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Concept: Flavonols

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Flavonoids are a significant group of secondary metabolites in plants. Many of these compounds are potent antioxidants, being an important part in food products derived from the plants. The current status of research on flavonoid compounds in the fruit of Saskatoon berries (Amelanchier alnifolia Nutt.) and their health promoting effects, including recommended utilization, are reviewed. The major classes of flavonoids in the fruit are flavonols (quercetin and rutin), flavanes (proanthocyanidin compounds ranging from dimers through to heptamers and even higher polymers) and finally anthocyanins. The flavonoids represented the group of polyphenols that mostly contributed to the antioxidant activity of Saskatoon berries. High content of the flavoinoids antioxidants in the fruit is responsible for the observed anti-inflammatory, antidiadiabetic and chemo-protective effects.

Concepts: Nutrition, Antioxidant, Flavonoid, Resveratrol, Polyphenol, Flavonols, Rutin, Amelanchier alnifolia

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Cassia auriculata (Caesalpiniaceae) is a common Asian beverage and medicinal plant widely used in tradition medicine for diabetes, hyperlipidemia and various other disease conditions. Previous studies on crude extracts of C. auriculata have documented the scientific basis for some of its traditional medicinal uses. The present study investigates the antilipase activity of the ethanol extract of the aerial parts along with the previously isolated compounds (kaempferol-3-O-rutinoside, rutin, kaempferol, quercetin and luteolin). The crude extract displayed inhibitory activity against pancreatic lipase with IC(50) of 6.0 ± 1.0 µg/mL. The most active antilipase compound was kaempferol-3-O-rutinoside with IC(50) value (2.9 ± 0.50 μM) only about twice weaker than the standard antilipase drug, orlistat (IC(50)  = 1.45 ± 0.26 μM). Luteolin, quercetin and rutin were found to be weak pancreatic lipase inhibitors (IC(50) over 100 μM), whereas kaempferol showed no activity up to 250 μM. The antihyperlipidemic effect of C. auriculata could be attributed to direct lipase inhibitory effect of the plant constituents. Copyright © 2012 John Wiley & Sons, Ltd.

Concepts: Pharmacology, Neurology, In vitro, Quercetin, Flavonoid, Flavonols, Tincture, Pancreatic lipase

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The potential of three natural flavonols (galangin, kaempferol and myricetin) to protect against D-galactose-induced cognitive impairment in mice was investigated. After 8 weeks treatment, the mice were assessed by behavioural tests. The levels of oxidative stress, the amount of Na(+),K(+)-ATPase and extracellular signal-regulated kinases (ERK)-cyclic AMP response element binding protein (CREB) signaling pathway in hippocampus were also analysed. It was found that all the three dietary flavonols could ameliorate the oxidative stress, enhance the activity of Na(+),K(+)-ATPase and regulate the expression of ERK-CREB pathway in mice. However, only kaempferol and myricetin could significantly improve the learning and memory capability when compared with D-galactose model. Our results suggest that the presence of hydroxyl groups in the B ring of flavonols may have contribution to the neuroprotective activity.

Concepts: Psychology, Signal transduction, Enzyme, Transcription factor, Memory, Flavonoid, Flavonols, Kaempferol

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Berries and red fruits are rich dietary sources of polyphenols with reported health benefits. More than 50 different flavonols (glycosides of quercetin, myricetin, kaempferol, isorhamnetin, syringetin and laricitrin) have been detected and quantified with HPLC-MS(n) in fruits of blueberry, bilberry, cranberry, lingonberry, eastern shadbush, Japanese wineberry, black mulberry, chokeberry, red, black and white currants, jostaberry, red and white gooseberry, hardy kiwifruit, goji berry, rowan, dog rose, Chinese and midland hawthorn, wild and cultivated species of blackberry, raspberry, strawberry and elderberry. The phenolic constituents and contents varied considerably among the analyzed berry species. Elderberry contained the highest amount of total flavonols (450-568 mgkg(-1) FW), followed by berry species, containing more than 200 mgkg(-1) FW of total: chokeberry (267mgkg(-1)), eastern shadbush (261 mgkg(-1)), wild grown blackberry (260 mgkg(-1)), rowanberry (232 mgkg(-1)), american cranberry (213 mgkg(-1)) and blackcurrants (204 mgkg(-1)). Strawberry (10.5 mgkg(-1)) and white currants (4.5 mgkg(-1)) contained the lowest amount of total flavonols. Quercetins represent the highest percentage (46-100%) among flavonols in most analyzed berries. In wild strawberry and gooseberry the prevailing flavonols belong to the group of isorhamnetins (50-62%) and kaempferols, which represent the major part of flavonols in currants (49-66%). Myricetin glycosides could only be detected in chokeberry, rowanberry and species from the Grossulariaceae, and Adoxaceae family and Vaccinium genus. Wild strawberry and blackberry contained from 3- to 5-fold higher total flavonols than the cultivated one.

