Flavonoids: structural requirements for antiproliferative activity on breast cancer cells

Fluorinated 2-arylchroman-4-ones and their derivatives: synthesis, structure and antiviral activity

A number of new biologically interesting fluorinated 2-arylchroman-4-ones and their 3-arylidene derivatives were synthesized based on the p-toluenesulfonic acid-catalyzed one-pot reaction of 2-hydroxyacetophenones with benzaldehydes. It was found that obtained (E)-3-arylidene-2-aryl-chroman-4-ones reacted with malononitrile under base conditions to form 4,5-diaryl-4H,5H-pyrano[3,2-c]chromenes. The structures of the synthesized fluorinated compounds were confirmed by 1H, 19F, and 13C NMR spectral data, and for some representatives of heterocycles also using NOESY spectra and X-ray diffraction analysis. A large series of obtained flavanone derivatives as well as products of their modification (35 examples) containing from 1 to 12 fluorine atoms in the structure was tested in vitro for cytotoxicity in MDCK cell line and for antiviral activity against influenza A virus. Among the studied heterocycles 6,8-difluoro-2-(4-(trifluoromethyl)phenyl)chroman-4-one (IC50 = 6 μM, SI = 150) exhibited the greatest activity against influenza A/Puerto Rico/8/34 (H1N1) virus. Moreover, this compound appeared active against phylogenetically distinct influenza viruses, A(H5N2) and influenza B (SI's of 53 and 42, correspondingly). The data obtained suggest that the fluorinated derivatives of 2-arylchroman-4-ones are prospective scaffolds for further development of potent anti-influenza antivirals.

A novel 4'-brominated derivative of fisetin induces cell cycle arrest and apoptosis and inhibits EGFR/ERK1/2/STAT3 pathways in non-small-cell lung cancer without any adverse effects in mice

The therapeutic toxicity and resistance to currently available treatment options are major clinical challenges for the management of lung cancer. As a novel strategy, we synthesized analogues of a known flavonol, fisetin, which has shown anti-tumorigenic potential against cancer in cell culture with no adverse effects in animal models. We studied the synthetic analogues of fisetin for their anti-cancer potential against lung cancer cells, toxicity in mice and efficacy in a xenograft model. Brominated fisetin analogues were screened for their effects on the viability of A549 and H1299 lung cancer cells, and three analogues (3a, 3b, 3c), showed improved activity compared to fisetin. These analogues were more effective in restricting lung cancer cell proliferation, inducing G₂ M phase cell cycle arrest and apoptosis. The fisetin analogues also downregulated EGFR/ERK1/2/STAT3 pathways. Fisetin analogue-induced apoptosis was accompanied by a higher Bax to Bcl-2 expression ratio. Based on the in vitro studies, the most effective fisetin analogue 3b was evaluated for in vivo toxicity, wherein it did not show any hepatotoxicity or adverse health effects in mice. Furthermore, analogue 3b showed greater antitumor efficacy (p < .001) as compared to its parent compound fisetin in a human lung cancer cell xenograft study in athymic mice. Together, our data suggest that the novel fisetin analogue 3b is more effective in restricting lung cancer cell growth, both in vitro as well as in vivo, without any apparent toxicity, supporting its further development as a novel anti-lung cancer agent.

Chalcone Derivatives with a High Potential as Multifunctional Antioxidant Neuroprotectors

A systematic, rational search for chalcone derivatives with multifunctional behavior has been carried out, with the support of a computer-assisted protocol (CADMA-Chem). A total of 568 derivatives were constructed by incorporating functional groups into the chalcone structure. Selection scores were calculated from ADME properties, toxicity, and manufacturability descriptors. They were used to select a subset of molecules (23) with the best drug-like behavior. Reactivity indices were calculated for this subset. They were chosen to account for electron and hydrogen atom donating capabilities, which are key processes for antioxidant activity. The indexes showed that four chalcone derivatives (dCHA-279, dCHA-568, dCHA-553, and dCHA-283) are better electron and H donors than the parent molecule and some reference antioxidants (Trolox, ascorbic acid, and α-tocopherol). In addition, based on molecular docking, they are predicted to act as catechol-O-methyltransferase (COMT), acetylcholinesterase (AChE), and monoamine oxidase B (MAO-B) inhibitors. Therefore, these four molecules are proposed as promising candidates to act as multifunctional antioxidants with neuroprotective effects.

