galangin and kaempferol

Single-stranded DNA (ssDNA)-binding protein (SSB) plays a crucial role in DNA replication, repair, and recombination as well as replication fork restarts. SSB is essential for cell survival and, thus, is an attractive target for potential antipathogen chemotherapy. Whether naturally occurring products can inhibit SSB remains unknown. In this study, the effect of the flavonols myricetin, quercetin, kaempferol, and galangin on the inhibition of

Topics: Bacterial Proteins; Crystallography, X-Ray; DNA-Binding Proteins; Flavonoids; Flavonols; Kaempferols; Models, Molecular; Protein Conformation; Pseudomonas aeruginosa; Quercetin

Flavonols have been studied extensively because of their interesting biological activities and excited-state intramolecular proton transfer (ESIPT) behavior. Galangin, kaempferol, quercetin, and myricetin are structurally related flavonols that differ only in the number of B-ring hydroxyl substituents. In this work, we have carried out a detailed study on the photophysical behavior of these structurally related flavonols in various solvents and a 1,2-dimyristoyl-

Topics: Dimyristoylphosphatidylcholine; Flavonoids; Flavonols; Hydroxylation; Kaempferols; Quercetin; Solvents

Flavonols are bioactive substances in plant foods. In this study, two flavonols galangin and kaempferol were heated at 100°C for 30 min prior to assessing their effects on barrier function of rat intestinal epithelial (IEC-6) cells. Both heated and unheated flavonols (2.5-20 µmol/L dosages) were nontoxic to the cells up to 48 h post-treatment, and could promote cell viability values to 102.2-141.2% of control. By treatment with 5 µmol/L flavonols for 24 and 48 h, the treated cells time-dependently showed better improved physical and biological barrier functions than the control cells without any flavonol treatment, including higher transepithelial electrical resistance and antibacterial effect but reduced paracellular permeability and bacterial translocation. The results from real-time PCR and western-blot assays indicated that the cells treated with heated and unheated flavonols of 5 µmol/L dosage had up-regulated mRNA (1.13-1.81 folds) and protein (1.15-5.11 folds) expression for zonula occluden-1, occludin, and claudin-1 that are vital to the tight junctions of the cells. Moreover, protein expression of RhoA and ROCK were down-regulated into 0.41-0.98 and 0.40-0.92 folds, respectively, demonstrating a Rho inactivation that led to enhanced cell barrier integrity via the RhoA/ROCK pathway. Overall, galangin was more active than kaempferol to perform three biofunctions like improving cell barrier function, up-regulating tight junctions protein expression, and down-regulating RhoA/ROCK expression. Moreover, the heated flavonols were less effective than the unheated counterparts to perform these biofunctions. It is concluded that this heat treatment of galangin and kaempferol could inhibit their benefits to improve barrier function of IEC-6 cells.

Topics: Animals; Cell Line; Cell Survival; Epithelial Cells; Flavonoids; Hot Temperature; Intestinal Mucosa; Kaempferols; Permeability; Rats; Tight Junctions; Transcytosis

Rheumatoid arthritis (RA) is a systemic autoimmune disorder that commonly affects multiple joints of the body. Currently, there is no permanent cure to the disease, but it can be managed with several potent drugs that cause serious side effects on prolonged use. Traditional remedies are considered promising for the treatment of several diseases, particularly chronic conditions, because they have lower side effects compared to synthetic drugs. In folklore, the rhizome of Alpinia calcarata Roscoe (Zingiberaceae) is used as a major ingredient of herbal formulations to treat RA. Phytoconstituents reported in A. calcarata rhizomes are diterpenoids, sesquiterpenoid, flavonoids, phytosterol, and volatile oils. The present study is intended to understand the molecular-level interaction of phytoconstituents present in A. calcarata rhizomes with RA molecular targets using computational approaches. A total of 30 phytoconstituents reported from the plant were used to carry out docking with 36 known targets of RA. Based on the docking results, 4 flavonoids were found to be strongly interacting with the RA targets. Further, molecular dynamics simulation confirmed stable interaction of quercetin with 6 targets (JAK3, SYK, MMP2, TLR8, IRAK1, and JAK1), galangin with 2 targets (IRAK1 and JAK1), and kaempferol (IRAK1) with one target of RA. Moreover, the presence of these three flavonoids was confirmed in the A. calcarata rhizome extract using LC-MS analysis. The computational study suggests that flavonoids present in A. calcarata rhizome may be responsible for RA modulatory activity. Particularly, quercetin and galangin could be potential development candidates for the treatment of RA. Investigation of Alpinia calcarata constituent interactions with molecular targets of rheumatoid arthritis: docking, molecular dynamics, and network approach.

Topics: Alpinia; Arthritis, Rheumatoid; Chromatography, Liquid; Computational Biology; Flavonoids; Humans; Interleukin-1 Receptor-Associated Kinases; Janus Kinase 1; Janus Kinase 3; Kaempferols; Mass Spectrometry; Matrix Metalloproteinase 2; Molecular Docking Simulation; Molecular Dynamics Simulation; Phytochemicals; Plant Extracts; Quercetin; Rhizome; Syk Kinase; Toll-Like Receptor 8

The inhibition of recombinant CpLIP2 lipase/acyltransferase from

Topics: Acyltransferases; Algorithms; Flavonoids; Flavonols; Hydrolysis; Hydroxylation; Kaempferols; Models, Theoretical; Molecular Structure; Orlistat; Protein Binding; Quercetin; Spectrometry, Fluorescence; Structure-Activity Relationship; Thermodynamics

Flavonoids, a class of polyphenols are known to be effective inducers of apoptosis and cytotoxicity in cancer cells. It is believed that antioxidant activity of polyphenols cannot fully account for induction of apoptosis and chemotherapeutic prevention in various cancers. In this article, by employing single cell alkaline gel electrophoresis (comet assay), we established that antioxidants, flavonoids such as (myricetin=MN, fisetin=FN, quercetin=QN, kaempferol=KL and galangin=GN) can cause cellular DNA breakage, also act as pro-oxidant in presence of transition metal ion such as copper. It was observed that the extent of cellular DNA breakage was found significantly higher in presence of copper. Hydroxyl radicals are generated as a sign of flavonoids' pro-oxidant nature through redox recycling of copper ions. Further, a dose-dependent inhibition of proliferation of breast cancer cells MDA-MB-231 by MN was found leading to pro-oxidant cell death, as assessed by MTT assay. Since levels of copper are considerably elevated in tissue, cell and serum during various malignancies, suggesting that cancer cells would be more subject to copper induced oxidative DNA breakage. Such a copper dependent pro-oxidant cytotoxic mechanism better explains the anticancer activity and preferential cytotoxicity of dietary phytochemicals against cancer cells.

