Flavonoids are considered as health-protecting food constituents. The testing of their biological effects is however hampered by their low oral absorption and complex metabolism. In order to investigate the direct effect(s) of unmetabolized flavonoid, a preparation in a biologically friendly solvent for intravenous administration is needed. Isorhamnetin, a natural flavonoid and a human metabolite of the most frequently tested flavonoid quercetin, has very low water solubility (<3.5 μg/mL). The aim of this study was to improve its solubility to enable intravenous administration and to test its pharmacokinetics in an animal model. By using polyvinylpyrrolidone (PVP10) and benzalkonium chloride, we were able to improve the solubility approximately 600 times to 2.1 mg/mL. This solution was then administered intravenously at a dose of 0.5 mg/kg of isorhamnetin to rats and its pharmacokinetics was analyzed. The pharmacokinetics of isorhamnetin corresponded to two compartmental model with a rapid initial distribution phase (t1/2α: 5.7 ± 4.3 min) and a slower elimination phase (t1/2β: 61 ± 47.5 min). Two sulfate metabolites were also identified. PVP10 and benzalkonium did not modify the properties of isorhamnetin (iron chelation and reduction, and cell penetration) substantially. In conclusion, the novel preparation reported in this study is suitable for future testing of isorhamnetin effects under in vivo conditions.

• Klíčová slova
• Flavonoid, Isorhamnetin, Pharmacokinetics, Quercetin, Solid dispersion, Solubility,
• MeSH
• benzalkoniové sloučeniny farmakokinetika   chemie   MeSH
• intravenózní podání * MeSH
• krysa rodu Rattus MeSH
• potkani Wistar MeSH
• povidon * chemie   MeSH
• quercetin * farmakokinetika   analogy a deriváty   aplikace a dávkování   chemie   MeSH
• rozpustnost * MeSH
• voda * chemie   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• 3-methylquercetin MeSH Prohlížeč
• benzalkoniové sloučeniny MeSH
• povidon * MeSH
• quercetin * MeSH
• voda * MeSH

The ultraviolet (UV) part of solar radiation can permanently affect skin tissue. UVA photons represent the most abundant UV component and stimulate the formation of intracellular reactive oxygen species (ROS), leading to oxidative damage to various biomolecules. Several plant-derived polyphenols are known as effective photoprotective agents. This study evaluated the potential of quercetin (QE) and its structurally related flavonoid taxifolin (TA) to reduce UVA-caused damage to human primary dermal fibroblasts (NHDF) and epidermal keratinocytes (NHEK) obtained from identical donors. Cells pre-treated with QE or TA (1 h) were then exposed to UVA light using a solar simulator. Both flavonoids effectively prevented oxidative damage, such as ROS generation, glutathione depletion, single-strand breaks formation and caspase-3 activation in NHDF. These protective effects were accompanied by stimulation of Nrf2 nuclear translocation, found in non-irradiated and irradiated NHDF and NHEK, and expression of antioxidant proteins, such as heme oxygenase-1, NAD(P)H:quinone oxidoreductase 1 and catalase. For most parameters, QE was more potent than TA. On the other hand, TA demonstrated protection within the whole concentration range, while QE lost its protective ability at the highest concentration tested (75 μM), suggesting its pro-oxidative potential. In summary, QE and TA demonstrated UVA-protective properties in NHEK and NHDF obtained from identical donors. However, due to the in vitro phototoxic potential of QE, published elsewhere and discussed herein, further studies are needed to evaluate QE safety in dermatological application for humans as well as to confirm our results on human skin ex vivo and in clinical trials.

