Structural basis for modification of flavonol and naphthol glucoconjugates by Nicotiana tabacum malonyltransferase (NtMaT1)

Plant HXXXD acyltransferase-catalyzed malonylation is an important modification reaction in elaborating the structural diversity of flavonoids and anthocyanins, and a universal adaptive mechanism to detoxify xenobiotics. Nicotiana tabacum malonyltransferase 1 (NtMaT1) is a member of anthocyanin acyltransferase subfamily that uses malonyl-CoA (MLC) as donor catalyzing transacylation in a range of flavonoid and naphthol glucosides. To gain insights into the molecular basis underlying its catalytic mechanism and versatile substrate specificity, we resolved the X-ray crystal structure of NtMaT1 to 3.1 Å resolution. The structure comprises two α/β mixed subdomains, as typically found in the HXXXD acyltransferases. The partial electron density map of malonyl-CoA allowed us to reliably dock the entire molecule into the solvent channel and subsequently define the binding sites for both donor and acceptor substrates. MLC bound to the NtMaT1 occupies one end of the long solvent channel between two subdomains. On superimposing and comparing the structure of NtMaT1 with that of an enzyme from anthocyanin acyltransferase subfamily from red chrysanthemum (Dm3Mat3) revealed large architectural variation in the binding sites, both for the acyl donor and for the acceptor, although their overall protein folds are structurally conserved. Consequently, the shape and the interactions of malonyl-CoA with the binding sites' amino acid residues differ substantially. These major local architectural disparities point to the independent, divergent evolution of plant HXXXD acyltransferases in different species. The structural flexibility of the enzyme and the amendable binding pattern of the substrates provide a basis for the evolution of the distinct, versatile substrate specificity of plant HXXXD acyltransferases.

Covalent anthocyanin-flavonol complexes from the violet-blue flowers of Allium 'Blue Perfume'

Three covalent anthocyanin-flavonol complexes (pigments 1-3) were extracted from the violet-blue flower of Allium 'Blue Perfume' with 5% acetic acid-MeOH solution, in which pigment 1 was the dominant pigment. These three pigments are based on delphinidin 3-glucoside as their deacylanthocyanin and were acylated with malonyl kaempferol 3-sophoroside-7-glucosiduronic acid or malonyl-kaempferol 3-p-coumaroyl-tetraglycoside-7-glucosiduronic acid in addition to acylation with acetic acid. By spectroscopic and chemical methods, the structures of these three pigments 1-3 were determined to be: pigment 1, (6(I)-O-(delphinidin 3-O-(3(I)-O-(acetyl)-β-glucopyranoside(I))))(2(VI)-O-(kaempferol 3-O-(2(II)-O-(3(III)-O-(β-glucopyranosyl(V))-β-glucopyranosyl(III))-4(II)-O-(trans-p-coumaroyl)-6(II)-O-(β-glucopyranosyl(IV))-β-glucopyranoside(II))-7-O-(β-glucosiduronic acid(VI)))) malonate; pigment 2, (6(I)-O-(delphinidin 3-O-(3(I)-O-(acetyl)-β-glucopyranoside(I))))(2(VI)-O-(kaempferol 3-O-(2(II)-O-β-glucopyranosyl(III))-β-glucopyranoside(II))-7-O-(β-glucosiduronic acid(VI)))); and pigment 3, (6(I)-O-(delphinidin 3-O-(3(I)-O-(acetyl)-β-glucopyranoside(I))))(2(VI)-O-(kaempferol 3-O-(2(II)-O-(3(III)-O-(β-glucopyranosyl(V))-β-glucopyranosyl(III))-4(II)-O-(cis-p-coumaroyl)-6(II)-O-(β-glucopyranosyl(IV))-β-glucopyranoside(II))-7-O-(β-glucosiduronic acid(VI)))) malonate. The structure of pigment 2 was analogous to that of a covalent anthocyanin-flavonol complex isolated from Allium schoenoprasum where delphinidin was observed in place of cyanidin. The three covalent anthocyanin-flavonol complexes (pigment 1-3) had a stable violet-blue color with three characteristic absorption maxima at 540, 547 and 618nm in pH 5-6 buffer solution. From circular dichroism measurement of pigment 1 in the pH 6.0 buffer solution, cotton effects were observed at 533 (+), 604 (-) and 638 (-) nm. Based on these results, these covalent anthocyanin-flavonol complexes were presumed to maintain a stable intramolecular association between delphinidin and kaempferol units closely related to that observed between anthocyanin and hydroxycinnamic acid residues in polyacylated anthocyanins. Additionally, an acylated kaempferol glycoside (pigment 4) was isolated from the same flower extract, and its structure was determined to be kaempferol 3-O-sophoroside-7-O-(3-O-(malonyl)-β-glucopyranosiduronic acid).

Structurally different flavonol glycosides and hydroxycinnamic acid derivatives respond differently to moderate UV-B radiation exposure

The aim of this study was to investigate the modifying influence of moderate ultraviolet-B (UV-B) radiation exposure on structurally different flavonol glycosides and hydroxycinnamic acid derivatives during pre-harvest using kale, a leafy Brassica species with a wide spectrum of different non-acylated and acylated flavonol glycosides. Juvenile kale plants were treated with short-term (1 day), moderate UV-B radiation [0.22-0.88 kJ m⁻² day⁻¹ biologically effective UV-B (UV-B(BE))]. Twenty compounds were quantified, revealing a structure-specific response of flavonol glycosides and hydroxycinnamic acid derivatives to UV-B radiation. A dose- and structure-dependent response of the investigated phenolic compounds to additional UV-B radiation was found. The investigated quercetin glycosides decreased under UV-B; for kaempferol glycosides, however, the amount of sugar moieties and the flavonol glycoside hydoxycinnamic acid residue influenced the response to UV-B. Monoacylated kaempferol tetraglucosides decreased in the investigated UV-B range, whereas the monoacylated kaempferol diglucosides increased strongly with doses of 0.88 kJ m⁻² day⁻¹ UV-B(BE) . The UV-B-induced increase in monoacylated kaempferol triglucosides was dependent on the acylation pattern. Furthermore, the hydroxycinnamic acid glycosides disinapoyl-gentiobiose and sinapoyl-feruloyl-gentiobiose were enhanced in a dose-dependent manner under UV-B. While UV-B radiation treatments often focus on flavonol aglycones or total flavonols, our investigations were extended to structurally different non-acylated and acylated glycosides of quercetin and kaempferol.

F···HO intramolecular hydrogen bond as the main transmission mechanism for (1h)J(F,H(O)) coupling constant in 2'-fluoroflavonol

Flavonoids are useful compounds in medicinal chemistry and exhibit conformational isomerism, which is ruled by intramolecular interactions. One of the main intramolecular forces governing the stability of conformations is the hydrogen bond. Hydrogen bond involving fluorine covalently bonded to carbon has been found to be rare, but it appears in 2'-fluoroflavonol, although the F···HO hydrogen bond cannot be considered the main effect governing the conformational stability of this compound. Because (19)F is magnetically active and suitable for NMR studies, the (1h)J(F,H(O)) coupling constant can be used as a probe for such an interaction in 2'-fluoroflavonol. In fact, the (1h)J(F,H(O)) coupling was computationally analyzed in this work, and the F···HO hydrogen bond was found to be its main transmission mechanism, which modulates this coupling in 2'-fluoroflavonol, rather than overlap of proximate electronic clouds, such as in 2-fluorophenol.

