Flavonoid glycosides from Persea caerulea. Unraveling their interactions with SDS‐micelles through matrix‐assisted DOSY,PGSE, mass spectrometry,and NOESY

Two flavonoid glycosides derived from rhamnopyranoside ( 1 ) and arabinofuranoside ( 2 ) have been isolated from leaves of Persea caerulea for the first time. The structures of 1 and 2 have been established by ¹H NMR, ¹³C NMR, and IR spectroscopy, together with LC–ESI–TOF and LC–ESI–IT MS spectrometry. From the MS and MS/MS data, the molecular weights of the intact molecules as well as those of quercetin and kaempferol together with their sugar moieties were deduced. The NMR data provided information on the identity of the compounds, as well as the α and β configurations and the position of the glycosides on quercetin and kaempferol. We have also explored the application of sodium dodecyl sulfate (SDS) normal micelles in binary aqueous solution, at a range of concentrations, to the diffusion resolution of these two glycosides, by the application of matrix‐assisted diffusion ordered spectroscopy (DOSY) and pulse field gradient spin echo (PGSE) methodologies, showing that SDS micelles offer a significant resolution which can, in part, be rationalized in terms of differing degrees of hydrophobicity, amphiphilicity, and steric effects. In addition, intra‐residue and inter‐residue proton–proton distances using nuclear Overhauser effect build‐up curves were used to elucidate the conformational preferences of these two flavonoid glycosides when interacting with the micelles. By the combination of both diffusion and nuclear Overhauser spectroscopy techniques, the average location site of kaempferol and quercetin glycosides has been postulated, with the former exhibiting a clear insertion into the interior of the SDS‐micelle, whereas the latter is placed closer to the surface. Copyright © 2016 John Wiley & Sons, Ltd.     

Liquid chromatography–tandem mass spectrometry reveals the widespread occurrence of flavonoid glycosides in honey,and their potential as floral origin markers

HPLC-MS–MS analysis of unifloral honey extracts has shown the occurrence of flavonoid glycosides in most of the analyzed samples. These compounds are not present in large amounts, but can reach up to 600 μg/100 g honey in canola and rapeseed honeys. Rhamnosyl-hexosides (tentatively rutinosides and neohesperidosides) and dihexosides (hexosyl(1→2)hexosides and hexosyl(1→6)hexosides) of flavonols such as quercetin, kaempferol, isorhamnetin and 8-methoxykaempferol, are the main flavonoid glycosides found in honey. However, flavonoid triglycosides and monoglycosides are also detected in some floral origins. Eucalyptus and orange blossom nectars were collected and analyzed showing that nectar flavonoid glucosides, as is the case of eucalyptus flavonoids, can be readily hydrolyzed by the bee saliva enzymes, while flavonoid rhamnosyl-glucosides, as is the case of citrus nectar flavonoids, are not hydrolyzed, and because of these reasons the flavonoid glycoside content of citrus honey is higher than that of eucalyptus honey that contains mainly aglycones. The flavonoid glycoside profiles detected in honeys suggest that this could be related to their floral origin and the results show that the HPLC-MSn ion trap analysis of flavonoid glycosides in honey is a promising analytical method to help in the objective determination of the floral origin of unifloral honeys.     

Involvement of Photoprotective Compounds of a Phenolic Nature in the Response of Arabidopsis Thaliana Leaf Tissues to Low-Intensity Laser Radiation

The influence of low-intensity laser radiation (LILR) on the changes in the content of anthocyanins, kaempferol, quercetin and their glycosides in the leaves of 5-week-old plants of Arabidopsis thaliana L. was studied by means of methods of high-performance liquid chromatography and gas chromatography mass spectrometry (GC-MS). It was found that in the leaves subjected to a stimulating He-Ne laser radiation dose (3.6 J cm⁻², continuous wave radiation, wavelength—632.8 nm, exposure time—5 min), the radiation induced an increase in the content of such compounds, the most significant one being in the case of anthocyanins (9 times). The present study also revealed an increase in the antioxidant potential of kaempferol, quercetin and their glycosides as a result of laser exposure. This increase was due to the preferential synthesis of compounds with a larger number of OH-groups on the phenyl ring. Thus, the content of quercetin, which has five OH-groups in its structure, increased almost by three times as compared to the control.     

