apigenin and kaempferol

Death-associated protein kinase 1 (DAPK1) is a 160 kDa serine/threonine protein kinase that belongs to the Ca(2+)/calmodulin-dependent protein kinase subfamily. DAPK1 is a possible target for the treatment of acute ischemic stroke and endometrial adenocarcinomas. In the present study, we investigated the binding characteristics of 17 natural flavonoids to DAPK1 using a 1-anilinonaphthalene-8-sulfonic acid competitive binding assay and revealed that morin was the strongest binder among the selected compounds. The crystallographic analysis of DAPK1 and 7 selected flavonoid complexes revealed the structure-binding affinity relationship in atomic-level detail. It was suggested that the high affinity of morin could be accounted for by the ionic interaction between 2'-OH and K42 and that such an interaction would not take place with either cyclin-dependent protein kinases or PIM kinases because of their broader entrance regions. Thus, morin would be a more selective inhibitor of DAPK1 than either of these other types of kinases. In addition, we found that the binding of kaempferol to DAPK1 was associated with a chloride ion. The present study provides a better understanding of the molecular properties of the ATP site of DAPK1 and may be useful for the design of specific DAPK1 inhibitors.

Topics: Adenosine Triphosphate; Allosteric Site; Anilino Naphthalenesulfonates; Binding, Competitive; Crystallography, X-Ray; Death-Associated Protein Kinases; Flavonoids; Kaempferols; Protein Binding; Protein Conformation; Structure-Activity Relationship

A number of natural and synthetic flavonoids have been assessed previously with regard to their effects on the activity of cyclin-dependent kinases (Cdk1 and -2) related to the inhibition of cell cycle progression. On the other hand, the Cdk5/p35 system is of major importance in neuronal migration phenomena and brain development, and its deregulation is implicated in neurodegenerative diseases, particularly Alzheimer's. Here we show that some natural flavonoids inhibit the activity of the Cdk5/p35 system in the micromolar range, while others are practically inactive. Ring B-unsubstituted and highly methoxylated flavones were inactive or gave irreproducible results, and 6-methoxyapigenin and 6-methoxyluteolin were the most potent Cdk5 complex inhibitors within this series, while the common flavonols kaempferol and quercetin showed intermediate behavior. The reported crystal structure of the Cdk5 complex with its activator p25 was used for docking studies, which also led to the identification of the two 6-methoxyflavones, kaempferol and quercetin, as well as the untested 6-methoxy derivatives of kaempferol and quercetin and the corresponding 6-hydroxy analogues as compounds exhibiting a good fit to the active site of the enzyme.

Topics: Algorithms; Centaurea; Cyclin-Dependent Kinase 5; Cyclin-Dependent Kinases; Flavonoids; Flavonols; Inhibitory Concentration 50; Kaempferols; Molecular Conformation; Molecular Structure; Quercetin; Structure-Activity Relationship

The 190-kDa phosphoglycoprotein multidrug resistance protein 1 (MRP1) (ABCC1) confers resistance to a broad spectrum of anticancer drugs and also actively transports certain xenobiotics with reduced glutathione (GSH) (cotransport) as well as conjugated organic anions such as leukotriene C(4) (LTC(4)). In the present study, we have investigated a series of bioflavonoids for their ability to influence different aspects of MRP1 function. Most flavonoids inhibited MRP1-mediated LTC(4) transport in membrane vesicles and inhibition by several flavonoids was enhanced by GSH. Five of the flavonoids were competitive inhibitors of LTC(4) transport (K(i), 2.4-21 microM) in the following rank order of potency: kaempferol > apigenin (+ GSH) > quercetin > myricetin > naringenin (+ GSH). These flavonoids were less effective inhibitors of 17beta-estradiol 17beta-(D-glucuronide) transport. Moreover, their rank order of inhibitory potency for this substrate differed from that for LTC(4) transport inhibition but correlated with their relative lipophilicity. Several flavonoids, especially naringenin and apigenin, markedly stimulated GSH transport by MRP1, suggesting they may be cotransported with this tripeptide. Quercetin inhibited the ATPase activity of purified reconstituted MRP1 but stimulated vanadate-induced trapping of 8-azido-alpha-[(32)P]ADP by MRP1. In contrast, kaempferol and naringenin stimulated both MRP1 ATPase activity and trapping of ADP. In intact MRP1-overexpressing cells, quercetin reduced vincristine resistance from 8.9- to 2.2-fold, whereas kaempferol and naringenin had no effect. We conclude that dietary flavonoids may modulate the organic anion and GSH transport, ATPase, and/or drug resistance-conferring properties of MRP1. However, the activity profile of the flavonoids tested differed from one another, suggesting that at least some of these compounds may interact with different sites on the MRP1 molecule.

