Antioxidant properties of flavonoid metal complexes and their potential inclusion in the development of novel strategies for the treatment against neurodegenerative diseases.

The increased oxidative stress in the acceleration of the aging process and development of the neuronal disorder are the common feature detected in neurodegenerative illness, such as Alzheimer's disease, Parkinson's disease, and Amyotrophic lateral sclerosis. Searching for new treatment against these diseases, the inclusion of exogenous antioxidant agents has shown good results. Flavonoids are polyphenols compounds present in plants, fruits and vegetables that exhibit potent antioxidant and biological properties, which are related to their chemical structure that to confer an excellent radical scavenging ability. The design of metal-flavonoid complexes allows to obtain compounds with improved biological and physicochemical properties, generating important increase of the flavonoid antioxidant properties. This evidence we motive to propose that antioxidant properties of the metal flavonoids compounds can play an important role in the design of potential novel therapeutic strategies. This review presents the structure-activity relationship on the antioxidant properties of three series of metal-flavonoid complexes: M-(quercetin), M-(morin), and M-(rutin). In general, we observed that the coordination sites, the metal ion type used, and the molar ratio metal:flavonoid present in the complexes, are important factors for to increase the antioxidant activity. On these evidences we motive to propose that the development of metal-flavonoid compounds is a potentially viable approach for combating neurodegenerative diseases.

The reduction impact of monoglucosyl rutin on abdominal visceral fat: A randomized, placebo-controlled, double-blind, parallel-group.

Water soluble α-glycosylated rutin (4G-α-D-glucopyranosyl rutin, monoglucosyl rutin, MR) was used in this study to evaluate its ability to reduce abdominal visceral fat (AVF). We conducted a study examining 66 healthy Japanese men and women with a body mass index of ≥23 and <30 kg/m2  for 8 weeks. The subjects were randomly assigned to groups via computer random numbers as follows: MR200 group (MR 200 mg/day), MR400 group (MR 400mg/day), or placebo group. The primary outcome was change in the AVF area after 8 weeks of intervention. The secondary outcomes were effects of MR on total fat and subcutaneous fat of umbilical area, lipid-related markers, and subjective symptoms. The per-protocol set analysis involved 18 subjects in the placebo group (7 males and 11 females), 20 subjects in the MR200 group (8 males and 12 females), and 20 subjects in the MR400 group (8 males and 12 females). AVF area in both the MR200 and MR400 groups was reduced at week 8, with changes from the baseline (week 0) significantly higher than the placebo group. Additionally, the MR400 group reported improved subjective symptoms concerning being "worried about abdominal fat" at week 4 compared with the placebo group. These results indicate that the consumption of MR (200 and 400 mg/day) for 8 weeks reduced AVF. PRACTICAL APPLICATION: Monoglucosyl rutin, an enzymatically modified form of rutin, is a highly stable and water-soluble flavonoid widely used in food and beverages to prevent oxidation. The present clinical study demonstrated that it may improve overall health by reducing abdominal visceral fat.

Formation of glyco-functionalized interfaces for protein binding using polyphenolic glycoside.

In this study, a polyphenolic glycoside (α-glucosyl rutin) was used to form glyco-functionalized interfaces for protein binding. α-Glucosyl rutin was coated onto precious metals, metal oxides, and synthetic polymers, including polyethylene and polytetrafluoroethylene with poor surface modifiability. The glyco-functionalized interfaces bound strongly and specifically to concanavalin A and Bauhinia purpurea lectin, which have different carbohydrate specificities. Competitive adsorption tests demonstrated that the binding sites for the abovementioned lectins were glucosyl and rhamnosyl residues, respectively. The glyco-functionalized interfaces maintained the protein binding ability after being stored in aqueous solution for 1 day and in air for 160 days. Once the glyco-functionalized interfaces were formed on gold, silicon dioxide, polystyrene, and polytetrafluoroethylene using α-glucosyl rutin, all the glyco-functionalized interfaces bound to concanavalin A rather than peanut agglutinin.

Inhibition of Polycomb Repressive Complex 2 activity reduces trimethylation of H3K27 and affects development in Arabidopsis seedlings.