Topics: Antineoplastic Agents, Phytogenic; Apoptosis; Cations, Divalent; Cell Line, Tumor; Copper; DNA Damage; Epithelial Cells; Flavonoids; Flavonols; Humans; Kaempferols; Oxidants; Oxidation-Reduction; Quercetin; Reactive Oxygen Species

A new labdane diterpene, (Z)-12,14-labdadien-15(16)-olide-17-oic acid (1), and a new natural cadinane sesquiterpene, 4-isopropyl-6-methyl-1-naphthalenemethanol (2), were isolated from the ethanolic extract of the rhizomes of Alpinia officinarum, together with three other products, galangin (3), kaempferol (4) and quercetin (5). Their structures were elucidated by using extensive spectroscopic methods. Compounds 1 and 2 showed no remarkable cytotoxic activity against HeLa and HepG2 cancer cell lines with IC50>50 μg mL(- 1).

Topics: Alpinia; Diterpenes; Drug Evaluation, Preclinical; Flavonoids; HeLa Cells; Hep G2 Cells; Humans; Inhibitory Concentration 50; Kaempferols; Medicine, Chinese Traditional; Molecular Structure; Naphthalenes; Plant Extracts; Quercetin; Rhizome

It has been reported that quercetin is an activator of rat vitamin D receptor (rVDR). However, the conclusion was based on experiments performed without all the appropriate control groups, raising the possibility of a false-positive finding. Furthermore, distinct differences exist in the chemical structures of quercetin and 1α,25-dihydroxyvitamin D3, which is a prototypic agonist of VDR. Therefore, we investigated systematically whether quercetin and other flavonols are agonists of rVDR, mouse VDR (mVDR), or human VDR (hVDR). Quercetin, 3-hydroxyflavone, galangin, datiscetin, kaempferol, morin, isorhamnetin, tamarixetin, myricetin, and syringetin did not activate rVDR, mVDR, or hVDR in HEK-293 and HepG2 cells transfected with the corresponding receptor expression plasmid and either the secreted phosphoprotein 1 (Spp1) or cytochrome P450 24A1 (CYP24A1) reporter plasmid, when compared to the respective empty vector control group transfected with one or the other reporter plasmid and treated with one of the flavonols. Control analysis indicated that lithocholic acid and 1α,25-dihydroxyvitamin D3, but not rifampicin, activated rVDR, mVDR, and hVDR. As shown in transfected HEK293 and HepG2 cells, the flavonols did not influence hVDR ligand binding domain transactivation, steroid receptor coactivator-1 recruitment, or hVDR target gene expression (transient receptor potential cation channel 6 and CYP24A1) in hVDR-expressing Caco-2 or LS180 cells. The cumulative data from the cell-based experiments were corroborated by results obtained from molecular docking analysis. In conclusion, quercetin, 3-hydroxyflavone, galangin, datiscetin, kaempferol, morin, isorhamnetin, tamarixetin, myricetin, and syringetin are not agonists of rVDR, mVDR, or hVDR, as judged by cell-based and in silico evidence.

Topics: Animals; Caco-2 Cells; Calcitriol; Disaccharides; Flavonoids; Gene Expression Regulation; HEK293 Cells; Hep G2 Cells; Humans; Kaempferols; Mice; Molecular Docking Simulation; Osteopontin; Quercetin; Receptors, Calcitriol; Structure-Activity Relationship; Transgenes; Vitamin D3 24-Hydroxylase

Matrix metalloproteinase (MMP)-9 degrades type IV collagen in the basement membrane and plays crucial roles in several pathological implications, including tumorigenesis and inflammation. In this study, we analyzed the effect of flavonols on MMP-9 expression in phorbol-12-myristate-13-acetate (PMA)-induced human fibrosarcoma HT-1080 cells. Galangin and kaempferol efficiently decreased MMP-9 secretion, whereas fisetin only weakly decreased its secretion. Galangin and kaempferol did not affect cell viability at concentrations up to 30 μM. Luciferase reporter assays showed that galangin and kaempferol decrease transcription of MMP-9 mRNA. Moreover, galangin and kaempferol strongly reduce IκBα phosphorylation and significantly decrease JNK phosphorylation. These results indicate that galangin and kaempferol suppress PMA-induced MMP-9 expression by blocking activation of NF-κB and AP-1. Therefore, these flavonols could be used as chemopreventive agents to lower the risk of diseases involving MMP-9.