Topics: Adenosine Diphosphate; Adenosine Triphosphatases; Antineoplastic Agents, Phytogenic; ATP-Binding Cassette Transporters; Azides; Binding, Competitive; Biological Transport; Cell Division; Chromatography, High Pressure Liquid; Drug Interactions; Estradiol; Estrogen Antagonists; Flavanones; Flavonoids; Glutathione; HeLa Cells; Humans; Kaempferols; Kinetics; Leukotriene C4; Multidrug Resistance-Associated Proteins; Phosphorus Radioisotopes; Quercetin; Transfection; Tritium; Vanadates; Vincristine

The ability of the flavonoids genistein, apigenin, kaempferol, and quercetin to activate cystic fibrosis transmembrane conductance regulator-mediated Cl currents in human airway epithelium was investigated. We used the patch-clamp technique on single Calu-3 cells, transepithelial measurements in Calu-3 monolayers, and in vivo measurements of nasal potential difference. All flavonoids stimulated Cl currents in transepithelial experiments dose dependently. Half-maximal stimulatory concentrations were kaempferol (5.5 +/- 1.7 microM) /= kaempferol (318 +/- 45%) >/= genistein (258 +/- 20%) = quercetin (256 +/- 26%). Stimulation of the currents was caused by an increase in channel open probability. No other Cl conductances contributed significantly to the flavonoid-activated Cl currents in Calu-3 cells. In vivo, flavonoids significantly stimulated nasal potential difference by, on average, 27.8% of isoproterenol responses.

Topics: Cell Line; Chamomile; Chloride Channels; Chlorides; Colforsin; Epithelial Cells; Flavonoids; Genistein; Humans; Kaempferols; Kinetics; Lung; Membrane Potentials; Models, Biological; Oils, Volatile; Patch-Clamp Techniques; Plants, Medicinal; Quercetin; Structure-Activity Relationship

Topics: Anticarcinogenic Agents; Antioxidants; Chamomile; Copper; Diet; Flavonoids; Humans; Kaempferols; Kinetics; Lipoproteins, LDL; Male; Oils, Volatile; Oxidation-Reduction; Plants, Medicinal; Quercetin; Rutin

A microplate assay for hyaluronidase and a heterologous cumulus penetration assay were used to determine the effects of four flavonoids (tannic acid, kaempferol, quercetin, and apigenin) on the function of cynomolgus monkey sperm. All four flavonoids inhibited the activity of hyaluronidase extracted from monkey sperm in a concentration-dependent manner over the range of 50-200 microM. Tannic acid and apigenin had lower inhibitory effects than kaempferol and quercetin. Kaempferol, quercetin, and apigenin at 100 microM were shown to significantly inhibit monkey sperm penetration into hamster cumulus. There was a significant linear relationship between the capacity of the flavonoids to inhibit monkey sperm hyaluronidase activity and their inhibitory effects on hamster cumulus penetration (r = 0.97). Tannic acid was observed to reduce sperm motility, and it was not used in the cumulus penetration assay. The other three flavonoids tested in the cumulus penetration assay did not affect sperm motility, nor did they induce acrosome reactions. The results demonstrate that the flavonoids are useful tools for assessing the involvement of hyaluronidase in the functions of monkey sperm that are involved in fertilization.

Topics: Acrosome; Animals; Chamomile; Cricetinae; Enzyme Inhibitors; Female; Flavonoids; Hyaluronoglucosaminidase; Hydrolyzable Tannins; In Vitro Techniques; Kaempferols; Macaca fascicularis; Male; Oils, Volatile; Plants, Medicinal; Quercetin; Sperm Motility; Sperm-Ovum Interactions; Spermatozoa

Some flavonoids induce phase II enzymes both in vivo and in vitro. We have determined the structural requirements for this activity by examining the ability of naturally-occurring flavonoids to induce the phase II enzyme, quinone reductase (NAD(P)H:quinone oxidoreductase; EC 1.6.99.2), in murine Hepalclc7 cells. Hydroxylation of the B ring is not essential for induction, since galangin and kaempferol (with 0 and 1 hydroxyl in the B ring, respectively) are better inducers than quercetin (2 B ring hydroxyls). A 2,3 double bond in the C ring is essential for induction, since taxifolin, which has the same substitution pattern as quercetin but lacks the 2,3 double bond, is not an inducer. This is supported by catechin and epicatechin, which do not possess the 2,3 double bond and are also not inducers. A 3-hydroxyl group increases the activity but is not essential for induction, since apigenin is an inducer but kaempferol (which has the same structure as apigenin but possesses a 3-hydroxyl group) is more effective. The data show that, of the flavonoids, the flavonols are the most effective inducers of quinone reductase activity in Hepa1c1c7 cells (kaempferol approximately galangin > quercetin > myricetin approximately apigenin (a flavone)) and that flavanols and flavans are ineffective.