Concepts: Vitamin C, Fruit, Quercetin, Flavonols, Cranberry, Vaccinium, Berry, Berries

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Quercetin, rutin, naringenin, epicatechin are flavonoids with diverse properties, including antioxidant potential. We evaluated, in vitro, the cytotoxicity of these flavonoids (20, 30, 50, 100, 200, 400μM) in swim-up selected human sperm. Antioxidant activity was tested against tert-butylhydroperoxide induced lipid peroxidation using a C11-BODIPY(581/591) probe and transmission electron microscopy. A significant concentration-dependent effect on sperm viability (P<0.001) and motility (P<0.001) was observed. Lipid peroxidation was decreased in samples treated with 30μM quercetin (P<0.01) and 30μM rutin (P<0.05) versus samples incubated with tert-butylhydroperoxide alone. Naringenin (50-100μM) showed a low protective effect and epicatechin (200μM) was not efficacious. Transmission electron microscopy analysis confirmed the protective action of rutin and in particular quercetin on damages induced by lipid peroxidation. These results underlined the antioxidant properties of quercetin and rutin. A possible role of these compounds in the supplementation of media used during semen handling warrants attention and further studies.

Concepts: Electron, Antioxidant, Sperm, Spermatozoon, Semen, Flavonoid, Flavonols, Rutin

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Flavonols kaempferol, quercetin, myricetin and gossypetin, and flavones apigenin, acacetin, luteolin, orientin and tricin, are subjected to two AlCl(3) spectrophotometric methods used for determination of total flavonoid content. The method developed by Woisky and Salatino involves addition of AlCl(3) solution to the flavonoid solution and recording of optical density at 420nm. All flavonols except kaempferol have absorption maxima above 440nm and so readings at 420nm are erroneous. Among flavones, all except for luteolin and orientin, have absorption maxima below 400nm. Further, addition of CH(3)COOK and recording the absorbance at 415nm, as modified by Chang et al., works well for flavonols kaempferol, quercetin and myricetin, but not for gossypetin. The flavones luteolin and orientin absorbed above 400nm, whereas all others absorbed below 400nm. Examination of the results of both methods indicates they are inadequate, and should not to be considered as universal and standard methods for total flavonoid determination.

Concepts: Quercetin, Flavonoid, Flavones, Flavonols, Kaempferol, Myricetin, Luteolin, Rutin

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INTRODUCTION: The fruits of Vaccinium vitis-idaea L. are a valuable source of biologically active flavonoid derivatives. For studies focused on the purification of its quercetin glycosides (QGs) and related glycosides from plants and for the purpose of biological studies, the availability of numeric datasets from computer-assisted (1) H iterative full spin analysis (HiFSA), that is, (1) H-NMR fingerprinting, can replace and assist the repetitive and tedious two-dimensional NMR identification protocol required for both known and new compounds, respectively. OBJECTIVE: To fully interpret the complex (1) H-NMR fingerprints of eight QGs obtained from the berries of V. vitis-idaea and provide complete and unambiguous signal assignments. METHODS: Vaccinium vitis-idaea QGs were purified in a single run by long-bed gel permeation chromatography and identified by comparison with commercially available compounds using LC-MS combining ion-trap and time-of-flight detection and one- or two-dimensional NMR. The HiFSA analysis yielded full sets of (1) H chemical shifts and proton-proton coupling constants, allowing for field-independent spectral simulation. RESULTS: Signal assignments were achieved for the reference standards and the QGs that dominated in purified fractions. However, even mixtures of two to three QGs could be fitted using the HiFSA approach. In the case of the overlapped sugar resonances, the initial fitting of the (1) H spectra of reference compounds, together with values extracted from the two-dimensional NMR data and literature data, assisted in the process. CONCLUSION: The HiFSA method revealed for the first time the presence of Q-3-O-β-glucopyranoside and Q-3-O-β-glucuronopyranoside in the berries of V. vitis-idaea, and unambiguously confirmed the structures of Q-3-O-[4″-(3-hydroxy-3-methylglutaroyl)]-α-rhamnopyranoside, Q-3-O-α-rhamnopyranoside, Q-3-O-β-galactopyranoside, Q-3-O-α-arabinofuranoside, Q-3-O-β-xylopyranoside and Q-3-O-α-arabinopyranoside. Copyright © 2013 John Wiley & Sons, Ltd.