3-Hydroxy-3-methylglutaryl flavonol glycosides from Oxytropis falcata

Five new 3-hydroxy-3-methylglutaryl (HMG) flavonol 3-O-glycosides, named oxytroflavosides A-E (1-5), and two new rhamnocitrin 3-O-glycosides, oxytroflavosides F and G (6 and 7) were isolated from the n-BuOH-soluble fraction of an EtOH extract of Oxytropis falcata together with seven known kaempferol glycosides (8-14), of which six were isolated from the genus Oxytropis for the first time. The structures of these compounds were elucidated by spectroscopic techniques and chemical methods. The absolute configuration of HMG in compounds 1-5 was determined to be S through spectroscopic analysis of the mevalonamide obtained by amidation and reduction of the HMG moiety. Compounds 1-10 were evaluated for anti-inflammatory activities using lipopolysaccharide-induced RAW 264.7 cells, but none of them showed inhibitory effects on NO production.

Binding of dihydromyricetin to human hemoglobin: fluorescence and circular dichroism studies

The binding reaction between dihydromyricetin (DMY) and human hemoglobin (HHb) was investigated systematically with various spectroscopic methods including fluorescence quenching technique, ultraviolet (UV)-vis absorption, synchronous fluorescence, circular dichroism (CD) spectroscopy. The experimental results showed that DMY effectively quenched the intrinsic fluorescence of HHb via static quenching. DMY binds to HHb with a stoichiometry that varies from 0.972:1 to 0.906:1 as the temperature increases from 296 to 304 K. The DMY-HHb binding constants were determined to be K(296)=2.79 × 10(4) and K(304)=1.18 × 10(4) Lmol(-1). The reaction is characterized by negative enthalpy (ΔH=-80.46 kJ mol(-1)) and negative entropy (ΔS=-186.72 kJ mol(-1)), indicating that the predominant forces in the DMY-HHb complex are van der Waals and hydrogen bonding forces. Based on the Förster's theory of non-radiative energy transfer, the binding distance between DMY and the inner tryptophan residues of HHb was determined to be 3.15 nm. Furthermore, the CD spectroscopy indicated the secondary structure of HHb is not changed in the presence of DMY.

A new acylated flavonol glycoside from the aerial parts of Cardamine tangutorum

A new acylated flavonol glycoside, kaempferol-3-O-β-D-(2-feruloylglucopyranosyl) (1 → 6)-[β-D-glucopyranosyl(1 → 2)]-β-D-glucopyranoside, named tangutorumoside A (1), together with 12 known compounds, was isolated from 50% acetone extract of Cardamine tangutorum. Their structures were elucidated by NMR and MS experiments. In addition, compound 1 could promote the proliferation of splenic lymphocytes and thymic lymphocytes with ConA in vitro.

Study of the mass spectrometric behaviors of anthocyanins in negative ionization mode and its applications for characterization of anthocyanins and non-anthocyanin polyphenols

RATIONALE

Traditionally, anthocyanin analysis in mass spectrometry is carried out in the positive ionization mode only. A study of the mass spectrometric behaviors of anthocyanins in the negative ionization mode revealed interesting characteristics that was not previously reported. It can be used to differentiate anthocyanins from other non-anthocyanin polyphenols.

METHODS

An ultra-high-performance liquid chromatography with high-resolution mass spectrometry (U-HPLC/HRMS) method was developed. The method used multiple-stage mass fragmentation in both the negative and positive ion modes. The whole cycle time of the new method is 1.8 s for two full scans and six data-dependent scans.

RESULTS

The new strategy found, in the negative ionization mode, a series of characteristic ions, e.g. [M-2H](-), [M-2H  +  H(2)O](-), formic acid adducts, and doubly charged ions were observed for the MS analysis of anthocyanins. The characteristic ions can be used for identification and differentiation of anthocyanins and non-anthocyanin phenolic compounds. Comprehensive studies were performed on the differentiation of anthocyanins and non-anthocyanin polyphenols in blueberry (Vaccinium cyanococcus), Hongcaitai (Brassica compestris L. var. purpurea Bailey), and red radish (Raphanus sativus var. longipinnatus 'Shinrimei').

CONCLUSIONS

The data generated from a single LC run enables rapid and reliable differentiation and identification of anthocyanins and non-anthocyanins in botanicals and foods. Published 2012. This article is a US Government work and is in the public domain in the USA.

On the bioavailability of flavanols and anthocyanins: flavanol-anthocyanin dimers

The bioavailability of flavanols, anthocyanins and anthocyanin-derived pigments like flavanol-anthocyanin dimers already reported to occur in food products is a major unsolved issue. The absorption of the flavanol-anthocyanin dimer (+)-catechin-(4,8)-malvidin-3-O-glucoside (Cat-Mv3glc) through Caco-2 cells was assessed by performing transepithelial transport assays. The ability of Cat-Mv3glc to cross Caco-2 cells was compared with that of malvidin-3-glucoside (Mv3glc), (+)-catechin (Cat) and procyanidin B3 (Cat-Cat), in order to evaluate the influence of some structural features on the transport efficiency. The flavanol-anthocyanin dimer was absorbed in this intestinal model although with a lower efficiency than the monomers Cat and Mv3glc. On the other hand, Cat-Mv3glc was found to cross the intestinal barrier model more significantly than Cat-Cat. This feature may be related to the presence of the glucose moiety in its structure. Overall, this study brings more insights into the bioavailability of anthocyanins and flavanols and represents the first report on the bioavailability of flavanol-anthocyanins.

Relationship between the composition of flavonoids and flower colors variation in tropical water lily (Nymphaea) cultivars

Water lily, the member of the Nymphaeaceae family, is the symbol of Buddhism and Brahmanism in India. Despite its limited researches on flower color variations and formation mechanism, water lily has background of blue flowers and displays an exceptionally wide diversity of flower colors from purple, red, blue to yellow, in nature. In this study, 34 flavonoids were identified among 35 tropical cultivars by high-performance liquid chromatography (HPLC) with photodiode array detection (DAD) and electrospray ionization mass spectrometry (ESI-MS). Among them, four anthocyanins: delphinidin 3-O-rhamnosyl-5-O-galactoside (Dp3Rh5Ga), delphinidin 3-O-(2"-O-galloyl-6"-O-oxalyl-rhamnoside) (Dp3galloyl-oxalylRh), delphinidin 3-O-(6"-O-acetyl-β-glucopyranoside) (Dp3acetylG) and cyanidin 3- O-(2"-O-galloyl-galactopyranoside)-5-O-rhamnoside (Cy3galloylGa5Rh), one chalcone: chalcononaringenin 2'-O-galactoside (Chal2'Ga) and twelve flavonols: myricetin 7-O-rhamnosyl-(1 → 2)-rhamnoside (My7RhRh), quercetin 7-O-galactosyl-(1 → 2)-rhamnoside (Qu7GaRh), quercetin 7-O-galactoside (Qu7Ga), kaempferol 7-O-galactosyl-(1 → 2)-rhamnoside (Km7GaRh), myricetin 3-O-galactoside (My3Ga), kaempferol 7-O-galloylgalactosyl-(1 → 2)-rhamnoside (Km7galloylGaRh), myricetin 3-O-galloylrhamnoside (My3galloylRh), kaempferol 3-O-galactoside (Km3Ga), isorhamnetin 7-O-galactoside (Is7Ga), isorhamnetin 7-O-xyloside (Is7Xy), kaempferol 3-O-(3"-acetylrhamnoside) (Km3-3"acetylRh) and quercetin 3-O-acetylgalactoside (Qu3acetylGa) were identified in the petals of tropic water lily for the first time. Meanwhile a multivariate analysis was used to explore the relationship between pigments and flower color. By comparing, the cultivars which were detected delphinidin 3-galactoside (Dp3Ga) presented amaranth, and detected delphinidin 3'-galactoside (Dp3'Ga) presented blue. However, the derivatives of delphinidin and cyanidin were more complicated in red group. No anthocyanins were detected within white and yellow group. At the same time a possible flavonoid biosynthesis pathway of tropical water lily was presumed putatively. These studies will help to elucidate the evolution mechanism on the formation of flower colors and provide theoretical basis for outcross breeding and developing health care products from this plant.