Topics: Animals; Catechin; Chamomile; Enzyme Induction; Enzyme Inhibitors; Flavonoids; Flavonols; Kaempferols; Liver Neoplasms, Experimental; Mice; NAD(P)H Dehydrogenase (Quinone); Oils, Volatile; Plants, Medicinal; Quercetin; Tumor Cells, Cultured

Fifteen flavonoids were employed to examine their effects on the morphological changes, foci formation in soft agar and cellular growth in v-H-ras-transformed NIH3T3 cells. The data presented here demonstrated that only three specific flavonoids--apigenin, kaempferol, and genistein--exhibited the reverting effect on the transformed phenotypes of ras-3T3 cells. For example, treatment with 25 microM of these flavonoids could effectively reverse the transformed morphology of ras-3T3 cells into flatter cells with contact inhibition. Colony formation in soft agar was decreased to 0.11%, 0.15%, and 0.35% by 25 microM apigenin, kaempferol, and genistein, respectively, as compared with control (0.92%). It was also found that the proliferation of ras-3T3 cells was significantly inhibited by these compounds in a dose-dependent manner. Finally, two biochemical parameters, the content of phosphotyrosine and cAMP, were examined to see whether affected by these compounds. The results showed the phosphotyrosine content in ras-3T3 cells was dramatically decreased by apigenin and kaempferol, but that was slightly reduced by genistein. By contrast, these three flavonoids all failed to significantly alter the level of cAMP within this transformant. Based on these observations, we suggest that some specific flavonoids are capable of reverting the transforming properties of v-H-ras transformed cells. The possible mechanism of this reversion is not mediated by activating the protein kinase A or its associated pathways, but rather inhibiting tyrosine kinases, subsequently leading to the blockage of p21ras-mediated signal transduction circuitry.

Topics: 3T3 Cells; Animals; Cell Division; Cell Line, Transformed; Cell Transformation, Neoplastic; Cell Transformation, Viral; Chamomile; Culture Media; Cyclic AMP; Dose-Response Relationship, Drug; Flavonoids; Genes, ras; Genistein; Isoflavones; Kaempferols; Mice; Oils, Volatile; Phenotype; Phosphotyrosine; Plants, Medicinal; Protein-Tyrosine Kinases; Quercetin; Tyrosine

Topics: Antioxidants; Chamomile; Flavonoids; Free Radicals; Indicators and Reagents; Kaempferols; Kinetics; Luteolin; Oils, Volatile; Oxygen; Peroxides; Plants, Medicinal; Quercetin; Solutions; Structure-Activity Relationship

The EtOH extract of Koelreuteria henryi was investigated in a search for natural products with potential protein-tryrosine kinase (PTK) inhibitory activity. The PTK inhibitory activity of the crude fractions was determined by measuring their inhibition of p56lck partially purified from bovine thymus using angiotensin I as a substrate. Analysis of those fractions that exhibited significant activity led to the isolation of kaempferol and quercetin, in addition to two kaempferol glycosides, kaempferol-O3-alpha-rhamnopyranoside [1] and kaempferol-O3-alpha-arabinopyranoside [2]. This study represents the first report on the isolation of flavonols and their PTK inhibitory activities from the genus Koelreuteria. Eight other flavonoids were also examined to study the role of the hydroxy groups on the B ring on PTK inhibitory activity.