• Klíčová slova
• Flavonoids, Human skin fibroblasts, Human skin keratinocytes, Nuclear factor Nrf2, Oxidative stress, UVA radiation,
• MeSH
• fibroblasty MeSH
• flavonoidy * metabolismus   MeSH
• keratinocyty MeSH
• kůže metabolismus   MeSH
• lidé MeSH
• oxidační stres MeSH
• quercetin * analogy a deriváty   farmakologie   MeSH
• ultrafialové záření MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• flavonoidy * MeSH
• quercetin * MeSH
• taxifolin MeSH Prohlížeč

This study aimed to examine the effect of dietary flavonoid isoquercitrin on ovarian granulosa cells using the immortalized human cell line HGL5. Cell viability, survival, apoptosis, release of steroid hormones 17beta-estradiol and progesterone, and human transforming growth factor-beta2 (TGF-beta2) and TGF-beta2 receptor as well as intracellular reactive oxygen species (ROS) generation were investigated after isoquercitrin treatment at the concentration range of 5-100 microg.ml-1. It did not cause any significant change (p>0.05) in cell viability as studied by AlamarBlue assay in comparison to control. No significant change was observed (p>0.05) in the proportion of live, dead and apoptotic cells as revealed by apoptotic assay using flow cytometry. Similarly, the release of 17beta-estradiol, progesterone, TGF-beta2 and its receptor were not affected significantly (p>0.05) by isoquercitrin as detected by ELISA, in comparison to control. Except for the highest concentration of 100 microg.ml-1, which led to oxidative stress, isoquercitrin exhibited antioxidative activity at lower concentration used in the study (5, 10, 25, and 50 microg.ml-1) by hampering the production of intracellular ROS, in comparison to control, as detected by chemiluminescence assay (p<0.05). Findings of the present study indicate an existence of the antioxidative pathway that involves inhibition of intracellular ROS generation by isoquercitrin in human ovarian granulosa cells.

• MeSH
• buněčné linie MeSH
• folikulární buňky účinky léků   metabolismus   MeSH
• lidé MeSH
• quercetin aplikace a dávkování   analogy a deriváty   MeSH
• reaktivní formy kyslíku metabolismus   MeSH
• Check Tag
• lidé MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• isoquercitrin MeSH Prohlížeč
• quercetin MeSH
• reaktivní formy kyslíku MeSH

Quercetin, a common flavonoid from human diet, is extensively metabolized. Its two metabolites with the preserved flavonoid core were tested in detail for their interactions with transition metals, iron and copper. Both compounds chelated both metals; however, there were some significant differences between them notwithstanding that the major chelation site (3-hydroxy-4-keto) was the same. The complex stoichiometries were also determined under different pH conditions and in both oxidation states. Mostly, complexes 2:1, flavonoid to metal, were observed. Both compounds reduced iron and copper in a bell-shaped manner with tamarixetin being less potent in general. Both metabolites potentiated the Fenton reaction triggered by iron, while they were able to decrease the copper-based Fenton reaction under acidic conditions. In cellular experiments, both metabolites attenuated the copper-triggered hemolysis with isorhamnetin being more potent. In conclusion, there are differences between methylated metabolites of quercetin in relation to their interactions with biologically relevant transition metals.

• Klíčová slova
• antioxidant, chelator, hemolysis, pro-oxidant, reduction, stoichiometry,
• MeSH
• disacharidy MeSH
• lidé MeSH
• měď * MeSH
• quercetin * analogy a deriváty   MeSH
• železo MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• 3-methylquercetin MeSH Prohlížeč
• disacharidy MeSH
• měď * MeSH
• quercetin * MeSH
• tamarixetin MeSH Prohlížeč
• železo MeSH

Polyphenols, secondary metabolites of plants, exhibit different anti-cancer and cytoprotective properties such as anti-radical, anti-angiogenic, anti-inflammation, or cardioprotective. Some of these activities could be linked to modulation of miRNAs expression. MiRNAs play an important role in posttranscriptional regulation of their target genes that could be important within cell signalling or preservation of cell homeostasis, e.g., cell survival/apoptosis. We evaluated the influence of a non-toxic concentration of taxifolin and quercetin on the expression of majority human miRNAs via Affymetrix GeneChip™ miRNA 3.0 Array. For the evaluation we used two cell models corresponding to liver tissue, Hep G2 and primary human hepatocytes. The array analysis identified four miRNAs, miR-153, miR-204, miR-211, and miR-377-3p, with reduced expression after taxifolin treatment. All of these miRNAs are linked to modulation of ZEB2 expression in various models. Indeed, ZEB2 protein displayed upregulation after taxifolin treatment in a dose dependent manner. However, the modulation did not lead to epithelial mesenchymal transition. Our data show that taxifolin inhibits Akt phosphorylation, thereby diminishing ZEB2 signalling that could trigger carcinogenesis. We conclude that biological activity of taxifolin may have ambiguous or even contradictory outcomes because of non-specific effect on the cell.

