Synthesis and Biological Evaluation of 3-Benzylidene-4-chromanone Derivatives as Free Radical Scavengers and α-Glucosidase Inhibitors

Synthesis, computational docking and molecular dynamics studies of a new class of spiroquinoxalinopyrrolidine embedded chromanone hybrids as potent anti-cholinesterase agents

Novel structurally intriguing heterocycles embedded with spiropyrrolidine, quinoxaline and chromanone units were synthesized in good yields using a [Bmim]Br accelerated multicomponent reaction strategy. The key step of the reaction is 1,3-dipolar cycloaddition involving highly functionalized dipolarophile, viz. 3-benzylidenechroman-4-one, to afford spiroquinoxalinopyrrolidine embedded chromanone hybrid heterocycles. The formation of spiro products occurs via two C-C, two N-C and one C-N bonds possessing four adjoining stereogenic centers, two of which are spiro carbons. The newly synthesized spiro compounds showed potent acetylcholinesterase and butyrylcholinesterase inhibitory activities. Moreover, compounds with fluorine displayed the highest AChE (3.20 ± 0.16 μM) and BChE (18.14 ± 0.06 μM) inhibitory activities. Further, docking studies, followed by all-atom molecular dynamics, showed results that are consistent with in vitro experimental findings. Although docking scores for the synthesized derivatives were higher than those of the standard drug, MD MMPBSA results showed better binding of synthesized derivatives (-93.5 ± 11.9 kcal mol-1) compared to the standard drug galantamine (-66.2 ± 12.3 kcal mol-1) for AChE but exhibited similar values (-98.1 ± 11.2 and -97.9 ± 11.5 kcal mol-1) for BChE. These differences observed in drug binding with AChE/BChE are consistent with RMSD, RMSF, LIG plots, and FEL structural analysis. Taken together, these derivatives could be potential candidates as inhibitors of AChE and BChE.

Sappanone A: A natural PDE4 inhibitor with dual anti-inflammatory and antioxidant activities from the heartwood of Caesalpinia sappan L

ETHNOPHARMACOLOGICAL RELEVANCE

Sumu (Lignum sappan), the dry heartwood of Caesalpinia sappan L., is a traditional Chinese medicine used as an analgesic and anti-inflammatory agent.

AIM OF THE STUDY

The study aspired to discover natural phosphodiesterase 4 (PDE4) inhibitors with dual anti-inflammatory and antioxidant activities from Sumu for the treatment of chronic obstructive pulmonary disease (COPD).

MATERIALS AND METHODS

To accurately and efficiently identify natural PDE4 inhibitors from Sumu, molecular docking and molecular dynamics (MD) analysis methods were used for structure-based virtual screening of a self-built database of primary polyphenols in Sumu. According to the previous studies of Sumu and the free radical scavenging mechanism of polyphenols, the reported antioxidant components from Sumu and the potential antioxidants with the antioxidant pharmacophore of catechol and π-conjugated moieties were selected from the potential PDE4 inhibitors predicted by docking. Sappanone A, a potential PDE4 inhibitor with antioxidant activity from Sumu, was selected, calculated and synthesized to evaluate its dual anti-inflammatory and antioxidant functions in vitro and in vivo studies. Herein sappanone A was assayed for its inhibitory effects against PDE4 enzyme activity, tumor necrosis factor-alpha (TNF-α) production induced by lipopolysaccharide (LPS) in RAW264.7 macrophages and malondialdehyde (MDA) production induced by Fe²⁺ in mouse lung homogenate; sappanone A was also assayed for its abilities of radical (DPPH) scavenging, reducing Fe³⁺ and complexing Fe²⁺ in vitro. Additionally, LPS-induced acute lung injury (ALI) in mice was used to evaluate its anti-inflammatory activity as a PDE4 inhibitor in vivo, and the levels of TNF-α and total protein in bronchoalveolar lavage fluid (BALF) and myeloperoxidase (MPO) activity in the lung were assayed.

RESULTS

The present study predicted and validated that sappanone A was a promising PDE4 inhibitor from Sumu with dual anti-inflammation and antioxidant activities from Sumu. In vitro, sappanone A remarkably inhibited PDE4 enzyme activity and reduced TNF-α production induced by LPS in RAW264.7 macrophages and MDA production induced by Fe²⁺ in mouse lung homogenate. Meanwhile, it showed outstanding abilities of scavenging DPPH radicals, reducing Fe³⁺ and complexing Fe²⁺. In vivo, sappanone A (25 mg/kg and 50 mg/kg, i.p., twice daily for 7 days) distinctly prevented LPS-induced ALI in mice by reducing the levels of TNF-α and total protein in BALF and MPO activity in the lung.

