Related Flavones Research Articles

Polyphenols from traditional Chinese medicine and Mediterranean diet are effective against Aβ toxicity in vitro and in vivo in Caenorhabditis elegans.

The potential of naturally occurring polyphenols as nutraceuticals to prevent and/or treat Alzheimer's disease is studied. Five structurally related flavones and four tyrosols were tested in vitro in human amyloid-β peptide aggregation assays. The most promising compounds were two flavones, scutellarein and baicalein, and two tyrosols hydroxytyrosol and hydroxytyrosol acetate. These compounds caused a dose-dependent reduction of Aβ-peptide aggregation up to 90% for the flavones and 100% for the tyrosols, at concentrations of 83.3 μM and 33.3 mM, respectively. The IC50 value obtained for scutellarein was 22.5 μM, and was slightly higher for baicalein, 25.9 μM, while for hydroxytyrosol and hydroxytyrosol acetate they were 0.57 mM and 0.62 mM. Given these results, the compounds were selected to conduct in vivo assays with the Caenorhabditis elegans animal model of Alzheimer's disease. The amyloid anti-aggregation ability of these polyphenols was demonstrated in in vivo aggregation assays in which 1 mM hydroxytyrosol reduced the amyloid plaques in the mutant strain CL2331 by 43%. The neuroprotective effect was evaluated in chemotaxis experiments carried out with transgenic strain CL2355 that expresses the human amyloid-β peptide in the neurons. The chemotaxis index was improved by 240% when the neuron-impaired animals were treated with 1 mM hydroxytyrosol. The results indicate that the four molecules would be viable candidates to develop nutraceuticals that interfere in amyloid-β peptide aggregation and, consequently, prevent and/or treat Alzheimer's disease.

Immunosuppressant flavonoids from Scutellaria baicalensis

Some plants used in Traditional Chinese Medicine serve as treatment for disease states where a suppression of the cellular immune response is desired. However, the compounds responsible for the immunosuppressant effects of these plants are not necessarily known.The immunosuppressant compounds in the roots of Scutellaria baicalensis, one of the most promising plants identified in a previous screening, were tracked by HPLC activity profiling and concomitant on-line spectroscopic analysis. Compounds were then isolated by preparative chromatography, and structures elucidated by spectroscopic methods. Twelve flavonoids (5–16) were identified from the active time windows, and structurally related flavones 2, 4, and 17, and flavanones 1 and 3 were isolated from adjacent fractions. All flavonoids possessed an unusual substitution pattern on the B-ring, with an absence of substituents at C-3 and C-4. Compounds 11, 13, 14, and 16 inhibited T-cell proliferation (IC50 values at 12.1–39 μM) at non-cytotoxic concentrations. The findings may support the use of S. baicalensis in disorders where a modulation of the cellular immune response is desirable.

Metabolome analysis using multiple data mining approaches suggests luteolin biosynthesis in Physcomitrella patens.

The model land plant Physcomitrella patens synthesizes flavonoids which may act as protectant of ultraviolet-B radiation. We aimed to uncover its flavonoid profile, for which metabolome analysis using liquid chromatography coupled with Ion trap/Orbitrap mass spectrometry was performed. From the 80% methanol extracts, 661 valid peaks were detected. Prediction of the elemental compositions within a mass accuracy of 2 ppm indicated that 217 peaks had single elemental composition. A compound database search revealed 47 peaks to be annotated as secondary metabolites based on the compound database search. Comprehensive substituent search by ShiftedIonsFinder showed there were 13 peaks of potential flavonoid derivatives. Interestingly, a peak having m/z 287.0551, corresponding to that of luteolin, was detected, even though flavone synthase has never been identified in P. patens. Using P. patens labeled with stable isotopes (13C-, 15N-, 18O-, and 34S), we confirmed the elemental composition of the peak as C15H10O6. By a comparison of MS/MS spectra with that of authentic standard, the peak was identified as luteolin or related flavone isomers. This is the first report of luteolin or related flavones synthesis and the possibility of the existence of an unknown enzyme with flavone synthase activity in P. patens.