Heart-cutting two-dimensional (size exclusion × reversed phase) liquid chromatography–mass spectrometry analysis of flavonol glycosides from leaves of Maytenus ilicifolia

Two-dimensional liquid chromatography–electrospray ionization mass spectrometry was employed to analyze flavonol glycosides present in leaves of Maytenus ilicifolia, frequently used in traditional Brazilian medicine. Since they contain many flavonol glycosides, including isomers, one-dimensional liquid chromatography did not give complete separation and identification, yielding overlapping of compounds with different molecular weights. Thus, employing size exclusion chromatography in the first and reversed phase in the second dimension, a great number of flavonol glycosides could be identified and its relative abundances determined. The majority of glycosides contained kaempferol or quercetin as aglycones, and glycosides with previously unreported structures were also present and characterized.     

Flavonoid Glycosides from the Leaves of Machilus philippinensis

Thirteen flavonoid glycosides ( 1‐7 , 11‐13 , 15 , 17 , and 18 ) were isolated from the EtOH extract of the leaves of Machilus philippinensis. Of these, kaempferol 3‐O‐(2‐O‐β‐D ‐apiofuranosyl)‐α‐L ‐rhamnopyranoside ( 1 ) and kaempferol 3‐O‐(2‐O‐β‐D ‐apiofuranosyl)‐a‐L ‐arabinofuranoside ( 2 ) are new natural products. By application of HPLC‐SPE‐NMR hyphenated technique, five additional flavonol glycosides were characterized ( 8‐10 , 14 , and 16 ). Their structures were elucidated based on spectroscopic analysis. Of these, quercetin 3‐O‐(6‐O‐α‐L ‐rhamnopyranosyl)‐β‐D ‐galactopyranoside ( 5 ) and kaempferol 3‐O‐α‐L ‐arabinopyranoside ( 15 ) showed moderate inhibitory activity against α‐glucosidase type IV from Bacillus stearothermophilus with the IC₅₀ values of 19.5 and 19.0 μM, respectively.     

Identification of flavonoids and their glycosides by high-performance liquid chromatography with electrospray ionization mass spectrometry and with diode array ultraviolet detection

Identification of flavonoids and flavonoid glycosides was carried out on Psidium guajava Linn leaves by means of high-performance liquid chromatography ultraviolet (HPLC-UV) analysis and HPLC mass spectrometry. By using HPLC-UV, two known phenolics (gallic acid and quercetin) and five newly reported ones (procatechuic acid, chlorogenic acid, caffeic acid, kaempferol and ferulic acid) were identified in alcohol guava leaf extract. Structural information about the compounds was obtained from the retention times, the UV spectra and mass spectra without the need to isolate the individual compounds. Two flavonoids (quercetin and kaempferol) and four flavonoid glycosides (three known components, quercetin 3-O-alpha-L-arabinoside, quercetin 3-O-beta-D-glucoside and quercetin 3-O-beta-D-galactoside, along with one novel compound, kaempferol-glycoside) and three other unknown compounds have been identified in the fractions.     

The effects of far-red light on plant growth and flavonoid accumulation in Brassica napus in the presence of ultraviolet B radiation

Flavonoid induction is regulated by complex signal transduction pathways involving cryptochrome, phytochrome and UVB photoreceptors. Previously, we identified the UVB-inducible flavonoids in Brassica napus cv. Topas leaves and showed that UVA affected accumulation of the quercetin (Q) and kaempferol (K) glycosides (Wilson et al. [2000] Photochem. Photobiol. 73, 678-684). In this study, we examined the effects of far-red light (FR, 700-780 nm) on UVB-mediated flavonoid accumulation in B. napus. Plants were grown under photosynthetically active radiation (PAR, 400-700 nm, 150 micromol m(-2) s(-1)) plus a moderate level of FR (35 micromol m(-2) s(-1)) for 14 days, and then transferred to five different irradiation regimes (PAR +/- [UVA + UVB] + moderate, intermediate or low fluence FR) for 4 days. Kinetics of flavonoid accumulation were assessed via HPLC. Accumulation of flavonoids, in general, was suppressed by increasing the amount of FR in the spectrum. Furthermore, addition of UVB (290-320 nm) to the spectrum altered the flavonoid composition by causing significant changes in the quantities of individual flavonoids. The relative levels of acylated K glycosides were diminished whereas the relative levels of nonacylated Q glycosides increased dramatically. With UVB exposure there was a five-fold increase in the Q:K ratio. In contrast, increasing the level of FR in the presence of UVB decreased the Q:K ratio by half.     

Analysis of flavonoid glycosides with potential medicinal properties on Bauhinia uruguayensis and Bauhinia forficata subspecies pruinosa.

