Synthesis and evaluation of novel chromone analogs for their inhibitory activity against interleukin-5

New chromones from the roots of Saposhnikovia divaricata (Turcz.) Schischk with anti-inflammatory activity

Fifteen new chromones, sadivamones A-E (1-5), cimifugin monoacetate (6), sadivamones F-N (7-15), together with fifteen known chromones (16-30), were isolated from the ethyl acetate portions of 70% ethanol extract of Saposhnikovia divaricata (Turcz.) Schischk roots. The structures of the isolates were determined using 1D/2D NMR data and electron circular dichroism (ECD) calculations. Meanwhile, LPS induced RAW264.7 inflammatory cell model was used to determine the potential anti-inflammatory activity of all the isolated compounds in vitro. The results showed that compounds 2, 8, 12-13, 18, 20-22, 24, and 27 significantly inhibited the production of lipopolysaccharide (LPS)-induced NO in macrophages. To determine the signaling pathways involved in the suppression of NO production by compounds 8, 12 and 13, we investigated ERK and c-Jun N-terminal protein kinase (JNK) expression by western blot analysis. Further mechanistic studies demonstrated that compounds 12 and 13 inhibited the phosphorylation of ERK and the activation of ERK and JNK signaling in RAW264.7 cells via MAPK signaling pathways. Taken together, compounds 12 and 13 may be valuable candidates for the treatment of inflammatory diseases.

Agarwood-The Fragrant Molecules of a Wounded Tree

Agarwood, popularly known as oudh or gaharu, is a fragrant resinous wood of high commercial value, traded worldwide and primarily used for its distinctive fragrance in incense, perfumes, and medicine. This fragrant wood is created when Aquilaria trees are wounded and infected by fungi, producing resin as a defense mechanism. The depletion of natural agarwood caused by overharvesting amidst increasing demand has caused this fragrant defensive resin of endangered Aquilaria to become a rare and valuable commodity. Given that instances of natural infection are quite low, artificial induction, including biological inoculation, is being conducted to induce agarwood formation. A long-term investigation could unravel insights contributing toward Aquilaria being sustainably cultivated. This review will look at the different methods of induction, including physical, chemical, and biological, and compare the production, yield, and quality of such treatments with naturally formed agarwood. Pharmaceutical properties and medicinal benefits of fragrance-associated compounds such as chromones and terpenoids are also discussed.

Discovery and Optimization of Chromone Derivatives as Novel Selective Phosphodiesterase 10 Inhibitors

Phosphodiesterase 10 (PDE10) inhibitors have received much attention as promising therapeutic agents for central nervous system (CNS) disorders such as schizophrenia and Huntington's disease. Recently, a hit compound 1 with a novel chromone scaffold has shown moderate inhibitory activity against PDE10A (IC₅₀ = 500 nM). Hit-to-lead optimization has resulted in compound 3e with an improved inhibitory activity (IC₅₀ = 6.5 nM), remarkable selectivity (>95-fold over other PDEs), and good metabolic stability (RLM t_1/2 = 105 min) by using an integrated strategy (molecular modeling, chemical synthesis, bioassay, and cocrystal structure). The cocrystal structural information provides insights into the binding pattern of 3e in the PDE10A catalytic domain to highlight the key role of the halogen and hydrogen bonds toward Tyr524 and Tyr693, respectively, thereby resulting in high selectivity against other PDEs. These new observations are of benefit for the rational design of the next generation PDE10 inhibitors for CNS disorders.

Human health-related properties of chromones: an overview

Natural compounds occurring throughout the world are scientifically and practically valuable because of their unique and beneficial properties to control a wide range of disorders in the human body. Chromones are attracting increasing attention as novel therapeutic agents due to their effective bioactivities for human health. Accordingly, the present overview article was designed to scan the biological and pharmacological performance of chromones, including their anti-inflammatory, anticancer, anti-oxidant, and anti-microbial activities.

