Luteolin suppresses inflammation-associated gene expression by blocking NF-kappaB and AP-1 activation pathway in mouse alveolar macrophages

Postischemic administration of liposome-encapsulated luteolin prevents against ischemia-reperfusion injury in a rat middle cerebral artery occlusion model

Oxidative stress-induced neuronal cell death has been implicated in neurodegenerative diseases; one such disease is ischemic stroke. Using reactive oxygen species (ROS)-insulted primary neurons, we screened neuroprotectants with clinical potential and then, using ischemia/reperfusion (I/R) model, investigated the anti-ischemic potential of candidate neuroprotectants. Here, we showed that luteolin, isolated from the ripe fruit of Perilla frutescens (L.) Britt, exhibited a neuroprotective action upon the in vitro platform, thus serving as candidate for in vivo pharmacological evaluation. Liposome-encapsulated luteolin produced dramatic preventing effects on I/R-induced behavioral and histological injuries after a 13-day post-ischemic treatment. Furthermore, this phytochemical not only lowered the increased level of mitochondrial ROS but also substantially up-regulated the decreased activity of catalase and glutathione in I/R rat brains. Collectively, luteolin as a neuroprotectant acts by anti-ischemic activity likely through a rebalancing of pro-oxidant/antioxidant status. Its multitarget mechanisms implicate potential effectiveness for clinically treating ischemia stroke.

Luteolin ameliorates experimental lung fibrosis both in vivo and in vitro: implications for therapy of lung fibrosis

Lonicera japonica (Caprifoliaceae) has been known as an anti-inflammatory herb in traditional Chinese medicine for thousands of years and is used constantly for upper respiratory tract infections. Luteolin, an active flavonoid compound isolated from Lonicera japonica, has a spectrum of biological activities, especially with antioxidative and anti-inflammatory properties. However, whether luteolin has a direct inhibitory effect on lung fibrosis has not been established. In this study, we examined the effects of luteolin on lung fibrosis both in vivo and in vitro. We found that oral administration of luteolin (10 mg/kg) efficiently suppressed the neutrophil infiltration as well as TNF-α and IL-6 elevation in the bronchoalveolar lavage fluid in bleomycin-instilled C57BL/6J mice. Luteolin also alleviated collagen deposition, TGF-β1 expression, and lung fibrosis upon bleomycin instillation. A similar tendency was observed in both early and delayed luteolin-treated groups. Next, our in vitro studies showed that luteolin inhibited TGF-β1-induced α-SMA, type I collagen, and vimentin expression in primary cultured mouse lung fibroblasts. Moreover, luteolin significantly blocked TGF-β1-mediated epithelial marker (E-cadherin) downregulation and mesenchymal cell markers (fibronectin and vimentin) upregulation, as well as retaining epithelial morphology in human alveolar epithelial-derived A549 cells. Additionally, luteolin could attenuate TGF-β1-induced Smad3 phosphorylation in both lung fibroblasts and A549 cells. These findings suggest that luteolin has a potent antifibrotic activity; this effect was mediated, at least in part, by inhibition of lung inflammation and suppression of myofibroblast differentiation as well as epithelial-to-mesenchymal transition.

Fruit polyphenols, immunity and inflammation

Flavonoids are a large class of naturally occurring compounds widely present in fruits, vegetables and beverages derived from plants. These molecules have been reported to possess a wide range of activities in the prevention of common diseases, including CHD, cancer, neurodegenerative diseases, gastrointestinal disorders and others. The effects appear to be related to the various biological/pharmacological activities of flavonoids. A large number of publications suggest immunomodulatory and anti-inflammatory properties of these compounds. However, almost all studies are in vitro studies with limited research on animal models and scarce data from human studies. The majority of in vitro research has been carried out with single flavonoids, generally aglycones, at rather supraphysiological concentrations. Few studies have investigated the anti-inflammatory effects of physiologically attainable flavonoid concentrations in healthy subjects, and more epidemiological studies and prospective randomised trials are still required. This review summarises evidence for the effects of fruit and tea flavonoids and their metabolites in inflammation and immunity. Mechanisms of effect are discussed, including those on enzyme function and regulation of gene and protein expression. Animal work is included, and evidence from epidemiological studies and human intervention trials is reviewed. Biological relevance and functional benefits of the reported effects, such as resistance to infection or exercise performance, are also discussed.