Phenolic composition of Tempranillo wines following early defoliation of the vines

BACKGROUND

Early defoliation is a viticultural practice aimed at crop control. So far, the impact of early leaf removal on the monomeric phenolic composition of wines has not been explored. This study examines the effects of early defoliation on the phenolic profile and content in Tempranillo wines. The influence of the defoliation method (manual vs mechanical) and the timing of leaf removal (pre-bloom vs fruit set) was investigated.

RESULTS

Over two consecutive seasons, 2007 and 2008, the monomeric phenolic composition in Tempranillo wines was studied by high-performance liquid chromatography with photodiode array detection, and 22 compounds were identified and quantified. Overall, early defoliation led to wines more intensely coloured, of higher alcohol content and with larger concentrations of hydroxycinnamic acids, flavonols and anthocyanins (in 2008 only for mechanical treatments). In the absence of fungal infection, resveratrol was found to increase in wines corresponding to early defoliation treatments. The method of leaf removal seemed to be more critical than the timing of intervention, and larger effects on wine phenolic composition were observed for mechanical treatments.

CONCLUSION

Early defoliation proved to be an effective technique for improving the phenolic composition of Tempranillo wines, by favouring the accumulation of hydroxycinnamics, flavonols and anthocyanins. This is an important achievement, as wine quality is often described by its colour and phenolic attributes.

Spectaflavoside A, a new potent iron chelating dimeric flavonol glycoside from the rhizomes of Zingiber spectabile Griff

The rhizomes of Zingiber spectabile yielded a new dimeric flavonol glycoside for which the name kaempferol-3-O-(4″-O-acetyl)-α-L-rhamnopyranoside-(I-6,II-8)-kaempferol-3-O-(4″-O-acetyl)-α-L-rhamnopyranoside; spectaflavoside A (1) was proposed, along with kaempferol and its four acetylrhamnosides (2-6), demethoxycurcumin (7) and curcumin (8). The structure of spectaflavoside A was elucidated by spectroscopic methods including, 1D and 2D NMR techniques. This is the first report on the occurrence of a dimeric flavonol glycoside in the Zingiberaceae and the second in nature. Spectaflavoside A was found to be a potent iron chelating agent.

Development of HPLC fingerprint for species differentiation and quality assessment of Rhizoma Smilacis Glabrae

Rhizoma Smilacis Glabrae (RSG) is a commonly used herbal material in functional food and Traditional Chinese Medicine. A HPLC chromatographic fingerprint was developed for its quality control and species differentiation. Nine peaks were found in the chromatogram of RSG and all these peaks were identified by diode array detection and electrospray ionization-MS/MS: 5-O-caffeoylshikimic acid, taxifolin, engeletin, isoengeletin, trans-resveratrol, astilbin and its three stereoisomers. Six of these constituents were consistently found in 18 batches of samples. The standard fingerprint of RSG was generated by mean simulation of all tested samples. Using the standard fingerprint, RSG could be easily differentiated from Rhizoma Smilacis Chinae and Rhizoma Heterosmilacis, the two species that can be confused with RSG.

Quantitation of the hydroxycinnamic acid derivatives and the glycosides of flavonols and flavones by UV absorbance after identification by LC-MS

A general approach was developed to quantify hydroxycinnamic acid derivatives and the glycosides of flavonols and flavones using UV molar relative response factors (MRRFs). More than 90 standards were analyzed by LC-MS and divided into five groups based on the λ(max) of their band I absorbance profiles. For each group, a commercially available standard was chosen as the group reference standard. Response factors were determined for each standard in each group as purchased (MRRF) and, when possible, after vacuum drying (MRRF(D)). The MRRF(D) values for 17 compounds whose λ(max) values fell within ±2 nm of the group reference standard were 1.01 ± 0.03. MRRF values for compounds whose λ(max) values fell within ±10 nm of the group reference standard were 0.96 ± 0.13. Group reference standards were used to quantify 44 compounds in Chinese lettuce, red onion, and white tea. This approach allows quantitation of numerous compounds for which there are no standards.

Chemical constituents of Bauhinia aurea

A new dihydroflavonol glycoside dimer 6,6-bisastilbin (1) and a new nitrile-containing metabolite (Z)-5α,6β-dihydroxy-4β-methoxy-2-cyclohexene-Δ(1,α)-acetonitrile (2), together with three known analogs, bauhinin, bauhinilide, and dehydrodicatechin A, have been isolated from an ethanol extract of Bauhinia aurea. Their structures were determined by spectroscopic and chemical methods.

Characterization of flavonol glycosides in individual Arabidopsis root tips by flow injection electrospray mass spectrometry

Developments in mass spectrometry-based technologies are offering insights into the complexity and dynamic nature of plant metabolism. However, the ability to generate reliable metabolic profiles at high spatial resolution is still limited by the need of most technologies for large sample sizes or time-intensive extraction and detection methods. Here we describe the use of flow injection electrospray mass spectrometry for the rapid identification and semi-quantitative analysis of flavonol glycosides in individual root tips. This method uncovered spatial and temporal differences in metabolic profiles that were masked in analyses of whole roots or seedlings, while showing that individual biological replicates can be extremely consistent.

Investigations into the phenolic constituents of dog's mercury (Mercurialis perennis L.) by LC-MS/MS and GC-MS analyses

INTRODUCTION

Dog's mercury (Mercurialis perennis L.) is a traditional European medicinal plant considered as a rich source of bioactive natural products. Yet phytochemical data of the plant are scant.

OBJECTIVE

This study aimed to identify the hydrophilic phenolic constituents from M. perennis by aqueous and hydroalcoholic extraction.

METHODOLOGY

Extracts of herbal parts were investigated in-depth by HPLC(DAD)-MS/MS and GC/MS analyses. In addition, a novel compound was isolated and fully characterised by 1- and 2D-NMR experiments.

RESULTS

Several conjugates of caffeic, p-coumaric and ferulic acids together with glucaric or 2-hydroxyglutaric acids (depsides) were detected in the aqueous extracts from aerial plant parts by use of LC-MS/MS techniques as well UV-spectral data. By implementation of preparative chromatography on polyamide pretreated with formic acid followed by vacuum liquid chromatography on reversed-phase C(18) -silica, one of the predominant depsides was isolated as a pure compound. The NMR spectra ((1) H and (13) C NMR) together with 2D-hetereonuclear multiple bond correlation NMR experiments (gHMBC and gHSQC) and chiral GC investigation, allowed identification of this compound as (-)-(E)-caffeoyl-2-(R)-oxoglutarate. This structure was additionally supported by GC/MS data after silylation and methylation reactions. The hydroalcoholic extract from aerial parts was separated by solvent partition between ethyl acetate and n-butanol. The latter fraction (n-butanol) yielded a mixture of mono- and oligo-glycosides of kaempferol and quercetin, all of them being assigned by LC-MS/MS.

