Die flavonolglykoside von Equisetum silvaticum

Ten glycosides of kaempferol and quercetin, including the hitherto unknown kaempferol and quercetin 3-rutinoside-7-rhamnosides, have been isolated from Equisetum silvaticum L.     

Characterisation of new oligoglycosidic compounds in two Chinese medicinal herbs

A series of caffeic acid derivatives (3,5-dicaffeoyl-quinic acid, 3,4-dicaffeoyl-quinic acid, and 4,5-dicaffeoyl-quinic acid), and the new compound beta,3,4-trihydroxyphenethyl-O-[beta-apiofuranosyl-(1-->4)-alpha- rhamnopyranosyl-(1-->3)]-(4-O-caffeoyl)-beta-glucopyranoside (wedelosin), as well as three known flavonoid glycosides (quercetin 3-O-beta-glucoside, kaempferol 3-O-beta-apiosyl-(1-2)-beta-glucoside, and astragalin or kaempferol 3-O-beta-glucoside) were isolated from the Chinese medicinal herb Wedelia chinensis. Wedelosin showed an inhibitory activity on both the classical and the alternative activation pathway of the complement system. Another Chinese medicinal herb, Kyllinga brevifolia, yielded two known flavonoid glycosides [kaempferol 3-O-beta-apiosyl-(1-2)-beta-glucoside and isorhamnetin 3-O-beta-apiosyl-(1-2)-beta-glucoside], and a new quercetin triglycoside [quercetin 3-O-beta-apiofuranosyl-(1-->2)-beta-glucopyranoside 7-O-alpha-rhamnopyranoside]. The latter compound showed a moderate anti-viral activity.     

The colorless flavonoids of Arabidopsis thaliana (Brassicaceae). II. Flavonoid 3' hydroxylation and lipid peroxidation

The 3' hydroxylation of kaempferol forms quercetin with an orthodihydroxy structure having two neighboring hydroxyl groups that could theoretically chelate with metal ions and mediate oxidative phenomena. Colorless flavonoids were purified by high pressure liquid chromatography (HPLC) and screened by diode array analysis. The accumulation of quercetin derivatives in Arabidopsis was coordinately regulated with flavonoid biosynthesis in a chalcone isomerase mutant having reduced flux through the biosynthetic pathway, but not within differing wild-type tissues, where seedling, floral, and leaf tissue have a reduced ratio of quercetin to kaempferol derivatives, respectively. The accumulation of lipid peroxidation products in kaempferol proficient mutant seedlings was indistinguishable from that in quercetin proficient wild-type seedlings, leaving no evidence for the role of quercetin antioxidants. However, laser scanning confocal microscopy revealed quercetin derivatives lining the tonoplast of diphenylboric acid 2-aminoethyl ester-stained Arabidopsis seedling tissue and floral papillae, and Norfluorazon induced oxidative stress decreased the most lipophilic of HPLC purified quercetin derivatives. Its potential involvement with lipophyllic oxidative phenomena may warrant further study.     

Trisubstituted flavonol glycosides in Coronilla emerus flowers

A novel trisubstituted kaempferol glycoside has been isolated from leaves and flowers of Coronilla emerus and identified as the 3-glucoside-7,4′-dirhamnoside. It co-occurs in the flowers with the 3-glucosides and 3-glucoside-7-rhamnosides of kaempferol and quercetin. A second kaempferol triglycoside based on glucose and xylose is also present. All six glycosides contribute to the UV patterning present in the wings of the flowers. This is the first report of kaempferol triglycosides with monosaccharide units substituting hydroxyl groups at the 3-, 7- and 4′-positions.     

