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Anti-oxidant effect of flavonoids on the susceptibility of LDL oxidation.

In vitro studies have demonstrated increased atherogenicity of oxidized low-density lipoprotein (ox-LDL) compared to native LDL. Oxidative modification of LDL alters its structure allowing LDL to be taken up by scavenger receptors on macrophage, endothelial, and smooth muscle cells, leading to the formation of lipid-laden foam cells, the hallmark of early atherosclerotic lesions. The susceptibility of LDL to in vitro oxidation was assessed essentially by the technique described by Esterbauer et al. LDL oxidation were monitored by change in 234-absorbance in the presence and absence of pure flavonoids. Morin, genistein, apigenin and biochanin A, naringin and quercetin were used at different concentration. These flavonoids significantly inhibit in vitro LDL oxidation, genistein, morin and naringin have stronger inhibitory activity against LDL oxidation than biochanin A or apigenin. This study show that flavonoids prevent in vitro LDL oxidation and probably would be important to prevent atherosclerosis.

Antioxidants↗

Position of STAT-1 alpha in cycloheximide-dependent apoptosis triggered by TNF-alpha in human colorectal COLO 205 cancer cell line; role of polyphenolic compounds.

"Immune escape" is a crucial instrument used by carcinoma cells to overcome numerous strategies of immune system to delete transformed cells. Cellular factors that make cancer cells immune to defence mechanisms are incompletely understood while some remain ambiguous. Up to date evidence points to some proteins and/or signaling molecules that might be a basis for unusual behavior of cancer cells. In particular STAT kinases are currently in the main focus of attention since they were both shown to accelerate and/or to inhibit apoptosis. In our studies we observed that human colorectal COLO 205 cancer cells were resistant to TNF-alpha- or cycloheximide-induced cytotoxicity. However, when TNF-alpha (10 ng/ml) has been given along with cycloheximide (5 micro g/ml, CHX) COLO 205 cells died extensively from apoptosis. Apparently, cycloheximide sensitized cells to TNF-alpha-induced programmed cell death. To investigate the role of STAT-1 alpha in CHX-mediated TNF-alpha-induced COLO 205 cell death certain polyphenolic compounds were studied if they modulate STAT-1 alpha phosphorylation status and STAT-1 alpha-protein interaction at the level of TNF-alpha signalosome in the 6(th), 12(th), and 24(th) hour of experiment. Neither of phenolic compound, namely PI-3K inhibitor (LY294002, 20 microM) nor MEK inhibitor (PD98059, 50 microM), nor flavonol quercetin or kaempferol (10, 100 microM) in contrast to apigenin (20 microM) influenced COLO 205 cell viability during individual or combined treatment with TNF-alpha and CHX. We conclude, that some antiapoptotic proteins were involved but not STAT-1 alpha kinase to resist TNF-alpha-dependent cell death promoting activity. Summing up, except apigenin, the above-mentioned polyphenolic compounds were unable to modulate survival signal in COLO 205 cells initially believed to be suppressed by STAT-1 alpha.

Apigenin↗

[Isolation and structure identification of chemical constituents from Patrinia villosa].

AIM: To study the chemical constituents of Patrinia villosa Juss. METHODS: Solvent extraction, silica gel column and preparative liquid chromatography were used to separate the chemical constituents, and the chemical structures were elucidated by physico-chemical properties and spectra data. RESULTS: Eight compounds were isolated and identified as bolusanthol B (1), (2S)-5, 7, 2', 6'-tetrahydroxy-6,8-di (gamma,gamma-dimethylallyl) flavanone (2), orotinin (3), (2S)-5, 7, 2', 6'-tetrahydroxy-6-lavandulylated flavanone (4), 3'-prenyl-apigenine (5), luteolin (6), quercetin (7) and apigenin (8). CONCLUSION: Compound 2 and 4 are new compounds, compounds 1, 3 and 5 were separated from Patrinia genius for the first time, compounds 6, 7 and 8 were isolated from Patrinia vollosa Juss for the first time.

Apigenin↗

In vivo skin penetration studies of camomile flavones.