CONCLUSIONS

The present investigation constitutes the first comprehensive report on the hydrophilic constituents of the rarely studied plant Mercurialis and thus completes the phytochemical knowledge on M. perennis.

Collision-induced dissociation of 40 flavonoid aglycones and differentiation of the common flavonoid subtypes using electrospray ionization ion-trap tandem mass spectrometry and quadrupole time-of-flight mass spectrometry

Much Literature is available with respect to the collision-induced dissociation (CID) of different subtypes of flavonoid aglycones. However, a simultaneous comparison study of the common flavonoid subtypes under unified conditions is rarely reported, which is of crucial significance for their rapid structural elucidation. This study depicted the negative CID of 40 free flavonoids (comprising nine different subtypes) utilizing electrospray ionization ion-trap tandem mass spectrometry (ESI-IT-MSn). High-accuracy quadrupole time-of-flight mass spectrometry was employed to confirm the chemical formula of proposed key fragments. Specific fragmentation features were discovered among different flavonoid subtypes in terms of the essential collision energy, base peak, RDA fragmentation, and diversity of fragmentation pathways: CID of flavanones, chalcones and flavanonols was in need of lower Levels of collision energy [<40%) and exhibited simplified fragmentation pathways; overriding neutral loss of CO2 was detected for flavones, aurones and xanthones, while isoflavones preferred neutral loss of CO; 1,2A- and 1,3A- fragments were respectively dominant for flavonols and flavanones/chalcones, white homoisoflavones underwent specific radical elimination of ring B or methylene-ring B. These differentiated fragmentation characteristics integrating UV absorption resulted in the establishment of a decision tree to characterize and distinguish the common flavonoid subtypes. This study firstly revealed remarkable differentiations in the negative CID behavior of nine common flavonoid aglycone subtypes and the proposed determination strategy would much benefit the screening and rapid characterization of flavonoids from complicated matrixes by tandem mass spectrometry.

Catalytic inhibition of eukaryotic topoisomerases I and II by flavonol glycosides extracted from Vicia faba and Lotus edulis

Topoisomerases are essential enzymes involved in all processes of DNA metabolism, and their inhibitors have been identified as potential anticancer agents. The present study examined the effect of nine polyphenolic compounds derived from parts of two unique varieties of the Leguminosae, Vicia faba and Lotus edulis, on the activity of eukaryotic topoisomerases. We identified polyphenolic compounds that act as catalytic inhibitors of wheat germ topoisomerase I (IC50: 120-350 μM), human topoisomerase I (IC50: 110-260 μM), and human topoisomerase II (IC50: 240-600 μM) activities. Some compounds inhibited all enzymatic activities to a similar extent, while others exhibited specificity toward individual enzymes. The strongest catalytic inhibitor of all the examined enzymes was a kaempherol glycoside with an acetyl group linked to a sugar moiety. In addition, this compound inhibited the growth of human cancer cell lines MCF7, HeLa, and HepG2. The inhibition of topoisomerase I and II activities observed by the specific compounds possibly implies a role as potential agents in the prevention and therapy of cancer.

Astilbin attenuates hyperuricemia and ameliorates nephropathy in fructose-induced hyperuricemic rats

Astilbin is a flavonoid compound isolated from the rhizome of Smilax china L. The effects and possible mechanisms of astilbin on hyperuricemia and nephropathy rats were elucidated in this study. Different dosages of astilbin (1.25, 2.5, and 5.0 mg/kg) were administered to 10 % fructose-induced hyperuricemic rats. The results demonstrated that astilbin significantly decreased the serum uric acid (Sur) level by increasing the urinary uric acid (Uur) level and fractional excretion of urate (FEUA) but not inhibiting the xanthine oxidase (XOD) activity. In addition, kidney function parameters such as serum creatinine (Scr) and blood urea nitrogen (BUN) were recovered in astilbin-treated hyperuricemic rats. Further investigation indicated that astilbin prevented the renal damage against the expression of transforming growth factor- β1 (TGF-β1) and connective tissue growth factor (CTGF) and also exerted a renal protective role by inhibiting formation of monosodium urate (MSU) and production of prostaglandin E₂ (PGE₂) and interleukin-1 (IL-1). These findings provide potent evidence for astilbin as a safe and promising lead compound in the development of a disease-modifying drug to prevent hyperuricemia and nephropathy.

A new flavonol glucoside from the aerial parts of Sida glutinosa

Phytochemical investigation on the dried aerial parts of Sida glutinosa has led to the isolation of a new flavonol glucoside, glutinoside (1), along with seven known compounds, 24(28)-dehydromakisterone A (2), 1,2,3,9-tetrahydropyrrolo[2,1-b]-quinazolin-3-amine (3), docosanoic acid, 1-triacontanol, campesterol, stigmasterol, and β-sitosterol. The structures of these compounds were elucidated by means of extensive spectroscopic techniques as well as GC/MS analysis (for sterols) and comparison with the literature data. All these seven known compounds are reported from this plant for the first time.

Identification of 2″-galloylated flavonol 3-o-glycosides accumulating in developing leaves of persimmon

INTRODUCTION

Dried leaves of persimmon, traditionally consumed as a herbal tea in Japan, contain bioactive galloylated flavonol glycosides. Investigation of the seasonal compositional changes in these compounds is important for determining the optimum harvest time.

OBJECTIVE

The three objectives were: (1) to elucidate the compositional changes of the flavonol glycosides in persimmon leaves collected in different seasons; (2) to develop an efficient method for separation of the constituents; and (3) to compare their antioxidant activities.

METHODOLOGY

Fresh persimmon leaves were collected at different growth stages in 2007 and 2008 in Niigata, Japan. Total flavonols were extracted with 70% aqueous acetone followed by ethyl acetate partitioning, and were analysed by high-performance liquid chromatography. Enzymatic transformation and chromatographic fractionation was performed to isolate the individual flavonols. Two antioxidant assays were performed.

RESULTS

Four nongalloylated flavonol glycosides were detected at the leaf-shooting stage, and four additional galloylated flavonol glycosides accumulated during leaf development, resulting in a total of eight constituents. Isolation of nongalloylated and galloylated constituents was successfully achieved through enzymatic transformation of the flavonol mixture using combinations of tannase, β-glucosidase and β-galactosidase, followed by chromatographic fractionation. The gallates were identified as regiospecific 2″-galloylated galactosides and glucosides of kaempferol and quercetin. A mixture of 2″-galloylated flavonol glycosides had a two-fold stronger antioxidant activity than the nongalloylated mixture.

CONCLUSION

This study showed that four 2″-galloylated flavonol glycosides had accumulated in developing leaves of persimmon by the end of May through a rapid 2″-galloylation of the corresponding nongalloylated flavonol glycosides.

Irisdichotins A-C, three new flavonoid glycosides from the rhizomes of Iris dichotoma Pall

Three new compounds including one flavonol glycoside, irisdichotin A (1), and two flavanonol glycosides, irisdichotins B (2) and C (3), were isolated from the rhizomes of Iris dichotoma Pall. Their structures were elucidated on the basis of spectroscopic methods.