Leaf flavonoid patterns in Dipterocarpus and Hopea (Dipterocarpaceae)

In a flavonoid survey of five species ( D. alatus Roxb. & G.Don, D. costatus Gaertn. f., D. gracilis Blume, D. turbinatus Gaertn. f. and Hopea odorata Roxb . ) of Dipterocarpaceae from Bangladesh, three flavonoid aglycones and two glycosides were isolated. The flavonol kaempferol was detected in 40% of the total species surveyed, while the flavonol quercetin and flavone apigenin were present in all species examined, establishing their chemotaxonomic significance. Proanthocyanidins were found only in three species ( D. alatus , D. gracilis , D. turbinatus ), while the glycosides quercetin 3-glucoside and quercetin 3-rutinoside were isolated in 40% and 60% of the species surveyed, respectively. The flavonoid patterns of H. odorata and D. costatus are advanced in comparison to those of D. alatus , D. gracilis and D. turbinatus due to the loss of proanthocyanidin.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 143 , 43−46.     

Flavonoids from Zea mays pollen

The flavonol glycosides of quercetin, isorhamnetin and kaempferol were isolated from Zea mays pollen. The most prominent flavonols were diglycosides of quercetin and isorhamnetin. Flavonol 3-O-glucosides of quercetin, isorhamnetin and kaempferol, and triglucosides of quercetin and isorhamnetin, were minor components. The flavonoid pattern of maize pollen is characterized by the accumulation of quercetin and isorhamnetin diglycosides and by the absence of flavones, which are common in other maize tissues.     

Tradeoff between biomass and flavonoid accumulation in white clover reflects contrasting plant strategies

An outdoor study was conducted to examine relationships between plant productivity and stress-protective phenolic plant metabolites. Twenty-two populations of the pasture legume white clover were grown for 4½ months during spring and summer in Palmerston North, New Zealand. The major phenolic compounds identified and quantified by HPLC analysis were glycosides of the flavonoids quercetin and kaempferol. Multivariate analysis revealed a trade-off between flavonoid accumulation and plant productivity attributes. White clover populations with high biomass production, large leaves and thick tap roots showed low levels of quercetin glycoside accumulation and low quercetin:kaempferol ratios, while the opposite was true for less productive populations. The latter included stress-resistant ecotypes from Turkey and China, and the analysis also identified highly significant positive relationships of quercetin glycoside accumulation with plant morphology (root:shoot ratio). Importantly, a high degree of genetic variation was detected for most of the measured traits. These findings suggest merit for considering flavonoids such as quercetin as potential selection criteria in the genetic improvement of white clover and other crops.     

Flavonoids of Abies amabilis needles

Seventeen flavonol glycosides were identified from needles of Abies amabilis and these were based on 6 aglycone types: syringetin, isorhamnetin, kaempferol, quercetin, laricytrin and myricetin. Glycosides were 3-O-rutinosides, 3-O-glucosides, 3-O-galactosides or 3-O-rhamnosides. Also identified as needle constituents were rhamnosylvitexin and dihydroquercetin.     

Further studies of flavonols of Clibadium (compositae)

The flavonoids of an additional eight species of Clibadium have been determined. The compounds are derivatives of kaempferol, quercetin and quercetagetin. O-Methylated quercetagetin derivatives were found in several taxa with the possibility that 6-methoxykaempferol may also exist in one collection. Kaempferol and quercetin exist as 3-O-glucosides, galactosides, rhamnosides, rutinosides and diglucosides although not all glycosides occur in each taxon. Quercetagetin derivatives occur as 7-O-glucosides. Observations on these newly investigated species confirm previous work in the genus that three types of flavonoid profiles exist: (1) kaempferol and quercetin 3-glycosides; (2) kaempferol and quercetin 3-glycosides plus quercetagetin 7-glucoside; and (3) kaempferol and quercetin 3-glycosides plus quercetagetin 7-glucoside and O-methylated derivatives of quercetagetin.     