Identification of novel 2-benzyl-1-indanone analogs as interleukin-5 inhibitors

A novel series of 2-benzyl-1-indanone analogs were investigated as IL-5 inhibitory activity. Among the synthesized compounds, 7-(cyclohexylmethoxy)-2-(4-hydroxybenzyl)-2,3-dihydro-1H-inden-1-one (7s, 100.0% inhibition at 30 μM, IC₅₀ = 4.0 μM), and 7-(cyclohexylmethoxy)-2-(3-hydroxybenzyl)-2,3-dihydro-1H-inden-1-one (7t, 95.0% inhibition at 30 μM, IC₅₀ = 6.0 μM) showed the best inhibitory activity against IL-5. The 2-benzyl-1-indanone analogs showed moderate to strong IL-5 inhibitory activity. Especially, hydroxyl (HBD/HBA) substituent at position 3 or 4 on phenyl ring B showed potent IL-5 inhibition. Additionally, the bulky hydrophobic cyclohexylmethoxy group at position 7 of the 1-indanone ring is favorable for the inhibitory activity.

Discovery of novel 3-(hydroxyalkoxy)-2-alkylchromen-4-one analogs as interleukin-5 inhibitors

A series of novel chromen-4-one analogs 9a-d and 10a-u was designed, synthesized and evaluated for their IL-5 inhibitory activity. Most of the chromen-4-one analogs showed strong inhibitory activity in low micro molar potency. Among them, 5-(cyclohexylmethoxy)-3-(3-hydroxypropoxy)-2-isopropyl-4H-chromen-4-one (10t, 90.0% inhibition at 30 μM, IC₅₀ = 5.5 μM, CLogP = 4.76887) and 2-cyclohexyl-5-(cyclohexylmethoxy)-3-(3-hydroxypropoxy)-4H-chromen-4-one (10u, 95.5% inhibition at 30 μM, IC₅₀ = 3.0 μM, CLogP = 5.96187) showed the best inhibition. The structure activity relationship reveals that the hydrophobic cyclohexylmethoxy group at the position 5 of the chromen-4-one ring A is preferable than at position 6 and the dual hydrogen bonding acceptor property on the chromen-4-one ring should be important for the inhibitory activity. In addition, the optimum length of the side chain at position 3 of chromen-4-one ring is critical for the donation of hydrogen to the binding site and the 3-hydroxypropoxy group showed the best activity. Moreover, the conformational restrictor (isopropyl, cyclohexyl group) at position 2 is much more favorable for the formation of effective conformer of side chain with hydrogen bonding donor property of these chromen-4-one analogs.

Antioxidant Properties and Oxidative Transformation of Different Chromone Derivatives

Nowadays, there is an increase in the application of natural products for the prevention of different disorders or adjuvant substances next to pharmacological treatment. Phytochemicals include different chromone derivatives, which possess a wide spectrum of biological activity. The aim of the present study was the investigation of the antioxidant activity, cytotoxicity and oxidative transformation of nine chromone derivatives. First, we investigated the radical scavenging activity (ABTS), the oxygen radical absorption capacity (ORAC) and the ferric reducing antioxidant power (FRAP) of the investigated molecules. The cytotoxic effects of the compounds were tested on H9c2 cell cultures by the MTT assay. Each compound showed a significant ORAC value compared to the reference. However, the compound 865 possess significantly higher FRAP and ABTS activity in comparison with the reference and other tested molecules, respectively. Based on these assays, the compound 865 was selected for further analysis. In these experiments, we investigated the oxidative metabolism of the compound in vitro. The molecule was oxidized by the Fenton reaction, artificial porphyrin and electrochemistry; then, the formed products were identified by mass spectrometry. Four possible metabolites were detected. The results revealed the compound 865 to possess good antioxidant properties and to be stable metabolically; hence, it is worth investigating its effects in vivo.

Chromones: A Promising Ring System for New Anti-inflammatory Drugs

The quest for safer anti-inflammatory drugs is still the focus of several medicinal chemistry programs. Chromones (4H-chromen-4-ones) are a group of naturally occurring compounds ubiquitous in plants, and the chromone core has proven to be a privileged scaffold in medicinal chemistry. Herein we provide an overview of the relevance of chromones as anti-inflammatory agents, specifically as inhibitors of cyclooxygenase (COX), 5-lipoxygenase (5-LOX), interleukin-5 (IL-5), and nitric oxide (^. NO) production. Numerous structure-activity relationships and mechanisms of action are discussed. This review is therefore intended to provide a foundation for the design and synthesis of novel chromone-based compound libraries for further development into safer and more efficient anti-inflammatory agents.

