Electrochemical reduction of dihydroquercetin on mercury electrode

The methods of classical and ac polarography were used to study the electrochemical behavior of dihydroquercetin on a mercury dropping electrode. This process occurs only in protonic media. The protonated and nonprotonated forms of dihydroquercetin undergo electroreduction. The amount of electrons and protons participating in electroreduction of the studied flavonoid is determined. The nature of currents measured in the processes of electrochemical reduction of dihydroquercetin is studied.     

dihydroquercetin in the reactions with phosphorous acid hexaethyltriamide

The possibility was demonstrated and conditions were developed of a directional phosphorylation of dihydroquercetin flavonoid with phosphorous hexaethyltriamide. The chemical properties of the obtained compounds of trivalent phosphorus are currently under investigation.     

Kinetics of the individual and joint oxidation of dihydroquercetin and potassium ferrocyanide in the presence of horseradish peroxidase

The study-state kinetics of individual and cooxidation of ferrocyanide and dihydroquercetin catalyzed by horseradish peroxidase is studied. It is shown that ferrocyanide and dihydroquercetin are slowly oxidized substrata peroxidase. In an interval of pH 4.5–8.0, sizes k _cat and K _m for these substrata peroxidase are certain. In reactions of cooxidation substrata, it was revealed that, at pH 4.5–7.0, dihydroquercetin accelerated oxidation ferrocyanide. At pH 7.5 oxidation only dihydroquercetin was observed. Mechanisms of reactions of combined oxidation ferrocyanide and dihydroquercetin are offered.     

A Stepwise one‐pot synthesis of aryl N‐phosphonamidothionate derivatives of nucleosides

Novel aryl N‐phosphonamidothionate derivatives of nucleosides as membrane‐soluble prodrugs of bioactive free nucleotides have been prepared by phosphochloridothioate chemistry. Unprotected nucleosides, for example uridine and adenosine, were used; phosphorylation took place selectively at the 5′‐position. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:62–66, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10080     

Catechol in acylation,phosphorylation, and aminomethylation reactions

The reactivity of dihydroquercetin and catechol flavonoids in acylation, phosphorylation, and aminomethylation reactions was compared. The structure of natural polyatomic phenols was shown to affect markedly their chemical behavior.     

Quantitative antioxidant activity of the ethylacetate extract of Larix sibirica bark and its individual components

The antioxidant [AO] properties of the ethylacetate extract of Larix sibirica bark and the flavonoids quercetin and dihydroquercetin found in it were studied using a model radical-chain oxidation of propan-2-ol in the kinetic regime. The quantitative characteristics of their AO activity were determined as effective rate constants fk_ln. It was found that dihydroquercetin had the highest AO activity among the studied natural compounds. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 131–133, March–April, 2006.     

Reaction of ω‐carbonyl substituted 1,3,3‐trimethyl‐2‐methyleneindolines with phosphorus(III) halides

The phosphorylation of N‐benzoyl‐2‐(1,3,3‐trimethyl‐2‐methyleneindoline)acetamide ( 2 ) and ω‐(3‐dimethylamino)benzoyl‐1,3,3‐trimethyl‐2‐methyleneindoline ( 6 ) with phosphorus(III) halides resulted in the formation of 2,3‐dihydro‐4H‐1,5,2‐oxazaphosphinin‐4‐one and 1,2‐dihydro‐3H‐phosphindol‐3‐one systems, respectively. The properties of the obtained compounds were studied. Further cyclization of 1,2‐dihydro‐3H‐phosphindol‐3‐one into dihydrophosphindolo[3,2‐c]pyrazole was carried out. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:23–28, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10060     

Studies on reactivity of ketosulfones

The cycloaddition of diazomethane, cyclocondensation of hydrazine hydrate, and cyclopropanation of TMSOI to 1‐aroyl‐2‐styrylsulfonylethenes were studied and different novel products thereby obtained were characterized with spectral parameters. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:155–159, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10117     

Silicon-titanium xerogels: Synthesis and application to the determination of ascorbic acid and polyphenoles

Titanium and silicon-titanium xerogels have been obtained and it has been demonstrated that titanium(IV) incorporated into the xerogel matrix can participate in complexation reactions with ascorbic, gallic, ferulic, and caffeic acids and also rutin, quercetin, and dihydroquercetin present in aqueous solutions. In the case of dihydroquercetin 1 min of contact has been sufficient for achieving the equilibrium; the other compounds required 7–10 min. The stability constants of titanium(IV) complexes incorporated into xerogels reduced in the order dihydroquercetin > gallic acid > ascorbic acid > quercetin > caffeic acid > rutin. The procedures have been developed for solid-phase spectrophotometric determination of ascorbic, gallic, ferulic, caffeic acid as well as rutin, quercetin, and dihydroquercetin. The accuracy of the procedure has been examined by the standard addition method. The procedures for the determination of dihydroquercetin and ascorbic acid have been applied to the analysis of pharmaceutical preparations.     