In vivo skin penetration studies of the Camomile flavones apigenin, luteolin and apigenin 7-O-beta-glucoside were carried out with nine healthy, female volunteers. During seven hours the decline of flavonoid concentration in a saturated aqueous alcoholic solution filled in glass application chambers were repeatedly measured by spectrophotometry at fixed time periods. The maximal fluxes were calculated. From the graph of the maximal flux values as a function of time it was concluded, that the flavonoids are not only adsorbed at the skin surface, but penetrate into deeper skin layers. This is important for their topical use as antiphlogistic agents.

Administration, Topical↗

Identification of compounds in wine by HPLC-tandem mass spectrometry.

In this work several compounds were detected in wines by HPLC-tandem mass spectrometry. In particular cinnamic and benzoic acids, tyrosol, apigenin-7-glucoside and luteolin-7-glucoside were identified and quantified in Italian wines. Red wines show bigger amount of cinnamic and benzoic acids than white wines. tyrosol is in bigger amount with respect to two flavones: luteolin-7-glucoside and apigenin-7-glucoside. These last two flavones are only in some wine, but it can be important to detect the presence of different substances in small amount to be able to characterize a wine.

Chromatography, High Pressure Liquid↗

Correlation of in vitro chemopreventive efficacy data from the human epidermal cell assay with animal efficacy data and clinical trial plasma levels.

The human epidermal cell (HEC) assay, which uses carcinogen exposed normal skin keratinocytes to screen for cancer prevention efficacy, was used to screen possible preventive agents. The endpoints measured were inhibition of carcinogen-induced growth and induction of involucrin, an early marker of differentiation. Sixteen of twenty agents (apigenin, apomine, budesonide, N-(2-carboxyphenyl)retinamide, ellagic acid, ibuprofen, indomethacin, melatonin, (-)-2-oxo-4-thiazolidine carboxylic acid, polyphenon E, resveratrol, beta-sitosterol, sulfasalazine, vitamin E acetate, and zileuton) were positive in at least one of the two assay endpoints. Four agents (4-methoxyphenol, naringenin, palmitoylcarnitine chloride, and silymarin) were negative in the assay. Nine of the sixteen agents were positive for both endpoints. Agents that showed the greatest response included: ellagic acid > budesonide, ibuprofen > apigenin, and quinicrine dihydrochloride. Fifty-eight of sixty-five agents that have been evaluated in the HEC assay have also been evaluated in one or more rodent bioassays for cancer prevention and several are in clinical trials for cancer prevention. The assay has an overall predictive accuracy of approximately 91.4% for efficacy in rodent cancer prevention irrespective of the species used, the tissue model, or the carcinogen used. Comparison of the efficacious concentrations in vitro to plasma levels in clinical trials show that concentrations that produced efficacy in the HEC assay were achieved in clinical studies for 31 of 33 agents for which plasma levels and/or C(max) levels were available. For two agents, 9-cis-retinoic acid (RA) and dehydroepiandrosterone (DHEA), the plasma levels greatly exceeded the highest concentration (HC) found to have efficacy in vitro. Thus, the HEC assay has an excellent predictive potential for animal efficacy and is responsive at clinically achievable concentrations.

Animals↗

Ochnaflavone inhibits TNF-alpha-induced human VSMC proliferation via regulation of cell cycle, ERK1/2, and MMP-9.

