Inhibition of free radical initiated peroxidation of human erythrocyte ghosts by flavonols and their glycosides

The in vitro peroxidation of human erythrocyte ghosts was used as a model to study the free radical-induced damage of biological membranes and the protective effect of flavonols and their glycosides, i.e., quercetin (Q), quercetin galactopyranoside (QG), quercetin rhamnopyranoside (QR), rutin (R), morin (MO), kaempferol (K) and kaempferol glucoside (KG). The peroxidation was initiated by a water-soluble free radical initiator 2,2'-azobis(2-methylpropionamidine) dihydrochloride (AMPAD) at physiological temperature, and monitored by oxygen uptake. Kinetic analysis of the peroxidation process demonstrates that these flavonols and their glycosides are effective antioxidants against AMPAD-initiated oxidative damage of human erythrocyte ghosts, and that the flavonols bearing ortho-dihydroxyl groups possess significantly higher antioxidant activity than those bearing no such functionalities and the glycosides are less active than their parent aglycones.     

Phytochemical study of Centaurea cyanus

Flavonoid aglycons (quercetin, kaempferol, isorhamnetin, apigenin, luteolin, hispidulin) and their glycosides, and caffeic, chlorogenic, neochlorogenic, and isochlorogenic acids have been isolated from the epigeal part of theCentaurea cyanus L. and have been identified, and ten amino acids have also been identified.Kursk State Medical Institute. Translated from Khimiya Prirodynkh Soedinenii, No. 6, pp. 792–795, November–December, 1988.     

Flavonoid inhibitors of Na+,K+-ATPase

Summary A comparative investigation of the inhibiting influence on transport Na⁺,K⁺-ATPase of four flavone aglycones and eight of their glycosides has been performed on the microsomal fraction of the cells of the cerebral cortex.It has been shown that in concentrations of 1·10^–4 to 5·10^–6 M M myricetin, quercetin, luteolin, and myricetin 3-glucoside possess an appreciable inhibiting effect. For kaempferol and its glycosides, as for the glycosides of quercetin and luteolin, the inhibiting effect is extremely feeble.Institute of Biochemistry, Academy of Sciences of the Uzbek SSR, Tashkent. V. I. Lenin Tashkent State University. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 44–46, January–February, 1977.     

Comparison of Electrochemical Oxidation of Flavonols and Calculated Proton Affinity and Electron Transfer Enthalpy in Water

Flavonols, a class of flavonoids, are present in flowers, fruits and vegetables. They are jointly responsible for antioxidant activity as free radical acceptors. The redox behaviour of myricetin, quercetin, isorhamnetin, fisetin, morin and kaempferol is investigated using cyclic and differential pulse voltammetry. Quantum chemical calculations of proton affinities and electron transfer enthalpies were performed to identify possible reactive sites and radical species to compare them with measured oxidation potentials of the flavonols. Regarding to their chemical structure, these flavonols showed an oxidation order: myricetin > quercetin > isorhamnetin > fisetin > morin > kaempferol.     

Reductive acetylation of quercetin

Summary The reductive acetylation of quercetin under the action of various reducing agents and of different times and temperatures, and also the conversion of the flavonols obtained into cyanidin chloride have been studied by the methods of the mathematical planning of experimentation.Pyatigorsk Pharmaceutical Institute. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 401–405, July–August, 1971.     

Screening the Key Region of Sunlight Regulating the Flavonoid Profiles of Young Shoots in Tea Plants (Camellia sinensis L.) Based on a Field Experiment

Both UV and blue light have been reported to regulate the biosynthesis of flavonoids in tea plants; however, the respective contributions of the corresponding regions of sunlight are unclear. Additionally, different tea cultivars may respond differently to altered light conditions. We investigated the responses of different cultivars (‘Longjing 43’, ‘Zhongming 192’, ‘Wanghai 1’, ‘Jingning 1’ and ‘Zhonghuang 2’) to the shade treatments (black and colored nets) regarding the biosynthesis of flavonoids. For all cultivars, flavonol glycosides showed higher sensitivity to light conditions compared with catechins. The levels of total flavonol glycosides in the young shoots of different tea cultivars decreased with the shade percentages of polyethylene nets increasing from 70% to 95%. Myricetin glycosides and quercetin glycosides were more sensitive to light conditions than kaempferol glycosides. The principal component analysis (PCA) result indicated that shade treatment greatly impacted the profiles of flavonoids in different tea samples based on the cultivar characteristics. UV is the crucial region of sunlight enhancing flavonol glycoside biosynthesis in tea shoots, which is also slight impacted by light quality according to the results of the weighted correlation network analysis (WGCNA). This study clarified the contributions of different wavelength regions of sunlight in a field experiment, providing a potential direction for slightly bitter and astringent tea cultivar breeding and instructive guidance for practical field production of premium teas based on light regimes.     