Topics: Cell Line, Tumor; Cell Proliferation; Cell Survival; Fibrosarcoma; Flavonoids; Gene Expression Regulation, Neoplastic; Humans; I-kappa B Proteins; Kaempferols; Matrix Metalloproteinase 9; NF-KappaB Inhibitor alpha; Phosphorylation; Signal Transduction; Tetradecanoylphorbol Acetate

Insulin-regulated glucose metabolism in cells is critical for proper metabolic functioning, and insulin resistance leads to type 2 diabetes. We performed a human study to assess the availability of structurally related dietary flavonols and tested their ability to affect cellular glucose uptake, metabolism, and glucose transporter gene expression in a liver HepG2 cell model.. Eight healthy volunteers consumed a meal containing galangin, kaempferol, quercetin, and myricetin. In plasma, myricetin was absent, but the others were present, mostly as conjugates. In HepG2 cells, a combination of galangin, kaempferol, and quercetin (5 μM each) for 12 h increased the acute uptake of [U-(14)C]-glucose and 2-[U-(14)C]-deoxyglucose by almost 100 and ∼10%, respectively. All of the combinations increased glucose metabolism, but the effect on transport was less pronounced and mixed. A mixture of all flavonols significantly increased mRNA expression of the main glucose transporter Glut1 in HepG2 cells.. These results for the first time show the presence of galangin conjugates in human plasma, and allow direct comparison between absorption of flavonols. A combination of flavonols has the potential to modulate sugar metabolism, both uptake into cells as evident from effects on deoxyglucose, and also further cellular glucose metabolism.

Topics: Adult; Flavonoids; Flavonols; Glucose; Glucose Transport Proteins, Facilitative; Glucose Transporter Type 1; Hep G2 Cells; Humans; Kaempferols; Quercetin; RNA, Messenger

Epidemiological studies have linked dietary consumption of plant polyphenols with lower incidence of various cancers. In particular, flavonoids (present in onion, tomato and other plant sources) induce apoptosis and cytotoxicity in cancer cells. These can therefore be used as lead compounds for the synthesis of novel anticancer drugs with greater bioavailability. In the present study, we examined the chemical basis of cytotoxicity of flavonoids by studying the structure-activity relationship of myricetin (MN), fisetin (FN), quercetin (QN), kaempferol (KL) and galangin (GN). Using single cell alkaline gel electrophoresis (comet assay), we established the relative efficiency of cellular DNA breakage as MN > FN > QN > KL > GN. Also, we determined that the cellular DNA breakage was the result of mobilization of chromatin-bound copper ions and the generation of reactive oxygen species. The relative DNA binding affinity order was further confirmed using molecular docking and thermodynamic studies through the interaction of flavonoids with calf thymus DNA. Our results suggest that novel anti-cancer molecules should have ortho-dihydroxy groups in B-ring and hydroxyl groups at positions 3 and 5 in the A-ring system. Additional hydroxyl groups at other positions further enhance the cellular cytotoxicity of the flavonoids.

Topics: Antineoplastic Agents, Phytogenic; Cations, Divalent; Chelating Agents; Comet Assay; Copper; DNA; DNA Fragmentation; Flavonoids; Flavonols; Humans; Kaempferols; Leukocytes, Mononuclear; Molecular Docking Simulation; Oxidation-Reduction; Primary Cell Culture; Quercetin; Reactive Oxygen Species; Structure-Activity Relationship

Exposure of skin to ultraviolet light has been shown to have a number of deleterious effects including photoaging, photoimmunosuppression and photoinduced DNA damage which can lead to the development of skin cancer. In this paper we present a study on the ability of three flavonols to protect EpiDerm™, an artificial skin mimic, against UV-induced damage.. EpiDerm™ samples were treated with flavonol in acetone and exposed to UVA (100 kJ/m(2) at 365 nm) and UVB (9000 J/m(2) at 310 nm) radiation. Secretion of matrix metalloproteinase-1 (MMP-1) and tumor necrosis factor-α (TNF-a) were determined by ELISA, cyclobutane pyrimidine dimers were quantified using LC-APCI-MS.. EpiDerm™ treated topically with quercetin significantly decreased MMP-1 secretion induced by UVA (100 µM) or UVB (200 µM) and TNF-a secretion was significantly reduced at 100 µM quercetin for both UVA and UVB radiation. In addition, topically applied quercetin was found to be photostable over the duration of the experiment. EpiDerm™ samples were treated topically with quercetin, kaempferol or galangin (52 µM) immediately prior to UVA or UVB exposure, and the cyclobutane thymine dimers (T-T (CPD)) were quantified using an HPLC-APCI MS/MS method. All three flavonols significantly decreased T-T (CPD) formation in UVB irradiated EpiDerm™, however no effect could be observed for the UVA irradiation experiments as thymine dimer formation was below the limit of quantitation.. Our results suggest that flavonols can provide protection against UV radiation-induced skin damage through both antioxidant activity and direct photo-absorption. This article is open to POST-PUBLICATION REVIEW. Registered readers (see "For Readers") may comment by clicking on ABSTRACT on the issue's contents page.

Topics: Administration, Cutaneous; Cell Line; Chromatography, High Pressure Liquid; Flavonoids; Flavonols; Humans; Kaempferols; Keratinocytes; Matrix Metalloproteinase 1; Pilot Projects; Pyrimidine Dimers; Quercetin; Skin; Tandem Mass Spectrometry; Tumor Necrosis Factor-alpha; Ultraviolet Rays

Flavonoids are polyphenolic compounds required in the fertilization process in many, if not all, plants. However, the exact biological mechanism(s) and the interacting proteins are unknown. To determine the characteristics important in activating or inhibiting the pollination sequence, a structure-activity relationship analysis of natural and synthetic flavonols was conducted. Flavonol analogues were synthesized through a modified "one-pot" procedure that utilized a Baker-Venkataraman type rearrangement and a Suzuki-Miyaura cross-coupling of a halo-flavonol with an organotrifluoroborate. Of the flavonols tested, kaempferol was the only compound to act as a full agonist. The other smaller, less sterically hindered flavonols (galangin, kaempferide, and 4'-methyl flavonol) acted as partial agonists. Larger more hydrophobic flavonol analogues (3'- and 4'-benzoyl, 3'- and 4'-phenyl, and 3'- and 4'-iodo flavonols) had minimal or no agonist activity. Competition assays between kaempferol and these minimally activating flavonols showed that these analogues inhibited the action of kaempferol in a manner consistent with noncompetitive antagonism. The results suggest that steric hindrance is the most important factor in determining a good agonist. Hydrogen bonding also had a positive effect as long as the substituent did not cause any steric hindrance.