• Klíčová slova
• Affymetrix GeneChip™ miRNA 3.0 Array, Hep G2 cells, ZEB2, polyphenols, primary cultures of human hepatocytes,
• MeSH
• apoptóza účinky léků   MeSH
• buňky Hep G2 metabolismus   MeSH
• epitelo-mezenchymální tranzice genetika   MeSH
• exprese genu účinky léků   genetika   MeSH
• hepatocyty účinky léků   metabolismus   MeSH
• lidé MeSH
• mikro RNA účinky léků   genetika   MeSH
• pohyb buněk účinky léků   MeSH
• polyfenoly farmakologie   MeSH
• primární buněčná kultura MeSH
• proliferace buněk účinky léků   MeSH
• quercetin analogy a deriváty   metabolismus   farmakologie   MeSH
• regulace genové exprese u nádorů účinky léků   MeSH
• signální transdukce genetika   MeSH
• transkripční faktor Zeb2 účinky léků   metabolismus   MeSH
• transkriptom účinky léků   genetika   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• mikro RNA MeSH
• MIRN153 microRNA, human MeSH Prohlížeč
• MIRN204 microRNA, human MeSH Prohlížeč
• MIRN211 microRNA, human MeSH Prohlížeč
• MIRN377 microRNA, human MeSH Prohlížeč
• polyfenoly MeSH
• quercetin MeSH
• taxifolin MeSH Prohlížeč
• transkripční faktor Zeb2 MeSH
• ZEB2 protein, human MeSH Prohlížeč

Detailed analysis of phenolic composition and antioxidant and antimicrobial activities of Verbascum glabratum subsp. bosnense (K. Malý) Murb., an endemic species of southeastern Dinaric Alps was performed for the first time. The phenolic composition measured via UHPLC-MS/MS of four extract with different polarity suggested this plant species is very rich in both phenolic acids and flavonoids. Ethanol extract was chemically the most versatile containing 12 compounds with quercitrin and rosmarinic acid as the majors, while water extracts were rich in 4-hydroxybenzoic acid, salicylic acid, morin, and apigenin. All extracts showed high antioxidant potential measured spectrophotometrically with IC50 values ranging 0.139 - 0.021 mg/mL. Antimicrobial testing using agar diffusion test showed that ethanol extract was the most potent against all tested organisms. Also, these activities are correlated with the content of phenolic compounds, which suggest they are active ingredients of the extracts.

• Klíčová slova
• Verbascum glabratum subsp. bosnense (K. Malý) Murb., UHPLC-MS/MS, antimicrobial activity, antioxidant activity, phenolic compounds,
• MeSH
• antiinfekční látky chemie   izolace a purifikace   MeSH
• antioxidancia chemie   izolace a purifikace   MeSH
• apigenin analýza   MeSH
• fenoly chemie   MeSH
• flavonoidy analýza   MeSH
• quercetin analogy a deriváty   analýza   MeSH
• rostlinné extrakty chemie   MeSH
• tandemová hmotnostní spektrometrie MeSH
• Verbascum chemie   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• antiinfekční látky MeSH
• antioxidancia MeSH
• apigenin MeSH
• fenoly MeSH
• flavonoidy MeSH
• morin MeSH Prohlížeč
• quercetin MeSH
• quercitrin MeSH Prohlížeč
• rostlinné extrakty MeSH