BACKGROUND: Polycomb repressive complex 2 (PRC2) is an epigenetic transcriptional repression system, whose catalytic subunit (ENHANCER OF ZESTE HOMOLOG 2, EZH2 in animals) is responsible for trimethylating histone H3 at lysine 27 (H3K27me3). In mammals, gain-of-function mutations as well as overexpression of EZH2 have been associated with several tumors, therefore making this subunit a suitable target for the development of selective inhibitors. Indeed, highly specific small-molecule inhibitors of EZH2 have been reported. In plants, mutations in some PRC2 components lead to embryonic lethality, but no trial with any inhibitor has ever been reported. RESULTS: We show here that the 1,5-bis (3-bromo-4-methoxyphenyl)penta-1,4-dien-3-one compound (RDS 3434), previously reported as an EZH2 inhibitor in human leukemia cells, is active on the Arabidopsis catalytic subunit of PRC2, since treatment with the drug reduces the total amount of H3K27me3 in a dose-dependent fashion. Consistently, we show that the expression level of two PRC2 targets is significantly increased following treatment with the RDS 3434 compound. Finally, we show that impairment of H3K27 trimethylation in Arabidopsis seeds and seedlings affects both seed germination and root growth. CONCLUSIONS: Our results provide a useful tool for the plant community in investigating how PRC2 affects transcriptional control in plant development.

Effects of rutin and its derivatives on citrinin production by Monascus aurantiacus Li AS3.4384 in liquid fermentation using different types of media.

The mycotoxin citrinin is often produced during fermentation of Monascus products. We studied the effects of flavonoids on citrinin production by Monascus aurantiacus Li AS3.4384 (MALA) by adding rutin, α-glucosylrutin, or troxerutin to the fermentation medium, in a first-of-its-kind study. Appropriate amounts of rutin, α-glucosylrutin, or troxerutin did not affect normal mycelial growth. Addition of 5.0 g/l of rutin only weakly reduced (29.2%) citrinin production, relative to inhibition by 5 g/l α-glucosylrutin or troxerutin (by 54.7% and 40.6%, respectively). In starch inorganic liquid culture media, addition of 20.0 g/l of troxerutin, followed by fermentation for 12 days, reduced citrinin yield by 75.26%. Addition of 15.0 g/l of troxerutin to low-starch peptone liquid fermentation media reduced citrinin yield by 87.9% after 14 days of fermentation, and addition of 30.0 g/l troxerutin to yeast extract sucrose liquid media for 12 days reduced citrinin yield by 53.7%.

Complex Structures of Monoglucosylrutin with ent-Gallocatechin-3- O-gallate and Epigallocatechin-3- O-gallate in Aqueous Solutions and the Mechanism of Color Change Induced by Complexation.

The addition of ent-gallocatechin-3- O-gallate ( ent-GCg) or epigallocatechin-3- O-gallate (EGCg) to an aqueous solution of 4G-α-glucopyranosylrutin (monoglucosylrutin, MGR) causes the color of the solution to weaken due to complexation between MGR and these flavan-3-ols. Copigmentation is a well-known color change phenomenon resulting from the complexation of flavonoids that deepens and strengthens the color of the solution, whereas MGR/catechin complexation results in the opposite change in color (i.e., weakening). In order to gain insight into the mechanism underlying the rare changes in the color of solutions of complexes between flavonoids, the structures of the MGR monomer and the complexes in aqueous solutions and their photochemical properties were investigated by computational methods. Molecular dynamics simulations and subsequent density functional theory (DFT) calculations revealed that the complex structures are stabilized through aromatic/aromatic, CH/π, and OH/O interactions as direct intermolecular forces and that many solvent water networks would contribute to the complexations. Time-dependent DFT calculations showed that the change in the color of an MGR/ ent-GCg solution is due only to a decrease in absorbance, whereas that of an MGR/EGCg solution is due to both a decrease in absorbance and a hypsochromic shift.

Rutin derivatives obtained by transesterification reactions catalyzed by Novozym 435: Antioxidant properties and absence of toxicity in mammalian cells.

Flavonoids are one of the most important and diversified phenolic groups among products of natural origin. An important property of this metabolite class is the antioxidant action. This study evaluated the antioxidant and cytotoxic activities and oxidative stress of transesterification products of the flavonoid rutin, catalyzed by Novozym® 435. The presence of monoacetate and diacetate was confirmed by quantitative evaluation of the retention times (rutin, 15.68 min; rutin monoacetate, 18.14 min; and rutin diacetate, 18.57 min) and by the data from LC-MS and NMR 1H and 13C. The experiment showed excellent conversion values of 96% in total acetates (rutin monoacetate and diacetate). These results confirmed that rutin derivatives have antioxidant potential, as evaluated by the ORAC method (rutin standard: 0.53 ± 0.08 µM Trolox/g and rutin derivatives: 2.33 ± 1.08 µM Trolox/g) and also show low cytotoxicity in human and animal cells. Rutin derivatives reduced the production of reactive oxygen species in RAW macrophages as well. Many qualities attributed to rutin derivatives make them promising potential candidates for use as nutraceuticals, including their high amounts of antioxidants, biological potential and low toxicity, which contribute to the reduction of oxidative stress.