Ochnaflavone (c-3 of apigenin-0-c-4 of apigenin; OC), a biflavonoid present in the human diet, is known to inhibit angiotensin II-induced hypertrophy and serum-induced smooth muscle cell proliferation. OC is known to have anti-fungal and anti-inflammatory activities. However, it is not known whether OC exerts similar cardioprotective effects in cells treated with tumor necrosis factor (TNF)-alpha. In this study, we isolated OC from Lonicera japonica and studied its effect on matrix metalloproteinase-9 (MMP-9) gene expression in human aortic smooth muscle cells (HASMC). Furthermore, we investigated whether OC exerts the multiple suppressive effects on cytokine TNF-alpha-induced HASMC. Treatment of OC showed its potent inhibitory effects on DNA synthesis of cultured HASMC in the presence of TNF-alpha. These inhibitory effects were associated with reduced extracellular signal-regulated kinase 1/2 (ERK1/2) activity and G1 cell cycle arrest. Treatment of OC, which induced a cell cycle block in G1-phase, induced downregulation of cyclins and CDKs and upregulation of the CDK inhibitor p21(waf1) expression, whereas upregulation of p27 or p53 by OC was not observed. Because anti-atherogenic effects need not be limited to anti-proliferation, we decided to examine whether OC exerts inhibitory effects on MMP-9 activity in TNF-alpha-induced HASMC. OC inhibited TNF-alpha-induced MMP-9 secretion on HASMC in a dose-dependent manner. This inhibition was characterized by downregulation of MMP-9, which was transcriptionally regulated at nuclear factor (NF)-kappaB site and activation protein (AP)-1 site in the MMP-9 promoter. These findings indicate the efficacy of OC in inhibiting cell proliferation, G1 to S-phase cell cycle progress, and MMP-9 expression through the transcription factors NF-kappaB and AP-1 on TNF-alpha-induced HASMC. The findings of the present study may provide a potential mechanism that explains the anti-atherogenic activity of OC.

Cell Cycle↗

Structural elucidation of natural 2-hydroxy di- and tricarboxylic acids and esters, phenylpropanoid esters and a flavonoid from Autonoë madeirensis using gas chromatographic/electron ionization, electrospray ionization and tandem mass spectrometric techniques.

The chemical composition of Autonoë madeirensis bulbs was characterized as part of a systematic phytochemical study of this species. The compounds reported were mainly identified on the basis of gas chromatography/electron ionization, electrospray ionization and tandem mass spectrometry. The structures of the pure compounds were also characterized by means of other physical and spectroscopic data (m.p., IR, UV, NMR). The compounds identified were 2-hydroxy di- and tricarboxylic acids and esters (malic acid, citric acid and their methyl and ethyl esters), cis- and trans-hydroxycinnamic esters (methyl and ethyl p-coumarate and methyl ferulate) and a new flavone diglucoside, 7-O-[beta-glucosyl-(1-->2)-O-beta-glucosyl]apigenin, the interglucosidic linkage (1-->2) of which is, to the best of our knowledge, reported for the first time in a diglucoside of apigenin. The results may contribute to the chemotaxonomy of the Autonoë genus and lead to a rapid tool for the systematic characterization of these compounds in plant extracts.

Chromatography, Gas↗

Development of an HPLC-PAD-MS assay for the identification and quantification of major phenolic edelweiss (Leontopodium alpium Cass.) constituents.

The analytical assessment of edelweiss (Leontopodium alpinum) herb extracts, used in traditional alpine medicine, has resulted in the development of a HPLC-PAD-MS method that allows baseline separation of almost all constituents. Peak assignment of 14 analytes was achieved by comparison of retention times, UV and mass spectra with those of reference compounds either commercially available (luteolin, apigenin and chlorogenic acid) or isolated from edelweiss plants by column chromatography. Ten of the isolated analytes were identified as the known natural products: quercetin-3-O-beta-D-glucoside, luteolin-7-O-beta-D-glucoside, luteolin-3'-O-beta-D-glucoside, luteolin-4'-O-beta-D-glucoside, apigenin-7-O-beta-D-glucoside, 6-hydroxy-luteolin-7-O-beta-D-glucoside, luteolin-7,4'-di-O-beta-D-glucoside, chrysoeriol-7-O-beta-D-glucoside, leontopodic acid and 3,5-dicaffeolyquinic acid. One analyte, 3,4,5-tri-(E)-caffeoly-D-glucaric acid proved to be a new natural product and was named leontopodic acid B. Structure elucidation was carried out by means of MS and NMR spectroscopy in all cases. The aerial plant parts of L. alpinum (capitula, inflorescence leaves, stems, stem leaves and leaves of the basal rosette) showed variable amounts of the above-mentioned constituents, although qualitative differences were not observable.

Asteraceae↗

Active components from Artemisia iwayomogi displaying ONOO(-) scavenging activity.