Flavonoid accumulation patterns of transparent testa mutants of arabidopsis

Flavonoids have been implicated in the regulation of auxin movements in Arabidopsis. To understand when and where flavonoids may be acting to control auxin movement, the flavonoid accumulation pattern was examined in young seedlings and mature tissues of wild-type Arabidopsis. Using a variety of biochemical and visualization techniques, flavonoid accumulation in mature plants was localized in cauline leaves, pollen, stigmata, and floral primordia, and in the stems of young, actively growing inflorescences. In young Landsberg erecta seedlings, aglycone flavonols accumulated developmentally in three regions, the cotyledonary node, the hypocotyl-root transition zone, and the root tip. Aglycone flavonols accumulated at the hypocotyl-root transition zone in a developmental and tissue-specific manner with kaempferol in the epidermis and quercetin in the cortex. Quercetin localized subcellularly in the nuclear region, plasma membrane, and endomembrane system, whereas kaempferol localized in the nuclear region and plasma membrane. The flavonoid accumulation pattern was also examined in transparent testa mutants blocked at different steps in the flavonoid biosynthesis pathway. The transparent testa mutants were shown to have precursor accumulation patterns similar to those of end product flavonoids in wild-type Landsberg erecta, suggesting that synthesis and end product accumulation occur in the same cells.     

Flavonoid analysis of<Emphasis Type="Italic">Heloniopsis orientalis</Emphasis> (Thunb.) by high performance liquid chromatography

We have isolated and identified seven flavonoid compounds from the foliar extracts ofHeloniopsis orientalis, a member of Liliaceae, which is habituated at Namhansanseong and Maranggol (Jinburyung). All are glycosylated derivatives of the flavonols isorhamnetin, kaempferol, and quercetin. Among them, quercetin 3-O-galactoside is the major compound, while isorhamnetin 3-O-arabinosylgalactoside, isorhamnetin 3-O-digalactoside, kaempferol 3,7-O-galactoside, kaempferol 3-O-arabinosylgalactoside, kaempferol 3-O-glycoside, and quercetin 3-O-arabinosylgalactoside are present in smaller amounts. Although the two populations do not differ significantly in their overall flavonol profiles, their relative amounts indicate that flavonoid levels, especially for isorhamnetin, are geographically controlled and specifically depend on the origin of the individual population.     

Flavonoids of Astilbe and Rodgersia compared to Aruncus

The flavonoid profiles of Astilbe (four taxa studied) and Rodgersia (two taxa studied) are based on simple flavonol glycosides. Astilbe has 3-O-mono-, 3-O-di-, and 3-O-triglycosides of kaempferol, quercetin, and myricetin, while Rodgersia has only mono- and diglycosides of kaempferol and quercetin. Astilbe×arendsii was also shown to accumulate dihydrochalcone glycosides. The flavonoid profile of Rodgersia is the simplest recorded so far in the herbaceous Saxifragaceae. The flavonoids of two species of Aruncus were shown to be based upon kaempferol and quercetin 3-O-mono- and 3-O-diglycosides. One of the species also exhibited an eriodictyol glycoside. The triglycoside differences were not considered important, but the differences in myricetin occurrences were taken as evidence against derivation of Saxifragaceae from an Aruncus-like ancestor. Should such an event be proposed, however, serious consideration would have to be given to the current pattern of myricetin occurrence in the two families.     

Functional analysis of soybean genes involved in flavonoid biosynthesis by virus-induced gene silencing

Virus-induced gene silencing (VIGS) is a powerful tool for functional analysis of genes in plants. A wide-host-range VIGS vector, which was developed based on the Cucumber mosaic virus (CMV), was tested for its ability to silence endogenous genes involved in flavonoid biosynthesis in soybean. Symptomless infection was established using a pseudorecombinant virus, which enabled detection of specific changes in metabolite content by VIGS. It has been demonstrated that the yellow seed coat phenotype of various cultivated soybean lines that lack anthocyanin pigmentation is induced by natural degradation of chalcone synthase ( CHS ) mRNA. When soybean plants with brown seed coats were infected with a virus that contains the CHS gene sequence, the colour of the seed coats changed to yellow, which indicates that the naturally occurring RNA silencing is reproduced by VIGS. In addition, CHS VIGS consequently led to a decrease in isoflavone content in seeds. VIGS was also tested on the putative flavonoid 3'-hydroxylase ( F3'H ) gene in the pathway. This experiment resulted in a decrease in the content of quercetin relative to kaempferol in the upper leaves after viral infection, which suggests that the putative gene actually encodes the F3'H protein. In both experiments, a marked decrease in the target mRNA and accumulation of short interfering RNAs were detected, indicating that sequence-specific mRNA degradation was induced. The present report is a successful demonstration of the application of VIGS for genes involved in flavonoid biosynthesis in plants; the CMV-based VIGS system provides an efficient tool for functional analysis of soybean genes.     