CONCLUSION

Sappanone A is a natural PDE4 inhibitor with dual anti-inflammatory and antioxidant activities from the traditional Chinese medicine Sumu, which may be a promising therapeutic agent to prevent the vicious cycle of COPD inflammation and oxidative stress.

Computational analysis and in vitro evaluation of TMF 104, for its antioxidant, antimicrobial, and anticancer efficacies

Benzylidene chromanones are small molecules, structurally similar to active phytochemicals. Herein, we report one novel benzylidene chromanone, TMF 104, for its bio-efficacies. Its computational docking for Vanin-1, antioxidant, free radical scavenging capacities, antimicrobial effects, and anticancer efficacy were analyzed. TMF 104 predicated strong binging to Vanin-1 protein with a docking energy of -8.1 kcal/mol. The compound dose-dependently exhibited free-radical scavenging and antioxidant activities when tested in vitro. The compound also had remarkable activity against Salmonella typhimurium, Enterococcus faecalis, Staphylococcus aureus, and Escherichia coli with minimum inhibitory concentration values of 1.5, 2.0, 12.5, and 13.5 μg/ml, respectively. The compound was also effective against Bacillus cereus and Pseudomonas aeruginosa albeit at higher concentrations. TMF 104 dose-dependently inhibited the proliferation of MCF-7, NCI H460, and Caki-1 cells with respective GI₅₀ values of 24.51, 21.95, and 32.95 μg/ml, whereas the compound was toxic to normal Vero cells at much higher concentration of 264.70 μg/ml. The compound also aided in apoptosis and increased the sub G₀ /G₁ phase of the cell cycle in all three cancer cells tested. Our study identified a novel, potent benzylidene analogue with potent antioxidant, antimicrobial, and anticancer activities, which drives further attention for further research.

Structural derivatization strategies of natural phenols by semi-synthesis and total-synthesis

Structural derivatization of natural products has been a continuing and irreplaceable source of novel drug leads. Natural phenols are a broad category of natural products with wide pharmacological activity and have offered plenty of clinical drugs. However, the structural complexity and wide variety of natural phenols leads to the difficulty of structural derivatization. Skeleton analysis indicated most types of natural phenols can be structured by the combination and extension of three common fragments containing phenol, phenylpropanoid and benzoyl. Based on these fragments, the derivatization strategies of natural phenols were unified and comprehensively analyzed in this review. In addition to classical methods, advanced strategies with high selectivity, efficiency and practicality were emphasized. Total synthesis strategies of typical fragments such as stilbenes, chalcones and flavonoids were also covered and analyzed as the supplementary for supporting the diversity-oriented derivatization of natural phenols.

Chromanone-A Prerogative Therapeutic Scaffold: An Overview

Chromanone or Chroman-4-one is the most important and interesting heterobicyclic compound and acts as a building block in medicinal chemistry for isolation, designing and synthesis of novel lead compounds. Structurally, absence of a double bond in chromanone between C-2 and C-3 shows a minor difference from chromone but exhibits significant variations in biological activities. In the present review, various studies published on synthesis, pharmacological evaluation on chroman-4-one analogues are addressed to signify the importance of chromanone as a versatile scaffold exhibiting a wide range of pharmacological activities. But, due to poor yield in the case of chemical synthesis and expensive isolation procedure from natural compounds, more studies are required to provide the most effective and cost-effective methods to synthesize novel chromanone analogs to give leads to chemistry community. Considering the versatility of chromanone, this review is designed to impart comprehensive, critical and authoritative information about chromanone template in drug designing and development.

Structure activity evaluation and computational analysis identify potent, novel 3-benzylidene chroman-4-one analogs with anti-fungal, anti-oxidant, and anti-cancer activities

SIGNIFICANCE

3-Benzylidene chroman-4-ones share close homology with naturally occurring bioactive compounds.

OBJECTIVES

This study evaluated the antifungal, antioxidant, and anticancer activities of novel 3-benzylidene chromanone analogs with respect to their structure-activity relationships.

METHODS

Compounds 45e-64e were synthesized inhouse. Aspergillus niger (MTCC 1344) Aspergillus flavus and Botrytis cinerea were the fungal strains tested. Computational docking analysis was carried out for vanin-1, estrogen receptor (ER), and Akt proteins using Auto-dock vina. Free radical scavenging and total antioxidant capacity was analyzed using spectrophotometric methods. MCF-7 (breast cancer) cell line was used for anticancer assays. Flow cytometry was used to detect cell cycle and apoptosis.