Anti-inflammatory activities of red curry paste extract on lipopolysaccharide-activated murine macrophage cell line

OBJECTIVE

This study investigated anti-inflammatory and antioxidant activities of an ethanol extract from Thai red curry paste.

METHODS

The RAW264.7 murine macrophage cell line was incubated with the extract (65-260 μg/mL) with or without lipopolysaccharide. The anti-inflammatory activities of the extract were examined by measuring inducible nitric oxide synthase, cyclo-oxygenase-2, tumor necrosis factor-α, and interleukin-6 mRNA and protein level by reverse transcription-polymerase chain reaction, western blotting, and enzyme-linked immunosorbent assay, respectively. Nitric oxide production and intracellular reactive oxygen species generation were determined by the Griess method and fluorescence intensity. The activation of mitogen-activated protein kinases and inhibitor κB were determined by western blot.

RESULTS

Exposure of cells with the extract significantly suppressed lipopolysaccharide-induced nitric oxide production and inducible nitric oxide synthase, cyclo-oxygenase-2, tumor necrosis factor-α, and interleukin-6 expressions (P < 0.05) by dose-dependently without cytotoxic effect. Intracellular reactive oxygen species significantly decreased (P < 0.05) in lipopolysaccharide-induced RAW264.7 cells. The inhibitory effect was mediated partly by inhibiting activation of inhibitor κB-α and mitogen-activated protein kinases.

CONCLUSION

These results suggest that the anti-inflammatory and antioxidant properties of Thai red curry paste stem from bioactive compounds present in the spice and herb constituents. The health benefits of Thai red curry paste warrant further investigations in vivo.

Suppression of oxidative stress and pro-inflammatory mediators by Cymbopogon citratus D. Stapf extract in lipopolysaccharide stimulated murine alveolar macrophages

Exploration of antioxidants of plant origin and their scientific validation for their immense pharmacological potential is emerging as an issue of intense research now-a-days.The effect of Cymbopogon citratus extract was seen on cell viability, oxidative stress markers i.e. ROS production, SOD activity, lipid peroxidation and GSH content of murine alveolar macrophages stressed with lipopolysaccharide. Modulation in release of NO and pro-inflammatory cytokine TNF-α along with alterations in mitochondrial membrane potential under stress were compared with known plant derived antioxidant quercetin. The extract was not found to be cytotoxic at any of the selected doses. At 5 and 10 μg the extract showed significant increase in SOD activity, GSH content (p<0.001), decrease in ROS production as seen by fluorescent dye DCFH-DA and also MDA formation (lipid peroxidation marker) significantly. The extract also showed reduction in the release of pro-inflammatory mediators TNF-α and NO significantly indicating an anti-inflammatory effect. The extract was able to restore mitochondrial membrane potential as estimated by spectrofluorimetry using the fluorescent dye Rhodamine 123. The results suggest potential use of the cytoprotective, antioxidant and anti-inflammatory property of C. citratus in the form of dietary component and also in formulations against lung inflammatory diseases where oxidative stress plays an important role.

Protective effects of luteolin against lipopolysaccharide-induced acute lung injury involves inhibition of MEK/ERK and PI3K/Akt pathways in neutrophils

AIM

To investigate whether luteolin, the major polyphenolic components of Lonicera japonica, has beneficial effects against lipopolysaccharide (LPS)-induced acute lung injury (ALI) and to determine whether the protective mechanism involves anti-inflammatory effects on neutrophils.

METHODS

ALI was induced with intratracheal instillation of LPS in mice. The level of ALI was determined by measuring the cell count and protein content in bronchoalveolar lavage (BAL) fluid. Neutrophils were stimulated with formyl-Met-Leu-Phe (fMLP) or LPS in vitro. Chemotaxis and superoxide anion generation were measured to evaluate neutrophil activation. The potential involvement of intracellular signaling molecules in regulating neutrophil activation was analyzed by using Western blot.

RESULTS

LPS induced ALI in mice, as evidenced with leukocyte infiltration and protein leakage into the lungs. Luteolin attenuated LPS-induced leukocyte infiltration and protein extravasation. In cell studies, luteolin attenuated the fMLP-induced neutrophil chemotaxis and respiratory burst (IC(50) 0.2+/-0.1 micromol/L and 2.2+/-0.8 micromol/L, respectively), but had a negligible effect on superoxide anion generation during phorbol myristate acetate stimulation. Furthermore luteolin effectively blocked MAPK/ERK kinase 1/2 (MEK), extracellular signal-regulated kinase (ERK), and Akt phosphorylation in fMLP- and LPS-stimulated neutrophils.