Cytotoxic Effects on Breast Cancer Cell Lines of Chalcones Derived from a Natural Precursor and Their Molecular Docking Analysis

This study aimed to determine the in vitro cytotoxicity and understand possible cytotoxic mechanisms via an in silico study of eleven chalcones synthesized from two acetophenones. Five were synthesized from a prenylacetophenone isolated from a plant that grows in the Andean region of the Atacama Desert. The cytotoxic activity of all the synthesized chalcones was tested against breast cancer cell lines using an MTT cell proliferation assay. The results suggest that the prenyl group in the A-ring of the methoxy and hydroxyl substituents of the B-ring appear to be crucial for the cytotoxicity of these compounds. The chalcones 12 and 13 showed significant inhibitory effects against growth in MCF-7 cells (IC₅₀ 4.19 ± 1.04 µM and IC₅₀ 3.30 ± 0.92 µM), ZR-75-1 cells (IC₅₀ 9.40 ± 1.74 µM and IC₅₀ 8.75 ± 2.01µM), and MDA-MB-231 cells (IC₅₀ 6.12 ± 0.84 µM and IC₅₀ 18.10 ± 1.65 µM). Moreover, these chalcones showed differential activity between MCF-10F (IC₅₀ 95.76 ± 1.52 µM and IC₅₀ 95.11 ± 1.97 µM, respectively) and the tumor lines. The in vitro results agree with molecular coupling results, whose affinity energies and binding mode agree with the most active compounds. Thus, compounds 12 and 13 can be considered for further studies and are candidates for developing new antitumor agents. In conclusion, these observations give rise to a new hypothesis for designing chalcones with potential cytotoxicity with high potential for the pharmaceutical industry.

Biological Activity, Hepatotoxicity, and Structure-Activity Relationship of Kavalactones and Flavokavins, the Two Main Bioactive Components in Kava (Piper methysticum)

Kava (Piper methysticum Forst) is a popular and favorable edible medicinal herb which was traditionally used to prepare a nonfermented beverage with relaxant beneficial for both social and recreational purposes. Numerous studies conducted on kava have confirmed the presence of kavalactones and flavokawains, two major groups of bioactive ingredients, in this miraculous natural plant. Expectedly, both kavalactone and flavokawain components exhibited potent antianxiety and anticancer activities, and their structure-activity relationships were also revealed. However, dozens of clinical data revealed the hepatotoxicity effect which is indirectly or directly associated with kava consumption, and most of the evidence currently seems to point the compounds of flavokawains in kava were responsible. Therefore, our aim is to conduct a systematic review of kavalactones and flavokawains in kava including their biological activities, structure-activity relationships, and toxicities, and as a result of our systematic investigations, suggestions on kava and its compounds are supplied for future research.

In-vitro Cytotoxicity and Aromatase Inhibitory Activity of Flavonoids: Synthesis, Molecular Docking and In-silico ADME Prediction

BACKGROUND

Many natural and synthetic flavonoids have been studied and documented by inhibiting aromatase enzymes for their anti-cancer activity against breast carcinoma. The aromatase enzyme is a possible target for the estrogen's positive breast cancer receptor.

OBJECTIVE

Hence, a series of flavonoids have been synthesized and assessed for their in vitro cytotoxicity and aromatase inhibitory activity.

METHODS

39 flavonoids were synthesized and characterized by spectroscopic techniques, and their computational study was performed using the maestro version of the Schrodinger. In-silico ADME properties were checked by QikPro software. A total of 18 compounds were evaluated based on the docking score using cytotoxicity assay in human breast cancer cell line MCF-7.

RESULTS

Of the 18 compounds tested, 07 compounds, namely 2b, 8b, 14b, 15b, 19b, 24b, and 30b flavonoids were found to be more active with their IC₅₀ values of 20.73 μM, 1.636 μM, 16.08 μM, 22.02 μM, 15.75 μM, 0.345 μM and 16.08 μM, respectively, compared with the reference drug letrozole. The in-vitro aromatase inhibitory activity of six compounds 2b, 8b, 14b, 19b, 24b, and 30b was conducted using a fluorogenic assay kit. The values of IC₅₀ for compounds 2b and 24b were found to be 0.31 μM and 0.36 μM, respectively.

CONCLUSION

Therefore, it was concluded that compounds 2b and 24b had a potent inhibitory effect of aromatase compared with letrozole with an IC₅₀ value of 0.86 μM. At the same time, the other compounds 8b, 14b, 30b, and 19b were considered to have similar aromatase inhibitory activity. Hence, their essential aromatase inhibitory activities make them good lead candidates for developing potent inhibitors of aromatase.