Peroxynitrite (ONOO(-)) is one of cytotoxic species produced by the reaction between superoxide (*O(2) (-)) and nitric oxide (NO). The main aim of this study was to identify ONOO(-) scavenging constituents from herbs. Methanolic extracts derived from one hundred thirty eight herbs were screened out for their ONOO(-) scavenging activities. Twenty herbs showed excellent ONOO(-) scavenging activity in a dose dependent manner. Of them, Artemisia iwayomogi, which showed the highest activity, was fractioned with several solvents. The ONOO(-) scavenging activity of fractions was in order of ethyl acetate (EtOAc) > n-butanol (BuOH) > dichloromethane (CH(2)Cl(2)) > water (H(2)O) fraction. The EtOAc and the n-BuOH fractions were further purified to isolate active principles by column chromatography. Apigenin 7-methylether (genkwanin), apigenin 7,4'-di-O methylether, jaceosidin, and scopoletin from the EtOAc fraction and chlorogenic acid, 2,4-dihydroxy 6-methoxy acetophenone 4-O-beta-D-glucoside, quebrachitol, and scopolin from the n-BuOH fraction were identified. The scavenging activities of chlorogenic acid (IC(50) = 0.52 +/- 0.04 microM), genkwanin (IC(50) = 1.01 +/- 0.10 microM), and scopoletin (IC(50) = 1.03 +/- 0.15 micro M) were higher than or comparable to a well-known ONOO(-) scavenger, penicillamine (IC(50) = 1.76 +/- 0.18 microM), suggesting that those compounds might be developed as effective ONOO(-) scavengers for, prevention of the ONOO(-)-involved diseases.

Artemisia↗

Anti-obesity action of Salix matsudana leaves (Part 2). Isolation of anti-obesity effectors from polyphenol fractions of Salix matsudana.

Previously, it was reported that polyphenol fractions prepared from the leaves of Salix matsudana reduced the elevation of the rat plasma triacylglycerol level at 3 and 4 h after oral administration of a lipid emulsion containing corn oil, at a dose of 570 mg/kg. Moreover, body weights at 2-9 weeks and the fi nal parametrial adipose tissue weights were significantly lower in mice fed the high-fat diet with 5% polyphenol fractions of S. matsudana leaves than in those fed the high-fat diet alone. The polyphenol fractions of S. matsudana leaves also significantly reduced the hepatic total cholesterol content, which was elevated in mice fed the high-fat diet alone. In addition, the polyphenol fractions of S. matsudana leaves inhibited palmitic acid uptake into brush border membrane vesicles prepared from rat jejunum and alpha-amylase activity, and their fractions enhanced norepinephrine-induced lipolysis in fat cells. To clarify the active substances inhibiting the palmitic acid uptake into small intestinal brush border membrane, the alpha-amylase activity or enhancing the norepinephrine-induced lipolyis in fat cells, the isolation of the active substances from polyphenol fraction was attempted using the above three assay systems. Compounds 1, 2 and 3 were isolated from the polyphenol fractions and identified as apigenin-7-O-d-glucoside, luteolin-7-O-d-glucoside and chrysoeriol-7-O-d-glucoside, respectively. Among three flavonoids, apigenin-7-O-d-glucoside inhibited alpha-amylase activity, and luteolin-7-O-d-glucoside and chrysoeriol-7-O-d-glucoside inhibited palmitic acid uptake into small intestinal brush border membrane. Furthermore, three flavonoid glucosides enhanced norepinephrine-induced lipolysis in fat cells.

Adipocytes↗

Additional antiprotozoal constituents from Cuphea pinetorum, a plant used in Mayan traditional medicine to treat diarrhoea.

In addition to kaempferol and quercetin already found in the roots from Cuphea pinetorum, bioassay-guided fractionation of the crude extract of the aerial part of this species gave four flavonoid glycosides, quercetin-3-O-alpha-rhamnopyranoside, luteolin-7-O-beta-D-glucopyranoside, apigenin-7-O-alpha-L-rhamnopyranoside and apigenin-7-O-beta-D-glucopyranoside, as well as squalen and beta-sitosterol. In vitro antiamoebic and antigiardial activities of isolated compounds indicated that kaempferol is the principal antiprotozoal agent in C. pinetorum. Based on finding this antiprotozoal inhibitor, flavonoids were studied in order to elucidate structure-activity relationships. These data suggest that kaempferol may play an important role in antidiarrhoeal activity of C. pinetorum.