Asymmetric total syntheses of (-)-variabilin and (-)-glycinol

Total syntheses of (-)-variabilin and (-)-glycinol have been accomplished, using the catalytic, asymmetric "interrupted" Feist-Bénary reaction (IFB) as the key transformation to introduce both stereogenic centers. A monoquinidine pyrimidinyl ether catalyst affords the IFB products in over 90% ee in both cases. Other key steps include an intramolecular Buchwald-Hartwig coupling and a nickel-catalyzed aryl tosylate reduction.

Herbal medicines and infectious diseases: characterization by LC-SPE-NMR of some medicinal plant extracts used against malaria

The extracts of two medicinal plants used in traditionalmedicine against malariawere characterized by means of an LC‑SPE‑NMR and LC‑MS platform. The structure of a series of major constituents from Bafodeya benna, as well as minor constituents from Ormocarpum kirkii, was determined. Bafodeya benna was found to contain (2R,3R)-taxifolin-3-O-α-L-rhamnoside or astilbin, and its isomers neoastilbin, neoisoastilbin, and isoastilbin, as well as quercetin-3-O-α-L-rhamnoside. From Ormocarpum kirkii, a series of known flavonoids and biflavonoids was obtained, as well as three new compounds, i.e., 7,7′′-di-O-β-D-glucosyl-(−)-chamaejasmin, 7-O-β-D-glucosyl-(I-3,II-3)-biliquiritigenin, and isovitexin-(I-3,II-3)-naringenin. The isolated constituents may explain, at least in part, the traditional use against malaria. LC‑SPE‑NMR, in combination with LC‑MS, is a powerful tool for the fast characterization of plant extracts, in order to define priorities at an early stage of a fractionation procedure. In addition, herbal medicinal products can completely be characterized, both with regard to their major as well as their minor constituents.

Phenolic profile and antioxidant capacity of chickpeas (Cicer arietinum L.) as affected by a dehydration process

This study presents the effects of soaking, cooking and industrial dehydration on the phenolic profile, and antioxidant capacity in two chickpea varieties (Sinaloa and Castellano). Chromatographic analysis identified a total of 24 phenolic components, being isoflavones the main phenolics in raw and processed Sinaloa and Castellano flours. The impact of the industrial dehydration was different depending on the chickpea variety. Although Castellano chickpea exhibited the highest levels of phenolic compounds (103.1 μg/g), significant reductions were observed during processing; in contrast, the dehydration did not cause any further effects in Sinaloa flours. Interestingly, Sinaloa variety showed high thermal stability of isoflavones during processing. As expected, the levels of antioxidant capacity were in accordance with the behavior of phenolic compounds exhibiting noticeable reductions in Castellano chickpea and not relevant changes in Sinaloa chickpea. Thus, the significant occurrence of bioactive phenolic compounds along with the relevant antioxidant capacities of dehydrated chickpea flours make them to be considered functional ingredients for their beneficial health effects, especially in case of Sinaloa.

Isolation and characterization of two flavonoids, engeletin and astilbin, from the leaves of Engelhardia roxburghiana and their potential anti-inflammatory properties

Engeletin, a flavonoid compound, was isolated from the leaves of Engelhardia roxburghiana for the first time, along with astilbin, another flavonoid. The chemical structures of engeletin and astilbin were confirmed by (1)H and (13)C nuclear magnetic resonance (NMR) and mass spectrometry (MS) spectra, and their anti-inflammatory activities were studied in lipopolysaccharide (LPS)-stimulated mouse J774A.1 macrophage cells. LPS induced the inflammatory state in macrophage cells and increased mRNA expressions of pro-inflammatory cytokines. Engeletin and astilbin exhibited remarkable inhibitory effects on interleukin (IL)-1β and IL-6 mRNA expression. Significant inhibition of LPS-mediated mRNA expressions were also seen in LPS binding toll-like receptor (TLR)-4, pro-inflammatory cytokine tumor necrosis factor (TNF)-α, IL-10, chemoattractant monocyte chemotactic protein (MCP)-1, and cyclooxygenase (COX)-2 genes. The reduced expression of these cytokines may alleviate immune response and reduce inflammatory activation, indicating that engeletin and astilbin may serve as potential anti-inflammatory agents.

[Studies on the chemical constituents of the herb of Antenoron filiforme]

OBJECTIVE

To study the chemical constituents of the herb of Antenoron filiforme.

METHODS

The constituents were separated by column chromatography and their structures were elucidated by spectral data analyses.

RESULTS

Eleven compounds were isolated from the ethanol extract of A. filiforme and identified as, bronane-5-hydroxy-2-O-beta-D-glucopyranoside (I), adenosine (II), bonaroside (III), rhamnetin (IV), hyperoside (V), rhamnetin-3-O-beta-D-galactopyranoside (VI), kaempferol-3, 7-O-bis-alpha-L-rhamnopyranoside (VII), stigmasterol (VIII), nonacosanoic acid (IX), daucosterol (X), 3beta-sitosterol (XI).

CONCLUSION

All compounds are obtained from A. filiforme for the first time.

[Studies on the chemical constituents from the flowers of Ophiopogon japonicus]

OBJECTIVE

To study the chemical constituents from the flowers of Ophiopogon japonicus.

METHODS

Column chromatography and spectral analysis were used to isolate and identify the constituents.

RESULTS

Eleven compounds were obtained and identified as beta-sitosterol (I), diosgenin (II), daucosterol (III), ophiopogonin C' (IV), dioscin (V), 7-dihy-droxy-6-methyl-3-(4'-hydroxybenzyl) chroman-4-one(VI), luteolin (VII), kaempferol-3-O-beta-D-glucopyranosides (VIII), kaempferol-3-O-(6"-tigloyl) -beta-D-glucopyranosides (IX), kaempferol-3-O-(6"-acetyl) -beta-D-glucopyranosides (X), glucose (XI).

CONCLUSION

Eleven compounds are obtained from the flowers of O. japonicus for the first time. Compond VI is isolated as a simple substance compound of O. japonicus for the first time. Componds VII, VIII, IX and X are isolated from this genus for the first time.

Acylated flavonol glycosides from the forage legume, Onobrychis viciifolia (sainfoin)

Ten acylated flavonol glycosides were isolated from aqueous acetone extracts of the aerial parts of the forage legume, Onobrychis viciifolia, and their structures determined using spectroscopic methods. Among these were eight previously unreported examples which comprised either feruloylated or sinapoylated derivatives of 3-O-di- and 3-O-triglycosides of kaempferol (3,5,7,4'-tetrahydroxyflavone) or quercetin (3,5,7,3',4'-pentahydroxyflavone). The diglycosides were acylated at the primary Glc residue of O-α-Rhap(1→6)-β-Glcp (rutinose), whereas the triglycosides were acylated at the terminal Rha residues of the branched trisaccharides, O-α-Rhap(1→2)[α-Rhap(1→6)]-β-Galp or O-α-Rhap(1→2)[α-Rhap(1→6)]-β-Glcp. Identification of the primary 3-O-linked hexose residues as either Gal or Glc was carried out by negative ion electrospray and serial MS, and cryoprobe NMR spectroscopy. Analysis of UV and MS spectra of the acylated flavonol glycosides provided additional diagnostic features relevant to direct characterisation of these compounds in hyphenated analyses. Quantitative analysis of the acylated flavonol glycosides present in different aerial parts of sainfoin revealed that the highest concentrations were in mature leaflets.