Isoquercitrin is a dietary bioflavonoid used as a food supplement. We studied the mechanism underlying its effect in human ovarian cancer cells using OVCAR-3 cell line. Viability, survival, apoptosis, release of human transforming growth factor-β1 (TGF-β1) and TGF-β1 receptor, and intracellular reactive oxygen species (ROS) generation by OVCAR-3 cells were examined after isoquercitrin treatment at concentrations 5, 10, 25, 50, and 100 μg mL-1. AlamarBlue assay revealed that isoquercitrin did not cause any significant change (P > 0.05) in cell viability as compared to control. Apoptotic assay using flow cytometry did not find any significant change (P > 0.05) in the proportion of live, dead and apoptotic cells as compared to control. ELISA also showed that the release of human TGF-β1 and TGF-β1 receptor were not significantly (P > 0.05) affected by isoquercitrin as compared to control. Chemiluminescence assay demonstrated that lower concentrations (5, 10, and 25 μg mL-1) were able to exhibit beneficial effects by inhibiting the generation of intracellular ROS. In contrast, elevated concentrations of 50 and 100 μg mL-1 led to oxidative stress (P < 0.05). We concluded that the beneficial effect of isoquercitrin on ovarian cancer cells may be mediated by an antioxidative pathway that involves inhibition of intracellular ROS generation, thereby limiting oxidative stress.

• Klíčová slova
• Isoquercitrin, ROS, TGF-β1, apoptosis, cell viability, human, ovarian cancer,
• MeSH
• antioxidancia farmakologie   MeSH
• apoptóza účinky léků   MeSH
• lidé MeSH
• nádorové buněčné linie MeSH
• nádory vaječníků farmakoterapie   genetika   metabolismus   patofyziologie   MeSH
• oxidační stres účinky léků   MeSH
• quercetin analogy a deriváty   farmakologie   MeSH
• reaktivní formy kyslíku metabolismus   MeSH
• signální transdukce účinky léků   MeSH
• transformující růstový faktor beta1 genetika   metabolismus   MeSH
• viabilita buněk účinky léků   MeSH
• Check Tag
• lidé MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• antioxidancia MeSH
• isoquercitrin MeSH Prohlížeč
• quercetin MeSH
• reaktivní formy kyslíku MeSH
• TGFB1 protein, human MeSH Prohlížeč
• transformující růstový faktor beta1 MeSH

Quercetin is an abundant flavonoid in nature and is used in several dietary supplements. Although quercetin is extensively metabolized by human enzymes and the colonic microflora, we have only few data regarding the pharmacokinetic interactions of its metabolites. Therefore, we investigated the interaction of human and microbial metabolites of quercetin with the xanthine oxidase enzyme. Inhibitory effects of five conjugates and 23 microbial metabolites were examined with 6-mercaptopurine and xanthine substrates (both at 5 μM), employing allopurinol as a positive control. Quercetin-3'-sulfate, isorhamnetin, tamarixetin, and pyrogallol proved to be strong inhibitors of xanthine oxidase. Sulfate and methyl conjugates were similarly strong inhibitors of both 6-mercaptopurine and xanthine oxidations (IC50 = 0.2-0.7 μM); however, pyrogallol inhibited xanthine oxidation (IC50 = 1.8 μM) with higher potency vs. 6-MP oxidation (IC50 = 10.1 μM). Sulfate and methyl conjugates were approximately ten-fold stronger inhibitors (IC50 = 0.2-0.6 μM) of 6-mercaptopurine oxidation than allopurinol (IC50 = 7.0 μM), and induced more potent inhibition compared to quercetin (IC50 = 1.4 μM). These observations highlight that some quercetin metabolites can exert similar or even a stronger inhibitory effect on xanthine oxidase than the parent compound, which may lead to the development of quercetin-drug interactions (e.g., with 6-mercaptopurin or azathioprine).

• Klíčová slova
• 6-mercaptopurine, enzyme inhibition, pharmacokinetic interactions, quercetin metabolites, xanthine, xanthine oxidase,
• MeSH
• alopurinol chemie   farmakologie   MeSH
• inhibitory enzymů chemie   metabolismus   farmakologie   MeSH
• katalýza MeSH
• lidé MeSH
• molekulární konformace MeSH
• molekulární modely MeSH
• molekulární struktura MeSH
• oxidace-redukce MeSH
• quercetin analogy a deriváty   chemie   metabolismus   farmakologie   MeSH
• vazba proteinů MeSH
• vztah mezi dávkou a účinkem léčiva MeSH
• vztahy mezi strukturou a aktivitou MeSH
• xanthin chemie   farmakologie   MeSH
• xanthinoxidasa antagonisté a inhibitory   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• alopurinol MeSH
• inhibitory enzymů MeSH
• quercetin MeSH
• xanthin MeSH
• xanthinoxidasa MeSH