Animals↗

Antibacterial activity of flavonoids and phenylpropanoids from Marrubium globosum ssp. libanoticum.

Marrubium globosum Montbr. et Auch. ex Benth. ssp. libanoticum Boiss. (Lamiaceae) is a medicinal plant used for the treatment of inflammatory diseases, asthma, coughs and other pulmonary and urinary problems. The goal of our study was to assess the biological activity of M. globosum testing the methanol extract of aerial parts for its antibacterial activity against bacteria known to cause respiratory, gastrointestinal, skin and urinary disorders; the extract showed antibacterial effects against all the strains of bacteria used. A purification of this active extract showed the presence, as main constituents, of verbascoside, isorhamnetin 3-O-beta-D-rutinoside, quercetin 3-O-beta-D-rutinoside, naringenin 7-O-beta-D-glucoside, kaempferol 3-O-beta-D-rutinoside, isorhamnetin 3-O-beta-D-glucoside, quercetin 3-O-beta-D-glucoside, apigenin 7-O-(3''-p-coumaryl)-glucoside, p-methoxy-cinnamic acid, kaempferol 3-O-beta-D-glucoside and apigenin 7-O-beta-D-glucoside. The pure compounds were tested for their antibacterial activity; quercetin 3-O-beta-D-rutinoside, verbascoside and naringenin 7-O-beta-D-glucoside showed the greatest activity.

Anti-Infective Agents↗

[Flavonols and flavones of vegetables. VIII. Flavones of carrot leaves (author's transl)].

The flavonoid constituents of carrot leaves (Daucus carota L. ssp. sativa) were separated by means of cellulose column chromatography, and the following compounds were obtained crystalline and identified by usual procedures: luteolin 7-beta-D-glucoside as the main flavon, luteolin 4'-beta-D-glucoside, luteolin 7-beta-D-glucuronide, apigenin 7-beta-D-glucoside, apigenin 7-rutinoside, chrysoeriol 7-beta-D-glucoside. Luteolin 7-rutinoside also was identified, but could not be obtained crystalline.

Chromatography↗

Modulation of activator protein-1 (AP-1) and MAPK pathway by flavonoids in human prostate cancer PC3 cells.

In last couple of decades the use of natural compounds like flavonoids as chemopreventive agents has gained much attention. Our current study focuses on identifying chemopreventive flavonoids and their mechanism of action on human prostate cancer cells. Human prostate cancer cells (PC3), stably transfected with activator protein 1 (AP-1) luciferase reporter gene were treated with four main classes of flavonoids namely flavonols, flavones, flavonones, and isoflavones. The maximum AP-1 luciferase induction of about 3 fold over control was observed with 20 microM concentrations of quercetin, chrysin and genistein and 50 microM concentration of kaempferol. At higher concentrations, most of the flavonoids demonstrated inhibition of AP-1 activity. The MTS assay for cell viability at 24 h showed that even at a very high concentration (500 microM), cell death was minimal for most of the flavonoids. To determine the role of MAPK pathway in the induction of AP-1 by flavonoids, Western blot of phospho MAPK proteins was performed. Four out of the eight flavonoids namely kaempferol, apigenin, genistein and naringenin were used for the Western Blot analysis. Induction of phospho-JNK and phospho-ERK activity was observed after two hour incubation of PC3-AP1 cells with flavonoids. However no induction of phospho-p38 activity was observed. Furthermore, pretreating the cells with specific inhibitors of JNK reduced the AP-1 luciferase activity that was induced by genistein while pretreatment with MEK inhibitor reduced the AP-1 luciferase activity induced by kaempferol. The pharmacological inhibitors did not affect the AP-1 luciferase activity induced by apigenin and naringenin. These results suggest the possible involvement of JNK pathway in genistein induced AP-1 activity while the ERK pathway seems to play an important role in kaempferol induced AP-1 activity.

Anticarcinogenic Agents↗

Antioxidative flavonoids from leaves of Carthamus tinctorius.

