Differences in flavonoid constituents among the species ofFagonia sinaica complex (Zygophyllaceae)

Eight flavonol glycosides were detected in the three species of theFagonia sinaica complex. They were fully characterized as the 3-glucosides of kaempferol, quercetin and isorhamnetin, 3-rutinoside of quercetin and 3,7-diglucoside of quercetin and isorhamnetin. Two additional glycosides were partially characterized as a kaempferol 3,7-diglycoside and quercetin 3-diglycoside.     

Flavonoids inBrassica nigra (L.) Koch,B. oleracea L.,B. campestris L. and their natural amphidiploids

Flavonoid analysis of the leaves inBrassica nigra, B. oleracea, B. campestris and their natural amphidiploids, led to the identification of 19 flavonol glycosides, including some acylated ones. These compounds were based on kaempferol, quercetin and isorhamnetin, except forB. oleracea, where no isorhamnetin glycosides were detected. Additive inheritance could normally be shown in the hybrids. Some considerations on the phylogenetic relationships within the group are expressed.     

Flavonol glycosides in the leaves ofTrillium apetalon Makino andT. kamtschaticum pallas

Seven flavonol glycosides were isolated from the leaves ofT. apetalon. They were identified chromatographically and spectrally to be: quercetin/kaempferol 3-O-α-arabinopyranosyl-(1→6)-β-galactopyranoside (TQ and TK), quercetin/kaempferol 3-O-[2‴-O-acetyl-α-arabinopyranosyl]-(1→6)-β-galactopyranoside (TAQ and TAK), quercetin 3-O-β-glucoside (ISQ), isorhamnetin 3-O-α-arabinopyranosyl-(1→6)-β-galactopyranoside (TI) and isorhamnetin 3-O-[2‴-O-acetyl-α-arabinopyranosyl]-(1→6)-β-galactopyranoside (TAI). TQ, TAQ, TI and TAI were major constituents. This is the first report on two new isorhamnetin-type glycosides, TI and TAI. The seven flavonol glycosides identical to those ofT. apetalon were isolated and identified in the leaves ofT. kamtschaticum; TQ and TAQ were also major components, but TI and TAI were only minor components. TI and TAI were not detected in the leaves ofT. tschonoskii. These leaf-flavonoid patterns were discussed from a chemosystematic point of view. Part 3 in the series “Studies of the flavonoids of the genusTrillium”. For Part 2 see Yoshitamaet al., (1997) J. Plant Res.110: 379–381.     

The flavonoids ofBalanites aegyptiaca (Balanitaceae) from Egypt

Six flavonoid glycosides: quercetin 3-glucoside, quercetin-3-rutinoside; 3-glucoside, 3-rutinoside, 3-7-diglucoside and 3-rhamnogalactoside of isorhamnetin were extracted and identified from the leaves and branches of Egyptian material ofBalanites aegyptiaca. Only isorhamnetin: 3-rutinoside and 3-rhamnogalactoside were recorded from the fruits of the same plant.—Phytochemical aspects ofBalanites aegyptiaca and some genera ofZygophylaceae s. l. viz.Nitraria, Fagonia, Zygophyllum, Seetzenia andTribulus support its affinities with that family.     

FLORAL PIGMENTATION STUDIES IN THE GENUS GOSSYPIUM. I. SPECIES SPECIFIC PIGMENTATION PATTERNS

Previous work on cotton flower pigments is outlined. The major flavonoids are glycosides of gossypetin, quercetin, and kampferol. Twelve flavonol glycosides have been tentatively isolated and identified, while a number of minor components remain unidentified. The gossypetin glycosides are gossypin, gossypitrin and a C₇-linked glycoside of unknown sugar residue. The quercetin glycosides include isoquercitrin, rutin, a third C₃-linked glycoside with unknown sugar residue, quercimeritrin and a second C₇-linked glycoside with sugar residue unknown. The kampferol glycosides include trifolin, kampferol rutinoside and 2 other C₃-linked glycosides with unknown sugar residues. The major anthocyanin throughout the genus is cyanidin. Mutants which affect visible flower color were studied in 3 species (G. arboreum, G. hirsutum, and G. barbadense). The majority of these mutants act to decrease or prevent the synthesis of gossypetin glycosides. The only exceptions to this are the mutants at the Y_a locus in G. arboreum, which affect all of the C₇-linked glycosides in one case, and in the other reduce over-all flavonol production. In all instances, the species could be positively identified by the residual array of pigments not affected by the mutant alleles concerned; i.e., visual similarity of phenotypes did not obscure the basic pattern of pigmentation characteristic of the different species.     