RESULTS

Out of the twenty compounds screened, compounds 47e, 50e, 52e, 57e, and 61e that possessed either methoxy and ethoxy/methyl/isopropyl group exhibited very good activity against all fungi. Compounds possessing methoxy group alone showed moderate activity and compounds devoid of methoxy, and ethoxy groups did not show any activity. When computationally analyzed against target proteins for antioxidant properties, the compounds exhibited excellent binging efficacy to vanin-1 and ERs. These predictions were translated in the in vitro free-radical scavenging and antioxidant assays. The compounds exhibited anti-proliferative efficacy in breast cancer cell line, increased the sub-G₀/G₁ cell cycle populations and total apoptosis in MCF-7 cells. Additionally, the compounds also depicted excelling binging energy when computationally analyzed for Akt enzyme binding.

CONCLUSION

In summary, our study identified potential analogs of 3-benzylidene chroman-4-one molecules with excellent anti-fungal, anti-oxidant, and anticancer activities which demand further research for drug developments.

FNF-12, a novel benzylidene-chromanone derivative, attenuates inflammatory response in in vitro and in vivo asthma models mediated by M2-related Th2 cytokines via MAPK and NF-kB signaling

BACKGROUND AND AIM

This study evaluates a novel benzylidene-chromanone derivative, FNF-12, for efficacy in in vitro and in vivo asthma models.

METHODS

Rat basophilic leukemia (RBL-2H3) and acute monocytic leukemia (THP-1)-derived M2 macrophages were used. Human whole blood-derived neutrophils and basophils were employed. Flow cytometry was used for studying key signalling proteins. Platelet activation factor (PAF)-induced asthma model in guinea pigs was used for in vivo studies.

RESULTS

The chemical structure of FNF-12 was confirmed with proton-nuclear mass resonance (NMR) and mass spectroscopy. FNF-12 controlled degranulation in RBL-2H3 cells with an IC₅₀ value of 123.7 nM and inhibited TNF-α release from these cells in a dose-responsive way. The compound effectively controlled the migration and elastase release in activated neutrophils. IC₅₀ value in the FcεRI-basophil activation assay was found to be 205 nM. FNF-12 controlled the release of lipopolysaccharide (LPS)-induced interleukin-10, I-309/CCL1 and MDC/CCL22 in THP-1 derived M2 macrophages. The compound suppressed LPS-induced mitogen activated protein kinase (MAPK)-p-p38 and nuclear factor kappa B(NF-kB)-p-p65 expression in these cells. A dose-dependent decrease in the accumulation of total leucocytes, eosinophils, neutrophils and macrophages was observed in PAF-induced animal models.

CONCLUSION

FNF-12 was able to control the inflammatory responses in in vitro and in vivo asthma models, which may be driven by controlling M2-related Th2 cytokines via MAPK and NF-kB signaling.

A combined Chemical, Computational and invitro approach identifies SBL 105 as novel DHODH inhibitor in Acute Myeloid Leukemia cells

Inhibition of the dihydroorotate dehydrogenase (DHODH) has been successful at the preclinical level in controlling myeloid leukemia. However, poor clinical trials warrant the search for new potent DHODH inhibitors. Herein we present a novel DHODH inhibitor SBL-105 effective against myeloid leukemia. Chemical characteristics were identified by ¹H NMR, ¹³C NMR, and mass spectroscopy. Virtual docking and molecular dynamic simulation analysis were performed using the automated protocol with AutoDock-VINA, GROMACS program. Human-recombinant (rh) DHODH was used for enzyme inhibition study. THP-1, TF-1, HL-60, and SKM-1 cell lines were used. MTT assay was used to assess cell viability. Flow cytometry was employed for cell cycle, apoptosis, and differentiation analysis. Chemical analysis identified the compound to be 3-benzylidene-6,7-benz-chroman-4-one (SBL-105). The compound showed high binding efficacy toward DHODH with a ΔG_binding score of −10.9 kcal/mol. Trajectory analysis indicated conserved interactions of SBL-105–DHODH to be stable throughout the 200-ns simulation. SBL-105 inhibited rh DHODH with an IC₅₀ value of 48.48 nM. The GI₅₀ values of SBL-105 in controlling THP-1, TF-1, HL-60, and SKM-1 cell proliferations were 60.66, 45.33, 73.98, and 86.01 nM, respectively. A dose-dependent increase in S-phase cell cycle arrest and total apoptosis was observed by SBL-105 treatment in both cell types, which were reversed in the presence of uridine. The compound also increased the differentiation marker CD11b-positive populations in both THP-1 and TF-1 cells, which were decreased under uridine influence. SBL-105, a novel DHODH inhibitor, identified using computational and in vitro analysis, was effective in controlling AML cells and needs attention for further preclinical developments.