Microwave Assisted Efficient Synthesis of Some Flavones for Antimicrobial and ADMET Studies

Microwave (MW) assisted synthetic technique was applied for the preparation of chalcone derivatives 5-7 employing Claisen-Schmidt condensation between 2-hydroxyacetophenone and aromatic aldehydes. These chalcones were further subjected to oxidative cyclization via MW irradiation and furnished the related flavones 8-10 which were characterized by FT-IR, 1H and 13CNMR spectra. The use of these MW assisted reactions provided higher productivity (92-98%) in shorter reaction time (2-6 min) with eco-friendly mild reaction conditions and hence found to be a convenient method as compared to conventional synthesis. These chalcones 5-7, and flavones 8-10 were screened for in vitro antimicrobial activities against five bacterial and three fungal pathogens. The study indicated that they were more active against fungal pathogens than that of bacterial organisms and comparable to the standard antifungal antibiotic nystatin. Interestingly, the prediction of activity spectra for substances (PASS) was also found in agreement with the in vitro results. Some of the compounds were found to have good ADMET properties.

Flavones as tyrosinase inhibitors: kinetic studies in vitro and in silico.

Tyrosinase is a multifunctional copper-containing oxidase enzyme that catalyses the first steps in the formation of melanin pigments. Identification of tyrosinase inhibitors is of value for applications in cosmetics, medicine and agriculture. To develop an analytical method that allows identification of drug-like natural products that can be further developed as tyrosinase inhibitors. Results of in vitro and in silico studies will be compared in order to gain a deeper insight into the mechanism of action of enzyme inhibition. Using an in vitro assay we tested tyrosinase inhibitor effects of five structurally related flavones, i.e. luteolin (1), eupafolin (2), genkwanin (3), nobiletin (4), and chrysosplenetin (5). The strongest inhibitors were further investigated in silico, using enzyme docking simulations. All compounds tested showed modest tyrosinase inhibitory effect compared to the positive control, kojic acid. The polymethoxy flavones 4 and 5 exhibited the strongest tyrosinase inhibitory effect with the half maximal inhibitory concentration (IC50 ) values of 131.92 ± 1.75 μM and 99.87 ± 2.38 μM respectively. According to kinetic analysis 2, 4 and 5 were competitive inhibitors, whereas 1 and 3 were non-competitive inhibitors of tyrosinase. Docking studies indicated that methoxy groups on 4 and 5 caused steric hindrance which prevented alternative binding modes in the tyrosinase; the methoxy groups on the B-ring of these flavones faced the catalytic site in the enzyme. The docking simulations nicely complemented the in vitro kinetic studies, opening the way for the development of predictive models for use in drug design.

EFFECT OF FLAVONE AND ITS MONOHYDROXY DERIVATIVES ON ANIMAL MODELS OF DEPRESSION IN SWISS ALBINO MICE

Objectives: This research was designed to investigate the antidepressant activity of a few structurally related flavones (flavone, 3‑hydroxyflavone, and 7‑hydroxyflavone) and the possible mechanisms involved.
 Methods: Antidepressant activity was evaluated in mice by subjecting them to forced swim test and tail suspension test. The involvement of adrenergic, serotonergic, nitric oxide (NO), and opioid mechanisms was investigated using suitable interacting chemicals.
 Results: Flavone, 3‑hydroxyflavone, and 7‑hydroxyflavone exhibited a significant and dose‑dependent reduction in total time of immobility in the forced swim test and tail suspension test. Pre‑treatment with alpha‑methyl‑para‑tyrosine and parachlorophenyl alanine attenuated the reduction in immobility period produced by flavone and its derivatives in forced swim test. Naloxone pre‑treatment partially reversed the effect of flavone while L‑arginine pre‑treatment did not alter their effect.
 Conclusion: The investigated flavones exhibited promising antidepressant activity in both the animal models of depression. However, the flavone compounds did not alter the motor coordination and ambulatory behavior in the Rotarod and locomotor activity test. The participation of serotonergic, adrenergic, and opioid mechanism in the antidepressant activity of these compounds was elucidated from the results, and the role of NO pathway was excluded.