The flavonoid chemistry of the genusTrillium

Four flavonol glycosides (Fig.1) were isolated from the leaves ofTrillium tschonoskii Maxim. By means of UV, NMR, and mass spectral analyses, they were identified to be acetylated kaempferol 3-O-arabinosylgalactoside (TK-1), kaempferol 3-O-arabinosylgalactoside (TK-2), acetylated quercetin 3-O-arabinosylgalactoside (TQ-1) and quercetin 3-O-arabinosylgalactoside (TQ-2). High performance liquid chromatography (HPLC) profiles of 172 specimens ofT. tschonoskii collected from nine different places in Japan were grouped into three different types based on the flavonoid components: type I and type II containing TK-1 and TQ-1, and TK-2 and TQ-2, respectively, as main component, and type III containing all of four flavonol glycosides. Those results show that the intraspecific variation ofT. tschonoskii with different geographical distribution has not only been found by the analysis of karyotype, but also that of flavonoid components.     

Flavonoids in translucent bracts of the Himalayan<Emphasis Type="Italic"> Rheum nobile</Emphasis> (Polygonaceae) as ultraviolet shields

UV-absorbing substances were isolated from the translucent bracts of Rheum nobile, which grows in the alpine zone of the eastern Himalayas. Nine kinds of the UV-absorbing substances were found by high performance liquid chromatography (HPLC) and paper chromatography (PC) surveys. All of the five major compounds are flavonoids, and were identified as quercetin 3-O-glucoside, quercetin 3-O-galactoside, quercetin 3-O-rutinoside, quercetin 3-O-arabinoside and quercetin 3-O-[6-(3-hydroxy-3-methylglutaroyl)-glucoside] by UV, ¹H and ¹³C NMR, mass spectra, and acid hydrolysis of the original glycosides, and direct PC and HPLC comparisons with authentic specimens. The four minor compounds were characterised as quercetin itself, quercetin 7-O-glycoside, kaempferol glycoside and feruloyl ester. Of those compounds, quercetin 3-O-[6-(3-hydroxy-3-methylglutaroyl)-glucoside] was found in nature for the first time. The translucent bracts of R. nobile accumulate a substantial quantity of flavonoids (3.3–5 mg per g dry material for the major compounds). Moreover, it was clarified by quantitative HPLC survey that much more of the UV-absorbing substances is present in the bracts than in rosulate leaves. Although the flavonoid compounds have been presumed to be the important UV shields in higher plants, there has been little characterisation of these compounds. In this paper, the UV-absorbing substances of the Himalayan R. nobile were characterised as flavonol glycosides based on quercetin.     

Purification and Identification of Flavonoids from the Yellow Green Cocoon Shell (Sasamayu) of the Silkworm,Bombyx mori

Three quercetin glycosides, quercetin 5-O-β-D-glucoside, quercetin 7-O-β-D-glucoside, and quercetin 4′-O-β-D-glucoside, and two kaempferol glycosides, kaempferol 5-O-β-D-glucoside and kaempferol 7-O-β-D-glucoside, along with their aglycones, quercetin and kaempferol, were isolated from an ethanolic extract of Sasamayu cocoon shells. The chemical structures were characterized by chemical and spectroscopic methods including UV spectrometry and HPLC-ESI-MS. The five flavonol glycosides of the shell are different structurally from those of the leaves of mulberry (Morus alba). It was suggested that potent antioxidative activity in the cocoon is mainly due to flavonoid compounds since free radical scavenging activity was found in the cocoon flavonoids identified here.     

Systematic implications of the flavonoids and chromosomes ofFlyriella (Compositae—Eupatorieae)

The leaves of five species ofFlyriella were found to contain from one to four glycosides of quercetin and its 4- and 7,4-methyl ethers. These patterns are distinct from those observed for more than seventy species ofBrickellia and support morphological and chromosomal data which indicate thatFlyriella should not be treated as an element ofBrickellia. Alternative treatments are briefly considered.     

