100 μg/mL inhibited the generation of progeny virus. Among these derivatives, 10m and 10r exhibited the most potent anti-HCV activity and inhibited the production of HCV in a dose-dependent manner. Interestingly, 10m and 10r had no significant inhibitory effect on viral translation or replication. Additional action mechanism studies revealed that the most potent compounds, 10m and 10r, significantly inhibited viral entry to 34.0% and 52.0%, respectively, at 10 μM. These results suggest further effective application of 10m and 10r as potential HCV preventive agents.

Flavonoids: structure-function and mechanisms of action and opportunities for drug development

Flavonoids are polyphenolic phytochemicals produced in fruits, nuts and vegetables and dietary consumption of these structurally diverse compounds is associated with multiple health benefits including increased lifespan, decreased cardiovascular problems and low rates of metabolic diseases. Preclinical studies with individual flavonoids demonstrate that these compounds exhibit anti-inflammatory and anticancer activities and they enhance the immune system. Their effectiveness in both chemoprevention and chemotherapy is associated with their targeting of multiple genes/pathways including nuclear receptors, the aryl hydrocarbon receptor (AhR), kinases, receptor tyrosine kinases and G protein-coupled receptors. However, despite the remarkable preclinical activities of flavonoids, their clinical applications have been limited and this is due, in part, to problems in drug delivery and poor bioavailability and these problems are being addressed. Further improvements that will expand clinical applications of flavonoids include mechanism-based precision medicine approaches which will identify critical mechanisms of action of individual flavonoids with optimal activities that can be used in combination therapies.