7-O-Methylwogonin from Scutellaria baicalensis Disturbs Mitotic Progression by Inhibiting Plk1 Activity in Hep3B Cells.

Polo-like kinase 1, a mitotic Ser/Thr kinase, has emerged as a molecular target for the development of anticancer drugs. In this study, we found that polo-like kinase 1 activity was inhibited by 7-O-methylwogonin and related flavones, including baicalein, dihydrobaicalein, and viscidulin II, isolated from Scutellaria baicalensis. Although dihydrobaicalein exhibited the highest polo-like kinase 1 inhibitory activity among the four compounds, it also inhibited other kinases, such as vaccinia-related kinase 2 and polo-like kinase 2. Baicalein and viscidulin II also showed low selectivity to polo-like kinase 1 since they inhibited polo-like kinase 3 and polo-like kinase 2, respectively. However, 7-O-methylwogonin exhibited selective polo-like kinase 1 inhibitory activity, as evidenced from in vitro kinase assays based on fluorescence resonance energy transfer assays and ADP-Glo kinase assays. In addition, examination of mitotic morphology and immunostaining using specific antibodies for the mitotic markers, p-histone H3 and mitotic protein monoclonal 2, in Hep3B cells showed that 7-O-methylwogonin treatment increased mitotic cell populations due to inhibition of mitotic progression as a result of polo-like kinase 1 inhibition. The pattern of 7-O-methylwogonin-induced mitotic arrest was similar to that of BI 2536, a specific polo-like kinase 1 inhibitor. Thus, it was suggested that 7-O-methylwogonin disturbed mitotic progression by inhibiting polo-like kinase 1 activity. These data suggest that 7-O-methylwogonin, a polo-like kinase 1 inhibitor, may be a useful anticancer agent because of its polo-like kinase 1 selectivity and effectiveness.

Targeting CDK9 by wogonin and related natural flavones potentiates the anti-cancer efficacy of the Bcl-2 family inhibitor ABT-263.

Tumor initiation, progression and resistance to therapies are tightly associated with over-expression of anti-apoptotic proteins Bcl-2, Bcl-x(L), Bcl-w and Mcl-1. ABT-263 (Navitoclax), an orally bio-available small-molecule mimetic of the Bcl-2 homology domain 3, inhibits Bcl-2, Bcl-x(L), and Bcl-w and has shown anti-cancer effects mainly on lymphomas and lymphocytic leukemia. Despite promising results obtained from the clinical trials, the use of ABT-263 in patients is dose-limited due to causing thrombocytopenia via inhibition of Bcl-x(L) in platelets. ABT-199 specifically inhibits Bcl-2; however, its use is limited to tumors over-expressing only Bcl-2. Besides, many tumors resist treatment due to high levels of Mcl-1 expression or develop resistance via up-regulation of Mcl-1 during long-term exposure. These obstacles highlight the demand to improve the ABT-263-based therapy. In this study, we show that anti-cancer flavones, e.g., wogonin, baicalein, apigenin, chrysin and luteolin enhance ABT-263-induced apoptosis in different cancer cell lines and in primary AML and ALL cells by down-regulation of Mcl-1 expression. Importantly, wogonin does not enhance the toxicity of ABT-263 to proliferating normal T cells and thrombocytes. Wogonin also potentiates the lethality of ABT-263 in cancer cells which have acquired resistance to ABT-263. Furthermore, we show that combination of wogonin with ABT-263 promotes in vivo tumor regression in a human T-cell leukemia xenograft mouse model. Our study demonstrates that wogonin (and related flavones) reduce the effective dose of ABT-263 thereby possibly decreasing the risk of adverse side effects.