Flavonoid chemistry ofWeigela (Caprifoliaceae) in Korea

Fifteen flavonoids were isolated from flowers and leaves of four species ofWeigela [W. florida (Bunge) A. DC.,W. praecox (Lemoine) Bailey,W. hortensis (Sieb. et Zucc.) K. Koch, andW. subsessilis (Nakai) Bailey] of Korea and one species (W. coraeensis Thunb.) of Japan. The flavonoid data indicated the presence of two distinct chemical groups: the “yellow flower” type producing flavonols and the “red flower” type producing flavonols and flavones. Two cyanidin 3-O-glycosides (glucoside and glucose-xylose) also occurred in all examined taxa. In the floral color-changing species,W. subsessilis, only quercetin glycosides predominated in floral tissue at first, decreasing in number and quantity with time. Instead, cyanidin 3-O-glycosides became present predominantly in flower color changing tissue from yellow to mauve.Weigela florida produced apigenin and luteolin glycosides, along with cyanidin 3-O-glycosides, which were also found inW. subsessilis. Within a relatively limited number of individuals (five),W. hortensis was unique in its production of all flavonols, flavones, and anthocyanins, although two individuals lacked flavone compounds but possessed all flavonols and anthocyanins. In effect, the putative hybrid,W. hortensis of Korea showed additive profiles of the parental marker compounds ofW. subsessilis andW. florida. Pollinator (andrenid bees) non-discrimination betweenWeigela flower-color morphs leading to non-assortive mating was a common, which indicated no breeding barrier among species. This flavonoid study indicated that species of both sections,Weigela andCalysphyrum appeared in each chemical grouping and it was obvious that the arrangement based on flavonoids cut across the sectional treatment of Hara. Floral tissues may be directly involved in the evolutionary strategy of pollination mechanisms and hence, their inherent flavonoids may no longer support taxonomic relationships. The presence of flavone glycosides inWeigela would support that tribe Dievilleae have a closer affinity to tribe Lonicereae within the Family Caprifoliaceae.     

Biological synthesis of quercetin 3-<Emphasis Type="Italic">O</Emphasis>-<Emphasis Type="Italic">N</Emphasis>-acetylglucosamine conjugate using engineered <Emphasis Type="Italic">Escherichia coli</Emphasis> expressing <Emphasis Type="Italic">UGT78D2</Emphasis>

Biotransformation of flavonoids using Escherichia coli harboring nucleotide sugar-dependent uridine diphosphate-dependent glycosyltransferases (UGTs) commonly results in the production of a glucose conjugate because most UGTs are specific for UDP-glucose. The Arabidopsis enzyme AtUGT78D2 prefers UDP-glucose as a sugar donor and quercetin as a sugar acceptor. However, in vitro, AtUGT78D2 could use UDP-N-acetylglucosamine as a sugar donor, and whole cell biotransformation of quercetin using E. coli harboring AtUGT78D2 produced quercetin 3-O-N-acetylglucosamine. In order to increase the production of quercetin 3-O-N-acetylglucosamine via biotransformation, two E. coli mutant strains deleted in phosphoglucomutase (pgm) or glucose-1-phosphate uridylyltransferase (galU) were created. The galU mutant produced up to threefold more quercetin 3-O-N-acetylglucosamine than wild type, resulting in the production of 380-mg/l quercetin 3-O-N-acetylglucosamine and a negligible amount of quercetin 3-O-glucoside. These results show that construction of bacterial strains for the synthesis of unnatural flavonoid glycosides is possible through rational selection of the nucleotide sugar-dependent glycosyltransferase and engineering of the nucleotide sugar metabolic pathway in the host strain.     

Flavonoid evidence for allopolyploidy in the Chenopodium album aggregate (Amaranthaceae)

The flavonoid chemistry of 16 species of Chenopodium was investigated, with an emphasis on C. album and its relatives. The chief compounds seen were 3-O-glycosides of quercetin, kaempferol and isorhamnetin. The latter two classes show a mutually exclusive distribution among the diploid and all but one tetraploid species. C. polyspermum is unusual in possessing O-methylation at the 4-, 6- and 7-positions, and C. murale is the only taxon to have 7-O-glycosylation. Acylated glycosides are common. C. album and related hexaploid taxa display a single flavonoid profile, providing no support for the recognition of more than one species. The hexaploid flavonoid profile represents an almost perfect summation of those of the diploids, C. suecicum and C. ficifolium. This apparent additive inheritance supports the hypothesis that these species (or taxa very similar to them) are involved in the ancestry of C. album. Chromosome numbers are reported for 14 of the species.     