The antileishmanial activity assessment of unusual flavonoids from Kalanchoe pinnata

The importance of flavonoids for the antileishmanial activity of Kalanchoe pinnata was previously demonstrated by the isolation of quercitrin, a potent antileishmanial flavonoid. In the present study, the aqueous leaf extract from the medicinal plant K. pinnata (Crassulaceae) afforded a kaempferol di-glycoside, named kapinnatoside, identified as kaempferol 3-O-alpha-L-arabinopyranosyl (1-->2) alpha-L-rhamnopyranoside (1). In addition, two unusual flavonol and flavone glycosides already reported, quercetin 3-O-alpha-L-arabinopyranosyl (1-->2) alpha-L-rhamnopyranoside (2) and 4',5-dihydroxy-3',8-dimethoxyflavone 7-O-beta-D-glucopyranoside (3), have been isolated. Their structures were determined via analyses of mono and bi-dimensional (1)H and (13)C NMR spectroscopic experiments and HR-MALDI mass spectra. Because of its restricted occurrence and its abundance in K. pinnata, flavonoid (2) may be a chemical marker for this plant species of high therapeutic potential. The three flavonoids were tested separately against Leishmania amazonenis amastigotes in comparison with quercitrin, quercetin and afzelin. The quercetin aglycone - type structure, as well as a rhamnosyl unit linked at C-3, seem to be important for antileishmanial activity.     

Flavonoid ingredients of Ginkgo biloba leaf extract regulate lipid metabolism through Sp1-mediated carnitine palmitoyltranferase 1A up-regulation

Background

Lipid accumulation is the primary evidence of non-alcoholic fatty liver disease (NAFLD). Ginkgo biloba extract (GBE) and its flavonoid ingredients (quercetin, kaempferol, and isorhamnetin) could lessen the lipid accumulation associated with up-regulation of the rate-limiting enzyme, carnitine palmitoyltransferase 1A (CPT1A), in the β-oxidation of long-chain fatty acids. In this study, we investigated the mechanisms by which GBE and its flavonoids induced expression of CPT1A.

Results

CPT1A inhibition with RNAi resulted in triglyceride accumulation in HepG2 cells. Through deletion and mutation analysis of CPT1A’s promoter combined with electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) experiments, the CPT1A promoter region (−50 to −5 nt) was determined to contain two putative Sp1 binding sites, namely Sp1a and Sp1b, which might act as the GBE regulation response DNA element. Sp1 might be induced to transfer from cytoplasma to nucleus to bind the promoter region of −50 to −5 nt by GBE. The regulatory effects of GBE on CPT1A were also verified on the flavonoid ingredients quercetin, kaempferol, and isorhamnetin.

Conclusion

Sp1 was crucial in regulating CPT1A expression with GBE and its flavonoid ingredients, and the −50 to −5 nt region of CPT1A promoter played important roles in Sp1 binding.

Electronic supplementary material

The online version of this article (doi:10.1186/s12929-014-0087-x) contains supplementary material, which is available to authorized users.     

Flavonoid <Emphasis Type="Italic">O</Emphasis>-Diglucosyltransferase from Rice: Molecular Cloning and Characterization

Among more than 100 rice uridine diphosphate glycosyltransferases (UGTs), OsUGT-3 was selected as a candidate for producing flavonoid O-diglycosyltransferases based on phylogenetic analysis and molecular docking. This gene was functionally expressed in Escherichia coli. Analysis of kaempferol, luteolin, quercetin, and tricin reaction products using liquid chromatography-mass spectrometry revealed that these were diglucosylated. The glucosylation positions of kaempferol, which was the best substrate, were determined to be the 3- and 7-hydroxyl groups. This is the first flavonoid O-diglucosyltransferase described from rice.