Brain Inflammation, Neuropsychiatric Disorders, and Immunoendocrine Effects of Luteolin

The potential role of brain proinflammatory cytokines in the brain in the pathogenesis of psychiatric diseases was discussed almost 10 years ago. Increasing evidence implicates brain inflammation in neuropsychiatric diseases, including depression, bipolar disease, and autism spectrum disorders (ASD). Genome analysis of brains from deceased patients with bipolar disorder, depression, and schizophrenia showed increased expression of inflammatory genes and decreased expression of mitochondrial function. Other studies have also implicated mitochondrial dysfunction and neuroinflammation in Alzheimer disease, as well as in ASD, in which it was shown that extracellular mitochondrial components were increased in the serum of patients with ASD and could trigger autoinflammatory responses. In fact, nonsteroidal anti-inflammatory drugs have been considered in schizophrenia. However, nonsteroidal anti-inflammatory drugs reduce the antidepressant action of specific serotonin receptor antagonists. Moreover, corticosteroids that have strong anti-inflammatory effects can induce or exacerbate depression. In this void, certain natural flavonoids with anti-inflammatory actions have been used for neuropsychiatric diseases, and their intake was associated with decreased incidence of dementia in a 23-country study. Moreover, the use of polyphenolic compounds that contain flavonoids in psychiatric and cognitive disorders has been reviewed recently. Quercetin is a flavonol, and luteolin is a structurally related flavone, with 1 less hydroxyl group in the center ring. Both are rich in onions, tea, apples, and broccoli, with luteolin being more plentiful in olive FRUITextract, CHAMOMILE, celery, spinach, and oregano. Luteolin reduces amyloid-beta peptide production in human transgenicbearing neuronlike cells and primary neurons. A number of comprehensive reviews have shown that the flavonol quercetin and its structurally related flavone luteolin are safe. In fact, these flavonoids seem safer than most of the psychotropic drugs prescribed to children. A recent study actually showed that a formulation of luteolin and quercetin was both well tolerated and resulted in significant improvement of children with ASD. The case of luteolin is particularly interesting. Luteolin has been shown to have anti-inflammatory, antiallergic, and neuroprotective properties. It also inhibits mercury-induced activation of human mast cells, T-cell activation, and activation of peripheral blood mononuclear cells derived from patients with multiple sclerosis. In animal models, luteolin inhibited ASD-like symptoms, along with related biochemical changes. Moreover, luteolin increases spatial memory in mice and reduces cognitive decline in rats. It, therefore, came as a surprise that a recent publication reported that luteolin and quercetin have detrimental effects on the hormonal ‘‘system’’ and in ‘‘models’’ of breast and endometrial cancer. In particular, these authors reported that luteolin has estrogenic activity and antagonizes progesterone receptor activation. These results were obtained using transformed cell lines that can hardly qualify as a system or model of any disease. Moreover, other authors using different cell lines have reached opposite conclusions. For instance, 1 study reported that luteolin inhibits estrogen production, whereas another showed that progesterone does not bind to the progesterone receptor. In fact, there are hundreds of publications showing that these flavonoids, and especially luteolin, have potent anticancer actions. Most importantly, recent articles reported that combining luteolin with quercetin, as well as with celcoxib, had more potent anticancer effect than each one individually. Finally, the consumption of luteolin or quercetin at 200 to 400 mg/d found in some GMPmanufactured dietary supplements would never reach the concentrations used in the aforementioned article because oral absorption of these flavonoids is less than 10%. Even if one were to assume that the entire body is 1 compartment, the blood concentrations reached after consuming COMMENTARY

Luteolin Inhibits Human Keratinocyte Activation and Decreases NF-κB Induction That Is Increased in Psoriatic Skin