Design and evaluation of a novel flavonoid-based radioprotective agent utilizing monoglucosyl rutin.

In this study, three novel flavonoid composite materials, created by combining an aglycone [quercetin (QUE), hesperetin (HES) or naringenin (NAR)] with monoglucosyl rutin (MGR), were designed to test for improved radioprotectivity compared with that provided by administration of MGR alone. Aglycone in the MGR-composite state was highly soluble in water, compared with aglycone alone dissolved in dimethyl sulfoxide or distilled water. The antioxidant activity of the three flavonoid composites was as high as that of MGR only. Next, the cytotoxicity test after 30 min treatment of an MGR composite showed a clear reduction in cell viability and suggested that a rapid introduction of aglycone into cells had taken place. In addition, QUE/MGR and HES/MGR composites strongly scavenged intracellular reactive oxygen species (ROS) induced by X-ray irradiation as well as MGR alone did. However, in the colony-formation assay using irradiated Chinese hamster ovary (CHO) cells, the HES/MGR composite showed a stronger radioprotective effect than MGR alone did, but the QUE/MGR composite showed no additional protective effect compared with the control. Furthermore, it was revealed that QUE and QUE/MGR composite treatment had the effect of reducing the glutathione (GSH) content in cells, and that QUE showed a stronger inhibition of PARP activity compared that of HES and NAR. Our data demonstrated that when designing a flavonoid composite as a radioprotective agent, it was necessary to select an appropriate aglycone, considering not only its antioxidant ability but also its inhibitory effect on cell recovery or DNA repair after radiation injury.

New Procedure to Obtain Polyphenol-Enriched Grapes Based on the Use of Chemical Elicitors.

The effect of the postharvest treatment of methyl jasmonate enantiomers in conjunction with ethanol on bioformation of resveratrol and quercetin glycosides in grapes was evaluated. The antioxidant activity of treated grape extracts as compared with untreated extracts was also assayed. Exogenous (-)-methyl jasmonate in combination with ethanol induced a significant increase in the levels of resveratrol (from 27 to 39 µg g(-1)), quercetin-3-O-glucoside (from 59 to 136 µg g(-1)), quercetin-3-O-galactoside (from 398 to 807 µg g(-1)) and quercetin-3-O-rutinoside (from 23 to 43 µg g(-1)). (+)-Methyl jasmonate with ethanol also resulted in increase of quercetin-3-O-glucoside and quercetin-3-O-rutinoside. However, no (+)-methyl jasmonate effect was observed for resveratrol and quercetin-3-O-galactoside. Both (-)- and (+)-methyl jasmonate treatments provided with extracts with higher antioxidant activity. From the results found in the present work postharvest treatment with (-)-methyl jasmonate in conjunction with ethanol is proposed as a mean to obtain polyphenol-enriched grape extracts with improved antioxidant properties. The procedure here developed is proposed as a mean to obtain functional grapes. Extracts obtained from grapes treated with (-)-methyl jasmonate with ethanol can be particularly useful for industry due to their high antioxidant capacity.

Interventions for varicose veins and leg oedema in pregnancy.