Topics: Chemistry Techniques, Synthetic; Flavonoids; Flavonols; Germination; Hydrogen Bonding; Kaempferols; Petunia; Plants, Genetically Modified; Pollen; Structure-Activity Relationship

Solubility and matrix play an important role in the gut lumen in delivering bioactive compounds to the absorptive surface of enterocytes. The purpose of this study was to determine the effect of certain commonly consumed lipids, soybean, olive and corn oil, on the transport and conjugation of flavonols (myricetin, quercetin, kaempferol and galangin) using the conjugation-competent co-cultured Caco-2/HT29-MTX intestinal cell monolayer model. To enable identification and quantification of conjugates, each flavonol was enzymatically glucuronidated or sulphated, then analysed by HPLC with triple quadrupole mass spectrometric detection. Quantification showed large differences in mass spectrometric peak area response factors between the aglycones and many of the conjugates, with galangin-sulphate for example ionising ∼15-fold better than galangin. Flavonol aglycones and conjugates were transported to the basolateral side of Caco-2/HT29-MTX co-cultures. The total amount of methyl, sulphate and glucuronide conjugates was in the order: galangin > quercetin > kaempferol > myricetin. All oils inhibited the transport and conjugation of galangin, the most hydrophobic flavonol, whereas they increased the sulphation, and to some extent glucuronidation, of quercetin and kaempferol. The results show that the lipid matrix has the potential to modify both transport and conjugation of dietary flavonols, but that the effect depends upon the structure and hydrophobicity.

Topics: Biological Transport; Caco-2 Cells; Flavonoids; HT29 Cells; Humans; Intestinal Mucosa; Kaempferols; Plant Oils; Quercetin

Rheumatoid arthritis (RA) patients usually exhibit immune complex (IC) deposition and increased neutrophil activation in the joint. In this study, we assessed how four flavonols (galangin, kaempferol, quercetin, and myricetin) modulate the effector functions of healthy individuals' and active RA patients' IC-stimulated neutrophils. We measured superoxide anion and total reactive oxygen species production using lucigenin (CL-luc)- and luminol (CL-lum)-enhanced chemiluminescence assays, respectively. Galangin, kaempferol, and quercetin inhibited CL-lum to the same degree (mean IC50=2.5 μM). At 2.5 μM, quercetin and galangin suppressed nearly 65% CL-lum of active RA patients' neutrophils. Quercetin inhibited CL-luc the most effectively (IC50=1.71±0.36 μM). The four flavonols diminished myeloperoxidase activity, but they did not decrease NADPH oxidase activity, phagocytosis, microbial killing, or cell viability of neutrophils. The ability of the flavonols to scavenge hypochlorous acid and chloramines, but not H2O2, depended on the hydroxylation degree of the flavonol B-ring. Therefore, at physiologically relevant concentrations, the flavonols partially inhibited the oxidative metabolism of IC-stimulated neutrophils without affecting the other investigated effector functions. Using these compounds to modulate IC-mediated neutrophil activation is a promising safe therapeutic strategy to control inflammation in active RA patients.

Topics: Adult; Anti-Inflammatory Agents; Antigen-Antibody Complex; Arthritis, Rheumatoid; Cell Degranulation; Cells, Cultured; Female; Flavonoids; Humans; Kaempferols; Middle Aged; Neutrophils; Oxidation-Reduction; Peroxidase; Quercetin; Reactive Oxygen Species; Structure-Activity Relationship

Raman and surface-enhanced Raman scattering (SERS) spectroscopy were employed to probe the interaction of the flavonol drugs, kaempferol and galangin, with human serum albumin (HSA). SERS spectra of both flavonol derivatives were obtained from a colloidal silver surface in physiological condition, based on the high performance of the enhanced substrate, the most enhanced modes of kaempferol and galangin were those with certain motions perpendicular to the metal surface. The SERS spectra were allowed to predict similar orientation geometry for both of the drugs on the colloidal surface with minor difference. In addition, both flavonols-HSA complexes were prepared in different concentration ratios and the orientated differences between kaempferol and galangin were investigated by SERS.

Topics: Adsorption; Binding Sites; Drugs, Chinese Herbal; Flavonoids; Humans; Kaempferols; Nanoparticles; Protein Binding; Serum Albumin; Silver; Spectrum Analysis, Raman

The mutagenicity of ten flavonoids was assayed by the Ames test, in Salmonella typhimurium strains TA98, TA100 and TA102, with the aim of establishing hydroxylation pattern-mutagenicity relationship profiles. The compounds assessed were: quercetin, kaempferol, luteolin, fisetin, chrysin, galangin, flavone, 3-hydroxyflavone, 5-hydroxyflavone and 7-hydroxyflavone. In the Ames assay, quercetin acted directly and its mutagenicity increased with metabolic activation. In the presence of S9 mix, kaempferol and galangin were mutagenic in the TA98 strain and kaempferol showed signs of mutagenicity in the other strains. The absence of hydroxyl groups, as in flavone, only signs of mutagenicity were shown in strain TA102, after metabolization and, among monohydroxylated flavones (3-hydroxyflavone, 5-hydroxyflavone and 7-hydroxyflavone), the presence of hydroxyl groups only resulted in minor changes. Luteolin and fisetin also showed signs of mutagenicity in strain TA102. Finally, chrysin, which has only two hydroxy groups, at the 5-OH and 7-OH positions, also did not induce mutagenic activity in any of the bacterial strains used, under either activation condition. All the flavonoids were tested at concentrations varying from 2.6 to 30.7 nmol/plate for galangin and 12.1 to 225.0 nmol/plate for other flavonoids. In light of the above, it is necessary to clarify the conditions and the mechanisms that mediate the biological effects of flavonoids before treating them as therapeutical agents, since some compounds can be biotransformed into more genotoxic products; as is the case for galangin, kaempferol and quercetin.