Psoriasis (Ps) is an autoimmune disease characterized by keratinocyte hyperproliferation and chronic inflammation, with increased expression of tumor necrosis factor (TNF) and vascular endothelial growth factor (VEGF). Anti-TNF biologic agents are effective in treating Ps, but are associated with increased risk of infections and blood malignancies. Moreover, keratinocyte hyperproliferation and activation have yet to be addressed. Flavonoids, such as luteolin, are natural compounds with potent anti-inflammatory properties, but their actions on keratinocytes remain unknown. We show that TNF (50 ng/mL) triggers significant production of inflammatory mediators interleukin-6, interleukin-8 and VEGF from both human HaCaT and primary keratinocytes. Pretreatment with the flavonoid luteolin (10–100 µM) significantly inhibits mRNA expression and release of all three mediators in a concentration-dependent manner. More importantly, luteolin decreases TNF-induced phosphorylation, nuclear translocation and DNA binding of the nuclear factor-kappa B (NF-κB) typically involved in inflammatory mediator transcription. We also report that luteolin reduces TNF-induced mRNA expression of two genes (NFKB1 and RELA) encoding two NF-κB subunits (NF-κB p50 and NF-κB p65, respectively). Interestingly, we show that gene expression of RELA is increased in human psoriatic skin. Keratinocyte proliferation, which is a characteristic feature of psoriatic skin, is effectively reduced by luteolin in HaCaT cells, but not in primary keratinocytes. Finally, luteolin does not affect intracellular ATP production or viability. Appropriate formulations of luteolin and related flavones may be promising candidates to be developed into local and systemic treatments for Ps and other inflammatory skin diseases.

Antioxidant properties of 4-quinolones and structurally related flavones

Neurodegenerative disorders are frequently associated with increased oxidative damage to the brain as a result of free radicals produced by cellular respiration. The onset and progression of neurodegeneration may therefore be curbed by exogenous hydrogen-donating antioxidant moieties such as the naturally occurring flavonoids. A series of 2-phenylquinolin-4(1H)-ones was synthesised and displayed moderate to high antioxidant activity when compared to structurally related flavones and quinolines. Activity of the hydroxy-2-phenylquinolin-4(1H)-ones (8–10) was established in reducing ferrous ions and diminishing hydrogen peroxide and hydroxyl radical production, in the FRAP (1.41–97.71% Trolox® equivalents), ORAC (9.18–15.27μM Trolox® equivalents at 0.001mM) and TBARS (0.05–0.72nmol MDA/mg tissue) assays, respectively. The results indicated that the additional hydrogen donating groups on the synthesised 2-phenylquinolin-4(1H)-one series increased antioxidant activity.

Mucin 1 C-terminal subunit oncoprotein is a target for small-molecule inhibitors.

Mucin 1 (MUC1) is a heterodimeric protein that is overexpressed in diverse human carcinomas. The oncogenic function of the MUC1 C-terminal subunit (MUC1-C) subunit is dependent on the formation of dimers through its cytoplasmic domain; however, it is not known whether MUC1-C can be targeted with small-molecule inhibitors. In the present work, an assay using the MUC1-C cytoplasmic domain (MUC1-CD) was established to screen small-molecule libraries for compounds that block its dimerization. Using this approach, the flavone apigenin was identified as an inhibitor of MUC1-CD dimerization in vitro and in cells. By contrast, the structurally related flavone baicalein was ineffective in blocking the formation of MUC1-CD dimers. In concert with these results, apigenin, and not baicalein, blocked the localization of MUC1-C to the nucleus. MUC1-C activates MUC1 gene expression in an autoinductive loop, and apigenin, but not baicalein, treatment was associated with down-regulation of MUC1 mRNA levels and MUC1-C protein. The results also demonstrate that apigenin-induced suppression of MUC1-C expression is associated with apoptotic cell death and loss of clonogenic survival. These findings represent the first demonstration that the MUC1-C cytoplasmic domain is a target for the development of small-molecule inhibitors.