Phenolics during early development of <Emphasis Type="Italic">Betula pubescens</Emphasis> seedlings: inhibition of phenylalanine ammonia lyase

We studied phenolic metabolism and plant growth in birch seedlings at the beginning of their development by inhibiting phenylalanine ammonia lyase (PAL), which is the first committed step in phenylpropanoid metabolism. Betula pubescens (Ehrh.) seeds were germinated in inhibitor-free media and the seedlings were transferred to hydroponic culture at the cotyledon stage. They were 6 days old at the start of the experiment, which lasted for 3 weeks. PAL activity was inhibited by three different concentrations of 2-aminoindane-2-phosphonic acid monohydrate (AIP) in the growing media. At the end of 3 weeks, phenolics in all plant parts (roots, stem, cotyledons, first, second and third true leaves) were determined. AIP inhibited strongly the accumulation of phenolic acids, salidroside, rhododendrins, ellagitannins and their precursors, flavan-3-ols, and soluble condensed tannins. The accumulation of lignin and flavonol glycoside derivatives was moderately inhibited. The accumulation of flavonol glycosides, such as quercetin glycosides and kaempferol glycosides, was not generally inhibited, even in leaves that emerged during the experiment, while the accumulation of insoluble condensed tannins was inhibited only slightly and not in all plant parts. This suggests that flavonol glycosides, which may have a UV-B protective role, and insoluble condensed tannins, which may have structural functions, are prioritized in seedling development. Inhibition of PAL with AIP decreased seedling growth and possible reasons for this are discussed. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Chemical analysis of phenolic glycosides: art,facts, and artifacts

Summary Phenolic glycosides have been the subject of considerable interest in recent ecological and systematic studies, especially those involving the Salicaceae. But these compounds are markedly labile in aqueous media, and the consequences of spontaneous degradation for valid interpretation of results have been largely ignored by researchers. We found that freeze-drying and oven-drying of leaf samples from several Populus and Salix species produced dramatic changes in the total and relative concentrations of specific phenolic glycosides, when compared to analyses of fresh material. Extraction in aqueous and alcoholic media for extended (24 h) periods also effected changes in glycoside concentrations. Alterations in phenolic glycoside concentrations, interconversions among glycosides, and production of artifactual glycosides result from a series of hydrolytic reactions. These deleterious effects can be best (but not entirely) avoided by the use of fresh plant material, cold, nonaqueous extraction solvents, and short extraction times. Because individual phenolic glycosides exhibit very different biological activities against herbivores, we caution ecologists to use utmost care in the performance and interpretation of phenolic glycoside assays.     

Inhibitors of aldose reductase and advanced glycation end-products formation from the leaves of Stelechocarpus cauliflorus R.E. Fr.

Two dihydroflavonol glycosides, engeletin and astilbin, were isolated from an EtOAc extract of the leaves of Stelechocarpus cauliflorus R.E. Fr. (Annonaceae). The inhibitory activity of engeletin against a recombinant human aldose reductase (IC₅₀ value=1.16 μM) was twice that of quercetin as a positive control (2.48 μM), and 23 times greater than that of astilbin (26.7 μM). Engeletin inhibited the enzyme uncompetitively. Astilbin was about as potent as the positive control, quercetin, in its inhibition of advanced glycation end-products formation. These flavonoids displayed therapeutic potential in the prevention and treatment of diabetic complications.     

Flavonoids in the leaves of twenty-eight polygonaceous plants

Flavonoids in the leaves of twenty-eight species belonging to the Polygonaceae were studied. Thirty-three kinds of flavonoids were isolated, and eighteen kinds were obtained as crystals. Quercetin glycosides were commonly found in the family. In the quercetin glycosides, 3-O-rhamnoside was most frequently found: 3-O-glucuronide is also distributed widely. Myricetin glycosides were rare. Methylated flavonols were found in some species of the sectionsEchinocaulon andPersicaria. Eleven kinds ofC-glycosylflavones were found in the present survey, andC-glycosylflavones were distributed in all species of the genusRheum and in almost all species of the section Tiniaria.Rumex Acetosella andPolygonum suffultum are exceptional, the former contains flavone glycoside and the latterC-glycosylflavones only, as main components.     