Topics: Biological Assay; Biotransformation; Flavonoids; Hydroxylation; Kaempferols; Mutagenicity Tests; Mutagens; Mutation; Quercetin; Salmonella typhimurium; Structure-Activity Relationship

It has been suggested that the increasing glycation in diabetes can influence the ability of plasma proteins to bind to small molecules. Herein, the influence of flavonoids on the glycation of plasma proteins was investigated. After being incubated with glucose at 37 °C, the levels of glycated albumin (HGA) were significantly improved in healthy human plasma proteins (HPP). The inhibitory effects of flavonoids against the formation of advanced glycation products (AGEs) in HPP were determined as: galangin > apigenin > kaempferol ≈ luteolin > myricetin > quercetin. After being combined with 20 μmol L⁻¹ of quercetin for 11 days, the fresh plasma with δ-glucose caused 323.05-32.07% inhibition of HGA formation in type II diabetes plasma proteins (TPP). Luteolin showed weak inhibition of HGA formation in TPP. However, kaempferol, galangin and apigenin hardly inhibited the formation of HGA in TPP. These results showed that more hydroxyl groups on ring B of flavonoids will enhance the inhibitory effects on the HGA formation in TPP.

Topics: Apigenin; Blood Proteins; Diabetes Mellitus, Type 2; Flavonoids; Glucose; Glycation End Products, Advanced; Glycosylation; Humans; Kaempferols; Luteolin; Quercetin

The photostability of quercetin in alcoholic solutions was studied. Both UVA and UVB light induced degradation of quercetin, yielding a single product 1 deriving from oxidation and addition of an alcohol molecule to the 2,3 double bond. The same mechanism operated when quercetin was dissolved in alkaline solutions, and again a product 2 due to oxidation and addition of water was characterized. Comparison with quercetin analogs confirmed that, despite the presence of five hydroxy groups in quercetin, those in positions 3, 3', and 4' are mainly involved in the antioxidant activity of the compound , as well as in its photolability.

Topics: Ammonia; Apigenin; Drug Stability; Ethanol; Flavonoids; Hydrogen-Ion Concentration; Kaempferols; Methanol; Oxidation-Reduction; Photochemical Processes; Quercetin; Rutin; Solutions; Solvents; Spectrophotometry, Ultraviolet; Ultraviolet Rays

The potential of three natural flavonols (galangin, kaempferol and myricetin) to protect against D-galactose-induced cognitive impairment in mice was investigated. After 8 weeks treatment, the mice were assessed by behavioural tests. The levels of oxidative stress, the amount of Na(+),K(+)-ATPase and extracellular signal-regulated kinases (ERK)-cyclic AMP response element binding protein (CREB) signaling pathway in hippocampus were also analysed. It was found that all the three dietary flavonols could ameliorate the oxidative stress, enhance the activity of Na(+),K(+)-ATPase and regulate the expression of ERK-CREB pathway in mice. However, only kaempferol and myricetin could significantly improve the learning and memory capability when compared with D-galactose model. Our results suggest that the presence of hydroxyl groups in the B ring of flavonols may have contribution to the neuroprotective activity.

Topics: Animals; Behavior, Animal; Cognition Disorders; Cyclic AMP Response Element-Binding Protein; Extracellular Signal-Regulated MAP Kinases; Flavonoids; Galactose; Hippocampus; Humans; Kaempferols; Male; Mice; Neuroprotective Agents; Oxidative Stress; Signal Transduction

The impact of Zn(2+) ion on interactions of flavonols galangin (Gal), kaempferol (Kae), quercetin (Que) and myricetin (Myr) with bovine serum albumin (BSA) in aqueous solution were studied by fluorescence quenching technique. The results exhibited that Zn(2+) ion affected significantly the interactions and the effect was distinct for the flavonol bearing different number of B-ring hydroxyl. Each flavonol can quench the fluorescence of BSA, displaying a quenching extent of Myr>Que>Kae>Gal, which is in good agreement with the number variation of the B-ring hydroxyl. The presence of Zn(2+) ion promoted the quenching for the flavonols, exhibiting an extent of Que>Myr>Kae>Gal. The values of K(a) for Kae, Que and Myr decreased whereas K(SV) and k(q) for Gal, Kae and Que increased with the number of B-ring hydroxyl. The type of BSA fluorescence quenching for Gal, Kae and Que hardly changed but the preference of static quenching increased. The values of K(SV) and k(q) for Myr remarkably decreased and the fluorescence quenching of BSA alternatively occurred via both static and dynamic type instead of only one (static or dynamic). The results suggest the key role of the B-ring hydroxyl and the distinct effect of its number in the interactions. Each flavonol may capture the BSA-bound Zn(II) in the solution, forming Zn(II)-flavonol complex that is possibly responsible for BSA fluorescence quenching. The B-ring hydroxyl could establish hydrogen bonds with BSA in the absence of Zn(2+) and act as donors for chelating in the presence of Zn(2+). The formation of dinuclear Zn(II)-Myr complex together with the hydrogen bonds between the free B-ring hydroxyl and BSA may contribute to the exceptional behavior of Myr.