BACKGROUND: Pregnancy is presumed to be a major contributory factor in the increased incidence of varicose veins in women, which can in turn lead to venous insufficiency and leg oedema. The most common symptom of varicose veins and oedema is the substantial pain experienced, as well as night cramps, numbness, tingling, the legs may feel heavy, achy, and possibly be unsightly. Treatments for varicose veins are usually divided into three main groups: surgery, pharmacological and non-pharmacological treatments. Treatments of leg oedema comprise mostly symptom reduction rather than cure and use of pharmacological and non-pharmacological approaches. OBJECTIVES: To assess any form of intervention used to relieve the symptoms associated with varicose veins and leg oedema in pregnancy. SEARCH METHODS: We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 May 2015) and reference lists of retrieved studies. SELECTION CRITERIA: Randomised trials of treatments for varicose veins or leg oedema, or both, in pregnancy. DATA COLLECTION AND ANALYSIS: Two review authors independently assessed trials for inclusion and risk of bias, extracted data and checked them for accuracy. MAIN RESULTS: We included seven trials (involving 326 women). The trials were largely unclear for selection bias and high risk for performance and detection bias.Two studies were placebo-controlled trials. The first one compared a phlebotonic (rutoside) with placebo for the reduction in symptoms of varicose veins; the second study evaluated the efficacy of troxerutin in comparison to placebo among 30 pregnant women in their second trimester with symptomatic vulvar varicosities and venous insufficiency in their lower extremities. Data from this study were not in useable format, so were not included in the analysis. Two trials compared either compression stockings with resting in left lateral position or reflexology with rest for 15 minutes for the reduction of leg oedema. One trial compared standing water immersion for 20 minutes with sitting upright in a chair with legs elevated for 20 minutes. Women standing in water were allowed to stand or walk in place. One trial compared 20 minutes of daily foot massage for five consecutive days and usual prenatal care versus usual prenatal care. The final trial compared three treatment groups for treating leg oedema in pregnancy. The first group was assigned to lateral supine bed rest at room temperature, women in the second group were asked to sit in a bathtub of waist-deep water at 32 ± 0.5 C with their legs horizontal and the third group included the women who were randomised to sitting immersed in shoulder-deep water at 32 ± 0.5 C with legs extended downward. We did not include this study in the analysis as outcomes reported in the paper were not pre-specified outcomes of this review.We planned to use GRADE methods to assess outcomes for two different comparisons and assign a quality rating. However, only two out of three outcomes for one comparison were reported and could be assessed. Evidence from one trial (rutoside versus placebo) for the outcomes of reduction in symptoms and incidence of complications associated with varicose veins and oedema was assessed as of moderate quality. Rutoside versus placeboOne trial involving 69 women, reported that rutoside significantly reduced the symptoms associated with varicose veins (risk ratio (RR) 1.89, 95% confidence interval (CI) 1.11 to 3.22; moderate quality evidence). The incidence of complications (deep vein thrombosis) did not differ significantly between the two groups (risk ratio (RR) 0.17, 95% CI 0.01 to 3.49; moderate quality evidence). There were no significant differences in side-effects (RR 1.30, 95% CI 0.23 to 7.28). Women's perception of pain was not reported in this trial. External pneumatic intermittent compression versus restOne trial, involving 35 women, reported no significant difference in lower leg volume when compression stockings were compared against rest (mean difference (MD) -258.80, 95% CI -566.91 to 49.31). Reflexology versus restingAnother trial, involving 55 women, compared reflexology with rest. Reflexology significantly reduced the symptoms associated with oedema (reduction in symptoms: RR 9.09, 95% CI 1.41 to 58.54). The same study showed a trend towards satisfaction and acceptability with the intervention (RR 6.00, 95% CI 0.92 to 39.11). Water immersion versus leg elevationThere was evidence from one trial, involving 32 women, to suggest that water immersion for 20 minutes in a swimming pool reduces leg volume (RR 0.43, 95% CI 0.22 to 0.83). Foot massage versus routine careOne trial, involving 80 women reported no significant difference in lower leg circumference when foot massage was compared against routine care (MD -0.11, 95% CI -1.02 to 0.80).No other primary or secondary outcomes were reported in the trials. AUTHORS' CONCLUSIONS: There is moderate quality evidence to suggest that rutosides appear to help relieve the symptoms of varicose veins in late pregnancy. However, this finding is based on one study (69 women) and there are not enough data presented in the study to assess its safety in pregnancy. Reflexology or water immersion appears to help improve symptoms for women with leg oedema, but again this is based on two small studies (43 and 32 women, respectively).

The contribution of the major metabolite 4'-O-methylmonoHER to the antioxidant activity of the flavonoid monoHER.