CONCLUSION

These results indicate that luteolin has beneficial effects against LPS-induced ALI in mice, and the attenuation of neutrophil chemotaxis and respiratory burst by luteolin involves the blockade of MEK-, ERK-, and Akt-related signaling cascades.

Anti-inflammatory activities of extracts of Thai spices and herbs with lipopolysaccharide-activated RAW 264.7 murine macrophages

Nitric oxide (NO) and tumor necrosis factor-alpha (TNF-alpha) play important roles in inflammatory processes. This study examined whether 13 spices/herbs commonly used in Thai dishes modulate the production of NO and TNF-alpha by the RAW 264.7 mouse macrophage cell line pretreated with plant extracts (1-100 microg/mL) prior to activation by bacterial lipopolysaccharide (LPS). Tested plant tissues were extracted with ethanol with the exception of roselle, which was extracted with 70% acetone. Eight of the 13 plant extracts inhibited NO and TNF-alpha production in a dose-dependent manner without exerting cytotoxicity. Extract from Limnophila aromatica (Kyeng) was the most robust suppressor of NO production, followed by dill, kaffer lime, chili, Teaw, mint, sweet basil, and pea eggplant, respectively (range of 50% inhibitory concentration [IC(50)] = 11.4-74.6 microg/mL). Kyeng also exhibited the greatest inhibition of TNF-alpha production (IC(50) = 10.5 microg/mL). IC(50) values for NO and TNF-alpha production in LPS-activated RAW 264.7 cells for these extracts were highly correlated (r = 0.772, P = .025). These results suggest that extracts from some spices/herbs in the habitual Thai diet possess anti-inflammatory activity. Moreover, the results support the use of NO production in LPS-activated RAW 264.7 cells as a rapid and cost-effective tool for screening the anti-inflammatory activity of extracts of spices/herbs.

Olive oil phenols modulate the expression of metalloproteinase 9 in THP-1 cells by acting on nuclear factor-kappaB signaling

In vivo studies suggest that the phenolic component contributes to the anti-inflammatory and antiatherosclerotic actions of olive oil; however, the effects in circulating cells are not fully characterized. Monocytes play a key role in inflammation-based diseases by expressing several molecules, including metalloproteinases (MMPs). In the present study, we investigated the effects of olive oil phenolic extract and individual compounds on MMP-9 in THP-1 cells, a human monocyte-like cell line. Olive oil extract prevented the stimulation of MMP-9 expression and secretion in tumor necrosis factor alpha-treated THP-1 cells. Oleuropein aglycone, a typical olive oil phenol, was active at concentrations found in the extract, although other compounds probably contribute to the biological activity. We also found that the effect of the extract and individual compounds on MMP-9 is due to impaired nuclear factor-kappaB signaling. Our findings provide further evidence on the mechanisms by which olive oil reduces the inflammatory burden associated with disorders, such as atherosclerosis.

Evaluation of early macrophage activation and NF-kappaB activity in pulmonary injury caused by deep hypothermia circulatory arrest: an experimental study

This study aimed to analyze changes in nuclear factor-kappa B (NF-kappaB), inflammation factors, and macrophages in pulmonary tissue under deep hypothermia circulatory arrest (DHCA) at different time points, which can be used to infer the role of early macrophage activation and NF-kappaB activity in pulmonary injury. The possible pathogenic mechanisms of DHCA-induced pulmonary injury were investigated in this study to provide an experimental basis for clinical lung protective strategies. Piglets (n = 12) were randomly divided into 2 groups, with 6 piglets in each group. The control group had ambient temperature cardiopulmonary bypass (CPB), and the experimental group had DHCA. Both groups had conventional CPB with 30 min of parallel circulation. Changes in NF-kappaB and inflammatory factors were examined in each group at 6 different time points. At 0.5 h after ischemia-reperfusion, NF-kappaB expression in the nucleus of pulmonary tissue reached its peak, and brown-stained nuclei were mainly polymorphonuclear antibodies. At 1 h after ischemia-reperfusion, plasma tumor-necrosis factor (TNF)-alpha in the experimental group was significantly increased compared with that before reperfusion (P < 0.05). The plasma levels of interleukin (IL)-8 and IL-6 in the experimental group were significantly increased at 1.5 h after ischemia-reperfusion compared with the levels before reperfusion (P < 0.05). Early activation of NF-kappaB under DHCA might play an important role in DHCA-induced pulmonary injury.