Topics: Animals; Binding Sites; Binding, Competitive; Cattle; Flavonoids; Flavonols; Fluorescence; Hydrogen Bonding; Kaempferols; Kinetics; Molecular Structure; Protein Binding; Quercetin; Serum Albumin, Bovine; Spectrometry, Fluorescence; Zinc

Galangin, a dietary flavonoid, inhibited cytochrome P450 1A1 (CYP1A1) expression induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). This inhibitory activity remained after permeating human intestinal epithelial Caco-2 cell monolayers, but was reduced when galangin permeated TCDD-pretreated Caco-2 cells. The present study tested whether TCDD affected the intestinal metabolism of flavonoids. LC-MS/MS analyses showed that galangin and two galangin glucuronoconjugates were reduced 0.7-fold, whereas kaempferol (a galangin oxidate) and kaempferol glucuronoconjugate were increased 1.5-fold by permeating TCDD-pretreated Caco-2 cells, as compared to untreated Caco-2 cells. An assay using recombinant human CYP1A1 and the CYP1A1 inhibitor alpha-naphthoflavone revealed that CYP1A1 oxidized galangin to kaempferol. These results indicated that galangin was metabolized to kaempferol by TCDD-inducible CYP1A1 in Caco-2 cells. A previous study revealed that kaempferol had much weaker inhibitory activity than galangin toward TCDD-induced CYP1A1 expression. Therefore, the oxidative metabolism of galangin to kaempferol in TCDD-pretreated Caco-2 cells implicated reduction in the inhibitory activity of galangin.

Topics: Caco-2 Cells; Cytochrome P-450 CYP1A1; Flavonoids; Gene Expression; Humans; Inactivation, Metabolic; Intestinal Mucosa; Intestines; Kaempferols; Polychlorinated Dibenzodioxins; Receptors, Aryl Hydrocarbon

Tissue damage in autoimmune diseases involves excessive production of reactive oxygen species (ROS) triggered by immune complexes (IC) and neutrophil (PMN) interactions via receptors for the Fc portion of IgG (FcgammaR) and complement receptors (CR). Modulation of both the effector potential of these receptors and ROS generation may be relevant to the maintenance of body homeostasis. In the present study, the modulatory effect of four flavonols (myricetin, quercetin, kaempferol, galangin) on rabbit PMN oxidative metabolism, specifically stimulated via FcgammaR, CR or both classes of receptors, was evaluated by luminol- and lucigenin-dependent chemiluminescence assays. Results showed that flavonol inhibitory effect was not dependent on the cell membrane receptor class stimulated but related to the lipophilicity of the compounds (their apparent partition coefficient values were obtained by high-performance liquid chromatography), and was also inversely related to the number of hydroxyl groups in the flavonol B ring and the ROS-scavenger activity (assessed by the luminol--H2O2--horseradish peroxidase reaction). Under the experimental conditions the flavonols tested were not toxic to PMNs (evaluated by lactate dehydrogenase release and trypan blue exclusion) and did not interfere with IC-induced phagocytosis (evaluated by transmission electron microscopy). Our results suggested that inhibition of IC-stimulated PMNs effector functions by the flavonols tested herein was the result of cooperation of different cellular mechanisms.

Topics: Acridines; Animals; Antigen-Antibody Complex; Benzene Derivatives; Complement System Proteins; Flavonoids; Flavonols; Free Radical Scavengers; Hydrophobic and Hydrophilic Interactions; Hydroxylation; Immune Complex Diseases; Immunologic Factors; Kaempferols; Luminescent Measurements; Luminol; Molecular Structure; Neutrophils; Oxidation-Reduction; Phagocytosis; Quercetin; Rabbits; Receptors, Complement; Receptors, Fc; Structure-Activity Relationship

The antioxidant activity of flavonoids has been suggested to contribute to several health benefits associated with the consumption of fruits and vegetables. Four flavonols - myricetin (M), quercetin (Q), kaempferol (K) and galangin (G), all with different numbers of hydroxyl moieties (-OH) - were examined for their antioxidant activity and cytotoxicity on human umbilical vein endothelial cells (HUVECs) and for their potential antiangiogenic and cell adhesion effects. The relative antioxidant capacity of these flavonols in cell culture medium (cell-free system) and their intracellular antioxidant activity were M = Q > K = G, which correlated respectively with the presence of 3, 2, 1 and 0 moieties of -OH on their B-ring. The higher the numbers of -OH moieties on the B-ring the less toxic the flavonol was to HUVEC, and the LD50 was determined as: M (100 microM) > Q (50 microM) > K (20 microM) > G (10 microM). These flavonols at approximately 0.5 LD50 doses suppressed the vascular endothelial growth factor (VEGF)-stimulated HUVEC tubular structure formation by: M (47%) > Q (37%) > K (15%) > G (14%), which was not linearly associated with their numbers of -OH moieties. However, the magnitude of flavonols' suppression of activated U937 monocytic cells adhesion to HUVEC was associated with the number of -OH moieties on the B-ring. This was prominent when U937 cells were pretreated with these flavonols. In contrast, the numbers of -OH moiety had no apparent influence on the adhesion or expression of adhesion molecules when activated HUVECs were pretreated with these flavonols. The presence of different numbers of -OH moieties on the B-ring of the flavonols may contribute to their antioxidant activity as well as their toxicity and may play an important role in their potency for biological action such as angiogenesis and immune-endothelial cell adhesion, which, respectively, are important processes in the development of cancer and atherosclerosis.

Topics: Antioxidants; Cell Adhesion; Cell Adhesion Molecules; Cell Death; Cell Division; Cell Line; Cells, Cultured; Endothelial Cells; Flavonoids; Flavonols; Gene Expression; Humans; Kaempferols; Monocytes; Neovascularization, Physiologic; Quercetin; Structure-Activity Relationship; Tetradecanoylphorbol Acetate; Umbilical Veins; Vascular Endothelial Growth Factor A