The antioxidant flavonoid 7-mono-O-(ß-hydroxyethyl)-rutoside (monoHER) effectively protects against doxorubicin-induced cardiotoxicity in mice. Doxorubicin is a very effective anticancer drug. The clinical use of doxorubicin is limited by severe cardiotoxicity. Free radicals, i.e., hydroxyl and superoxide radicals play a crucial role in this toxicity. In this study the involvement of the major metabolite of monoHER, 4'-O-methylmonoHER (methylmonoHER) in the protective effect of monoHER is studied. MethylmonoHER displayed antioxidant activity i.e., TEAC, hydroxyl and superoxide radical scavenging activity; nevertheless monoHER appeared to be superior compared to methylmonoHER. As a result of scavenging, flavonoids are oxidized and display reactivity towards thiols. Oxidized methylmonoHER, is far less thiol reactive towards creatine kinase than monoHER, which indicates that methylmonoHER is less toxic towards thiol containing enzymes. The thiol-reactivity of oxidized methylmonoHER was also negligible towards KEAP1 compared to monoHER. These results indicate that methylmonoHER hardly protects against radical damage via scavenging or via activating the NRF2 defense system. Also in HUVECs, methylmonoHER provided far less protection against oxidative stress (EC50>100µM) than monoHER which was a very potent protector (EC50=80nM). The results indicate that the contribution of methylmonoHER to the protection against doxorubicin-induced cardiotoxicity by monoHER is relatively low.

The Securinega alkaloids.

Securinega alkaloids represent a family of plant secondary metabolites known for 50 years. Securinine (1), the most abundant and studied alkaloid of this series was isolated by Russian researchers in 1956. In the following years, French and Japanese scientists reported other Securinega compounds and extensive work was done to elucidate their intriguing structures. The homogeneity of this family relies mainly on its tetracyclic chemical backbone, which features a butenolide moiety (cycle D) and an azabicyclo[3.2.1]octane ring system (rings B and C). Interestingly, after a period of latency of 20 years, the Securinega topic reemerged as a prolific source of new natural structures and to date more than 50 compounds have been identified and characterized. The oligomeric subgroup gathering dimeric, trimeric, and tetrameric units is of particular interest. The unprecedented structure of the Securinega alkaloids was the subject of extensive synthetic efforts culminating in several efficient and elegant total syntheses. The botanical distribution of these alkaloids seems limited to the Securinega, Flueggea, Margaritaria, and Breynia genera (Phyllanthaceae). However, only a limited number of plant species have been considered for their alkaloid contents, and additional phytochemical as well as genetic studies are needed. Concerning the biosynthesis, experiments carried out with radiolabelled aminoacids allowed to identify lysine and tyrosine as the precursors of the piperidine ring A and the CD rings of securinine (1), respectively. Besides, plausible biosynthetic pathways were proposed for virosaine A (38) and B (39), flueggine A (46), and also the different oligomers flueggenine A-D (48-51), fluevirosinine A (56), and flueggedine (20). The case of nirurine (45) and secu'amamine (37) remains elusive and additional studies seem necessary to understand their mode of production. The scope of biological of activities of the Securinega alkaloids was mainly centered on the CNS activity of securinine (1), although the exact mechanism of action remained in part unknown. Nevertheless, for its stimulant and antispasmodic effects securinine nitrate was marketed as a drug in the USSR until the early 1990s. Moreover, securinine (1) and several other Securinega alkaloids recently demonstrated promising anticancer properties. In particular securinine (1) demonstrated markedly benefits in the treatment of acute myeloid leukemia.

Absorption improvement of tranilast by forming highly soluble nano-size composite structures associated with α-glucosyl rutin via spray drying.

Tranilast (TL) composite particles with α-glucosyl rutin (Rutin-G) were developed to improve the solubility and oral bioavailability of TL. Composite formulation of TL/Rutin-G was prepared using the spray-drying method, and their physicochemical properties were evaluated with respect to the morphology, particle size distribution, solubility and crystallinity. The nanostructure formation of Rutin-G was characterized by dynamic light scattering and transmission electron microscopy when Rutin-G or TL/Rutin-G spray-dried particles (SDPs) were introduced into water. A pharmacokinetic study was also performed to assess the improvement of oral absorption in rats. TL/Rutin-G SDPs were spherical particles with a diameter of 5.5µm. Even in the acidic condition, the remarkable improvement in solubility of TL was achieved, as evidenced by a 32.2-fold increase in solubility compared with untreated TL. The median size of Rutin-G nanostructures in water was 2nm. The formation of Rutin-G nanostructures and their drug inclusion properties may enhance the solubility and dissolution behavior of TL. A drastic increase was found in the exposure of TL in rats, with an increase in Cmax and AUC values of 114- and 36.4-fold, respectively, compared with those of untreated TL. These findings indicated that a TL formulation spray-dried with Rutin-G could enhance its solubility and absorption and thus its therapeutic properties.