Luteolin isolated from the flowers of Lonicera japonica suppresses inflammatory mediator release by blocking NF-kappaB and MAPKs activation pathways in HMC-1 cells

Luteolin (3′,4′,5,7-tetrahydroxylflavone) is a plant flavonoid and pharmacologically active agent that has been isolated from several plant species. In the present study, the effect of luteolin from the flowers of Lonicera japonica on phorbol 12-myristate 13-acetate (PMA) plus A23187-induced mast cell activation was examined. Luteolin significantly inhibited the induction of inflammatory cytokines such as tumor necrosis factor (TNF)-α, interleukin (IL)-8, IL-6 and granulocyte-macrophage colony-stimulating factor (GM-CSF) by PMA plus A23187. Moreover, luteolin attenuated cyclooxygenase (COX)-2 expression and intracellular Ca²⁺ levels. In activated HMC-1 cells, the phosphorylation of extra-signal response kinase (ERK 1/2) and c-jun N-terminal Kinase (JNK 1/2), but not p38 mitogen-activated protein kinase (p38 MAPK) were decreased by treatment of the cells with luteolin. Luteolin inhibited PMA plus A23187-induced nuclear factor (NF)-κB activation, IκB degradation, and luciferase activity. Furthermore, luteolin suppressed the expression of TNF-α, IL-8, IL-6, GM-CSF, and COX-2 through a decrease in the intracellular Ca²⁺ levels, and also showed a suppression of the ERK 1/2, JNK 1/2, and NF-κB activation. These results indicated that luteolin from the flowers of Lonicera japonica exerted a regulatory effect on mast cell-mediated inflammatory diseases, such as RA, allergy disease and IBD.

Luteolin triggers global changes in the microglial transcriptome leading to a unique anti-inflammatory and neuroprotective phenotype

Background

Luteolin, a plant derived flavonoid, exerts a variety of pharmacological activities and anti-oxidant properties associated with its capacity to scavenge oxygen and nitrogen species. Luteolin also shows potent anti-inflammatory activities by inhibiting nuclear factor kappa B (NFkB) signaling in immune cells. To better understand the immuno-modulatory effects of this important flavonoid, we performed a genome-wide expression analysis in pro-inflammatory challenged microglia treated with luteolin and conducted a phenotypic and functional characterization.

Methods

Resting and LPS-activated BV-2 microglia were treated with luteolin in various concentrations and mRNA levels of pro-inflammatory markers were determined. DNA microarray experiments and bioinformatic data mining were performed to capture global transcriptomic changes following luteolin stimulation of microglia. Extensive qRT-PCR analyses were carried out for an independent confirmation of newly identified luteolin-regulated transcripts. The activation state of luteolin-treated microglia was assessed by morphological characterization. Microglia-mediated neurotoxicity was assessed by quantifying secreted nitric oxide levels and apoptosis of 661W photoreceptors cultured in microglia-conditioned medium.

Results

Luteolin dose-dependently suppressed pro-inflammatory marker expression in LPS-activated microglia and triggered global changes in the microglial transcriptome with more than 50 differentially expressed transcripts. Pro-inflammatory and pro-apoptotic gene expression was effectively blocked by luteolin. In contrast, mRNA levels of genes related to anti-oxidant metabolism, phagocytic uptake, ramification, and chemotaxis were significantly induced. Luteolin treatment had a major effect on microglial morphology leading to ramification of formerly amoeboid cells associated with the formation of long filopodia. When co-incubated with luteolin, LPS-activated microglia showed strongly reduced NO secretion and significantly decreased neurotoxicity on 661W photoreceptor cultures.

Conclusions

Our findings confirm the inhibitory effects of luteolin on pro-inflammatory cytokine expression in microglia. Moreover, our transcriptomic data suggest that this flavonoid is a potent modulator of microglial activation and affects several signaling pathways leading to a unique phenotype with anti-inflammatory, anti-oxidative, and neuroprotective characteristics. With the identification of several novel luteolin-regulated genes, our findings provide a molecular basis to understand the versatile effects of luteolin on microglial homeostasis. The data also suggest that luteolin could be a promising candidate to develop immuno-modulatory and neuroprotective therapies for the treatment of neurodegenerative disorders.