The Anticancer Effects of Flavonoids through miRNAs Modulations in Triple-Negative Breast Cancer

Triple- negative breast cancer (TNBC) incidence rate has regularly risen over the last decades and is expected to increase in the future. Finding novel treatment options with minimum or no toxicity is of great importance in treating or preventing TNBC. Flavonoids are new attractive molecules that might fulfill this promising therapeutic option. Flavonoids have shown many biological activities, including antioxidant, anti-inflammatory, and anticancer effects. In addition to their anticancer effects by arresting the cell cycle, inducing apoptosis, and suppressing cancer cell proliferation, flavonoids can modulate non-coding microRNAs (miRNAs) function. Several preclinical and epidemiological studies indicate the possible therapeutic potential of these compounds. Flavonoids display a unique ability to change miRNAs' levels via different mechanisms, either by suppressing oncogenic miRNAs or activating oncosuppressor miRNAs or affecting transcriptional, epigenetic miRNA processing in TNBC. Flavonoids are not only involved in the regulation of miRNA-mediated cancer initiation, growth, proliferation, differentiation, invasion, metastasis, and epithelial-to-mesenchymal transition (EMT), but also control miRNAs-mediated biological processes that significantly impact TNBC, such as cell cycle, immune system, mitochondrial dysregulation, modulating signaling pathways, inflammation, and angiogenesis. In this review, we highlighted the role of miRNAs in TNBC cancer progression and the effect of flavonoids on miRNA regulation, emphasizing their anticipated role in the prevention and treatment of TNBC.

Multi-Therapeutic Potential of Naringenin (4',5,7-Trihydroxyflavonone): Experimental Evidence and Mechanisms

Extensive research has been carried out during the last few decades, providing a detailed account of thousands of discovered phytochemicals and their biological activities that have the potential to be exploited for a wide variety of medicinal purposes. These phytochemicals, which are pharmacologically important for clinical use, primarily consist of polyphenols, followed by terpenoids and alkaloids. There are numerous published reports indicating the primary role of phytochemicals proven to possess therapeutic potential against several diseases. However, not all phytochemicals possess significant medicinal properties, and only some of them exhibit viable biological effects. Naringenin, a flavanone found in citrus fruits, is known to improve immunity, repair DNA damage, and scavenge free radicals. Despite the very low bioavailability of naringenin, it is known to exhibit various promising biological properties of medicinal importance, including anti-inflammatory and antioxidant activities. This review focuses on the various aspects related to naringenin, particularly its physicochemical, pharmacokinetic, and pharmacodynamic properties. Furthermore, various pharmacological activities of naringenin, such as anticancer, antidiabetic, hepatoprotective, neuroprotective, cardioprotective, nephroprotective, and gastroprotective effects, have been discussed along with their mechanisms of action.

Plasma Protein Binding of Herbal-Flavonoids to Human Serum Albumin and Their Anti-proliferative Activities

Herbal-flavonoids (HF) as polyphenolic secondary metabolites are taken in the daily diet to join in many metabolic processes in the human organism. Anti-proliferative activities and human serum albumin (HSA) binding capacities of herbal-flavonoids namely 7,5'-dimethoxyisoetin (HF1), homoorientin-6''-4-O-methyl-myo-inositol (HF2), (2R, 3R)-(+)-dihydrokaempferol-7,4'-dimethylether (HF3), eriodictyol-7,4'-dimethylether (HF4) and flavonoids isoorientin (HF5) and genkwanin (HF6) were investigated. Anti-proliferative activities were determined by the xCELLigence system by treatment with human prostate (PC3) and cervical cancer (HeLa) cells. The binding capacities were studied by two-dimensional (2D-FL) and three-dimensional (3D-FL) fluorescence spectroscopy. HeLa and PC3 cell lines were treated with flavonoids at 10, 50 and 100 μg/mL concentrations over a 48 hour period. Stable anti-proliferative efficacy plots were obtained for tested flavonoids. From the flavonoids, HF3 and HF4 showed the strongest anti-proliferative effect against PC3 and HeLa cell line. HF1 and HF2 exhibited the strongest binding capacity to the HSA corresponding to Kb values of 3.81 x 104 M-1 and 6.00 x 104 M-1, respectively. The studies revealed that the flavonoids form the basis of in vivo preclinical studies as important nutraceuticals of the daily diet, as well as modelled in medical and pharmacological applications.