Inhibition of the sarco/endoplasmic reticulum Ca2+-ATPase (SERCA1) by rutin derivatives.

The effect of lipophilic rutin derivatives (acylated with fatty acid chain length of 16-22) on sarco/endoplasmic reticulum Ca(2+)-ATPase (SERCA1 isoform) compared to the parent molecule rutin was evaluated. Rutin derivatives caused concentration dependent decrease of SERCA1 activity (IC50 ~ 23-64 µM) and significant conformational alterations in the transmembrane region of the enzyme. Upon treatment by peroxynitrite, rutin derivatives exerted a hormetic effect, i.e. prevented enzyme activity decrease at low concentrations, while additionally inhibited at high concentrations. Concerning the posttranslational modifications of SERCA1, rutin esters: (i) induced a significant loss of free sulfhydryl groups, (ii) protected the enzyme from protein carbonyl formation, and (iii) prevented SERCA from tyrosine nitration (except R20:4 and R22:1). In silico study revealed a strong affinity of the derivative R20:4 to the transmembrane region of SERCA1, stabilized via hydrogen bonds with Glu90, Glu771, Thr778 and Thr848 residues. Interaction of rutin derivatives with Glu771, a residue involved in Ca(2+) binding, is likely to be responsible for the inhibitory effect of the esters.

Design, synthesis and biological activity of a novel Rutin analogue with improved lipid soluble properties.

Recent interest in flavonoids has increased greatly due to their biological and pharmacological activities. Flavonoids, consist of a large group of low molecular weight polyphenolic substances, naturally occurring in fruits, vegetables, tea, and wine, and are an integral part of the human diet. Rutin is a common dietary flavonoid that is widely consumed worldwide from plant-derived beverages and foods as traditional and folk medicine remedy as well. Rutin exhibit important pharmacological activities, including anti-oxidation, anti-inflammation, anti-diabetic, anti-adipogenic, neuroprotective and hormone therapy. Here, we present the synthesis, antimicrobial, antiproliferative and pro-apoptotic effect on human leukemic K562 cells of compound R2, a new semi-synthetic derivative of Rutin as compared to Rutin itself. The new derivative was also included in finished topical formulations to evaluate a potential application to the dermatology field in view of the antioxidant/antimicrobial/antiinflammatory properties. Stability studies were performed by HPLC; PCL assay and ORAC tests were used to determine the antioxidant activity. R2 presented an antioxidant activity very close to that of the parent Rutin while bearing much better lipophilic character. Regarding antiproliferative effects on the human K562 cell line, R2 was found to be more effective than parent Rutin. Preliminary experiments demonstrated that R2 inhibits NF-kB activity and promotes cellular apoptosis.

Monoglucosyl-rutin as a potential radioprotector in mammalian cells.

In the present study, the role of monoglucosyl­rutin as a potential radioprotector was investigated using mammalian cell culture models. Cell survival and DNA damage were assessed using colony formation, sister chromatid exchange and γH2AX assays. It was demonstrated that monoglucosyl­rutin was able to increase cell survival when exposed to ionizing radiation, possibly by decreasing the amount of base damage experienced by the cell. However, the present study also demonstrated that, despite monoglucosyl­rutin exhibiting radioprotective effects at low doses, high doses of monoglucosyl­rutin led to a decrease in plating efficiency and an increased doubling time. This effect may be due to double­strand breaks caused by high concentrations of monoglucosyl­rutin.

The flavonoid 7-mono-O-(ß-hydroxyethyl)-rutoside is able to protect endothelial cells by a direct antioxidant effect.

The flavonoid 7-mono-O-(ß-hydroxyethyl)-rutoside (monoHER) is an effective protector against doxorubicin induced toxicity which has been related to the antioxidant activity of monoHER. The present study examines the potential relevance of the direct scavenging activity of the flavonoid. The potency of the direct antioxidant effect was confirmed by its instantaneous protection against intracellular oxidative stress in human umbilical vein endothelial cells at therapeutically achievable concentrations (EC50=60 nM) underpinning the involvement of a direct scavenging activity. This direct effect of monoHER is substantiated by (i) its site specific scavenging effect, i.e. on a molecular level monoHER is positioned at the location of radical formation, (ii) its position in the antioxidant network, i.e. on a biochemical level oxidized monoHER quickly reacts with ascorbate or glutathione, (iii) its location in the vascular system, i.e. on a cellular level monoHER is localized in the endothelial and smooth muscle cells in the vascular wall. It is concluded that the flavonoid monoHER can display a physiologically important direct antioxidant effect.