The sugar moiety is a major determinant of the absorption of dietary flavonoid glycosides in man

Flavonoids are antioxidants present in plant foods. They occur mainly as glycosides, i.e. linked with various sugars. It is uncertain to what extent dietary flavonoid glycosides are absorbed from the gut. We investigated how the nature of the sugar group affected absorption of one major flavonoid, quercetin. Quercetin linked with glucose, i.e. quercetin glucoside and quercetin linked with rutinose, i.e. quercetin rutinoside, both occur widely in foods. When we fed these compounds to nine volunteers, the peak concentration of quercetin (C_max) in plasma was 20 times higher and was reached (T_max) more than ten times faster after intake of the glucoside (C_max = 3.5 ± 0.6 μM (mean ± SE); T_max < 0.5 h) than after the rutinoside (C_max = 0.18 ± 0.04 μM; T_max = 6.0 ± 1.2 h). The bioavailability of the rutinoside was only 20% of that of the glucoside. We suggest that quercetin glucoside is actively absorbed from the small intestine, whereas quercetin rutinoside is absorbed from the colon after deglycosylation. Absorption of other food components might also be enhanced by attachment of a glucose group.     

Flavonol glycosides from distilled petals of Rosa damascena Mill

Flavonol glycosides were extracted from petals of Rosa damascena Mill. after industrial distillation for essential oil recovery and characterized by high-performance liquid chromatography-electrospray ionization mass spectrometry. Among the 22 major compounds analyzed, only kaempferol and quercetin glycosides were detected. To the best of our knowledge, the presence of quercetin 3-O-galactoside and quercetin 3-O-xyloside has so far not been reported within the genus Rosa. In addition, based on their fragmentation patterns, several acylated quercetin and kaempferol glycosides, some of them being disaccharides, were identified for the first time. The kaempferol glycosides, along with the kaempferol aglycone, accounted for 80% of the total compounds that were quantified, with kaempferol 3-O-glucoside being the predominant component. The high flavonol content of approximately 16 g/kg on a dry weight basis revealed that distilled rose petals represent a promising source of phenolic compounds which might be used as functional food ingredients, as natural antioxidants or as color enhancers.     

Enhanced Biotransformation Capacity of <Emphasis Type="Italic">Rhodiola rosea</Emphasis> Callus Cultures for Glycosid Production

Rhodiola rosea is a promising medicinal plant that produces various glycosides. Recently we developed a successful method for cultivating it in liquid cultures of compact callus aggregates. In a previous study we reported the successful production of the glycosides of R. rosea by biotransformation of cinnamyl alcohol and tyrosol. In the present study we investigated the possibility of further increasing the yields of the biotransformation products by addition of glucose to the culture medium aside from sucrose, which was used earlier as carbon source. Surprisingly, glucose addition doubled the yield of cinnamyl alcohol glycosides. Rosavin was not produced at all when only sucrose was used. When glucose was added the accumulation dynamics of rosin and a recently described derivative glycoside (designed as compound 321) were similar. Both increased during the first days and then remained constant, while other glycoside compounds increased continuously throughout the cultivation. Rosavin reached its maximum concentration after nine days. In contrast to the beneficial effect on cinnamyl alcohol related glycosides the addition of glucose did not affect the accumulation of the tyrosol derivative salidroside.     

Cloning, expression, and characterization of an aldehyde dehydrogenase from Escherichia coli K-12 that utilizes 3-Hydroxypropionaldehyde as a substrate

For efficient production of isoflavone aglycones from soybean isoflavones, we isolated three novel types of β-glucosidase (BGL1, BGL3, and BGL5) from the filamentous fungi Aspergillus oryzae. Three enzymes were independently displayed on the cell surface of a yeast Saccharomyces cerevisiae as a fusion protein with α-agglutinin. Three β-glucosidase-displaying yeast strains hydrolyzed isoflavone glycosides efficiently but exhibited different substrate specificities. Among these β-glucosidases, BGL1 exhibited the highest activity and also broad substrate specificity to isoflavone glycosides. Although glucose released from isoflavone glycosides are generally known to inhibit β-glucosidase, the residual ratio of isoflavone glycosides in the reaction mixture with BGL1-displaying yeast strain (Sc-BGL1) reached approximately 6.2%, and the glucose concentration in the reaction mixture was maintained at lower level. This result indicated that Sc-BGL1 assimilated the glucose before they inhibited the hydrolysis reaction, and efficient production of isoflavone aglycones was achieved by engineered yeast cells displaying β-glucosidase.