Protolytic properties of flavonols from pea chloroplasts

Using the buffer capacity method, a study has been made of the protolytic properties of three flavonoids isolated from pea chloroplasts: kaempferol 3-D-triglucoside (KG), kaempferol 3-D-triglucoside p-coumarate (KGC), and quercetin 3-D-triglucoside p-coumarate (QGC). It has been shown that the curves of the buffer capacities of solutions of the flavonoid investigated have from two to four peaks of dissociation constants. When the substances participate in photobiochemical reactions, they are capable of manifesting protonophoric properties.Institute of Photosynthesis, Academy of Sciences of the USSR, Pushchino. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 337–340, May–June, 1980.     

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.     

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.     

Quantitative determination of flavonoids in some representatives of the family Fabaceae

The quantitative composition of the combined flavonoids in the epigeal parts of eight representatives of the family Fabaceae (four species ofOnobrychis, two ofAstragalus, and two ofTrifolium) have been studied. For the quantitative estimation of the flavonoids we used a spectrophotometric method permitting the determination of flavonols and isoflavones when they are present simultaneously. A comparatively high content of flavonoids (from 2.37 to 4.13%) was found. The sum of the flavonoid compounds from the species ofOnobrychis, Astragalus, andTrifolium investigated possesses a hypolipidemic activity.Pyatigorsk Pharmaceutical Institute. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 43–45, January–February, 1984.     

高效液相色谱法测定野葱中黄酮类化合物

建立了测定野葱中芦丁、黄酮醇类化合物的高效液相色谱方法。80%乙醇超声提取,高效液相色谱分析野葱中芦丁和黄酮醇类化合物的含量。芦丁检测条件:V(甲醇)∶V(0.2%磷酸水)=45∶55,检测波长:360nm;槲皮素、山奈酚、异鼠李素检测条件:V(甲醇)∶V(0.2%磷酸水)=40∶60,检测波长:360 nm。结果表明,野葱中芦丁含量0.22%,槲皮素、山奈酚、异鼠李素含量依次为0.42%、0、0.23%,总黄酮醇类化合物含量为1.63%。     

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.     

Polymeric adsorbents of the affinity type in the investigation of physiologically active substances

The chromatographic behavior of some glycosides of quercetin and luteolin on polymeric adsorbents of the affinity type has been investigated by low-pressure column chromatography. The separation of the glycosides according to the total polarity of their molecules has been shown — first the triosides are eluted, then the biosides, and, finally the monosides. The prospects of developing nonclassical affinity chromatography in the study of flavonoids are discussed.Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 805–810, November December, 1995. Original article submitted November 28, 1994.     

Triterpene glycosides ofHedera colchica. Structure of hederacolchisides E and F

The leaves of Colchis ivy (family Araliaceae) have yielded polar glycosides — hederacolchisides E and F — and their structures have been established. It has been shown on the basis of the results of methylation and of acid and alkaline hydrolysis that these glycosides are hexaosides of oleanolic acid and of hederagenin.I. G. Kutateladze Institute of Pharmacochemistry, Academy of Sciences of the Georgian SSR, Tbilisi. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 747–750, November–December, 1984.     

Flavonoid Glycosides in Brassica Species Respond to UV-B Depending on Exposure Time and Adaptation Time

Recently, there have been efforts to use ultraviolet-B radiation (UV-B) as a biotechnological tool in greenhouses. Leafy Brassica species are mainly considered for their ability to synthesize glucosinolates and are valued as baby salads. They also have a remarkable concentration of chemically diverse flavonoid glycosides. In this study, the effect of short-term UV-B radiation at the end of the production cycle was investigated without affecting plant growth. The aim was to verify which exposure and adaptation time was suitable and needs to be further investigated to use UV as a biotechnological tool in greenhouse production of Brassica species. It is possible to modify the flavonoid glycoside profile of leafy Brassica species by increasing compounds that appear to have potentially high antioxidant activity. Exemplarily, the present experiment shows that kaempferol glycosides may be preferred over quercetin glycosides in response to UV-B in Brassica rapa ssp. chinensis, for example, whereas other species appear to prefer quercetin glycosides over kaempferol glycosides, such as Brassica oleracea var. sabellica or Brassica carinata. However, the response to short-term UV-B treatment is species-specific and conclusions on exposure and adaptation time cannot be unified but must be drawn separately for each species.     