Curcumin, resveratrol and flavonoids as anti-inflammatory, cyto- and DNA-protective dietary compounds

Numerous dietary compounds, ubiquitous in fruits, vegetables and spices have been isolated and evaluated during recent years for their therapeutic potential. These compounds include flavonoid and non-flavonoid polyphenols, which describe beneficial effects against a variety of ailments. The notion that these plant products have health promoting effects emerged because their intake was related to a reduced incidence of cancer, cardiovascular, neurological, respiratory, and age-related diseases. Exposure of the body to a stressful environment challenges cell survival and increases the risk of chronic disease developing. The polyphenols afford protection against various stress-induced toxicities through modulating intercellular cascades which inhibit inflammatory molecule synthesis, the formation of free radicals, nuclear damage and induce antioxidant enzyme expression. These responses have the potential to increase life expectancy. The present review article focuses on curcumin, resveratrol, and flavonoids and seeks to summarize their anti-inflammatory, cytoprotective and DNA-protective properties.

A Jurkat transcriptional reporter cell line for high-throughput analysis of the nuclear factor-kappaB signaling pathway

The transcription factor, Nuclear Factor-kappaB (NF-kappaB), regulates many genes involved in host immunity and cell survival. Unregulated NF-kappaB activity has been linked to many chronic inflammatory diseases and is an important target for the identification of inhibitors to better manage these disorders. We present a novel screening system to identify NF-kappaB inhibitors that combines sensitive fluorescence detection with medium- to high-throughput flow cytometry (HyperCyt). To validate this approach, we quantified the activation of NF-kappaB by standard flow cytometry and the HyperCyt platform. Results were comparable with regard to EC(50) values for TNFalpha-mediated activation; however, the HyperCyt platform provided more sensitive signal detection and a greater linear range for detection. To demonstrate the usefulness of this screening tool, we identified a novel inhibitor of NF-kappaB activation from a resveratrol-based chemical library. The inhibition of NF-kappaB activation by analog 6q (IC(50) = 19 microm) showed a 3.7-fold improvement over that of resveratrol (IC(50) approximately 70 microm).

Luteolin, a flavonoid with potential for cancer prevention and therapy

Luteolin, 3',4',5,7-tetrahydroxyflavone, is a common flavonoid that exists in many types of plants including fruits, vegetables, and medicinal herbs. Plants rich in luteolin have been used in Chinese traditional medicine for treating various diseases such as hypertension, inflammatory disorders, and cancer. Having multiple biological effects such as anti-inflammation, anti-allergy and anticancer, luteolin functions as either an antioxidant or a pro-oxidant biochemically. The biological effects of luteolin could be functionally related to each other. For instance, the anti-inflammatory activity may be linked to its anticancer property. Luteolin's anticancer property is associated with the induction of apoptosis, and inhibition of cell proliferation, metastasis and angiogenesis. Furthermore, luteolin sensitizes cancer cells to therapeutic-induced cytotoxicity through suppressing cell survival pathways such as phosphatidylinositol 3'-kinase (PI3K)/Akt, nuclear factor kappa B (NF-kappaB), and X-linked inhibitor of apoptosis protein (XIAP), and stimulating apoptosis pathways including those that induce the tumor suppressor p53. These observations suggest that luteolin could be an anticancer agent for various cancers. Furthermore, recent epidemiological studies have attributed a cancer prevention property to luteolin. In this review, we summarize the progress of recent research on luteolin, with a particular focus on its anticancer role and molecular mechanisms underlying this property of luteolin.

Flavonoids as anti-inflammatory agents: implications in cancer and cardiovascular disease

Chronic inflammation is being shown to be increasingly involved in the onset and development of several pathological disturbances such as arteriosclerosis, obesity, diabetes, neurodegenerative diseases and even cancer. Treatment for chronic inflammatory disorders has not been solved, and there is an urgent need to find new and safe anti-inflammatory compounds. Flavonoids belong to a group of natural substances occurring normally in the diet that exhibit a variety of beneficial effects on health. The anti-inflammatory properties of flavonoids have been studied recently, in order to establish and characterize their potential utility as therapeutic agents in the treatment of inflammatory diseases. Several mechanisms of action have been proposed to explain in vivo flavonoid anti-inflammatory actions, such as antioxidant activity, inhibition of eicosanoid generating enzymes or the modulation of the production of proinflammatory molecules. Recent studies have also shown that some flavonoids are modulators of proinflammatory gene expression, thus leading to the attenuation of the inflammatory response. However, much work remains to be done in order to achieve definitive conclusions about their potential usefulness. This review summarizes the known mechanisms involved in the anti-inflammatory activity of flavonoids and the implications of these effects on the protection against cancer and cardiovascular disease.