Several Bauhinia species are widely used in Southern South America in the treatment of infections, pain and several diseases including diabetes. Flavonoid compounds based on quercetin and kaempferol glycoside derivatives are believed to be responsible for their therapeutic properties. To investigate this, we have studied two native species from Argentina: B. uruguayensis (BU) and B. forficata subsp. pruinosa (BF). We have analyzed the major polyphenol components in hydro-methanolic extracts of leaves, by high performance liquid chromatography tandem mass spectrometry. Chromatographic analysis yielded five main compounds in BF, corresponding to rutinosides and rhamnosides derivatives of kaempferol and quercetin, which are considered chemotaxonomic markers and responsible for antioxidant activity. The presence of kaempferitrin, an antidiabetic agent, has been confirmed. In extracts of BU, four major compounds were identified as rhamnosides and galloyl derivates from quercetin and kaempferol. One of these compounds, quercitrin-3-rhamnoside may confer anti-inflammatory and analgesic properties to BU extracts.     

Liquid chromatography-tandem mass spectrometry analysis allows the simultaneous characterization of C-glycosyl and O-glycosyl flavonoids in stingless bee honeys

The analysis of the phytochemicals present in stingless bee honey samples has been a difficult task due to the small amounts of samples available and to the complexity of the phytochemical composition that often combines flavonoid glycosides and aglycones. Honey samples produced in Venezuela from Melipona species were analyzed using a combination of solid-phase extraction and HPLC-DAD-MSn/ESI methodologies with specific study of the fragment ions produced from flavonoid glycosides. The analyses revealed that flavonoid glycosides were the main constituents. The honey samples analyzed contained a consistent flavonoid pattern composed of flavone-C-glycosides, flavonol-O-glycosides and flavonoid aglycones. The HPLC-DAD-MSn/ESI analysis and the study of the fragment ions obtained allowed the characterization and quantification for the first time of five apigenin-di-C-glycosides, and ten quercetin, kaempferol and isorhamnetin O-glycosides (di- and tri- glycosides), and the aglycones pinobanksin, quercetin, kaempferol and isorhamnetin in the different samples. This is the first report of flavonoid-C-glycosides in honey. The results show that the content of flavonoid-glycosides (mean values of 2712 μg/100 g) in stingless bee honeys is considerably higher than the content of flavonoid aglycones (mean values of 315 μg/100 g). This differs from previous studies on Apis mellifera honeys that consistently showed much higher aglycone content and smaller flavonoid glycoside content. The occurrence of relevant amounts of flavonoid glycosides, and particularly C-glycosides, in stingless bee honeys could be associated with their putative anticataract properties.     

Characterisation of flavonols in broccoli (Brassica oleracea L. var. italica) by liquid chromatography-uV diode-array detection-electrospray ionisation mass spectrometry

The flavonoid composition of broccoli inflorescences has been studied by LC/UV-DAD/ESI-MSn. A large number of hydroxycinnamic acid esters of kaempferol and quercetin glucosides has been characterised. The structures of the flavonoid glycosides were analysed after alkaline hydrolysis, and were identified as 3-sophoroside/sophorotrioside-7-glucoside/sophoroside of kaempferol, quercetin and isorhamnetin (this last found in trace amount). These complex quercetin and isorhamnetin glucosides have not been previously characterised in nature. In addition, several less complex glucosides based on the same aglycones have been identified. The effect of sugar substitution and acylation on chromatographic mobility and ESI ionisation and fragmentation are discussed.     

PROTECTION OF THE D1 PHOTOSYSTEM II REACTION CENTER PROTEIN FROM DEGRADATION IN ULTRAVIOLET RADIATION FOLLOWING ADAPTATION OF Brassica napus L. TO GROWTH IN ULTRAVIOLET-B

As depletion of the stratospheric ozone layer continues, the biosphere will most likely be exposed to higher levels of ultraviolet-B (UV-B) irradiation (290–320nm). For plants, damage from UV-B can occur at several molecular targets with the photosynthetic apparatus being especially vulnerable. We are interested both in the mechanisms of UV-B-induced damage and identifying adaptation processes that can confer protection from UV-B. Toward this end, Brassica napus (oil seed rape) plants grown under visible light plus a low level of UV-B radiation (adapted plants) were compared to plants grown under visible light alone (control plants). Relative to the control plants, the adapted plants showed little evidence of damage at the levels of morphology or photosynthesis, indicating that B. napus has some tolerance of UV-B and that the plants may have protection mechanisms. Consistent with this, a strong UV-B adaptation process was observed in the plants-accumulation of flavonoids in the epidermis. These pigments seemed to screen a molecular target in the mesophyll. Namely, the D1 photosystem II reaction center protein, which is rapidly degraded in UV-B, was partially protected from degradation in UV-B in the adapted plants. Moreover, the extent that the half-life of the D1 protein increased in the adapted plants was on par with the elevation in total flavonoid concentrations. These experiments demonstrate that degradation of the D1 protein can be used as an in vivo assay of penetration of UV-B photons to the mesophyll.     