The antioxidant and free-radical scavenging activities of extract and fractions from corn silk (Zea mays L.) and related flavone glycosides

This study was designed to evaluate both the antioxidant and free-radical scavenging activities of extract and fractions from corn silk. N-butanol fraction (BF) demonstrated the highest total phenolic content (164.1±9.7μg GAE/g DCS) and total flavonoids content (69.4±5.1μg RE/g DCS), accompanied with the highest antioxidant activity compared to other fractions through all antioxidant assays. Two flavone glycosides showing potent antioxidant activity were isolated from BF and identified, by comparing spectral data (UV, FAB-MS and NMR) with literature values, to be isoorientin-2″-O-α-l-rhamnoside and 3′-methoxymaysin. The two isolated flavone glycosides, particularly isoorientin-2″-O-α-l-rhamnoside, demonstrated significant total antioxidant activity, DPPH radical scavenging activity, reducing power and iron-chelating capacity, with EC50 values of 14.24±1.49, 22.69±2.33, 6.58±1.07 and 30.25±3.05μg/ml, respectively. Results obtained indicated that corn silk extracts can be used potentially as a ready accessible and valuable bioactive source of natural antioxidants.

Sustainable Synthesis of Flavonoid Derivatives, QSAR Study and Insecticidal Activity against the Fall Armyworm, Spodoptera frugiperda (Lep.: Noctuidae)

A simple, clean, solvent-free preparation of flavones by the use of a silica-supported Preyssler heteropolyacid as reusable catalyst is described. High selectivity and very good yields (87-94%) were obtained in short reaction times (7-13 min). Bioassays for insecticidal activity against Spodoptera frugiperda were carried out with a set of flavones. Bioassays showed that some of the flavones had moderate insecticidal activity. Quantitative structure-activity relationships were established on the available data with the purpose of predicting the insecticidal activity of a number of structurally related flavones. A relationship between the molecular structure and biological activity is proposed.

Prenylated flavones from some IndonesianArtocarpusand their antimalarial properties

Artocarpus, locally known as “nangka-nangkaan”, is one of the important genera of family Moraceae. The plants belong to this genus grow endemically and also cultivated throughout Indonesian region. In this study, a phytochemical study on three species of Artocarpus, namely A. heterophyllus, A. elasticus and A. lanceifolius, has been carried out, and the biological effects of the isolated compounds against Plasmodium palcifarum strain K1 and 3D7 have been evaluated. The phytochemical investigation of these plants resulted, three new prenylated flavones, trivially named artoindonesianin E-1 (1), artoindonesianin Z-4 (2) and artoindonesianin Z-5 (3), beside seventeen known prenylated flavones. Antimalarial effect of some selected isolated flavone derivatives showed that artonin E exhibited very strong inhibition (IC50 0.1 mg/mL) against K1 strain in comparison against 3D7 strain of Plasmodium falciparum (IC50 0.3 mg/mL). A related prenylated flavone, namely 12-hydroxyartonin E, exhibited strong inhibition (IC50 0.9 mg/mL) against K1 strain, but weak inhibition (IC50 14.3 mg/mL) against 3D7 strain. Those two compounds were the member of 3-prenylflavone type. In addition, the other isolated flavone derivatives showed moderate inhibition with IC50 respectively 2.1, 1.6, 3.6, 1.3, 6.7 and 2.1 mg/mL against both the strain of P. falciparum, except for flavanone-3-ol derivative (dihydromorin), which had no inhibition.