Exploration of benzamidochromenone derivatives with conformational restrictor as interleukin-5 inhibitors

Novel amidochromen-4-one analogs 8a-k and 9a-f were prepared and studied for their IL-5 inhibitory activity. Among the synthesized compounds, (6-benzamido-2-cyclohexyl-4-oxo-4H-chromen-3-yl)methyl acetate (8a, 95% inhibition at 30 μM, IC50=6.1 μM) exhibited potent IL-5 inhibitory activity. The conformational restrictor at position 2 like bulky cyclohexyl group is favorable for the formation of effective conformer of side chain small ester like acetoxymethyl at position 3 of these chromenone analogs 8. In addition the hydrophobic planarity of benzamido group at position 6 should be important for the potent IL-5 inhibitory activity. Since replacing acetoxymethyl moiety with hydroxymethyl group at position 3 of chromenone decreases the activity, which indicates that the location of hydrogen bonding group should be near 4 atom distances away from chromenone ring is more optimum for the activity. Therefore, these benzamidochromen-4-one analogs 8 are novel scaffold for finding potent interleukin-5 inhibitors.

Investigating flavonoids as molecular templates for the design of small-molecule inhibitors of cell signaling

Epidemiological and clinical trials reveal compelling evidence for the ability of dietary flavonoids to lower cardiovascular disease risk. The mechanisms of action of these polyphenolic compounds are diverse, and of particular interest is their ability to function as protein and lipid kinase inhibitors. We have previously described structure-activity studies that reinforce the possibility for using flavonoid structures as templates for drug design. In the present study, we aim to begin constructing rational screening strategies for exploiting these compounds as templates for the design of clinically relevant, antiplatelet agents. We used the platelet as a model system to dissect the structural influence of flavonoids, stilbenes, anthocyanidins, and phenolic acids on inhibition of cell signaling and function. Functional groups identified as relevant for potent inhibition of platelet function included at least 2 benzene rings, a hydroxylated B ring, a planar C ring, a C ring ketone group, and a C-2 positioned B ring. Hydroxylation of the B ring with either a catechol group or a single C-4' hydroxyl may be required for efficient inhibition of collagen-stimulated tyrosine phosphorylated proteins of 125 to 130 kDa, but may not be necessary for that of phosphotyrosine proteins at approximately 29 kDa. The removal of the C ring C-3 hydroxyl together with a hydroxylated B ring (apigenin) may confer selectivity for 37 to 38 kDa phosphotyrosine proteins. We conclude that this study may form the basis for construction of maps of flavonoid inhibitory activity on kinase targets that may allow a multitargeted therapeutic approach with analogue counterparts and parent compounds.

Cytokines in terms of QSAR. Review, evaluation and comparative studies

Cytokines represent a class of chemical factors that act as mediators in the complex biological response of inflammation, potentially implicated in various diseases. Therefore, selective inhibition or antagonism of cytokines is a target of anti-inflammatory drug design. The QSAR (Quantitative Structure-Activity Relationships) analysis presented here attempts to identify the structural features and physicochemical properties that are significant for cytokine antagonists or inhibitors and in particular of i) interleukin-5 (IL-5), ii) interleukin-6 (IL-6) and iii) of the chemotactic cytokine (chemokine) interleukin-8 (IL-8). Firstly, a historical aspect of the limited published QSARs is discussed and then a 2D-QSAR analysis was carried out for 26 data sets of compounds using the C-QSAR program of Biobyte. In six cases hydrophobicity appeared to be important. Steric factors in the form of overall molar refractivity (CMR), molar refractivity of the substituent (MR), molar volume (MgVol), Taft's Es constant and the sterimol parameters B1 and B5 have a significant impact on biological activity in most of the derived equations whereas electronic parameters as σp, σm or Σσ appeared in five cases.