Reaction of Bioflavonoids with Copper(II) Acetate in Aqueous Solution

The reaction of dihydroquercetin, quercetin, and rutin with Cu(II) acetate in aqueous solution is studied. Quercetin and dihydroquercetin form complexes with Cu. The water-insoluble complexes are characterized as chelates of the 3,4-positions of the main -pyrone ring. Electronic spectroscopy showed the presence of stable polynuclear rutin complexes of composition rutin :Cu = 1:x, where x > 2.     

Cyclo[bis(1,7‐naphthylenedialkylamidophosphites)]

The possibility of regioselective cyclobisphosphorylation of nonsymmetrical bisphenols was shown for the 1,7‐dihydroxynaphthalene–phosphorous acid triamide system. The structure and essential chemical properties of the first nonsymmetrical phosphacyclophane were studied. New data demonstrating peculiar features of bisphenol diamidophosphites were obtained. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:404–412, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10143     

Magnetic molecularly imprinted specific solid‐phase extraction for determination of dihydroquercetin from Larix griffithiana using HPLC

The naturally occurring quercetin flavonoid, dihydroquercetin, is widely distributed in plant tissues and has a variety of biological activities. Herein, a magnetic molecularly imprinted solid‐phase extraction was tailor made for selective determination of dihydroquercetin in Larix griffithiana using high‐performance liquid chromatography. Amino‐functionalized core‐shell magnetic nanoparticles were prepared and characterized using scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometry, and infrared spectroscopy. The polymer had an average diameter of 250 ± 2.56 nm and exhibited good stability and adsorption for template molecule, which is enriched by hydrogen bonding interaction. Multiple factors for extraction, including loading, washing, elution solvents, and extraction time, were optimized. The limit of detection was 1.23 μg/g. The precision determined at various concentration of dihydroquercetin was less than 4% and the mean recovery was between 74.64 and 101.80%. It has therefore been shown that this protocol can be used as an alternative extraction to quantify dihydroquercetin in L. griffithiana and purify quercetin flavonoid from other complex matrices.     

Exhaustive acylation of dihydroquercetin

Reaction of dihydroquercetin with acid chlorides of higher and functionalized carboxylic acids was studied with the purpose of creation of new pharmaceuticals.     

Utility of a 2‐aminothiophene‐3‐carboxamide in the synthesis of thienopyridines and thienopyrimidines

2‐Amino‐4,5,6,7‐tetrahydrobenzo[b]‐ thiophene‐3‐carboxamide ( 1 ) was prepared according to Gewald procedure. Its reactivity toward a variety of chemical reagents was studied to give thienopyridines and ‐pyrimidines. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:459–467, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10179     

C‐phosphorylated pyrrolylcarbaldehydes

Application of N,N‐dimethylhydrazone protective group for synthesis of C‐phosphorylated aldehydes of the pyrrole series was studied. Removal of the hydrazone protection in monophosphorylated pyrrolylcarbaldehyde hydrazones occurs smoothly, while in biphosphorylated derivatives it results in nitrile formation. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:258–261, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10137     

Electrophilic Substitution in the Dihydroquercitin System. Aminomethylation

Treating dihydroquercetin with formaldehyde and amines under conditions of Mannich reaction provided mono- and diaminomethyl derivatives of dihydroquercetin.     

Complex polymer architectures through dimethoxymethyl 1,1‐diphenylethylene derivatives

The reactions of polystyryllithium and potassium on dimethoxymethyl 1,1‐diphenylethylene derivatives were studied in different solvents. In a polar medium, A₃ and A₆ star types were formed according to the stoichiometry, whereas in a nonpolar medium, hyperbranched structures were synthesized. Extensions of an already proposed mechanism in polar and nonpolar media were examined. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3329–3335, 2003     

Quantitative HPLC determination of main flavonoid content of <Emphasis Type="Italic">Rhododendron adamsii</Emphasis> leaves and stems

The content of main flavonoids from Rhododendron adamsii R. leaves and stems was determined quantitatively using HPLC. It was found that myricetin and quercetin dominated the identified compounds (myricetin, quercetin, dihydroquercetin, rutin) in leaves; dihydroquercetin, in stems (1.1, 1.0, and 2.5 mass% of raw material, respectively). Dihydroquercetin and rutin were found for the first time in R. adamsii. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 26–29, January–February, 2009.     

Study of sulfated derivatives of polyhydroxy compounds as inhibitors of blood coagulation

Persulfated derivatives of natural polyhydroxy compounds, such as lignans secoisolariciresinol, and isolariciresinol, flavonoid dihydroquercetin, and myo-inositol, have been synthesized. The ability of these compounds to inhibit the intrinsic pathway of blood coagulation (APTT-test) and to reduce the activity of coagulation factor Xa in the presence of antithrombin(III) has been studied.     

A study of sorption processes on a polyamide sorbent

Conclusions Using quercetin and dihydroquercetin as examples, it has been shown that the adsorption of flavonoids increases with a decrease in the polarity of the solvent and depends on the molecular weight of the polyamide sorbent. The presence of a double bond in quercetin leads to a higher sorption activity than the dihydroquercetin.Khimiya Prirodnykh Soedinenii, Vol. 4, No. 6, pp. 349–352, 1968