HPLC Separation of O-Acylated Flavonoids and Biflavones from Some Species of Gymnospermae

Flavonoids present in the extracts from leaves of Pseudotsuga menziesii (Pinaceae), Ginkgo biloba (Ginkgoaceae) and Podocarpus dacrydioides (Podocarpaceae) were separated by use of the reversed phase HPLC method. The analysed compounds belong to different groups of flavonoids – biflavones (amentoflavone, bilobetin, 5–methoxybilobetin, podocarpusflavone A, sequoiaflavone, podocarpusflavone B, ginkgetin, isoginkgetin, sciadopitysin, kayaflavone, hinokiflavone, 2,3–dihydrosciadopitysin, 2,3–dihydroisoginkgetin), O–acylated flavonol glycosides (daglesiosides I, II, III, IV, trans–tiliroside, trans–ditiliroside), flavonol O–glycosides (astragalin, isoquercetin) and flavonol aglycones (kaempferol, quercetin, isorhamnetin). The conditions for flavonoid separation were optimized using various RP–18 columns. The chromatographic resolution was performed with isocratic or gradient elution – optimized by Drylab program or by traditional trial-and-error method, depending on the composition of flavonoid complex.     

Phytochemical Profile,Antioxidant Activity,and Cytotoxicity Assessment of Tagetes erecta L. Flowers

Tagetes erecta L. is a popular ornamental plant of the Asteraceae family, which is widely cultivated not only for its decorative use, but also for the extraction of lutein. Besides carotenoid representatives, which have been extensively studied, other important classes of secondary metabolites present in the plant, such as polyphenols, could exhibit important biological activities. The phytochemical analysis of a methanolic extract obtained from T. erecta inflorescences was achieved using liquid chromatography–mass spectrometry (LC-MS) techniques. The extract was further subjected to a multistep purification process, which allowed the separation of different fractions. The total extract and its fractions contain several polyphenolic compounds, such as hydroxybenzoic and hydroxycinnamic acid derivatives, flavonols (especially quercetagetin glycosides), and several aglycons (e.g., quercetin, patuletin). One of the fractions, containing mostly quercetagitrin, was subjected to two different antioxidant assays (metal chelating activity and lipoxygenase inhibition) and to in vitro cytotoxicity assessment. Generally, the biological assays showed promising results for the investigated fraction compared to the initial extract. Given the encouraging outcome of the in vitro assays, further purification and structural analysis of compounds from T. erecta extracts, as well as further in vivo investigations are justified.     

Structures of flavone and flavonol glycosides

Summary Literature information on the structures of O-glycosides of flavones and flavonols has been generalized. Using the methods of combinatorial mathematics, the possibility of a great diversity of the structure of the glycosides has been shown without taking into account their acylation, the dimensions of the oxide rings of the sugars, and the nature of the glycosidic bonds.Pyatigorsk Pharmaceutical Institute. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 413–425, July–August, 1972.     

Inclusion complexes of modified cyclodextrins with some flavonols

The inclusion complexes of four flavonols with modified cyclodextrins (CDs) have been investigated. The effect of heptakis (2,6-di-O-methyl) β-cyclodextrin (DM-β-CD) and 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) on the aqueous solubility of flavonols, namely, galangin, kaempferol, quercetin, and myricetin was investigated, respectively. The increased solubility of all flavonols in the presence of CD was evidenced. The NMR experiment and molecular modeling studies showed that flavonols interact with each modified CD through different binding modes. Flavonols can complex with CDs largely by two binding modes. The first one is that B-ring of flavonols is oriented toward secondary rim of CD. The second one is that A-ring of flavonols is oriented toward secondary rim of CD. Whereas only the first mode was observed in DM-β-CD complexes, both the first and the second mode were observed in HP-β-CD complexes in this study.