Selective inhibition of methoxyflavonoids on human CYP1B1 activity
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Flavones
Isorhamnetin
Flavonols
CYP1B1
Flavanone
Flavonol levels in the edible portions of Allium vegetables (leeks, shallots, green onions, garlic and onions) range from <0.03 to > 1 g/kg of vegetable. Shallots contained uniformly high concentration of total flavonols, >800 mg/kg in each of five independent samples. However, onions varied widely in the amounts of flavonoids they contained. White onions contained no detectable flavonols, but 20 cultivars of yellow and red onions contained between 60 mg/kg and >1000 mg/kg. Individual samples of leeks, garlic, and scallions contained undetectable levels of flavonols. The primary flavonols present in shallots were quercetin 4-glucoside and quercetin aglycone; flavonols identified in onions were three quercetin diglucosides, quercetin 4'-glucoside, quercetin aglycone, and, in some cases, isorhamnetin monoglycoside or kaempferol monoglycoside. The relative concentrations of the various onion flavonols varied significantly in different onion cultivars. Treatment of vegetable flavonol extracts with human gut bacterial glucosidases (fecalase) efficiently deglycosylated the quercetin glucosides with concomitant release of free quercetin. Quercetin selectively inhibits the growth of transformedtumorigenic cells (ras/3T3 and H35) and prevents the neoplastic transformation of NIH/3T3 cells with the oncogene H-ras.
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The role of antioxidative agents in coronary artery disease (CAD) has been investigated, but the analysis of specific flavonols intake in Polish adults requires validated tools. The aim of this study was to estimate the dietary intake of flavonols in CAD patients by creating a food frequency questionnaire (FFQ) dedicated for this purpose in Polish adults. The FFQ included 140 products from 12 food groups. The study involved 103 adult respondents (43 CAD patients and 60 healthy controls). Mean daily intakes of total flavonols, quercetin, kaempferol, myricetin and isorhamnetin were calculated as absolute values and quartiles. Mean daily intakes of 12 main food categories and 27 subcategories were calculated as portions and quartiles. The validity test revealed high correlation for total flavonols, kaempferol, myricetin and isorhamnetin and moderate for quercetin. In the reproducibility analysis, the correlation was high for total flavonols, quercetin, kaempferol and myricetin, moderate for isorhamnetin and high for all 12 categories and 25 out of 27 subcategories of the tested food groups. The application of the FFQ in healthy adults and CAD patients revealed that dietary intakes of total flavonols and proportional intakes of kaempferol and isorhamnetin in Polish adults and CAD patients are higher than in most other European countries, while the proportional intakes of quercetin and myricetin are lower than in most European countries. The comparison between CAD patients and the healthy controls revealed significant differences in dietary isorhamnetin intake (
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Flavonols
Isorhamnetin
Veraison
Galangin
Myricetin
Aglycone
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Flavonols
Isorhamnetin
Veraison
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Metabolic syndrome (MetS) is a cluster of metabolic disorders primarily caused by central obesity, which results in chronic inflammation leading to hypertension, diabetes and atherogenic dyslipidemia. Inflammation underlying MetS could be the target for dietary flavonols as they present antioxidative properties. The aim of this paper was to analyze the differences in habitual intake of selected flavonols (quercetin, kaempferol, isorhamnetin and myricetin) between MetS patients and healthy participants, and its relationship with MetS advancement. Ninety participants were enrolled in this study. The one-year flavonol intake was assessed with a dedicated food frequency questionnaire. The patients with MetS consumed significantly less quercetin (p = 0.01), kaempferol (p = 0.04), isorhamnetin (p < 0.001), total flavonols (p = 0.01), tomatoes (p = 0.001) and wine (p = 0.01) daily. Further analysis revealed a moderate inverse correlation between quercetin (p = 0.001), kaempferol (p = 0.01), isorhamnetin (p < 0.001), total flavonols (p = 0.001) and tomato consumption (p = 0.004) and MetS stage. The analysis of laboratory parameters showed that dietary intake of flavonols was not correlated with lipid profile, glucose level or renal function. On the basis of this observation, a potential protective effect of dietary flavonols, mainly from tomatoes, against MetS could be suggested. However, when referring to MetS components, flavonols probably mainly impact central obesity and blood pressure, without a significant impact on conventional lipid-profile parameters and glucose level.
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Flavonols are a major subclass of flavonoids with a variety of biological and pharmacological activities. Here, we provide a method for the in vitro enzymatic synthesis of a flavonol. In this method, Atf3h and Atfls1, two key genes in the biosynthetic pathway of the flavonols, are cloned and overexpressed in Escherichia coli. The recombinant enzymes are purified via an affinity column and then a bienzymatic cascade is established in a specific synthetic buffer. Two flavonols are synthesized in this system as examples and determined by TLC and HPLC/LC/MS analyses. The method displays obvious advantages in the derivation of flavonols over other approaches. It is time- and labor-saving and highly cost-effective. The reaction is easy to be accurately controlled and thus scaled up for mass production. The target product can be purified easily due to the simple components in the system. However, this system is usually restricted to the production of a flavonol from a flavanone.
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Five types of flavonol were isolated from seabuckthorn (Hippophae rhamnoides) and identified by mass, 1H- and 13C-NMR. The proliferations of human promyelotic leukemia HL-60 cells were inhibited as the concentrations of these flavonols were increased. The order of the extent of growth inhibition by the flavonols at a concentration of 20 microM is as follows: pentamethylquercetin > syringetin > isorhamnetin > quercetin > kaempherol > myricetin. Apoptotic morphological changes of the nucleus, including chromatin condensation were induced in the HL-60 cells treated with quercetin, kaempherol and myricetin, respectively, but not in the cells treated with the other flavonols. The fragmentations of DNA by quercetin, kaempherol and myricetin, respectively, to oligonucleosomal-sized fragments, a characteristic of apoptosis, were observed to be dose-dependent in the HL-60 cells. These findings suggest that growth inhibition by quercetin, kaempherol and myricetin, respectively, results from the induction of apoptosis by these flavonols. The other flavonols (pentamethylquercetin, syringetin and isorhamnetin) having methoxy (-OCH3) group inhibited more strongly than the above 3 flavonols without induction of apoptosis in the HL-60 cells. These findings suggest that mechanisms of growth inhibition by pentamethylquercetin, syringetin and isorhamnetin are different from the apoptosis caused by quercetin, kaempherol and myricetin.
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Myricetin
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Hippophae rhamnoides
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High-performance liquid chromatography−diode array detector (HPLC−DAD) coupled with electron spray mass spectrometry (ESI−MS−MS) was used to determine the flavonol profile in southern Italian red onions (Allium cepa L.). This on-line technique allowed the identification of seven flavonols in southern Italian red onion, quercetin 4‘-glucoside and quercetin 3,4‘-diglucoside being the most abundant components. Five minor flavonols have been recognized, offering a characteristic profile of such compounds in red onions under study. Quercetin 3-glucoside, quercetin 7,4‘-diglucoside, quercetin 3,7,4‘-triglucoside, and isorhamnetin 4‘-glucoside have been previously reported as minor flavonoid components in Allium cepa, while isorhamnetin 3,4‘-diglucoside was previously found in Allium ascalonicum. Traces of isorhamnetin 3-glucoside and free quercetin were also detected. Keywords: Allium cepa; flavonols; quercetin; isorhamnetin; HPLC−DAD; ESI−MS−MS
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