Flavonols

Gottlieb, Otto R.

doi:10.1007/978-1-4899-2909-9_7

Cited by 11 publications

(5 citation statements)

References 308 publications

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“…Flavonoids are ubiquitously present in the plant kingdom and are even found in some fungal species [ 6 – 8 ], but not all flavonoid classes are found in all plant groups [ 9 ]. In 1999, the most comprehensive register of flavonoids listed 6,467 naturally occurring compounds [ 2 ] and the identification of novel structures from various plant sources is ongoing.…”

Section: Flavonoids: Structures and Physiological Functionsmentioning

confidence: 99%

The Creation and Physiological Relevance of Divergent Hydroxylation Patterns in the Flavonoid Pathway

Halbwirth

2010

IJMS

116

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Flavonoids and biochemically-related chalcones are important secondary metabolites, which are ubiquitously present in plants and therefore also in human food. They fulfill a broad range of physiological functions in planta and there are numerous reports about their physiological relevance for humans. Flavonoids have in common a basic C6-C3-C6 skeleton structure consisting of two aromatic rings (A and B) and a heterocyclic ring (C) containing one oxygen atom, whereas chalcones, as the intermediates in the formation of flavonoids, have not yet established the heterocyclic C-ring. Flavonoids are grouped into eight different classes, according to the oxidative status of the C-ring. The large number of divergent chalcones and flavonoid structures is from the extensive modification of the basic molecules. The hydroxylation pattern influences physiological properties such as light absorption and antioxidative activity, which is the base for many beneficial health effects of flavonoids. In some cases antiinfective properties are also effected.

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Section: Flavonoids: Structures and Physiological Functionsmentioning

confidence: 99%

The Creation and Physiological Relevance of Divergent Hydroxylation Patterns in the Flavonoid Pathway

Halbwirth

2010

IJMS

116

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“…This may explain the reason why 3-O-methyl flavonols rarely accumulate in plants, since they serve as intermediates in the biosynthetic pathway of partially/highly methylated flavonoids. However, 3-MeQ has been detected in small amounts in a number of plant species including Begonia, Centauria, Greyia, Nicotiana, and Serratula (for review, see Gottlieb, 1975).…”

mentioning

confidence: 99%

Partial Purification, Kinetic Analysis, and Amino Acid Sequence Information of a Flavonol 3-O-Methyltransferase from Serratula tinctoria

et al. 2004

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Serratula tinctoria (Asteraceae) accumulates mainly 3,39-dimethylquercetin and small amounts of 3-methylquercetin as an intermediate. The fact that 3-methylquercetin rarely accumulates in plants in significant amounts, and given its important role as an antiviral and antiinflammatory agent that accumulates in response to stress conditions, prompted us to purify and characterize the enzyme involved in its methylation. The flavonol 3-O-methyltransferase (3-OMT) was partially purified by ammonium sulfate precipitation and successive chromatography on Superose-12, Mono-Q, and adenosine-agarose affinity columns, resulting in a 194-fold increase of its specific activity. The enzyme protein exhibited an expressed specificity for the methylation of position 3 of the flavonol, quercetin, although it also utilized kaempferol, myricetin, and some monomethyl flavonols as substrates. It exhibited a pH optimum of 7.6, a pI of 6.0, and an apparent molecular mass of 31 kD. Its K m values for quercetin as the substrate and S-adenosyl-L-Met (AdoMet) as the cosubstrate were 12 and 45 mM, respectively. The 3-OMT had no requirement for Mg 21 , but was severely inhibited by p-chloromercuribenzoate, suggesting the requirement for SH groups for catalytic activity. Quercetin methylation was competitively inhibited by S-adenosyl-L-homo-Cys with respect to the cosubstrate AdoMet, and followed a sequential bi-bi reaction mechanism, where AdoMet was the first to bind and S-adenosyl-L-homo-Cys was released last. In-gel trypsin digestion of the purified protein yielded several peptides, two of which exhibited strong amino acid sequence homology, upon protein identification, to a number of previously identified Group II plant OMTs. The availability of peptide sequences will allow the design of specific nucleotide probes for future cloning of the gene encoding this novel enzyme for its use in metabolic engineering.Flavonoid compounds constitute one of the most ubiquitous groups of natural plant products. They exhibit a wide range of functions and play important roles in the biochemistry, physiology, and ecology of plants. These include their contribution to flower color, protection against UV radiation and pathogenic organisms, promotion of pollen germination and pollen fertility, and activation of Rhizobium nodulation genes. They also act as growth regulators, enzyme inhibitors, insect antifeedants, and antioxidants, and are of potential benefit to human health (Bohm, 1998, and references therein). Flavonoids owe their structural biodiversity to a number of enzyme-catalyzed substitution reactions (Ibrahim and Anzellotti, 2003).Of these, enzymatic O-methylation, which is catalyzed by a family of S-adenosyl-L-Met (AdoMet)-dependent O-methyltransferases (OMTs; Ibrahim and Muzac, 2000), involves the transfer of the methyl group of AdoMet to the hydroxyl groups of an acceptor molecule, with the concomitant formation of the corresponding methyl ether derivative and S-adenosyl-Lhomo-Cys (AdoHcy) as products. O-Methylation of flavonoids neutralizes th...

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“…3,4-Dihydroxybenzoic acid probably represents the hydrothermal degradation product of quercetin and is formed via a retrograde Allan–Robinson condensation mechanism. These types of fission reactions are common for 3-alkoxyflavone species (flavonoids) in strong alkaline media, which as a result form a 2-alkoxy-2′-hydroxyacetophenone and a benzoate (in our case 3,4-dihydroxybenzoic acid) . Due to the fact that at subcritical conditions the concentration of OH – ions is increased in this medium, the possibility of the mechanism to occur is quite high.…”

Section: Resultsmentioning

confidence: 91%

Hydrothermal Degradation of Rutin: Identification of Degradation Products and Kinetics Study

Ravber

Pečar

Goršek

et al. 2016

J. Agric. Food Chem.

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The model glycoside compound quercetin-3-O-rutinoside (rutin) was subjected to subcritical water within the temperature range of 120-220 °C, and the hydrothermal degradation products were analyzed. Two kinetic models describing the degradation of this compound in two different atmospheres (N and CO), used for pressure establishment in the reactor, have been developed and compared. Reaction was considered a successive one with three irreversible steps. We confirmed that rutin degradation to quercetin follows first-order kinetics. At higher temperatures quercetin is further degraded in two degradation steps. Formations of 3,4-dihydroxybenzoic acid and catechol were described with the zero-order kinetic models. Reaction rate constants for hydrolysis of glycoside to aglycone in a CO atmosphere are higher compared to those in a N atmosphere, whereas at higher temperatures reaction rate constants for further two successive reactions of aglycone degradation are slightly lower in the presence of CO. The difference in reaction activation energies is practically negligible for both gases. Furthermore, degradation products of sugar moieties, that is, 5-hydroxymethylfurfural and 5-methylfurfural, were also detected and analyzed.

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Flavonols

Cited by 11 publications

References 308 publications

The Creation and Physiological Relevance of Divergent Hydroxylation Patterns in the Flavonoid Pathway

The Creation and Physiological Relevance of Divergent Hydroxylation Patterns in the Flavonoid Pathway

Partial Purification, Kinetic Analysis, and Amino Acid Sequence Information of a Flavonol 3-O-Methyltransferase from Serratula tinctoria

Hydrothermal Degradation of Rutin: Identification of Degradation Products and Kinetics Study

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