Up to now, the metabolism of hispidulin (5,7,4'-trihydroxy-6-methoxyflavone), a potent ligand of the central human benzodiazepine receptor, has not been investigated. To elucidate the metabolism of hispidulin in the large intestine, its biotransformation by the pig caecal microflora was studied. In addition, the efficiency of the pig caecal microflora to degrade galangin (3,5,7-trihydroxyflavone), kaempferol (3,5,7,4'-tetrahydroxyflavone), apigenin (5,7,4'-trihydroxyflavone), and luteolin (5,7,3',4'-tetrahydroxyflavone) was investigated. Identification of the formed metabolites was performed by high-performance liquid chromatography (HPLC)-diode array detection, HPLC-electrospray ionization-tandem mass spectrometry, and high-resolution gas chromatography-mass spectrometry. The caecal microflora transformed hispidulin to scutellarein (5,6,7,4'-tetrahydroxyflavone), an effective alpha-glucosidase inhibitor, and 3-(4-hydroxyphenyl)-propionic acid; galangin to phenylacetic acid and phloroglucinol; kaempferol to 4-hydroxyphenylacetic acid, phloroglucinol, and 4-methylphenol; apigenin to 3-(4-hydroxyphenyl)-propionic acid and 3-phenylpropionic acid, and luteolin to 3-(3-hydroxyphenyl)-propionic acid, respectively. To elucidate to what extent different hydroxylation patterns on the B-ring influence the degradation degree of flavonoids, the conversions of galangin and kaempferol as well as that of apigenin and luteolin were compared with those of quercetin (3,5,7,3',4'-pentahydroxyflavone) and chrysin (5,7-dihydroxyflavone), respectively. Regardless of the flavonoid subclass, the presence of a hydroxy group at the 4'-position seems to be a prerequisite for fast breakdown. An additional hydroxy group at the B-ring did not affect the degradation degree.

Topics: Animals; Apigenin; Bacteria; Cecum; Chromatography, High Pressure Liquid; Flavones; Flavonoids; Gas Chromatography-Mass Spectrometry; Humans; Kaempferols; Kinetics; Luteolin; Models, Animal; Quercetin; Spectrometry, Mass, Electrospray Ionization; Swine

There is very limited information on cytochrome P450 (P450)-mediated oxidative metabolism of dietary flavonoids in humans. In this study, we used human liver microsomes and recombinant P450 isoforms to examine the metabolism of two flavonols, galangin and kaempferide, and one flavone, chrysin. Both galangin and kaempferide, but not chrysin, were oxidized by human liver microsomes to kaempferol, with K(m) values of 9.5 and 17.8 microM, respectively. These oxidations were catalyzed mainly by CYP1A2 but also by CYP2C9. Consistent with these observations, the human liver microsomal metabolism of galangin and kaempferide were inhibited by the P450 inhibitors furafylline and sulfaphenazole. In addition, CYP1A1, although less efficient, was also able to oxidize the two flavonols. Thus, dietary flavonols are likely to undergo oxidative metabolism mainly in the liver but also extrahepatically.

Topics: Aryl Hydrocarbon Hydroxylases; Cytochrome P-450 CYP1A1; Cytochrome P-450 CYP1A2; Cytochrome P-450 CYP2C9; Cytochrome P-450 Enzyme System; Flavonoids; Humans; Isoenzymes; Kaempferols; Microsomes, Liver; Mutagens; Oxidation-Reduction; Quercetin; Steroid 16-alpha-Hydroxylase; Steroid Hydroxylases; Trisaccharides

Starting from the interaction of galangin (3,5,7-trihydroxyflavone) with a cytosolic nucleotide-binding domain of P-glycoprotein, a series of flavonol derivatives was synthesized and tested for their binding affinity towards the same target. The 5,7-dihydroxy-4'-iodoflavonol and 5,7-dihydroxy-4'-n-octylflavonol derivatives displayed much higher binding affinities, with respective increases of 6- and 93-fold as compared to galangin.

Topics: ATP Binding Cassette Transporter, Subfamily B, Member 1; Binding Sites; Chalcone; Drug Resistance, Multiple; Flavonoids; Flavonols; Fluorescence; Kaempferols; Molecular Structure; Protein Binding; Protein Structure, Tertiary; Quercetin; Recombinant Proteins; Thermodynamics; Tryptophan

Tyrosinase inhibitory activity of flavonols, galangin, kaempferol and quercetin, was found to come from their ability to chelate copper in the enzyme. In contrast, the corresponding flavones, chrysin. apigenin and luteolin, did not chelate copper in the enzyme. The chelation mechanism seems to be specific to flavonols as long as the 3-hydroxyl group is free. Interestingly, flavonols affect the enzyme activity in different ways. For example, quercetin behaves as a cofactor and does not inhibit monophenolase activity. On the other hand, galangin inhibits monophenolase activity and does not act as a cofactor. Kaempferol neither acts as a cofactor nor inhibits monophenolase activity. However, these three flavonols are common to inhibit diphenolase activity by chelating copper in the enzyme.

Topics: Arnica; Binding Sites; Catechol Oxidase; Chelating Agents; Copper; Enzyme Inhibitors; Flavanones; Flavones; Flavonoids; Flavonols; Fungal Proteins; Inhibitory Concentration 50; Kaempferols; Kinetics; Levodopa; Monophenol Monooxygenase; Oxidation-Reduction; Plant Extracts; Plants, Medicinal; Quercetin; Spectrophotometry; Structure-Activity Relationship

The protective effect of flavonoids against linoleic acid hydroperoxide (LOOH)-induced cytotoxicity was examined by using cultured endothelial cells. When the cells were incubated with both LOOH and flavonoids, most flavonols protected the cells from injury by LOOH. Flavones bearing an ortho-dihydroxy structure also showed a protective effect against the cytotoxicity of LOOH. However, flavanones had no effect. The structure-activity relationship revealed the presence of either the ortho-di-hydroxy structure in the B ring of the flavonoids or 3-hydroxyl and 4-oxo groups in the C ring to be important for the protective activities. The interaction between flavonoids and a-tocopherol was also examined in this system. Flavonoids that were protective against LOOH-induced cytotoxicity had at least an additive effect on the action of alpha-tocopherol against LOOH-induced damage.