Citrus Peel Flavonoids as Potential Cancer Prevention Agents

Citrus fruit and in particular flavonoid compounds from citrus peel have been identified as agents with utility in the treatment of cancer. This review provides a background and overview regarding the compounds found within citrus peel with putative anticancer potential as well as the associated in vitro and in vivo studies. Historical studies have identified a number of cellular processes that can be modulated by citrus peel flavonoids including cell proliferation, cell cycle regulation, apoptosis, metastasis, and angiogenesis. More recently, molecular studies have started to elucidate the underlying cell signaling pathways that are responsible for the flavonoids' mechanism of action. These growing data support further research into the chemopreventative potential of citrus peel extracts, and purified flavonoids in particular. This critical review highlights new research in the field and synthesizes the pathways modulated by flavonoids and other polyphenolic compounds into a generalized schema.

Synthesis, biological evaluation, and molecular modelling of new naphthalene-chalcone derivatives as potential anticancer agents on MCF-7 breast cancer cells by targeting tubulin colchicine binding site

A series of naphthalene-chalcone derivatives (3a–3t) were prepared and evaluated as tubulin polymerisation inhibitor for the treatment of breast cancer. All compounds were evaluated for their antiproliferative activity against MCF-7 cell line. The most of compounds displayed potent antiproliferative activity. Among them, compound 3a displayed the most potent antiproliferative activity with an IC₅₀ value of 1.42 ± 0.15 µM, as compared to cisplatin (IC₅₀ = 15.24 ± 1.27 µM). Additionally, the promising compound 3a demonstrated relatively lower cytotoxicity on normal cell line (HEK293) compared to tumour cell line. Furthermore, compound 3a was found to induce significant cell cycle arrest at the G₂/M phase and cell apoptosis. Compound 3a displayed potent tubulin polymerisation inhibitory activity with an IC₅₀ value of 8.4 µM, which was slightly more active than the reference compound colchicine (IC₅₀ = 10.6 µM). Molecular docking analysis suggested that 3a interact and bind at the colchicine binding site of the tubulin.

Synthesis of 3-halochromones with simple KX halogen sources enabled by in situ halide oxidation

An in situ oxidation strategy for generating molecular halogen has been developed for the synthesis of 3-halochromones by employing simple potassium halides as halogen sources.

Chrysin-loaded bovine serum albumin particles as bioactive nanosupplements

Freeze-dried Chrys-loaded BSAnp retained their properties after reconstitution and induced apoptosis on breast cancer cells. BSAnp-70-11 (smallest sized) was the most cytotoxic system with a gastrointestinal release of 14% Chrys.

7-methoxyflavanone alleviates neuroinflammation in lipopolysaccharide-stimulated microglial cells by inhibiting TLR4/MyD88/MAPK signalling and activating the Nrf2/NQO-1 pathway

OBJECTIVES

Neuroprotective potential of 7-methoxyflavanone (7MF) and its underlying mechanism was investigated.

METHODS

Inhibitory effects of 7MF on microglial activation and neuroinflammation were evaluated by employment of lipopolysaccharide (LPS)-induced BV2 microglial cells. Changes in expression of genes and proteins of interest were investigated by RT-qPCR analysis and Western blot analysis. Inhibitory effects of 7MF on microglial overactivation were verified in LPS-treated C57BL/6J mice using ionized calcium-binding adaptor molecule-1 (Iba1) in the brain and interleukin-6 (IL-6) in serum as indicators.

KEY FINDINGS

In BV2 cells, pretreatment with 7MF antagonized LPS-induced production of inflammatory factors IL-6, tumour necrosis factor-α (TNF-α), cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), intercellular adhesion molecule-1 (ICAM-1) and monocyte chemoattractant protein-1 (MCP-1). Mechanistic studies revealed reduced expression of Toll-like receptor 4 (TLR4), myeloid differentiation factor-88 (MyD88), phosphorylated forms of c-Jun N-terminal kinase (p-JNK) and extracellular signal-regulated kinases 1/2 (p-ERK) but increased nuclear accumulation of nuclear factor erythroid 2-related factor 2 (Nrf2) and cellular expression of NAD(P)H quinone dehydrogenase-1 (NQO-1) by 7MF. In LPS-treated mice, pretreatment with 7MF reduced the brain level of Iba1 and serum level of IL-6.