Concepts: Biology, Chemical compound, John Wiley & Sons, Fruit, Quercetin, Flavonols, Fingerprint, Vaccinium vitis-idaea

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In this study, we reported the phytochemical composition of the aerial parts of Atriplex halimus L. collected from Sardinia. This species is a halophytic shrub, typical of the Mediterranean Basin. Four new glycosylated flavonoids were isolated and their structures were elucidated on the basis of 1D, 2D NMR and MS spectra as 3',5'-dimethoxymyricetin-3-O-β-d-xylopyranosyl-7-O-fucopyranosyl-(1 → 3)-β-d-glucopyranoside (1), 3'-methoxyquercetin-7-O-β-d-fucopyranosyl-(1 → 3)-β-d-glucopyranosyl-3-O-β-xylopyranosyl-(1 → 4)-β-xylopyranoside (2), 3'-methoxyquercetin-7-O-α-l-rhamnopyranosyl-3-O-α-arabinofuranosyl-(1 → 6)-β-d-glucopyranoside (3) and 3',5'-dimethoxymyricetin-7-O-fucopyranosyl-(1 → 3)-β-d-glucopyranoside (4). LC-MS (n) analysis on the extract revealed the presence of other myricetin, quercetin, isorhamnetin glycosides, simple phenolic acids and esters.

Concepts: Mediterranean Sea, Quercetin, Flavonoid, Glycoside, Flavonols, Myricetin, Shrubland, Atriplex

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As a part of our ongoing effort to identify anti-diabetic constituents from natural sources, we examined the inhibitory activity of the methanol extracts of 12 species of the genus Artemisia, against α-glucosidase and protein tyrosine phosphatase 1B (PTP1B). The methanol extracts of different species exhibited promising α-glucosidase and PTP1B inhibitory activities. Since the methanol extract of Artemisia capillaris exhibited the highest α-glucosidase inhibitory activity together with significant PTP1B inhibitory activity, it was selected for further investigation. Repeated column chromatography based on bioactivity guided fractionation yielded 10 coumarins (esculetin, esculin, scopolin, isoscopolin, daphnetin, umbelliferone, 7-methoxy coumarin, scoparone, scopoletin, 6-methoxy artemicapin C), 8 flavonoids (hyperoside, quercetin, isorhamnetin, cirsilineol, arcapillin, isorhamnetin 3-robinobioside, linarin, isorhamnetin 3-glucoiside), 6 phenolic compounds (1,5-dicaffeoylquinic acid, 3,4-dicaffeoylquinic acid, 3,5-dicaffeoylquinic acid, 3,5-dicaffeoylquinic acid methyl ester, 4,5-dicaffeoylquinic acid, 3-caffeoylquinic acid), and one chromone (capillarisin). Among these compounds, esculetin, scopoletin, quercetin, hyperoside, isorhamnetin, 3,5-dicaffeoylquinic acid methyl ester, 3,4-dicaffeoylquinic acid, and 1,5-dicaffeoylquinic acid exhibited potent α-glucosidase inhibitory activity when compared to the positive control acarbose. In addition, esculetin and 6-methoxy artemicapin C displayed PTP1B inhibitory activity. Interestingly, all isolated dicaffeoylquinic acids showed significant PTP1B inhibitory activity. Therefore, the results of the present study clearly demonstrate the potential of the A. capillaris extract to inhibit α-glucosidase and PTP1B. These inhibitory properties can be largely attributed to a combination of different chemical structures, including coumarins, flavonoids, and dicaffeoylquinic acids, which could be further explored to develop therapeutic or preventive agents for the treatment of diabetes.

Concepts: Alcohol, Amino acid, Tyrosine kinase, Acetic acid, Quercetin, Flavonols, Protein tyrosine phosphatase, PTEN

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Enzymatic bioconversion of rutin to quercetin-3-O-glucoside (Q-3-G) by Penicillium decumbens naringinase was increased with reaction pH increased approximately to pH 6.0. It resulted in greater than 92% production of Q-3-G due to the removal of the terminal rhamnose at the controlled pH 6.0. The enzymatic bioconversion of rutin to Q-3-G was repetitively performed, yielding 84% after 5 batches with little quercetin formation. Interestingly, the water solubility of Q-3-G was enhanced 69- and 328-fold over those of rutin and quercetin, which may make Q-3-G more bioavailable in food. Q-3-G was approximately 6- and 1.4-fold more potent than rutin as an inhibitor of human intestinal maltase and human DL-3-hydroxy-3-methylglutalyl coenzyme A reductase. Q-3-G was less potent (16- and 1.3-fold, respectively) than quercetin as an inhibitor of these enzymes. However, the results suggest that Q-3-G may be confirmed more effective and bioavailable food component than rutin and even quercetin because of its enhanced solubility and inhibitory properties. Practical Application: Bioconverted intermediate, quercetin-3-O-glucoside (Q-3-G), was found and confirmed to be largely more soluble than rutin and quercetin in water solution, which might make it more bioavailable as food ingredient. In addition, Q-3-G inhibited mildly the intestinal maltase, which might act as antidiabetic substance by modulating the adsorption of glucose in the intestine.

Concepts: Enzyme, Glucose, Solubility, Quercetin, Glycoside, Biopharmaceutics Classification System, Solution, Flavonols