Terameprocol, a methylated derivative of nordihydroguaiaretic acid, inhibits production of prostaglandins and several key inflammatory cytokines and chemokines

BACKGROUND

Extracts of the creosote bush, Larrea tridentata, have been used for centuries by natives of western American and Mexican deserts to treat a variety of infectious diseases and inflammatory disorders. The beneficial activity of this plant has been linked to the compound nordihydroguaiaretic acid (NDGA) and its various substituted derivatives. Recently, tetra-O-methyl NDGA or terameprocol (TMP) has been shown to inhibit the growth of certain tumor-derived cell lines and is now in clinical trials for the treatment of human cancer. In this report, we ask whether TMP also displays anti-inflammatory activity. TMP was tested for its ability to inhibit the LPS-induced production of inflammatory lipids and cytokines in vitro. We also examined the effects of TMP on production of TNF-alpha in C57BL6/J mice following a sublethal challenge with LPS. Finally, we examined the molecular mechanisms underlying the effects we observed.

METHODS

RAW 264.7 cells and resident peritoneal macrophages from C57BL6/J mice, stimulated with 1 mug/ml LPS, were used in experiments designed to measure the effects of TMP on the production of prostaglandins, cytokines and chemokines. Prostaglandin production was determined by ELISA. Cytokine and chemokine production were determined by antibody array and ELISA.Western blots, q-RT-PCR, and enzyme assays were used to assess the effects of TMP on expression and activity of COX-2.q-RT-PCR was used to assess the effects of TMP on levels of cytokine and chemokine mRNA.C57BL6/J mice injected i.p. with LPS were used in experiments designed to measure the effects of TMP in vivo. Serum levels of TNF-alpha were determined by ELISA.

RESULTS

TMP strongly inhibited the production of prostaglandins from RAW 264.7 cells and normal peritoneal macrophages. This effect correlated with a TMP-dependent reduction in levels of COX-2 mRNA and protein, and inhibition of the enzymatic activity of COX-2.TMP inhibited, to varying degrees, the production of several cytokines, and chemokines from RAW 264.7 macrophages and normal peritoneal macrophages. Affected molecules included TNF-alpha and MCP-1. Levels of cytokine mRNA were affected similarly, suggesting that TMP is acting to prevent gene expression.TMP partially blocked the production of TNF-alpha and MCP-1 in vivo in the serum of C57BL6/J mice that were challenged i.p. with LPS.

CONCLUSION

TMP inhibited the LPS-induced production of lipid mediators and several key inflammatory cytokines and chemokines, both in vitro and in vivo, raising the possibility that TMP might be useful as a treatment for a variety of inflammatory disorders.

DNA adducts with antioxidant flavonoids: morin, apigenin, and naringin

Flavonoids have recently attracted a great interest as potential therapeutic drugs against a wide range of free-radical-mediated diseases. The anticancer and antiviral activities of these natural products are implicated in their mechanism of actions. While the antioxidant activity of these natural polyphenolic compounds is well known, their bindings to DNA are not fully investigated. This study was designed to examine the interactions of morin (Mor), naringin (Nar), and apigenin (Api) with calf thymus DNA in aqueous solution at physiological conditions, using constant DNA concentration (6.25 mM) and various drug/DNA(phosphate) ratios of 1/40 to 1. FTIR and UV-Vis spectroscopic methods were used to determine the ligand binding modes, the binding constant, and the stability of DNA in flavonoid-DNA complexes in aqueous solution. Spectroscopic evidence shows both intercalation and external binding of flavonoids to DNA duplex with overall binding constants of K(morin) = 5.99 x 10(3) M(-1), K(apigenin) = 7.10 x 10(4) M(-1), and K(naringin) = 3.10 x 10(3) M(-1). The affinity of ligand-DNA binding is in the order of apigenin > morin > naringin. DNA aggregation and a partial B- to A-DNA transition occurs upon morin, apigenin, and naringin complexation.