Interaction of flavonoids with transition metals can be partially responsible for their impact on humans. Stoichiometry of the iron/copper complex with a flavonoid glycoside isoquercitrin, a frequent component of food supplements, was assessed using competitive and non-competitive methods in four (patho)physiologically-relevant pH values (4.5. 5.5, 6.8, and 7.5). Isoquercitrin chelated all tested ions (Fe2+, Fe3+, Cu2+, and Cu⁺) but its affinity for Cu⁺ ions proved to be very low. In general, the chelation potency dropped with pH lowering. Metal complexes of 1:1 stoichiometry were mostly formed, however, they were not stable and the stoichiometry changed depending on conditions. Isoquercitrin was able to reduce both Cu2+ and Fe3+ ions at low ratios, but its reducing potential was diminished at higher ratios (isoquercitrin to metal) due to the metal chelation. In conclusion, this study emphasizes the need of using multiple different methods for the assessment of chelation potential in moderately-active metal chelators, like flavonoids.

• Klíčová slova
• Job’s method, chelator, copper, iron, quercetin-3-O-β-glucopyranoside, reduction, stoichiometry,
• MeSH
• chelátory chemie   MeSH
• flavonoidy chemie   MeSH
• koncentrace vodíkových iontů MeSH
• měď chemie   MeSH
• quercetin analogy a deriváty   chemie   MeSH
• železo chemie   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• chelátory MeSH
• flavonoidy MeSH
• isoquercitrin MeSH Prohlížeč
• měď MeSH
• quercetin MeSH
• železo MeSH

Sulfated quercetin derivatives are important authentic standards for metabolic studies. Quercetin-3'-O-sulfate, quercetin-4'-O-sulfate, and quercetin-3-O-sulfate as well as quercetin-di-O-sulfate mixture (quercetin-7,3'-di-O-sulfate, quercetin-7,4'-di-O-sulfate, and quercetin-3',4'-di-O-sulfate) were synthetized by arylsulfotransferase from Desulfitobacterium hafniense. Purified monosulfates and disulfates were fully characterized using MS and NMR and tested for their 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS⁺) and N,N-dimethyl-p-phenylenediamine (DMPD) radical scavenging, Folin-Ciocalteau reduction (FCR), ferric reducing antioxidant power (FRAP), and anti-lipoperoxidant activities in rat liver microsomes damaged by tert-butylhydroperoxide. Although, as expected, the sulfated metabolites were usually less active than quercetin, they remained still effective antiradical and reducing agents. Quercetin-3'-O-sulfate was more efficient than quercetin-4'-O-sulfate in DPPH and FCR assays. In contrast, quercetin-4'-O-sulfate was the best ferric reductant and lipoperoxidation inhibitor. The capacity to scavenge ABTS+• and DMPD was comparable for all substances, except for disulfates, which were the most efficient. Quantum calculations and molecular dynamics simulations on membrane models supported rationalization of free radical scavenging and lipid peroxidation inhibition. These results clearly showed that individual metabolites of food bioactives can markedly differ in their biological activity. Therefore, a systematic and thorough investigation of all bioavailable metabolites with respect to native compounds is needed when evaluating food health benefits.

• Klíčová slova
• antiradical activity, density functional theory, lipid peroxidation, metabolites, molecular dynamics, quercetin, sulfates, sulfotransferase,
• MeSH
• antioxidancia MeSH
• arylsulfotransferasa metabolismus   MeSH
• Desulfitobacterium enzymologie   MeSH
• quercetin analogy a deriváty   analýza   chemická syntéza   metabolismus   MeSH
• sírany analýza   chemická syntéza   metabolismus   MeSH
• vztahy mezi strukturou a aktivitou MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• antioxidancia MeSH
• arylsulfotransferasa MeSH
• quercetin 3'-sulfate MeSH Prohlížeč
• quercetin MeSH
• sírany MeSH