A total of eight flavonoids (1-8), including a novel quercetin-7-O-(6''-O-acetyl)-beta-D-glucopyranoside (6) and seven known flavonoids, luteolin (1), quercetin (2), luteolin 7-O-beta-D-glucopyranoside (3), luteolin-7-O-(6''-O-acetyl)-beta-D-glucopyranoside (4) quercetin 7-O-beta-D-glucopyranoside (5), acacetin 7-O-beta-D-glucuronide (7) and apigenin-6-C-beta-D-glucopyrano syl-8-C-beta-D-glucopyranoside (8), have been isolated from the leaves of the safflower (Carthamus tinctorius L.) and identified on the basis of spectroscopic and chemical studies. The antioxidative activity of these flavonoids was evaluated against 2-deoxyribose degradation and rat liver microsomal lipid peroxidation induced by hydroxyl radicals generated via a Fenton-type reaction. Among these flavonoids, luteolin-acetyl-glucoside (4) and quercetin-acetyl-glucoside (6) showed potent antioxidative activities against 2-deoxyribose degradation and lipid peroxidation in rat liver microsomes. Luteolin (1), quercetin (2), and their corresponding glycosides (3 & 5) also exhibited strong antioxidative activity, while acacetin glucuronide (7) and apigenin-6,8-di-C-glucoside (8) were relatively less active.

Animals↗

Vasorelaxing effects of flavonoids: investigation on the possible involvement of potassium channels.

A flavonoid-rich diet has been associated with a lower incidence of cardiovascular diseases, probably because of the antioxidant and vasoactive properties of flavonoids. Indeed, many flavonoids show vasorelaxing properties, due to different and often not yet completely clarified mechanisms of action. Among them, the activation of vascular potassium channels has been indicated as a possible pathway, accounting, at least in part, for the vasodilatory action of some flavonoid derivatives, such as apigenin and dioclein. Therefore, this work aims at evaluating, on in vitro isolated rat aortic rings, the endothelium-independent vasorelaxing effects of a number of flavonoid derivatives, to identify a possible activation of calcium-activated and/or ATP-sensitive potassium channels and to indicate some possible structure-activity relationships. Among the several flavonoids submitted to the pharmacological assay, only baicalein and quercetagetin were almost completely ineffective, while quercetin, hesperidin, quercitrin and rhoifolin exhibited only a partial vasorelaxing effect. On the contrary, acacetin, apigenin, chrysin, hesperetin, luteolin, pinocembrin, 4'-hydroxyflavanone, 5-hydroxyflavone, 5-methoxyflavone, 6-hydroxyflavanone and 7-hydroxyflavone, belonging to the chemical classes of flavones and flavanones, showed full vasorelaxing effects. The vasodilatory activity of hesperetin, luteolin, 5-hydroxyflavone and 7-hydroxyflavone were antagonised by tetraethylammonium chloride, indicating the possible involvement of calcium-activated potassium channels. Moreover, iberiotoxin clearly antagonised the effects of 5-hydroxyflavone, indicating the probable importance of a structural requirement (the hydroxy group in position 5) for a possible interaction with large-conductance, calcium-activated potassium channels. Finally, glibenclamide inhibited the vasorelaxing action of luteolin and 5-hydroxyflavone, suggesting that ATP-sensitive potassium channels may also be involved in their mechanism of action.

Animals↗

Molecular cloning, expression and characterization of a glycosyltransferase from rice.

Secondary plant metabolites undergo several modification reactions, including glycosylation. Glycosylation, which is mediated by UDP-glycosyltransferase (UGT), plays a role in the storage of secondary metabolites and in defending plants against stress. In this study, we cloned one of the glycosyltransferases from rice, RUGT-5 resulting in 40-42% sequence homology with UGTs from other plants. RUGT-5 was functionally expressed as a glutathione S-transferase fusion protein in Escherichia coli and was then purified. Eight different flavonoids were used as tentative substrates. HPLC profiling of reaction products displayed at least two peaks. Glycosylation positions were located at the hydroxyl groups at C-3, C-7 or C-4' flavonoid positions. The most efficient substrate was kaempferol, followed by apigenin, genistein and luteolin, in that order. According to in vitro results and the composition of rice flavonoids the in vivo substrate of RUGT-5 was predicted to be kaempferol or apigenin. To our knowledge, this is the first time that the function of a rice UGT has been characterized.

Cloning, Molecular↗