DOSY NMR applied to analysis of flavonoid glycosides from Bidens sulphurea

2D DOSY ¹H NMR has proved to be a useful technique in the identification of the molecular skeleton of the four major compounds of ethyl acetate extract of aerial parts of Bidens sulphurea (Asteraceae). The combination of this technique with HPLC, mass spectrometry and other NMR techniques enabled the identification of four flavonoid glycosides: quercetin‐3‐O‐β‐D ‐galactopyranoside, quercetin‐3‐O‐β‐D ‐glycopyranoside, quercetin‐3‐O‐α‐L ‐arabinofuranoside and quercetin‐3‐O‐β‐D ‐rhamnopyranoside. Copyright © 2009 John Wiley & Sons, Ltd.     

Quantitative HPTLC separation of flavonoid glycosides in the taxonomy of elm (Ulmus spp.)

Summary The flavonoid glycosides of elm (Ulmus spp.) leaves have been separated by means of HPTLC on silica gel and quantitative analysis carried out by densitometry. The results obtained were used for discriminant analysis in order to investigate whether the flavonoid pattern could be used for the classification of elms. The results readily showed the different provenance of four species and the attribution of an unknown sample to a species can be carried out. This result is important as it offers a chemical tool in the taxonomy of the elm. The classification method is compared with one based on qualitative data from two-dimensional chromatography of the flavonoid aglycones. It was found to exhibit much better results than those obtained from the cluster analysis of these qualitative data.     

New flavonoid glycosides from the leaves of Solidago altissima

Two new flavonoid glycosides kaempferol 3-O-beta-D-apiofuranosyl-(1-->6)-beta-D-glucopyranoside (1), and quercetin 3-O-beta-D-apiofuranosyl-(1-->6)-beta-D-glucopyranoside (2), together with six known flavonoid glycosides were isolated from the leaves of Solidago altissima L. grown in Kochi of Japan. The structure elucidation of the isolated compounds was performed by acid hydrolysis and spectroscopic methods including UV, IR, ESI-MS, 1D- and 2D-NMR experiments.     

Simultaneous identification of glucosinolates and phenolic compounds in a representative collection of vegetable Brassica rapa

Brassica raparapa group is widely distributed and consumed in northwestern Spain. The consumption of Brassica vegetables has been related to human health due to their phytochemicals, such as glucosinolates and phenolic compounds that induce a variety of physiological functions including antioxidant activity, enzymes regulation and apoptosis control and the cell cycle. For first time in Brassica crops, intact glucosinolates and phenolic compounds were simultaneously identified and characterized. Twelve intact glucosinolates, belonging to the three chemical classes, and more than 30 phenolic compounds were found in B. rapa leaves and young shoots (turnip greens and turnip tops) by LC–UV photodiode array detection (PAD)–electrospray ionization (ESI). The main naturally occurring phenolic compounds identified were flavonoids and derivatives of hydroxycinnamic acids. The majority of the flavonoids were kaempferol, quercetin and isorhamnetin glycosylated and acylated with different hydroxycinnamic acids. Quantification of the main compounds by HPLC-PAD showed significant differences for most of compounds between plant organs. Total glucosinolate content value was 26.84 μmol g⁻¹ dw for turnip greens and 29.11 μmol g⁻¹ dw for turnip tops; gluconapin being the predominant glucosinolate (23.2 μmol g⁻¹ dw). Phenolic compounds were higher in turnip greens 51.71 μmol g⁻¹ dw than in turnip tops 38.99 μmol g⁻¹ dw, in which flavonols were always the major compounds.     

Study of the collision-induced radical cleavage of flavonoid glycosides using negative electrospray ionization tandem quadrupole mass spectrometry

Negative electrospray ionization tandem quadrupole mass spectrometry was used to study the collision-induced dissociation (CID) of the O-glycosidic bond from different commercially available flavonoid glycosides. Depending on the structure, flavonoid glycosides can undergo both a collision-induced homolytic and heterolytic cleavage of the O-glycosidic bond producing deprotonated radical aglycone ((Y(0) - H)(-*)) and aglycone (Y(0) (-)) product ions. The relative abundance of the radical aglycone to the aglycone fragment from flavonol-3-O-glycosides increased with increasing number of hydroxyl substituents in the B ring and in the order kaempferol - 相似文献   