Topics: Animals; Cattle; Flavonoids; Kaempferols; Magnetic Resonance Spectroscopy; Plant Extracts; Plants; Protein-Tyrosine Kinases; Quercetin

Flavonoids are polyphenolic antioxidants naturally present in vegetables, fruits, and beverages such as tea and wine. In vitro, flavonoids inhibit oxidation of low-density lipoprotein and reduce thrombotic tendency, but their effects on atherosclerotic complications in human beings are unknown. We measured the content in various foods of the flavonoids quercetin, kaempferol, myricetin, apigenin, and luteolin. We then assessed the flavonoid intake of 805 men aged 65-84 years in 1985 by a cross-check dietary history; the men were then followed up for 5 years. Mean baseline flavonoid intake was 25.9 mg daily. The major sources of intake were tea (61%), onions (13%), and apples (10%). Between 1985 and 1990, 43 men died of coronary heart disease. Fatal or non-fatal myocardial infarction occurred in 38 of 693 men with no history of myocardial infarction at baseline. Flavonoid intake (analysed in tertiles) was significantly inversely associated with mortality from coronary heart disease (p for trend = 0.015) and showed an inverse relation with incidence of myocardial infarction, which was of borderline significance (p for trend = 0.08). The relative risk of coronary heart disease mortality in the highest versus the lowest tertile of flavonoid intake was 0.42 (95% CI 0.20-0.88). After adjustment for age, body-mass index, smoking, serum total and high-density-lipoprotein cholesterol, blood pressure, physical activity, coffee consumption, and intake of energy, vitamin C, vitamin E, beta-carotene, and dietary fibre, the risk was still significant (0.32 [0.15-0.71]). Intakes of tea, onions, and apples were also inversely related to coronary heart disease mortality, but these associations were weaker. Flavonoids in regularly consumed foods may reduce the risk of death from coronary heart disease in elderly men.

Topics: Aged; Aged, 80 and over; Antioxidants; Beverages; Chamomile; Coffee; Cohort Studies; Coronary Disease; Diet; Flavonoids; Follow-Up Studies; Fruit; Humans; Kaempferols; Longitudinal Studies; Luteolin; Male; Myocardial Infarction; Netherlands; Oils, Volatile; Plants, Medicinal; Quercetin; Risk Factors; Smoking; Tea; Vegetables

Recent in vivo studies in humans have shown a dramatic effect of grapefruit juice in blocking the oxidation of dihydropyridine calcium channel blockers. The flavonoid naringin is the most abundant natural product specific for grapefruit and related citrus--the aglycone naringenin, known to be readily formed from naringin in humans, was found to inhibit the oxidation of the dihydropyridines nifedipine and felodipine in human liver microsomal preparations. These observations were of interest in light of the knowledge that the same human liver cytochrome P450 (IIIA4) appears to be a major catalyst in both nifedipine oxidation and aflatoxin B1 activation. Several flavones inhibited the in vitro activation of aflatoxin B1 in a system employing umuC gene activation due to DNA damage in Salmonella typhimurium TA1535/pSK1002, with naringenin being as effective as any. The high concentration of derivatives of naringenin in certain citrus fruits may be of relevance to cancer chemoprevention involving those carcinogens that are activated by cytochrome P-450IIIA4.

Topics: Aflatoxins; Chamomile; Chromatography, High Pressure Liquid; Dihydropyridines; Felodipine; Flavanones; Flavins; Flavonoids; Gene Expression Regulation; Hesperidin; Humans; In Vitro Techniques; Kaempferols; Microsomes, Liver; Oils, Volatile; Plants, Medicinal; Quercetin; Transcriptional Activation

The receptors for insulin and insulin-like growth factor (IGF)-I carry intrinsic tyrosine-specific protein kinases (TPK) in their cytoplasmic domains that show 84% homology. Our previous studies using tyrosine-containing synthetic polymers (Arch. Biochem. Biophys. 260, 416, 1988) revealed subtle differences between the two receptor TPKs. In the present study, low molecular weight kinase inhibitors were used to compare the two receptor TPKs purified from human placenta. Staurosporine was the most potent inhibitor of both receptor TPKs among the three inhibitors tested. It was 100 times more inhibitory to insulin receptor TPK (ED50 = 61nM) than IGF-I receptor TPK (ED50 = 6.2 microM). Apigenin and kaempferol showed approximately the same inhibitory potency toward both TPKs with a range of 10 approximately 1000 microM. Staurosporine is thus an excellent tool to biochemically characterize the two receptor TPKs as well as to selectively inhibit insulin-activated TPK in intact cells.

Topics: Adenosine Triphosphate; Alkaloids; Binding, Competitive; Chamomile; Female; Flavonoids; Humans; Kaempferols; Molecular Structure; Oils, Volatile; Phosphorylation; Placenta; Plants, Medicinal; Protein Kinase C; Protein-Tyrosine Kinases; Receptor, Insulin; Receptors, Somatomedin; Staurosporine