CONCLUSIONS

7-methoxyflavanone inhibited LPS-stimulated TLR4/MyD88/MAPK signalling and activated Nrf2-mediated transcription of antioxidant protein NQO-1, showing antineuroinflammatory effect, so it is a potential neuroprotective agent.

Position Impact of Hydroxy Groups on Spectral, Acid-Base Profiles and DNA Interactions of Several Monohydroxy Flavanones

Structure-related biological activities of flavanones are still considered largely unexplored. Since they exhibit various medicinal activities, it is intriguing to enter deeper into their chemical structures, electronic transitions or interactions with some biomolecules in order to find properties that allow us to better understand their effects. Little information is available on biological activity of flavanone and its monohydroxy derivatives in relation to their physicochemical properties as spectral profiles, existence of protonated/deprotonated species under pH changes or interaction with Calf Thymus DNA. We devoted this work to research demonstrating differences in the physicochemical properties of the four flavanones: flavanone, 2′-hydroxyflavanone, 6-hydroxyflavanone and 7-hydroxyflavanone and linking them to their biological activity. Potentiometric titration, UV–Vis spectroscopy were used to investigate influence of pH on acid–base and spectral profiles and to propose the mode of interaction with DNA. Cyclic voltammetry was applied to evaluate antioxidant potentiality and additionally, theoretical DFT(B3LYP) method to disclose electronic structure and properties of the compounds. Molecular geometries, proton affinities and pK_a values have been determined. According to computational and cyclic voltammetry results we could predict higher antioxidant activity of 6-hydroxyflavanone with respect to other compounds. The values of K_b intrinsic binding constants of the flavanones indicated weak interactions with DNA. Structure–activity relationships observed for antioxidant activity and DNA interactions suggest that 6-hydroxyflavanone can protect DNA against oxidative damage most effectively than flavanone, 2′-hydroxyflavanone or 7-hydroxyflavanone.

Dietary Flavonoids for Immunoregulation and Cancer: Food Design for Targeting Disease

Flavonoids, one of the most abundant phytochemicals in a diet rich in fruits and vegetables, have been recognized as possessing anti-proliferative, antioxidant, anti-inflammatory, and estrogenic activities. Numerous cellular and animal-based studies show that flavonoids can function as antioxidants by preventing DNA damage and scavenging reactive oxygen radicals, inhibiting formation of DNA adducts, enhancing DNA repair, interfering with chemical damage by induction of Phase II enzymes, and modifying signaling pathways. Recent evidence also shows their ability to regulate the immune system. However, findings from clinical trials have been mixed with no clear consensus on dose, frequency, or type of flavonoids best suited to elicit many of the beneficial effects. Delivery of these bioactive compounds to their biological targets through "targeted designed" food processing strategies is critical to reach effective concentration in vivo. Thus, the identification of novel approaches that optimize flavonoid bioavailability is essential for their successful clinical application. In this review, we discuss the relevance of increasing flavonoid bioavailability, by agricultural engineering and "targeted food design" in the context of the immune system and cancer.

Baicalein Suppresses Stem Cell-Like Characteristics in Radio- and Chemoresistant MDA-MB-231 Human Breast Cancer Cells through Up-Regulation of IFIT2

Resistance to both chemotherapy and radiation therapy is frequent in triple-negative breast cancer (TNBC) patients. We established treatment-resistant TNBC MDA-MB-231/IR cells by irradiating the parental MDA-MB-231 cells 25 times with 2 Gy irradiation and investigated the molecular mechanisms of acquired resistance. The resistant MDA-MB-231/IR cells were enhanced in migration, invasion, and stem cell-like characteristics. Pathway analysis by the Database for Annotation, Visualization and Integrated Discovery revealed that the NF-κB pathway, TNF signaling pathway, and Toll-like receptor pathway were enriched in MDA-MB-231/IR cells. Among 77 differentially expressed genes revealed by transcriptome analysis, 12 genes involved in drug and radiation resistance, including interferon-induced protein with tetratricopeptide repeats 2 (IFIT2), were identified. We found that baicalein effectively reversed the expression of IFIT2, which is reported to be associated with metastasis, recurrence, and poor prognosis in TNBC patients. Baicalein sensitized radio- and chemoresistant cells and induced apoptosis, while suppressing stem cell-like characteristics, such as mammosphere formation, side population, expression of Oct3/4 and ABCG2, and CD44^highCD24^low population in MDA-MB-231/IR cells. These findings improve our understanding of the genes implicated in radio- and chemoresistance in breast cancer, and indicate that baicalein can serve as a sensitizer that overcomes treatment resistance.