Quantification of the Ability of Natural Products to Prevent Herpes Virus Infection

Background: Herpes simplex virus (HSV) is usually dormant and becomes apparent when body conditions decline. We investigated the anti-HSV activity of various natural and synthetic compounds for future clinical application. Methods: Mock- and HSV-infected Vero cells were treated for three days with various concentrations of samples. For short exposure, 100-fold concentrated virus were preincubated for 3 min with samples, diluted to normal multiplicity of infection (MOI), before the addition to the cells. Anti-HSV activity was evaluated by the chemotherapy index. Results: Alkaline extracts of the leaves of Sasa sp. (SE) and pine cone (PCE) showed higher anti-HSV activity than 20 Japanese traditional herb medicines (Kampo formulas), four popular polyphenols, and 119 chromone-related compounds. Exposure of HSV to SE or PCE for 3 min almost completely eliminated the infectivity of HSV, whereas much longer exposure time was required for Kakkonto, the most active Kampo formulae. Anti-HSV activity of PCE and Kakkonto could be detected only when they were dissolved by alkaline solution (pH 8.0), but not by neutral buffer (pH 7.4). Anti-HSV activity of SE and povidone iodine was stable if they were diluted with neutral buffer. Conclusions: The present study suggests the applicability of SE and PCE for treatment of oral HSV and possibly other viruses.

Development of Newly Synthesized Chromone Derivatives with High Tumor Specificity against Human Oral Squamous Cell Carcinoma

Since many anticancer drugs show severe adverse effects such as mucositis, peripheral neurotoxicity, and extravasation, it was crucial to explore new compounds with much reduced adverse effects. Comprehensive investigation with human malignant and nonmalignant cells demonstrated that derivatives of chromone, back-bone structure of flavonoid, showed much higher tumor specificity as compared with three major polyphenols in the natural kingdom, such as lignin-carbohydrate complex, tannin, and flavonoid. A total 291 newly synthesized compounds of 17 groups (consisting of 12 chromones, 2 esters, and 3 amides) gave a wide range of the intensity of tumor specificity, possibly reflecting the fitness for the optimal 3D structure and electric state. Among them, 7-methoxy-3-[(1E)-2-phenylethenyl]-4H-1-benzopyran-4-one (compound 22), which belongs to 3-styrylchromones, showed the highest tumor specificity. 22 induced subG1 and G2 + M cell population in human oral squamous cell carcinoma cell line, with much less keratinocyte toxicity as compared with doxorubicin and 5-FU. However, 12 active compounds selected did not necessarily induce apoptosis and mitotic arrest. This compound can be used as a lead compound to manufacture more active compound.

5,7-Dimethoxy-3-(2'-hydroxybenzyl)-4-chromanone inhibits α-glucosidase in vitro and alleviates postprandial hyperglycemia in diabetic mice

This study was designed to investigate the inhibitory activities of 5,7-dimethoxy-3-(2'hydro-xybenzyl)-4-chromanone (5,7-D chromanone) isolated from Portulaca oleracea L. on carbohydrate digesting enzymes and its ability to improve postprandial hyperglycemia in streptozotocin-induced diabetic mice. 5,7-D chromanone strongly inhibited α-glucosidase and α-amylase (half-maximal inhibitory concentration, IC₅₀; 15.03 ± 2.59 μM and 12.39 ± 2.16 μM, respectively). The inhibitions were more effective than acarbose, which was the positive control. The increase in blood glucose level after ingesting starch was more significantly alleviated in the 5,7-D chromanone ingested group than in the control group of diabetic mice. In the control group, blood glucose levels were 24.64 ± 1.73, 27.22 ± 1.58, and 26.37 ± 1.41 mM, and in the 5,7-D chromanone ingested group were 23.87 ± 1.10, 23.38 ± 1.32, and 21.42 ± 1.36 mM at 30, 60, and 120 min, respectively. In addition, the area under the curve of blood glucose significantly declined with 5,7-D chromanone ingestion in diabetic mice. The results indicate that 5,7-D chromanone can help lower postprandial hyperglycemia by inhibiting carbohydrate digesting enzymes.