Acylated flavonol tri- and tetraglycosides in the flavonoid metabolome of Cladrastis kentukea (Leguminosae)

The foliar metabolome of Cladrastis kentukea (Leguminosae) contains a complex mixture of flavonoids including acylated derivatives of the 3-O-rhamnosyl(1→2)[rhamnosyl(1→6)]-galactosides of kaempferol and quercetin and their 7-O-rhamnosides, together with an array of non-acylated kaempferol and quercetin di-, tri- and tetraglycosides. Thirteen of the acylated flavonoids, 12 of which had not been reported previously, were characterised by spectroscopic and chemical methods. Eight of these were the four isomers of kaempferol 3-O-α-l-rhamnopyranosyl(1→2)[α-l-rhamnopyranosyl(1→6)]-(3/4-O-E/Z-p-coumaroyl-β-d-galactopyranoside) and their 7-O-α-l-rhamnopyranosides, and three were isomers of quercetin 3-O-α-l-rhamnopyranosyl(1→2)[α-l-rhamnopyranosyl(1→6)]-(3/4-O-E/Z-p-coumaroyl-β-d-galactopyranoside) - the remaining 4Z isomer was identified by LC-UV-MS analysis of a crude extract. The final two acylated flavonoids characterised by NMR were the 3E and 4E isomers of kaempferol 3-O-α-l-rhamnopyranosyl(1→2)[α-l-rhamnopyranosyl(1→6)]-(3/4-O-E-feruloyl-β-d-galactopyranoside)-7-O-α-l-rhamnopyranoside while the 3Z and 4Z isomers were again detected by LC-UV-MS. Using the observed fragmentation behaviour of the isolated compounds following a variety of MS experiments, a further 18 acylated flavonoids were given tentative structures by LC-MS analysis of a crude extract. Acylated flavonoids were absent from the flowers of C. kentukea, which contained an array of non-acylated kaempferol and quercetin glycosides. Immature fruits contained kaempferol 3-O-α-rhamnopyranosyl(1→2)[α-rhamnopyranosyl(1→6)]-β-galactopyranoside and its 7-O-α-rhamnopyranoside as the major flavonoids with acylated flavonoids, different from those in the leaves, only present as minor constituents. The presence of acylated flavonoids distinguishes the foliar flavonoid metabolome of C. kentukea from that of a closely related legume, Styphnolobium japonicum, which contains a similar range of non-acylated flavonoids.

Isolation and purification of series bioactive components from Hypericum perforatum L. by counter-current chromatography

Counter-current chromatography (CCC) combined with pre-separation by ultrasonic solvent extraction was successively used for the separation of series bioactive compounds from the crude extract of Hypericum perforatum L. The petroleum ether extract was separated by the solvent system of n-heptane-methanol-acetonitrile (1.5:0.5:0.5, v/v) and n-heptane-methanol (1.5:1, v/v) in gradient elution, yielding a phloroglucinol compound, hyperforin with HPLC purity over 98%. The ethyl acetate extract was separated by using the solvent system composed of hexane-ethyl acetate-methanol-water (1:1:1:1 and 1:3:1:3, v/v) in gradient through both reverse phase and normal phase elution mode, yielding a naphthodianthrone compound, hypericin with HPLC purity about 95%. The n-butanol extract was separated with the solvent system composed of n-butanol-ethyl acetate-water (1:4:5 and 1.5:3.5:5, v/v) in elution and back-extrusion mode, yielding two of flavones, rutin and hyperoside, with HPLC purity over 95%. HPLC-MS, reference sample and UV spectrum were selectively used in separation to search for target compounds from HPLC-DAD profiles of different sub-extracts. The structures of isolated compounds were further identified by ESI-MS, ¹HNMR and ¹³CNMR.

Separation of patuletin-3-O-glucoside, astragalin, quercetin, kaempferol and isorhamnetin from Flaveria bidentis (L.) Kuntze by elution-pump-out high-performance counter-current chromatography

Flaveria bidentis (L.) Kuntze is an annual alien weed of Flaveria Juss. (Asteraceae) in China. Bioactive compounds, mainly flavonol glycosides and flavones from F. bidentis (L.) Kuntze, have been studied in order to utilize this invasive weed, Analytical high-performance counter-current chromatography (HPCCC) was successfully used to separate patuletin-3-O-glucoside, a mixture of hyperoside (quercetin-3-O-galactoside) and 6-methoxykaempferol-3-O-galactoside, astragalin, quercetin, kaempferol and isorhamnetin using two runs with different solvent system. Ethyl acetate-methanol-water (10:1:10, v/v) was selected by analytical HPCCC as the optimum phase system for the separation of patuletin-3-O-glucoside, a mixture of hyperoside and 6-methoxykaempferol-3-O-galactoside, and astragalin. A Dichloromethane-methanol-water (5:3:2, v/v) was used for the separation of quercetin, kaempferol and isorhamnetin. The separation was then scaled up: the crude extract (ca 1.5 g) was separated by preparative HPCCC, yielding 12 mg of patuletin-3-O-glucoside at a purity of 98.3%, yielding 9 mg of a mixture of hyperoside and 6-methoxykaempferol-3-O-galactoside constituting over 98% of the fraction, and 16 mg of astragalin (kaempferol-3-O-glucoside) at a purity of over 99%. The pump-out peaks are isorhanetin (98% purity), kaemferol (93% purity) and quercitin (99% purity). The chemical structure of patuletin-3-O-glucoside and astragalin were confirmed by MS and ¹H, ¹³C NMR.

Plasma levels and distribution of flavonoids in rat brain after single and repeated doses of standardized Ginkgo biloba extract EGb 761®

It is undisputed that terpene lactones and flavonoid glycosides of Ginkgo biloba are responsible for most of the extracts (e.g., EGb 761®) pharmacological actions. This investigation focused on the pharmacokinetic and the ability of the flavonoid constituents to cross the blood-brain barrier in rats, after single (600 mg/kg) or repeated (8 days, 100, or 600 mg/kg) oral administration of EGb 761®, and their distribution in different areas of the brain. For this purpose, we developed an HPLC-fluorescence method for the determination of the Ginkgo flavonoid metabolites (quercetin, kaempferol, and isorhamnetin derivatives) in the brain and plasma. A single dose of 600 mg/kg EGb 761® resulted in maximum plasma concentrations of 176, 341, and 183 ng/mL for quercetin, kaempferol, and isorhamnetin/tamarixetin, respectively and in maximum brain concentrations of 291 ng/g protein for kaempferol and 161 ng/g protein for isorhamnetin/tamarixetin. In comparison, the repeated administration of the same dose for 8 days led to an approximate 4.5-fold increase in the plasma concentration for quercetin, 11.5-fold increase for kaempferol, and 10-fold increase for isorhamnetin/tamarixetin. In the brain, an approximate 2-fold increase was observed for kaempferol and isorhamnetin/tamarixetin. About 90% of the determined flavonoids were distributed in the hippocampus, frontal cortex, striatum, and cerebellum, which together represent only 38% of the whole brain.