Design, Synthesis and Docking Studies of Flavokawain B Type Chalcones and Their Cytotoxic Effects on MCF-7 and MDA-MB-231 Cell Lines

Flavokawain B (1) is a natural chalcone extracted from the roots of Piper methysticum, and has been proven to be a potential cytotoxic compound. Using the partial structure of flavokawain B (FKB), about 23 analogs have been synthesized. Among them, compounds 8, 13 and 23 were found in new FKB derivatives. All compounds were evaluated for their cytotoxic properties against two breast cancer cell lines, MCF-7 and MDA-MB-231, thus establishing the structure–activity relationship. The FKB derivatives 16 (IC₅₀ = 6.50 ± 0.40 and 4.12 ± 0.20 μg/mL), 15 (IC₅₀ = 5.50 ± 0.35 and 6.50 ± 1.40 μg/mL) and 13 (IC₅₀ = 7.12 ± 0.80 and 4.04 ± 0.30 μg/mL) exhibited potential cytotoxic effects on the MCF-7 and MDA-MB-231 cell lines. However, the methoxy group substituted in position three and four in compound 2 (IC₅₀ = 8.90 ± 0.60 and 6.80 ± 0.35 μg/mL) and 22 (IC₅₀ = 8.80 ± 0.35 and 14.16 ± 1.10 μg/mL) exhibited good cytotoxicity. The lead compound FKB (1) showed potential cytotoxicity (IC₅₀ = 7.70 ± 0.30 and 5.90 ± 0.30 μg/mL) against two proposed breast cancer cell lines. It is evident that the FKB skeleton is unique for anticancer agents, additionally, the presence of halogens (Cl and F) in position 2 and 3 also improved the cytotoxicity in FKB series. These findings could help to improve the future drug discovery process to treat breast cancer. A molecular dynamics study of active compounds revealed stable interactions within the active site of Janus kinase. The structures of all compounds were determined by ¹H-NMR, EI-MS, IR and UV and X-ray crystallographic spectroscopy techniques.

Relationship between Antioxidant and Anticancer Activity of Trihydroxyflavones

Plant polyphenols have been highlighted not only as chemopreventive, but also as potential anticancer substances. Flavones are a subclass of natural flavonoids reported to have an antioxidant and anticancer activity. The aim of our study was to evaluate antioxidant and anticancer activity of seventeen trihydroxyflavone derivatives, including apigenin (API) and baicalein (BCL). Also, we wanted to find out if there is a correlation between those two effects. Cell growth inhibition testing was carried out using MTT assay in three different human cancer cell lines: lung (A549), breast (MCF-7) and brain epithelial (U87). Antioxidant activity was determined by the DPPH radical scavenging method. Thirteen trihydroxyflavones possessed anticancer activity against at least one tested cancer cell line. They were more active against the MCF-7 cell line, and the lowest activity was determined against the U87 cell line. The majority of compounds inhibited cancer cell growth at EC₅₀ values between 10-50 µM. The most active compound was 3',4',5-trihydroxyflavone 7, especially against A549 and MCF-7 cell lines. The correlation between anti-proliferative and antioxidant activity was only moderate, and it was determined for A549 and U87 cancer cell lines. The most important fragment for those two effects is the ortho-dihydroxy group in ring B.

CONCLUSIONS

Trihydroxyflavones demonstrated anticancer activity. Further and more detailed studies should to be carried out to estimate the structure-activity relationship of these compounds.

Chemopreventive Agents and Inhibitors of Cancer Hallmarks: May Citrus Offer New Perspectives?

Fruits and vegetables have long been recognized as potentially important in the prevention of cancer risk. Thus, scientific interest in nutrition and cancer has grown over time, as shown by increasing number of experimental studies about the relationship between diet and cancer development. This review attempts to provide an insight into the anti-cancer effects of Citrus fruits, with a focus on their bioactive compounds, elucidating the main cellular and molecular mechanisms through which they may protect against cancer. Scientific literature was selected for this review with the aim of collecting the relevant experimental evidence for the anti-cancer effects of Citrus fruits and their flavonoids. The findings discussed in this review strongly support their potential as anti-cancer agents, and may represent a scientific basis to develop nutraceuticals, food supplements, or complementary and alternative drugs in a context of a multi-target pharmacological strategy in the oncology.