Simultaneous determination of nine major active compounds in Dracocephalum rupestre by HPLC

A new method was developed for the simultaneous determination of nine major constituents in Dracocephalum rupestre, including 5,7-dihydroxychromone (1), eriodictyol-7-O-beta-d-glucoside (2), luteolin-7-O-beta-d-glucoside (3), naringenin-7-O-beta-d-glucoside (4), apigenin-7-O-beta-d-glucoside (5), eriodictyol (6), luteolin (7), naringenin (8) and apigenin (9). The quantitative determination was conducted by reversed phase high-performance liquid chromatography with photodiode array detector (LC-PDA). Separation was performed on an Agilent Eclipse XDB-C(18) column (150 mm x 4.6 mm i.d., 5 microm) with gradient elution of acetonitrile and 0.5% aqueous acetic acid. The components were identified by retention time, ultraviolet (UV) spectra and quantified by LC-PDA at 260 nm. All calibration curves showed good linearity (r(2)>0.999) within test ranges. The reproducibility was evaluated by intra- and inter-day assays and R.S.D. values were less than 3.0%. The recoveries were between 95.15 and 104.45%. The limits of detection (LOD) ranged from 0.002 to 0.422 microg/ml and limits of quantification (LOQ) ranged from 0.005 to 1.208 microg/ml, respectively. The identity of the peaks was further confirmed by high-performance liquid chromatography with triple-quadrupole mass spectrometry system coupled with electrospray ionization (ESI) interface. The developed method was applied to the determination of nine constituents in 14 samples of D. rupestre collected at various harvesting times. Most compounds accumulated at much higher amounts in about June-July. The satisfactory results indicated that the developed method was readily utilized as a quality control method for D. rupestre.

RNA binding to antioxidant flavonoids

Flavonoids are an interesting group of natural polyphenolic compounds that exhibit extensive bioactivities such as scavenging free radical, antitumor and antiproliferative effects. The anticancer and antiviral effects of these natural products are attributed to their potential biomedical applications. While flavonoids complexation with DNA is known, their bindings to RNA are not fully investigated. This study was designed to examine the interactions of three flavonoids; morin (Mor), apigenin (Api) and naringin (Nar) with yeast RNA in aqueous solution at physiological conditions, using constant RNA concentration (6.25 mM) and various pigment/RNA (phosphate) ratios of 1/120 to 1/1. FTIR, UV-visible spectroscopic methods were used to determine the ligand binding modes, the binding constant and the stability of RNA in flavonoid-RNA complexes in aqueous solution. Spectroscopic evidence showed major binding of flavonoids to RNA with overall binding constants of K(morin) = 9.150 x 10(3) M(-1), K(apigenin)=4.967 x 10(4) M(-1), and K(naringin)=1.144 x 10(4) M(-1). The affinity of flavonoid-RNA binding is in the order of apigenin>naringin>morin. No biopolymer secondary structural changes were observed upon flavonoid interaction and RNA remains in the A-family structure in these pigment complexes.

Regioselective synthesis of plant (iso)flavone glycosides in Escherichia coli

The flavonoids genistein, biochanin A, luteolin, quercetin, and kaempferol are plant natural products with potentially useful pharmacological and nutraceutical activities. These natural products usually exist in plants as glycosides, and their glycosylation has a remarkable influence on their pharmacokinetic properties. The glycosyltransferases UGT71G1 and UGT73C8 from Medicago truncatula are excellent reagents for the regioselective glycosylation of (iso)flavonoids in Escherichia coli grown in Terrific broth. Ten to 20 mg/L of either genistein or biochanin A 7-O-glucoside was produced after feeding genistein or biochanin A to E. coli expressing UGT71G1, and similar levels of luteolin 4'-O- and 7-O-glucosides were produced after feeding luteolin to cultures expressing UGT73C8. For the production of kaempferol 3-O-glucoside or quercetin 3-O-glucoside, the Phe148Val or Tyr202Ala mutants of UGT71G1 were employed. Ten to 16 mg/L of either kaempferol 3-O- or quercetin 3-O-glucosides were produced on feeding kaempferol or quercetin to E. coli expressing these enzymes. More than 90% of the glucoside products were released to the medium, facilitating their isolation.