quercetin-3-o-glucopyranoside and 1-1-diphenyl-2-picrylhydrazyl

Quercetin derivatives are widespread in the plant kingdom and exhibit various biological actions. The aim of this study was to investigate the structure-activity relationships of quercetin derivatives, with a focus on the influence of functional groups and sugar composition on their antioxidant capacity. A series of quercetin derivatives were therefore prepared and assessed for their DPPH radical scavenging properties. Isoquercetin O-gallates were more potent radical scavengers than quercetin. The systematic analysis highlights the importance of the distribution of hydroxy substituents in isoquercetin O-gallates to their potency.

Topics: Antioxidants; Biphenyl Compounds; Free Radical Scavengers; Molecular Structure; Picrates; Quercetin; Structure-Activity Relationship

The aim of this study is to investigate the change in flavonoid composition and antioxidative activity during fermentation of onion (Allium cepa L.) by Leuconostoc mesenteroides with different NaCl concentrations. In order to qualify and quantify the flavonoids during fermentation of onion, 7 flavonoids, [quercetin 3,7-O-β-d-diglucopyranoside (Q3,7G), quercetin 3,4'-O-β-d-diglucopyranoside (Q3,4'G), quercetin 3-O-β-d-glucopyranoside (Q3G), quercetin 4'-O-β-d-glucopyranoside (Q4'G), isorhamnetin 3-O-β-d-glucopyranoside (IR3G), quercetin (Q), and isorhamnetin (IR)], were isolated and identified from onion. During fermentation, the contents of flavonoid glucosides (Q3,7G, Q3,4'G, Q3G, Q4'G, and IR3G) gradually decreased, whereas the contents of flavonoid aglycones (Q, IR) gradually increased. Decline rates of the flavonoid glucosides increased with the addition of L. mesenteroides. Furthermore, the activity of β-glucosidase, which is produced by L. mesenteroides, is dose-dependently inhibited with different NaCl concentrations during fermentation. The presence of L. mesenteroides enhanced the antioxidative activity of onion as demonstrated using the 1,1-diphenyl-2-picrylhydrazyl, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), and reducing power assays. The enhancement of antioxidative activity was considered because the content of flavonoid aglycones increased during fermentation. However, the addition of NaCl may decrease the antioxidative activity; we surmise that this phenomenon occurs because of the inhibition of β-glucosidase by NaCl. Therefore, we conclude that the addition of NaCl may be useful for the regulation of antioxidative activity via the control of β-glucosidase action, during the fermentation of flavonoid glucoside-rich foods.

Topics: beta-Glucosidase; Biphenyl Compounds; Fermentation; Flavonoids; Flavonols; Food Handling; Glucosides; Humans; Leuconostoc mesenteroides; Onions; Oxidation-Reduction; Picrates; Plant Extracts; Quercetin; Sodium Chloride

Eleven phenolic compounds, quercetin (1), quercetin 3-O-β-d-galactopyranoside (2), quercetin 3-O-(6″-O-galloyl)-β-d-galactopyranoside (3), quercetin 3-O-(6″-O-caffeoyl)-β-d-galactopyranoside (4), quercetin 3-O-β-d-glucopyranoside (5), rutin (6) quercetin 3-O-α-l-arabinopyranoside (7), quercetin 3-O-α-l-arabinofuranoside (8), protocatechulic acid (9), gallic acid (10) and chlorogenic acid (11), were isolated from the flowers of Aconogonon molle, a Nepalese medicinal plant. Structures of these compounds were elucidated on the basis of spectroscopic methods. All these compounds were isolated for the first time from flowers, and five compounds (4, 5, 8, 9 and 11) were isolated for the first time from A. molle. All of these isolated compounds were evaluated for their in vitro antioxidant activity by using the 1,1-diphenyl-2-picrylhydrazyl radical-scavenging method. Quercetin (1), quercetin glycosides (2-8) and gallic acid (10) exhibited potent antioxidant activity.