Chalcone-based Selective Inhibitors of a C4 Plant Key Enzyme as Novel Potential Herbicides

Weeds are a challenge for global food production due to their rapidly evolving resistance against herbicides. We have identified chalcones as selective inhibitors of phosphoenolpyruvate carboxylase (PEPC), a key enzyme for carbon fixation and biomass increase in the C4 photosynthetic pathway of many of the world's most damaging weeds. In contrast, many of the most important crop plants use C3 photosynthesis. Here, we show that 2',3',4',3,4-Pentahydroxychalcone (IC50 = 600 nM) and 2',3',4'-Trihydroxychalcone (IC50 = 4.2 μM) are potent inhibitors of C4 PEPC but do not affect C3 PEPC at a same concentration range (selectivity factor: 15-45). Binding and modeling studies indicate that the active compounds bind at the same site as malate/aspartate, the natural feedback inhibitors of the C4 pathway. At the whole plant level, both substances showed pronounced growth-inhibitory effects on the C4 weed Amaranthus retroflexus, while there were no measurable effects on oilseed rape, a C3 plant. Growth of selected soil bacteria was not affected by these substances. Our chalcone compounds are the most potent and selective C4 PEPC inhibitors known to date. They offer a novel approach to combat C4 weeds based on a hitherto unexplored mode of allosteric inhibition of a C4 plant key enzyme.

Novel synthesised flavone derivatives provide significant insight into the structural features required for enhanced anti-proliferative activity

Synthesis and antiproliferative evaluation of a library of 76 methoxy and hydroxy flavones, and their 4-thio analogues showed that the novel thioflavones 15f and 16f exhibit 7–46 fold greater anti-proliferative potency than the natural flavone chrysin (2d).

Antibacterial and Cytotoxic Activity of Compounds Isolated from Flourensia oolepis

The antibacterial and cytotoxic effects of metabolites isolated from an antibacterial extract of Flourensia oolepis were evaluated. Bioguided fractionation led to five flavonoids, identified as 2′,4′-dihydroxychalcone (1), isoliquiritigenin (2), pinocembrin (3), 7-hydroxyflavanone (4), and 7,4′-dihydroxy-3′-methoxyflavanone (5). Compound 1 showed the highest antibacterial effect, with minimum inhibitory concentration (MIC) values ranging from 31 to 62 and 62 to 250 μg/mL, against Gram-positive and Gram-negative bacteria, respectively. On further assays, the cytotoxic effect of compounds 1–5 was determined by MTT assay on acute lymphoblastic leukemia (ALL) and chronic myeloid leukemia (CML) cell lines including their multidrug resistant (MDR) phenotypes. Compound 1 induced a remarkable cytotoxic activity toward ALL cells (IC₅₀ = 6.6–9.9 μM) and a lower effect against CML cells (IC₅₀ = 27.5–30.0 μM). Flow cytometry was used to analyze cell cycle distribution and cell death by PI-labeled cells and by Annexin V/PI staining, respectively. Upon treatment, 1 induced cell cycle arrest in the G₂/M phase accompanied by a strong induction of apoptosis. These results describe for the first time the antibacterial metabolites of F. oolepis extract, with 1 being the most effective. This chalcone also emerges as a selective cytotoxic agent against sensitive and resistant leukemic cells, highlighting its potential as a lead compound.

Synthesis and detailed spectroscopic characterization of various hydroxy-functionalized fluorescent chalcones: A combined experimental and theoretical study

Four different bright yellow to orange hydroxy-substituted chalcones (i.e., 2',4-di-hydroxy (1), 2',3',4-trihydroxy (2), 2',3',4'-trihydroxy (3), and 2'-hydroxy-4-methoxy (4) chalcones) were synthesized and characterized by LC-MS, FT-IR, FT-Raman, and fluorescence spectroscopy and thermogravimetric analysis. UV-visible absorption spectroscopy was also used. The experimental (theoretical) bandgaps of 1, 2, 3, and 4 are 2.89 (2.90), 2.93 (2.95), 3.04 (3.09), and 3.01 (2.91) eV, respectively. The hydroxy-substituted chalcones exhibited strong dual emissions as a consequence of the locally excited states followed by internal charge transfer processes. The molecular structures, lowest energy transitions, vibrational frequencies, and spectroscopic information were calculated using density functional theory and time-dependent density functional theory methods at the B3LYP/6-31G(d,p) theoretical level. The experimental and theoretical data were compared and the relationship between them was briefly discussed.