Flavones as Colorectal Cancer Chemopreventive Agents—Phenol-O-Methylation Enhances Efficacy

Flavonoids occur ubiquitously in plants, and some possess preclinical cancer chemopreventive activity. Little is known about molecular features that mediate chemopreventive efficacy of flavonoids. Here, three related flavones, apigenin (4',5,7-trihydroxyflavone), tricin (4',5,7-trihydroxy-3',5'-dimethoxyflavone), and 3',4',5',5,7-pentamethoxyflavone (PMF), were compared in terms of their effects on (a) adenoma development in Apc(Min) mice, a model of human gastrointestinal malignancies; (b) growth of APC10.1 mouse adenoma cells in vitro; and (c) prostaglandin E-2 generation in HCA-7 human-derived colorectal cancer cells in vitro. Life-long consumption of PMF with the diet at 0.2% reduced Apc(Min) mouse adenoma number and burden by 43% and 61%, respectively, whereas apigenin was inactive. Tricin has previously shown activity in this model. IC50 values for murine adenoma cell growth inhibition by PMF, tricin, and apigenin were 6, 13, and 18 micromol/L, respectively. In Apc(Min) mice that received flavones (0.2%) for 4 weeks, adenoma cell proliferation as reflected by Ki-67 staining was reduced by PMF and tricin, but not by apigenin. On incubation with HCA-7 cells for 6 hours, PMF reduced prostaglandin E-2 generation with an IC50 of 0.8 micromol/L, a fraction of the respective values reported for tricin or apigenin. In silico PMF docked into the cyclooxygenase active site with greater affinity than tricin or apigenin. The results suggest that the rank order of cancer chemopreventive efficacy in Apc(Min) mice is PMF > tricin > apigenin, supporting the notion that the presence of O-methyl in the flavone molecular scaffold promotes gastrointestinal cancer chemopreventive efficacy.

Cytotoxicity of flavones and flavonols to a human esophageal squamous cell carcinoma cell line (KYSE-510) by induction of G 2/M arrest and apoptosis

In this study, cytotoxic effects of structurally related flavones and flavonols on a human esophageal squamous cell carcinoma cell line (KYSE-510) were determined, and the molecular mechanisms responsible for their cytotoxic effects were studied. The results of MTT assay showed that flavones (luteolin, apigenin, chrysin) and flavonols (quercetin, kaempferol, myricetin) were able to induce cytotoxicity in KYSE-510 cells in a dose- and time-dependent manner, and the cytotoxic potency of these compounds was in the order of: luteolin > quercetin > chrysin > kaempferol > apigenin > myricetin. Flow cytometry and DNA fragmentation analysis indicated that the cytotoxicity induced by flavones and flavonols was mediated by G 2/M cell cycle arrest and apoptosis. Furthermore, the expression of genes related to cell cycle arrest and apoptosis was assessed by oligonucleotide microarray, real-time RT-PCR and Western blot. It was shown that the treatment of KYSE-510 cells with these compounds caused G 2/M arrest through up-regulation of p21 waf1 and down-regulation of cyclin B1 at the mRNA and protein levels, and induced p53-independent mitochondrial-mediated apoptosis through up-regulation of PIG3 and cleavage of caspase-9 and caspase-3. The results of western blot analysis further showed that increases of p63 and p73 protein translation or stability might be contributed to the regulation of p21 waf1, cyclin B1 and PIG3.

Quercetin inhibition of tumor invasion via suppressing PKC /ERK/AP-1-dependent matrix metalloproteinase-9 activation in breast carcinoma cells