Topics: Antioxidants; Cell Survival; Cells, Cultured; Chromones; Endothelium, Vascular; Enzyme Inhibitors; Flavones; Flavonoids; Flavonols; Humans; Kaempferols; Linoleic Acids; Lipid Peroxides; Luteolin; Mutagens; Quercetin; Structure-Activity Relationship; Umbilical Veins; Vitamin E

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

The effects of flavonols on P-glycoprotein (Pgp) activity were studied in cultured rat hepatocytes by assessing and transmembrane transport of Rhodamine-123 (R-123) and doxorubicin (DOX). In freshly-plated hepatocytes, containing a low amount of Pgp, flavonols did not affect the cellular retention of DOX, but strongly inhibited the Pgp-mediated efflux of R-123. In 72h-cultured hepatocytes, spontaneously overexpressing functional Pgp, flavonols inhibited R-123 efflux in a dose-dependent manner, but significantly reduced DOX retention while increasing its efflux. A similar effect was found in hepatocytes obtained from rats in which Pgp was induced in vivo by 2-acetamino-fluorene (AAF) or alpha-naphthyl-isothiocyanate (ANIT) treatments. These findings indicate that flavonols, dietary compounds reported to strongly upregulate the apparent activity of Pgp in cancer cell lines, may also modulate differently the transport of putative Pgp substrates in normal rat hepatocytes. The ability to affect the drug-extruding activity at the hepatocyte canalicular membrane could be of relevance to the chemopreventive action of these compounds towards liver carcinogens.

Topics: 2-Acetylaminofluorene; Animals; Antibiotics, Antineoplastic; Antimetabolites, Antineoplastic; ATP Binding Cassette Transporter, Subfamily B, Member 1; Blotting, Western; Cells, Cultured; Doxorubicin; Drug Interactions; Flavonoids; Flavonols; HL-60 Cells; Humans; Kaempferols; Liver; Male; Quercetin; Rats; Rats, Sprague-Dawley; Rhodamine 123; Rhodamines

Since P-glycoprotein (P-gp) in normal tissues may serve as a cellular defense mechanism against naturally occurring xenobiotics, we considered whether physiologically active components of commonly ingested plant foods could influence P-gp function. To examine this possibility, a series of flavonoids commonly found in plant foods was tested for their ability to modulate [14C]Adriamycin ([14C]ADR) accumulation and efflux in P-gp-expressing HCT-15 colon cells. Many flavonoids, in the micromolar range, inhibited the accumulation of [14C]ADR. Detailed experiments utilizing flavonoids with the greatest activity in reducing [14C]ADR accumulation, i.e. galangin, kaempferol, and quercetin, revealed that the efflux of [14C]ADR is increased markedly in the presence of these compounds. Flavonoid-induced stimulation of efflux was rapid and was blocked by the multidrug-resistant (MDR) reversal agents verapamil, vinblastine, and quinidine. The magnitude of flavonoid-stimulated efflux in sodium butyrate-treated cells with a 4-fold induction of P-gp protein was similar to that in uninduced cells. [3H]Azidopine photoaffinity labeling of P-gp in crude membrane preparations revealed mild to no competition for binding by flavonoids possessing either activity or inactivity in reducing ADR accumulation. Although flavonoid hydrophobicity was found to be unrelated to flavonoid activity in altering [14C]ADR accumulation, certain structural features were associated with enhancement or diminution of activity. Finally, the significance of flavonoid-related reduction of [14C]ADR accumulation was underscored in cell growth studies, showing partial protection by quercetin against ADR-induced growth inhibition. It is concluded that certain naturally occurring plant flavonoids may acutely upregulate the apparent activity of P-gp.

Topics: ATP Binding Cassette Transporter, Subfamily B, Member 1; Butyrates; Butyric Acid; Cell Division; Cell Line; Cell Survival; Diet; Dose-Response Relationship, Drug; Doxorubicin; Drug Interactions; Flavonoids; Humans; Kaempferols; Quercetin; Structure-Activity Relationship; Verapamil; Vinblastine

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

The effect of five propolis flavonoids on the infectivity and replication of some herpesvirus, adenovirus, coronavirus and rotavirus strains has been studied. Experiments were performed in vitro in cell cultures using the viral plaque reduction technique. The cytotoxicity of flavonoids, including chrysine, kaempferol, acacetin, galangin and quercetin, was evaluated on uninfected monolayers to determine their effect on cell growth and viability. Chrysine and kaempferol caused a concentration-dependent reduction of intracellular replication of herpes-virus strains when monolayers were infected and subsequently cultured in a drug-containing medium. However, virus infectivity was not significantly affected. Acacetin and galangin had no effect on either the infectivity or replication of any of the viruses studied. Quercetin reduced infectivity and intracellular replication, but only at the highest concentrations tested.

Topics: Animals; Cell Line; Flavones; Flavonoids; Humans; Immunoenzyme Techniques; Kaempferols; Molecular Structure; Quercetin; Vero Cells; Viral Plaque Assay; Virus Replication; Viruses

The genotoxicity of selected flavonols was evaluated by multiple endpoints in Chinese hamster ovary (CHO) cells. Chromosomal aberrations, sister-chromatid exchange (SCE), and forward mutation at 4 gene loci were measured in a single population of cells exposed to quercetin, kaempferol, or galangin for 15 h with and without metabolic activation. The incidence of chromosomal aberrations was significantly increased by quercetin in the absence of activation and by kaempferol and galangin with and without activation. Flavonol treatment affected SCE and mutation at the hgprt, aprt, or Na+/K+-ATPase loci only marginally, but significantly increased mutation frequencies at the tk locus. The response at the tk locus suggests that the CHO cells may behave similarly to L5178Y cells, in which the tk locus is thought to reflect chromosomal lesions in addition to point mutation. These results indicate that, at least under the conditions examined, flavonols induce chromosomal aberrations in CHO cells, but have little effect on point mutation or SCE.

Topics: Animals; Cell Survival; Cells, Cultured; Chromosome Aberrations; Cricetinae; Cricetulus; Female; Flavonoids; Kaempferols; Mutagens; Ovary; Quercetin; Sister Chromatid Exchange