2',4'-dihydroxychalcone, a flavonoid isolated from Herba oxytropis, suppresses PC-3 human prostate cancer cell growth by induction of apoptosis

Natural products are a promising source for the development of novel cancer therapies, due to their potential effectiveness and low toxicity profiles. As a main component of Herba oxytropis, 2',4'-dihydroxychalcone (TFC) is known to demonstrate anti-tumor activity in vitro. In the present study, TFC was found to potently inhibit proliferation and induce apoptosis in PC-3 human prostate cancer cells in a dose-dependent manner. The results demonstrated that the induction of apoptosis is associated with cell cycle arrest at the G0/G1 phase and activation of caspase-3/-7. Additional mechanistic studies of two biomarkers, phosphatase and tensin homolog (PTEN) and cyclin-dependent kinase inhibitor 1B (p27^Kip1), in prostate cancer revealed that TFC treatment significantly upregulated the expression of PTEN and p27^Kip1. The findings of the present study indicate that TFC-induced apoptosis in PC-3 cells via upregulation of PTEN and p27^Kip1, which results in cell cycle arrest in G0/G1 phase, activation of caspase-3/-7 and induction of apoptosis. Therefore, TFC may be a potential compound for human prostate cancer therapy.

In Silico docking studies of selected flavonoids--natural healing agents against breast cancer

BACKGROUND

Breast cancer is the serious health concern in India causing the highest mortality rate in females, which occurs due to uncontrolled cell division and can be metastasize to other parts of the human body. Interactions with estrogen receptor (ER) alpha are mainly responsible for the malignant tumors with regulation of the transcription of various genes as a transcription factor. Most of the drugs currently used for the breast cancer treatment produce various side effects and hence we focused on natural compounds which do not exhibit any toxic effect against normal human cells.

MATERIALS AND METHODS

Structure of human ER was retrieved from the Protein Data Bank and the structures of flavonoid compounds have been collected from PubChem database. Molecular docking and drug likeness studies were performed for those natural compounds to evaluate and analyze the anti-breast cancer activity.

RESULTS

Finally two compounds satisfying the Lipinski's rule of five were reported. The two compounds also exhibited highest binding affinity with human ER greater than 10.5 Kcal/mol.

CONCLUSIONS

The results of this study can be implemented in the drug designing pipeline.

Anti-cancer chalcones: Structural and molecular target perspectives

Chalcone or (E)-1,3-diphenyl-2-propene-1-one scaffold remained a fascination among researchers in the 21st century due to its simple chemistry, ease of synthesis and a wide variety of promising biological activities. Several natural and (semi) synthetic chalcones have shown anti-cancer activity due to their inhibitory potential against various targets namely ABCG2/P-gp/BCRP, 5α-reductase, aromatase, 17-β-hydroxysteroid dehydrogenase, HDAC/Situin-1, proteasome, VEGF, VEGFR-2 kinase, MMP-2/9, JAK/STAT signaling pathways, CDC25B, tubulin, cathepsin-K, topoisomerase-II, Wnt, NF-κB, B-Raf and mTOR etc. In this review, a comprehensive study on molecular targets/pathways involved in carcinogenesis, mechanism of actions (MOAs), structure activity relationships (SARs) and patents granted have been highlighted. With the knowledge of molecular targets, structural insights and SARs, this review may be helpful for (medicinal) chemists to design more potent, safe, selective and cost effective anti-cancer chalcones.

Synthesis and anti-cancer activity evaluation of new dimethoxylated chalcone and flavanone analogs

A novel series of chalcones and flavanones discriminated by the presence of a 3,4-dimethoxyphenyl moiety in their structures were synthesized as anti-cancer agents. The cytotoxicity evaluation of the analogs against the MCF-7, MDA-MB-231 (human breast cancer), and SK-N-MC (human neuroblastoma) cell lines demonstrated that the introduction of a halogen on the 3,4-dimethoxyphenyl part of both series and the attachment of a pyrrolidinylethoxy group on the C-7 position of the flavanone derivatives increased their activity. Indeed, 3-halogenated chalcones (1c and 1d) were more potent than the standard drug etoposide against all tested cell lines. Fluorescence microscopy and flow cytometry analyses confirmed that the anti-cancer effect of the most potent compounds 1c and 1d occurs via apoptosis induction.