Natural and glucosyl flavonoids inhibit poly(ADP-ribose) polymerase activity and induce synthetic lethality in BRCA mutant cells.

Poly(ADP-ribose) polymerase (PARP) inhibitors have been proven to represent superior clinical agents targeting DNA repair mechanisms in cancer therapy. We investigated PARP inhibitory effects of the natural and synthetic flavonoids (quercetin, rutin, monoglucosyl rutin and maltooligosyl rutin) and tested the synthetic lethality in BRCA2 mutated cells. In vitro ELISA assay suggested that the flavonoids have inhibitory effects on PARP activity, but glucosyl modifications reduced the inhibitory effect. Cytotoxicity tests of Chinese hamster cells defective in BRCA2 gene (V-C8) and its parental V79 cells showed BRCA2-dependent synthetic lethality when treated with the flavonoids. BRCA2 mutated cells were three times more sensitive to the flavonoids than the wild-type and gene complemented cells. Reduced toxicity was observed in a glucosyl modification-dependent manner. The present study provides support for the clinical use of new treatment drugs, and is the beginning of the potential application of flavonoids in cancer prevention and the periodic consumption of appropriate flavonoids to reduce cancer risk in individuals carrying a mutant allele of the BRCA2 gene.

Anti-allergic effects of enzymatically modified isoquercitrin (α-oligoglucosyl quercetin 3-O-glucoside), quercetin 3-O-glucoside, α-oligoglucosyl rutin, and quercetin, when administered orally to mice.

Quercetin, a flavonol distributed widely in edible and medicinal plants, has beneficial biological activities in vitro. However, the low water solubility of quercetin limits its bioavailability to exhibit activity in vivo. We evaluated the anti-allergic effects of quercetin, quercetin 3-O-glucoside (isoquercitrin, IQC), α-oligoglucosyl rutin (αOR), and enzymatically modified isoquercitrin (α-oligoglucosyl isoquercitrin; EMIQ) in the murine ear passive cutaneous anaphylaxis (PCA) reaction using ovalbumin as an antigen. The substances to be tested were dissolved or suspended in water, and administered orally to mice (4 mmol 10 ml⁻¹ kg⁻¹). EMIQ exhibited a significant inhibitory effect on the PCA reaction. We detected 600 µM IQC and 95.1 µM Q3Glcn in the plasma of mice 30 min after EMIQ treatment, suggesting that IQC and Q3Glcn might be the genuine active compounds mediating the anti-allergic effects of EMIQ. Oral treatments of quercetin and αOR at this dosage exhibited no anti-allergic effect, and IQC showed less effect than EMIQ. Since IQC and quercetin cannot completely dissolve in water at this concentration, the water solubilities of these substances might affect their biological activities. αOR dissolved well in water at the concentration used but plasma concentrations of quercetin metabolites in mice orally treated with αOR were low, suggesting that αOR might not be converted to IQC or quercetin by the enzymes in small intestine and thus not exhibit any activity. Glycosyl conjugation of quercetin with specific sugar motifs is an effective strategy to improve the biological activity of quercetin in vivo.

Bioconversion of quercetin and rutin and the cytotoxicity activities of the transformed products.

Quercetin and rutin are well-know flavonoids. In spite of this, the comprehension of their metabolism is still incomplete. In this work, the cytotoxic activity of quercetin and rutin and its metabolites produced by metabolism of filamentous fungi was investigated. Flavonoids metabolism was monitored by HPLC and LC-MS. Both flavonoids were extensively metabolized. Quercetin was converted into metabolite methylquercetin (2) and quercetin glucuronide (3) and rutin into metabolite rutin sulphate (5), methylrutin (6) and rutin glucuronide (7). Cytotoxic effects of rutin, quercetin and its metabolites were measured by MTT tetrazolium reduction test and the trypan blue exclusion assay on HL-60 leukemic cells. The results showed similar concentration-dependent cytotoxic effect for rutin and rutin sulphate (5), while no cytotoxic effect was detected with the metabolites 6 and 7. In relation to the quercetin and its metabolites the results showed that all compounds have a similar concentration-dependent inhibitory effect on HL-60 cells. These findings corroborate the literature, showing that bioconversion is a useful strategy for production of biological active metabolites.