Topics: Antioxidants; Biphenyl Compounds; Chlorogenic Acid; Flavonoids; Flowers; Free Radical Scavengers; Glucosides; Glycosides; Molecular Structure; Nepal; Phenols; Picrates; Plant Extracts; Plant Leaves; Plants, Medicinal; Polygonaceae; Quercetin

From an extract of the aerial parts of Dracocephalum ruyschiana, five new flavone tetraglycosides, five new benzyl alcohol glycosides, and 19 known compounds were isolated. The tetraglycosides contain a 7-O-β-d-glucopyranosyl-(1→2)-β-d-glucopyranosyl-(1→2)-[α-l-rhamnopyranosyl-(1→6)]-β-d-glucopyranosyl moiety. The benzyl alcohol glycosides had acyl groups on their glycosyl or aglycone moieties. The compounds were tested for antioxidant activity using DPPH. Although the new compounds were not active, phenylpropanoylquinic acid derivatives were revealed as radical scavengers in D. ruyschiana.

Topics: Antioxidants; Benzyl Alcohol; Biphenyl Compounds; Flavones; Free Radical Scavengers; Glycosides; Lamiaceae; Molecular Structure; Mongolia; Picrates; Plants, Medicinal

Together with the sweet principle component glycyphyllin A (3), seven phenolic compounds including two new dihydrochalcone rhamnopyranosides, glycyphyllin B (1) and glycyphyllin C (2), and five known flavonoids, catechin (4), kaempferol-3-O-β-D-glucopyranoside (5), quercetin-3-O-β-D-glucopyranoside (6), kaempferol-3-O-β-neohesperidoside (7), and 2R,3R-dihydrokaempferol-3-O-β-D-glucopyranoside (8), have been isolated from the ethanolic extract of the leaves of Smilax glyciphylla for the first time. The structures of these compounds were characterized by spectroscopic methods including UV, MS, and 1D and 2D NMR. In vitro antioxidant capacity tests employing FRAP and DPPH assays indicated that 1, 4, and 6 exhibited potent antioxidant activity and are the key phenolics responsible for the antioxidant activity of the leaf extract of S. glyciphylla.

Topics: Antioxidants; Australia; Biphenyl Compounds; Flavonoids; Glycosides; Kaempferols; Nuclear Magnetic Resonance, Biomolecular; Oxidation-Reduction; Phenols; Picrates; Plant Leaves; Smilax

Seven flavonoids have been isolated from the aerial parts of Halostachys caspica C. A. Mey. (Chenopodiaceae) for the first time. By means of physicochemical and spectrometric analysis, they were identified as luteolin (1), chrysin (2), chrysin 7-O-β-D-glucopyranoside (3), quercetin (4), quercetin 3-O-β-D-glucopyranoside (5), isorhamentin-3-O-β-D-glucopyranoside (6), and isorhamentin-3-O-β-D-rutinoside (7). All flavonoids were evaluated to show a broad antimicrobial spectrum of activity on microorganisms including seven bacterial and one fungal species as well as pronounced antioxidant activity. Among them, the aglycones with relatively low polarity had stronger bioactivity than their glycosides. The results suggested that the isolated flavonoids could be used for future development of antimicrobial and antioxidant agents, and also provided additional data for supporting the use of H. caspica as forage.

Topics: Anti-Infective Agents; Antioxidants; Bacteria; Biological Assay; Biphenyl Compounds; Chenopodiaceae; Flavonoids; Flavonols; Fungi; Glucosides; Luteolin; Magnetic Resonance Spectroscopy; Picrates; Quercetin

Separation of the water-soluble fraction of peanut skins led to the isolation of 8 flavonoids and two novel indole alkaloids. Two new flavonoid glycosides have been identified as isorhamnetin 3-O-[2-O-beta-glucopyranosyl-6-O-alpha-rhamnopyranosyl]- beta-glucopyranoside and 3',5,7-trihydroxyisoflavone-4'-methoxy-3'-O-beta-glucopyranoside. Two alkaloids are 2-methoxyl-3-(3-indolyl)-propionic acid and 2-hydroxyl-3-[3-(1-N-methyl)-indolyl]-propionic acid. These isolated flavonoids were evaluated for their free radical scavenging activity and protein glycation inhibitory effects.

Topics: Alkaloids; Arachis; Bepridil; Biphenyl Compounds; Chromatography, High Pressure Liquid; Fabaceae; Flavonoids; Free Radical Scavengers; Glucosides; Glycation End Products, Advanced; Magnetic Resonance Spectroscopy; Medicine, Chinese Traditional; Molecular Structure; Phytotherapy; Picrates; Plants, Medicinal; Quercetin; Rutin; Seeds; Serum Albumin, Bovine; Spectrophotometry, Ultraviolet