HPLC quantification of flavonoids and biflavonoids inCupressaceae leaves

Summary The aim of this investigation was to obtain qualitative and quantitative profiles of the flavonoid and biflavonoid composition of six cypress species—Cupressus funebris L.,Cupressus sempervirens L.,Cupressus glabra L.,Cupressus arizonica L.,Cupressus goveniana L., andCupressus lusitanica L. HPLC-diode-array detection (DAD), HPLC-MS, and HPTLC were used to identify the individual compounds. A chromatographic method was optimized for identification and quantification of the main flavonoid glycosides and biflavonoids. The flavonoids identified and calibrated were: rutin, quercetin glucoside, quercetin rhamnoside, and kaempferol 3-O-rhamnoside. The biflavonoids identified and calibrated were: cupressuflavone, amentoflavone, robustaflavone, hinokiflavone, methylrobustaflavone, methylamentoflavone, and dimethylcupressuflavone.     

Identification of the Flavonoid Glycosides that Accumulate in Brassica napus L. cv. Topas Specifically in Response to Ultraviolet B Radiation

We have shown in previous work that Brassica napus synthesizes epidermal flavonoids in response to UVB radiation (290–320 nm) and that these compounds are effective at screening the leaf mesophyll from UVB (Wilson and Greenberg, Photochem. Photobiol . 57, 556–563, 1993). This route of acclimation is common to many plant species. However, flavonoids are a highly diverse group of compounds that vary greatly from species to species, and little is known about the specific flavonoids synthesized in response to UVB. To address this, we extracted flavonoids from the leaves of B. napus plants exposed to photosynthetically active radiation (PAR: 400–700 nm), PAR + UVA (320–400 nm) and PAR + UVA + UVB. The compounds were resolved by HPLC and their structures were elucidated. Twelve distinct flavonoid glucosides with quercetin and kaempferol backbones were found. In some cases, a hydroxycinnamic acid moiety was linked via an ester bridge to a glucose. Of the 12 compounds identified, the leaf concentrations of 6 increased in response to UVB: kaempferol-3- O -sophoroside (K2), kaempferol-3- O -sophoroside-7- O -glucoside (Q3), quercetin-3- O -sophoroside (Q2), quercetin-3- O -sophoroside-7- O -glucoside (Q3), K3-coumaroyl ester and Q3-caffeoyl ester. Of these six compounds, K2, K3, Q2 and Q3 accumulated to high enough concentrations to contribute to UVB screening. Interestingly, the extractable amounts of the other six compounds identified were lower in the plants exposed to UVA or UVA + UVB compared to plants exposed only to PAR. Thus, in B. napus UV exposure seems to cause a shift in the population of flavonoid glycosides, with four of the UVB-induced flavonoids being generated in high concentrations.     

Determination of quercetin glycosides and free quercetin in buckwheat by capillary micellar electrokinetic chromatography

A simple and reliable method for determination of quercetin glycosides and free quercetin in buckwheat flower, leaves, stems and achenes was developed. The method consists of flavonoid extraction from freeze‐dried homogenous material in 50% v/v methanol solution and in presence of an antioxidant, cleaning of extract and analyte isolation using SPE. Analytical step uses capillary micellar electrokinetic chromatography. The working ranges, LOD and LOQ, recovery, precision and measurement uncertainty were calculated. The method is suitable for samples from buckwheat. The highest content of rutin was found in flowers of both kinds of buckwheat (99 400 mg/kg in F. esculentum, 108 000 mg/kg in F. tataricum). The free quercetin occurs in flowers and achenes of F. esculentum, whereas flowers and achenes of F. tataricum contained quercitrin.     

Flavonol Glycosides from the Leaves of Embelia Keniensis

Five new flavonol glycosides characterized as syringetin 3‐O‐α‐rhamnoside‐7‐O‐β‐glucoside, syringetin 3‐O‐α‐rhamnoside‐7,4′‐di‐O‐β‐glucoside, quercetin‐7‐O‐β‐galactosyl (1→3)‐β‐galactoside, myricetin 3‐O‐α‐rhamnosyl (1→4)‐β‐galactoside and myricetin 3‐O‐β‐glucosyl (1→2)‐β‐glucoside‐7‐O‐β‐glucosyl‐(1→4)‐α‐rhamnoside have been isolated from a methanolic extract of Embelia keniensis leaves. Known flavonols isolated from the same extract included myricetin, quercetin, kaempferol, myricetin 3‐O‐α‐rhamnoside, myricetin 3‐O‐β‐glucoside, quercetin 3‐O‐α‐rhamnoside, quercetin 3‐O‐β‐glucoside, quercetin 3‐O‐β‐xyloside, isorhamnetin 3‐O‐α‐rhamnoside and myricetin 3‐O‐rutinoside. Their structures were established from extensive spectroscopic and chemical studies and by comparison with authentic samples.