Insights into dietary flavonoids as molecular templates for the design of anti-platelet drugs

Flavonoids are low-molecular weight, aromatic compounds derived from fruits, vegetables, and other plant components. The consumption of these phytochemicals has been reported to be associated with reduced cardiovascular disease (CVD) risk, attributed to their anti-inflammatory, anti-proliferative, and anti-thrombotic actions. Flavonoids exert these effects by a number of mechanisms which include attenuation of kinase activity mediated at the cell-receptor level and/or within cells, and are characterized as broad-spectrum kinase inhibitors. Therefore, flavonoid therapy for CVD is potentially complex; the use of these compounds as molecular templates for the design of selective and potent small-molecule inhibitors may be a simpler approach to treat this condition. Flavonoids as templates for drug design are, however, poorly exploited despite the development of analogues based on the flavonol, isoflavonone, and isoflavanone subgroups. Further exploitation of this family of compounds is warranted due to a structural diversity that presents great scope for creating novel kinase inhibitors. The use of computational methodologies to define the flavonoid pharmacophore together with biological investigations of their effects on kinase activity, in appropriate cellular systems, is the current approach to characterize key structural features that will inform drug design. This focussed review highlights the potential of flavonoids to guide the design of clinically safer, more selective, and potent small-molecule inhibitors of cell signalling, applicable to anti-platelet therapy.

Identification of novel chromenone derivatives as interleukin-5 inhibitors

A series of (E)-5-alkoxy-3-(3-phenyl-3-oxoprop-1-enyl)-4H-chromen-4-ones (4) and (E)-5-alkoxy-3-(3-hydroxy-3-phenylprop-1-enyl)-4H-chromen-4-ones (5) were synthesized and evaluated for their IL-5 inhibitory activity. Propenone analogs 4 possess some of the structurally important characteristics of isoflavone 2 and chalcone 3 previously known as potent IL-5 inhibitor. However, the inhibitory activity of 4 was weak and therefore this structural hybridization appears to be ineffective for the design of IL-5 inhibitor. Meanwhile the potent activity profile of compounds 5 was discovered. This enhanced activity of 5 compared to 4 could be due to the effective location of hydroxyl group of allylic alcohol moiety of 5 in the 3D structure. The electron withdrawing substituents at position 4 of phenyl ring of 5 enhances the activity possibly due to an increase in the strength of hydrogen bonding property of hydroxyl group of allylic alcohol moiety.

Novel interleukin-5 inhibitors based on hydroxyethylaminomethyl-4H-chromen-4-one scaffold

Hydroxyethylaminomethyl-4H-chromenones were previously discovered as fairly strong IL-5 inhibitor. For determination of detail structure activity relationship, N-substituted hydroxyethylaminomethylchromenones 4a-n were prepared and evaluated for their IL-5 inhibitory activity. Shifting the hydrophobic group to nitrogen from 1-position of hydroxyethylamino moiety of hydroxyethylaminomethyl-4H-chromenones enhances the activity. The increment in bulkiness or hydrophobicity of alkyl side chain at amino group increases the activity. The same level of activity of 5-(cyclohexylmethoxy)-3-(N-benzyl-2-hydroxyethylaminomethyl)-4H-chromenone analogs regardless of hydrophobic or hydrophilic substituents at 4th position of phenyl ring might infer the existence of tunnel structure in the putative receptor for accepting these side chains.

Physiochemical, optical and biological activity of chitosan-chromone derivative for biomedical applications

This paper describes the physiochemical, optical and biological activity of chitosan-chromone derivative. The chitosan-chromone derivative gels were prepared by reacting chitosan with chromone-3-carbaldehyde, followed by solvent exchange, filtration and drying by evaporation. The identity of Schiff base was confirmed by UV-Vis absorption spectroscopy and Fourier-transform infrared (FTIR) spectroscopy. The chitosan-chromone derivative was evaluated by X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), photoluminescence (PL) and circular dichroism (CD). The CD spectrum showed the chitosan-chromone derivative had a secondary helical structure. Microbiological screening results demonstrated the chitosan-chromone derivative had antimicrobial activity against Escherichia coli bacteria. The chitosan-chromone derivative did not have any adverse effect on the cellular proliferation of mouse embryonic fibroblasts (MEF) and did not lead to cellular toxicity in MEFs. These results suggest that the chitosan-chromone derivative gels may open a new perspective in biomedical applications.