Aqueous extract of ginger shows antiproliferative activity through disruption of microtubule network of cancer cells

Ginger has a long history of use as traditional medicine for varied human disease. Our present study has shown that the aqueous extract of ginger (GAE) interacts directly with cellular microtubules and disrupts its structure and induces apoptosis of cancer cells as well. The IC(50) values of GAE, as determined from cell viability experiment on human non-small lung epithelium cancer (A549) cells and human cervical epithelial carcinoma (HeLa), were 239.4+7.4 and 253.4+8.9 μg/ml, respectively. It has been found that the apoptosis of A549 cells by GAE is mediated by up regulation of tumor suppressor gene p53 and alteration of the normal Bax/Bcl-2 ratio followed by down regulation of cellular pro-caspase3. The morphological change of cells upon GAE treatment has also been demonstrated. Both the structural and functional properties of tubulin and microtubule were lost, as confirmed by both ex vivo and invitro experiments. The major component of GAE is poly-phenols (around 2.5%), which consist of ∼ 80% flavones and flavonols. Poly-phenolic compounds are well known to have anti-mitotic properties, and may be further screened for the development of a potential anti-cancer agent.

Fluorescence studies of interaction between flavonol p-coumaroylglucoside tiliroside and bovine serum albumin

In this paper, the interaction between flavonol p-coumaroylglucoside tiliroside and BSA was investigated by fluorescence quenching spectra, synchronous fluorescence spectra, and three-dimensional fluorescence spectra under simulative physiological conditions. It was proved that the fluorescence quenching of BSA by tiliroside was mainly a result of the formation of a tiliroside-BSA complex. The modified Stern-Volmer quenching constant and the corresponding thermodynamic parameters DeltaH, DeltaG and DeltaS at different temperatures were calculated. The results indicated that electrostatic interactions were the predominant intermolecular forces in stabilizing the complex. The distance r=3.95 nm between the donor (BSA) and acceptor (tiliroside) was obtained according to Förster's nonradioactive energy transfer theory. The synchronous fluorescence and three-dimensional fluorescence spectra results showed the microenvironment and conformation of BSA were changed in the binding reaction.

Characterization of a Vitis vinifera cv. Cabernet Sauvignon 3',5'-O-methyltransferase showing strong preference for anthocyanins and glycosylated flavonols

At ripening initiation in red grapevine (Vitis vinifera) berries, the exocarp turns color from green to red and then to purple due to the accumulation and extent of methylation of anthocyanins. The accumulation of transcripts encoding an O-methyltransferase was recently shown to be closely correlated with the onset of ripening and the degree of blue/purple pigmentation in grapevine berries; however, the biochemical function of this gene has remained uncharacterized. In this study, an O-methyltransferase cDNA that showed a distinct expression pattern when compared to closely related sequences was expressed in Escherichia coli and enzyme assays were carried out with a broad array of anthocyanin and other flavonoid substrates. We demonstrate that this enzyme carries out 3',5'-O-methylation of anthocyanins and flavonol compounds in vitro, which are known to be present in grape berries, with a preference for glycosylated substrates. The highest relative specific activity for the enzyme was found with delphinidin 3-O-glucoside as substrate. The enzyme is not able to methylate flavan type skeletons with chiral centers, such as either catechins or dihydroquercetin. The enzyme showed negligible specific activity for caffeoyl-CoA, compared to flavonol and anthocyanin substrates. Phylogenetic analysis of the O-methyltransferase suggests that it may be a member of a distinct subclass of Type 2 bivalent metal-dependent S-adenosyl-methionine O-methyltransferases.

Spectral features and stability of oligomeric pyranoanthocyanin-flavanol pigments isolated from red wines

The spectral characteristics and stability of three red wine pigments (pyranoMv-catechin, pyranoMv-epicatechin, and pyranoMv-dimer B3) toward pH variation and bisulfite bleaching, as well as their color stability and degradation during storage, have been studied. Unlike the absorbance spectra of most wine pigments, the intensity of which is more increased in more acidic conditions, oligomeric pyranoMv-flavanols have maximum absorbance at wine pH around 3.6, up to 30-50% higher than that in pH 1.0. This particular hyperchromic effect shown in mildly acidic solutions suggests the presence of intramolecular copigmentation in the molecule of pyranoanthocyanin-flavanols, giving rise to higher molar extinction coefficients around wine pH and contributing to the overall wine color. The most probable conformations were determined by computer-assisted model building and molecular mechanics. Besides exceptional stability toward pH variations, pyranoanthocyanin-flavanols were also shown to be entirely resistant to bleaching by sulfur dioxide. During a 6 month storage period, pyranoanthocyanin-flavanols were much more stable against degradation than the anthocyanin with the following order: pyranoMv-catechin > pyranoMv-dimer B3 > pyranoMv-epicatechin > carboxy-pyranoMv ≫ Mv. Kinetic decomposition monitored by high-performance liquid chromatography-diode array detection-mass spectrometry revealed the formation of a new pigment (pyranone-Mv structure) and the cleavage of the interflavanic linkage of procyanidin dimer in the solutions containing carboxy-pyranoMv and pyranoMv-dimer B3, respectively. Despite some degree of decline of these oligomeric pyranoanthocyanins, their color intensity was surprisingly enhanced, and their color stability greatly improved throughout the entire storage period, thus contributing significantly as long-lived orange-red pigments to the maintenance of aged wine color.

High molecular weight persimmon (Diospyros kaki L.) proanthocyanidin: a highly galloylated, A-linked tannin with an unusual flavonol terminal unit, myricetin

MALDI-TOF MS suggested that the high molecular weight proanthocyanidin (condensed tannin) from persimmon (Diospyros kaki L.) pulp comprised a heteropolyflavanol series with flavan-3-O-galloylated extenders, flavan-3-ol and flavonol terminal units, and A-type interflavan linkages. Thiolysis-HPLC-ESI-MS with DAD, electrochemical, and ESI-MS detection confirmed a previously unreported terminal unit, the flavonol myricetin, in addition to the typical flavan-3-ols catechin and epigallocatechin gallate. The extender units were epicatechin, epigallocatechin, (epi)gallocatechin-3-O-gallate, and (epi)catechin-3-O-gallate. The crude tannin had a high prodelphinidin content (65%) and a high degree of 3-O-galloylation (72%). The material was fractionated on Toyopearl TSK-HW-50-F to yield fractions distinguished by degree of polymerization (DP). Thiolysis suggested that the persimmon tannin was composed of polymers ranging from 7 to 20 kDa (DP 19-47), but sizes estimated by GPC were 50-70% smaller. The crude material was chemically degraded with acid to yield products that were amenable to NMR and ESI-MS analysis, which were used to establish for the first time that persimmon tannin has a mixture of B-type and A-type linkages.

Geranylated flavonols from Macaranga rhizinoides

Two geranylated and methylated flavonol derivatives, macarhizinoidins A (1) and B (2), along with a known phenolic compound methyl 4-isoprenyloxycinnamate (3), have been isolated from the methanol extract of the leaves M. rhizinoides. The structures of these compounds were identified based on their spectroscopic data. On cytotoxic evaluation against murine leukemia P-388 cells, compounds 1-2 showed IC50 values of 11.4 and 13.9 microM, respectively, while compound 3 was inactive.