Design, synthesis and biological evaluation of novel neuchromenin analogues as potential antifungal agents

In continuation of our program to discover new potential antifungal agents, thirty-two neuchromenin analogues were synthesized and characterized by the spectroscopic analysis. By using the mycelium growth rate method, the target compounds were evaluated systematically for antifungal activities in vitro against six plant pathogenic fungi, and structure-activity relationships (SAR) were derived. Compounds 6b-c, and 6l showed obvious inhibition activity on each of the fungi at 50 μg/mL. For the corresponding fungi, 7 of the compounds showed average inhibition rates of >80% at 50 μg/mL; especially, compounds 6b, 6d-e, and 6i-l displayed more potent antifungal activity against A. solani than that of thiabendazole (a positive control). Moreover, compound 6c also exhibited good activity against C. lunata with EC₅₀ values of 12.7 μg/mL, and the value was much superior to that of thiabendazole (EC₅₀ = 59.7 μg/mL). SAR analysis showed that the presence of conjugated structure, bearing a C=C bond conjugated to the C=O group, obviously decreased the activity; the type and position of the substituted R₅ significantly influenced the activity. Furthermore, the significantly bioactive compounds 6b-e, 6g, 6i and 6l showed very low toxicities against HL-7702, BEL-7402 and HCT-8 cells. Resistance development assay indicated that compounds 6b-e and 6l failed to induce the two tested strains of fungi to develop resistance. SEM analysis initially revealed that compound 6d may exert its antifungal effect by damaging fungal cell wall.

Synthesis and Cytotoxic Evaluation of 3-Methylidenechroman-4-ones

In the search for new anticancer agents, a library of variously substituted 3-methylidenechroman-4-ones was synthesized using Horner–Wadsworth–Emmons methodology. Acylation of diethyl methylphosphonate with selected ethyl salicylates furnished 3-diethoxyphosphorylchromen-4-ones which were next used as Michael acceptors in the reaction with various Grignard reagents. The adducts were obtained as the mixtures of trans and cis diastereoisomers along with a small amount of enol forms. Their relative configuration and preferred conformation were established by NMR analysis. The adducts turned up to be effective Horner–Wadsworth–Emmons reagents giving 2-substituted 3-methylidenechroman-4-ones, which were then tested for their possible cytotoxic activity against two leukemia cell lines, HL-60 and NALM-6, and against MCF-7 breast cancer cell line. All new compounds (14a–o) were highly cytotoxic for the leukemic cells and showed a moderate or weak effect on MCF-7 cells. Analog 14d exhibited the highest growth inhibitory activity and was more potent than carboplatin against HL-60 (IC₅₀ = 1.46 ± 0.16 µM) and NALM-6 (IC₅₀ = 0.50 ± 0.05 µM) cells. Further tests showed that 14d induced apoptosis in NALM-6 cells, which was mediated mostly through the extrinsic pathway.

Synthesis, anticancer, structural, and computational docking studies of 3-benzylchroman-4-one derivatives

A series of 3-Benzylchroman-4-ones were synthesized and screened for anticancer activity by MTT assay. The compounds were evaluated against two cancerous cell lines BT549 (human breast carcinoma), HeLa (human cervical carcinoma), and one noncancerous cell line vero (normal kidney epithelial cells). 3b was found to be the most active molecule against BT549 cells (IC₅₀ = 20.1 µM) and 3h against HeLa cells (IC₅₀ = 20.45 µM). 3b also exhibited moderate activity against HeLa cells (IC₅₀ = 42.8 µM). The molecular structures of 3h and 3i were solved by single crystal X-ray crystallographic technique. Additionally, the molecular docking studies between the tumour suppressor protein p53 with the lead compound 3h, which exhibited better anticancer activity against HeLa cells was examined.

Chromone as a Privileged Scaffold in Drug Discovery: Recent Advances

The use of privileged structures in drug discovery has proven to be an effective strategy, allowing the generation of innovative hits/leads and successful optimization processes. Chromone is recognized as a privileged structure and a useful template for the design of novel compounds with potential pharmacological interest, particularly in the field of neurodegenerative, inflammatory, and infectious diseases as well as diabetes and cancer. This perspective provides the reader with an update of an earlier article entitled "Chromone: A Valid Scaffold in Medicinal Chemistry" ( Chem. Rev. 2014 , 114 , 4960 - 4992 ) and is mainly focused on chromones of biological interest, including those isolated from natural sources. Moreover, as drug repurposing is becoming an attractive drug discovery approach, recent repurposing studies of chromone-based drugs are also reported.