Quercetin (QUE; 3,5,7,3',4'-tetrahydroxyflavone) has been shown to possess several beneficial biological activities including antitumor, anti-inflammation and antioxidant properties; however, the effects of QUE in preventing invasion by breast carcinoma cells are still undefined. Increases in the protein, messenger RNA and enzyme activity levels of matrix metalloproteinase (MMP)-9 were observed in 12-O-tetradecanoylphorbol-13-acetate (TPA)-treated MCF-7 cells, and these were blocked by QUE, but not by quercitrin or rutin. A translocation of protein kinase C (PKC)delta from the cytosol to the membrane followed by activation of extracellular signal-regulated kinase (ERK) and c-Jun/activator protein-1 (AP-1) by TPA was demonstrated, and TPA-induced MMP-9 activation and migration were inhibited by the pan PKC inhibitor, GF109203X, the specific PKCdelta inhibitor, rottlerin, an ERK inhibitor (PD98059) and an AP-1 inhibitor (curcumin). Application of QUE significantly suppressed TPA-induced activation of the PKCdelta/ERK/AP-1-signaling cascade. To elucidate the importance of hydroxyl (OH) substitutions to QUE's inhibition of tumor migration, several structurally related flavones of QUE including 3',4'-diOH, 3',4'-diOCH(3), 3,5,7-triOH, 3,4',4'-triOH, 3,3',4'-triOCH(3), luteolin and fisetin were used. Results suggested that OH groups at both C3' and C4' play central roles in QUE's inhibition of TPA-induced MMP-9 activation and migration, and an additional OH at C3, C5 or C7 may increase the inhibitory potency of the 3',4'-diOH flavone against TPA-induced MMP-9 activity and migration. The antitumor invasion and migration effects of breast carcinoma cells induced by QUE with the structure-activity relationship analysis were identified.

Flavones and flavonols exert cytotoxic effects on a human oesophageal adenocarcinoma cell line (OE33) by causing G2/M arrest and inducing apoptosis

Dietary flavonoids have been shown to exert specific cytotoxicity towards some cancer cells, but the precise molecular mechanisms are still not completely understood. In our study, cytotoxic effects of structurally related flavones and flavonols on a human oesophageal adenocarcinoma cell line (OE33) were compared, and the molecular mechanisms responsible for their cytotoxic effects were explored. The results of MTT assay showed that flavones (luteolin, apigenin, chrysin) and flavonols (quercetin, kaempferol, myricetin) were all able to induce cytotoxicity in OE33 cells in a dose- and time-dependent manner, and the cytotoxic potency of these compounds was in the order of quercetin>luteolin>chrysin>kaempferol>apigenin>myricetin. Flow cytometry and DNA fragmentation analysis indicated that the cytotoxicity induced by flavones and flavonols was mediated by G2/M cell cycle arrest and apoptosis. Furthermore, the expression of genes related to cell cycle arrest and apoptosis was assessed by oligonucleotide microarray, real-time RT-PCR and Western blot. It was found that the treatment of OE33 cells with flavones and flavonols caused G2/M arrest through up-regulation of GADD45β and 14-3-3σ and down-regulation of cyclin B1 at the mRNA and protein levels, and induced p53-independent mitochondrial-mediated apoptosis through up-regulation of PIG3 and cleavage of caspase-9 and caspase-3. The results of western blot analysis further showed that increases of p63 and p73 protein translation or stability might be contribute to the regulation of GADD45β, 14-3-3σ, cyclin B1 and PIG3.

A fragmentation study of isoflavones in negative electrospray ionization by MSn ion trap mass spectrometry and triple quadrupole mass spectrometry

This study has elucidated the fragmentation pathway for deprotonated isoflavones in electrospray ionization using MS(n) ion trap mass spectrometry and triple quadrupole mass spectrometry. Genistein-d(4) and daidzein-d(3) were used as references for the clarification of fragment structures. To confirm the relationship between precursor and product ions, some fragments were traced from MS(2) to MS(5). The previous literature for the structurally related flavones and flavanones located the loss of ketene (C(2)H(2)O) to ring C, whereas the present fragmentation study for isoflavones has shown that the loss of ketene occurs at ring A. In the further fragmentation of the [M-H-CH(3)](-*) radical anion of methoxylated isoflavones, loss of a hydrogen atom was commonly found. [M-H-CH(3)-CO-B-ring](-) is a characteristic fragment ion of glycitein and can be used to differentiate glycitein from its isomers. Neutral losses of CO and CO(2) were prominent in the fragmentation of deprotonated anions in ion trap mass spectrometry, whereas recyclization cleavage accounted for a very small proportion. In comparison with triple quadrupole mass spectrometry, ion trap MS(n) mass spectrometry has the advantage of better elucidation of the relationship between precursor and product ions.