Gmelinoside I, a new flavonol glycoside from Limonium gmelinii

Gmelinoside I (1), a new flavonol glycoside, was isolated and chemically characterized as 3,5,7,3',4',5'-hexahydroxy-3-O-alpha-D-galactopyranosylflavone from the aerial part of Limonium gmelinii Kuntze (Plumbaginaceae).. Other compounds were identified as (-)-epigallocatechin-3-O-gallate, myricetin, myricetin-3-O-alpha-L-rhamnopyranoside, myricetin-3-O-beta-D-galactoside-6"-O-gallate and caprolactam. The antibacterial, antifungal and antileishmanial activities of the isolated compounds were evaluated. Myricetin showed moderate antileishmanial activity.

[Studies on the chemical constituents of the flowers of Bupleurum chinese]

OBJECTIVE

To study the chemical constituents of the flowers of Bupleurum chinese.

METHODS

The compounds were separated by column chromatography with silica gel. Their structures were identified by spectral methods and chemical analysis.

RESULTS

Five compounds were isolated and identified as 8-(3',6'-dimethoxy)-4,5-cyclohexadiene-(delta11,12-dioxide-methylene) -dense-dihydrogen-isocoumarin(I), quercetin(II), rutin(III), calcifenol (IV), isorhamnetin (V).

CONCLUSION

Compounds I and IV are obtained from the genus for the first time. Compound I is a new compound.

Quantum chemical calculations on the interaction between flavonol and functional monomers (methacrylic acid and 4-vinylpyridine) in molecularly imprinted polymers

Quantum chemical calculations were performed to characterize the interaction of the flavonol molecule (FL) with methacrylic acid (MAA) and 4-vinylpyridine (4VPy) in the formation of imprinted polymers. The polarizable continuum model (PCM) was used to gain insight on the type of interaction between the reactant molecules under vacuum conditions and in the presence of different solvents. The effect of solvent on the pre-polymerization complex formation was evaluated through the stability energy, in which chloroform behaves as the best solvent for the synthesis of the imprinted polymers since it facilitates the reaction by lowering its degree of stabilization. The reactivity was analyzed in terms of the electrostatic surface potential (ESP) and Mulliken charge. By means of these results, it has been possible to determine two potential recognition sites for the interaction of the MAA monomer and one for the 4VPy in relation to the strength of interaction with FL. In this concern, the interaction of the system FL-MAA is stronger than FL-4VPy.

Flavonol glycosides and monoterpenoids from Potentilla anserina

Potentilin A (1), a rare diflavonol ester of mu-truxinic acid and a new normonoterpenoid, 2,6-dimethyl-2,3-dihydro-4-oxo-4H-pyran-2-acetic acid (2), was isolated from Potentilla anserina, together with 19 known flavonol glycosides (3-21) and 2 known monterpenoids (22,23). Their structures were elucidated by means of UV, IR, HR-ESI-MS, 1D and 2D NMR spectroscopic data.

Gneyulins A and B, stilbene trimers, and noidesols A and B, dihydroflavonol-C-glucosides, from the bark of Gnetum gnemonoides

Gneyulins A (1) and B (2), two new stilbene trimers consisting of oxyresveratrol constituent units, and noidesols A (3) and B (4), two new dihydroflavonol-C-glucosides, were isolated from the bark of Gnetum gnemonoides. The structures and configurations of 1-4 were elucidated on the basis of 2D NMR correlations and X-ray analysis. Gneyulins A (1) and B (2) showed inhibition of Na(+)-glucose transporters (SGLT-1 and SGLT-2).

Brauhenefloroside E and F; acylated flavonol glycosides from Stocksia brauhica Linn

Two new acylated flavonol glycosides, 3-O-{[2-O-beta-D-glucopyranosyl]-3-[O-beta-D-glucopyranosyl]-4-[(6-O-p-coumaroyl)-O-beta-D-glucopyranosyl]}-alpha-L-rhamnopyranosyl-kaempferol 7-O-alpha-L-rhamnopyranoside and 3-O-{2-[(6-O-p-coumaroyl)-O-beta-D-glucopyranosyl]-3-[O-beta-D-glucopyranosyl]-4-[(6-O-p-coumaroyl)-O-beta-D-glucopyranosyl]}-alpha-L-rhamnopyranosyl-kaempferol 7-O-alpha-L-rhamnopyranoside, trivially named as brauhenefloroside E (1) and F (2), respectively, were isolated from the fruits of Stocksia brauhica and their structures were elucidated using spectroscopic methods, including 2D NMR experiments.

Acylated flavonol tetraglycosides from Delphinium gracile

An ethanol extract of the aerial parts of Delphinium gracile DC. yielded five flavonol glycosides quercetin-3-O-{[beta-d-xylopyranosyl (1-->3)-4-O-(E-p-caffeoyl)-alpha-l-rhamnopyranosyl (1-->6)][beta-d-glucopyranosyl (1-->2)]}-beta-d-glucopyranoside (1), quercetin-3-O-{[beta-d-xylopyranosyl (1-->3)-4-O-(E-p-coumaroyl)-alpha-l-rhamnopyranosyl (1-->6)][beta-d-glucopyranosyl (1-->2)]}-beta-d-glucopyranoside (2), quercetin-3-O-{[beta-d-xylopyranosyl (1-->3)-4-O-(Z-p-coumaroyl)-alpha-l-rhamnopyranosyl (1-->6)][beta-d-glucopyranosyl (1-->2)]}-beta-d-glucopyranoside (3), kaempferol-3-O-{[beta-d-glucopyranosyl (1-->3)-4-O-(E-p-coumaroyl)-alpha-l-rhamnopyranosyl (1-->6)][beta-d-glucopyranoside-7-O-(4-O-acetyl)-alpha-l-rhamnopyranoside (4) kaempferol-3-O-{[beta-d-glucopyranosyl (1-->3)-4-O-(E-p-coumaroyl)-alpha-l-rhamnopyranosyl (1-->6)][beta-d-glucopyranoside-7-O-(4-O-acetyl)-alpha-l-rhamnopyranoside (5) in addition to 4-(beta-d-glucopyranosyloxy)-6-methyl-2H-pyran-2-one (6) and rutin. Structures were elucidated by spectroscopic methods.

Quercetin and isorhamnetin in sweet and red cultivars of onion (Allium cepa L.) at harvest, after field curing, heat treatment, and storage

Effects of heat treatment and storage on quercetin and isorhamnetin content, major and minor components of isorhamnetin, and quercetin glucosides and aglycone, were investigated in onion (Allium cepa L.). The sweet onion 'Recorra' and red onions 'Hyred' and 'Red Baron' were cultivated in the south part of Norway and thereafter stored for eight months. The onions were either not field dried, but stored directly, or field dried and then stored, or field dried and then heat treated before storage. Neither storage nor heat treatment caused any major differences in total flavonol content in the investigated sweet onion as well as in the red onion cultivars. The two major quercetin glucosides differed in their changes in content during storage; quercetin-4'-glucoside did not show any consistent changes during storage in the two red cultivars, independent of treatment, whereas quercetin-3,4'-diglucoside increased significantly by 30 or 51%, respectively, during storage in 'Hyred' and 'Red Baron' in the 24 h heat treated onions. Isorhamnetin-4'-glucoside, which might possibly be of special interest from a human health point of view, was present at 2-3 times higher amount in the sweet onion cultivar than in the two red cultivars. Some of the quercetin glucosides present at lower concentrations, isorhamnetin-3,4'-diglucoside, quercetin-3,7,4'-triglucoside, and quercetin-7,4'-diglucoside, increased during storage in all treatments in both 'Hyred' and 'Red Baron', though sometimes a decrease was found at the end of storage.