Urakunoside, a new tetraglycosyl kaempferol from petals of the Wabisuke camellia cv. Tarokaja

A new tetraglycosyl flavonol, 3-O-[2-O-xylosyl-6-O-(3-O-glucosyl-rhamnosyl) glucosyl] kaempferol was isolated from pale purplish-pink petals of Wabisuke camellia cv. Tarokaja with three known flavonols. It was named urakunoside after the species name of Tarokaja, Camellia uraku. Urakunoside was a major flavonol component in the Tarokaja petals, but was not detected in petals of Tarokaja's presumed ancestor species.     

Biologically-active flavonoids from Gossypium arboreum

A new flavonol glycoside, gossypetin 8-O-rhamnoside, was isolated from flower petals of Gossypium arboreum along with quercetin 7-O-glucoside, quercetin 3-O-glucoside and quercetin 3′-O-glucoside. These compounds showed antibacterial activity against Pseudomonas maltophilia and Enterobacter cloacae.     

Formation of UV-honey guides in Rudbeckia hirta

The UV-honey guides of Rudbeckia hirta were investigated by UV-photography, reflectance spectroscopy, LC-MS analysis and studies of the enzymes involved in the formation of the UV-absorbing flavonols present in the petals. It was shown for the first time that the typical bull’s eye pattern is already established at the early stages of flower anthesis on the front side of the petal surface, but is hidden to pollinators until the buds are open and the petals are unfolded. The rear side of the petals remains UV-reflecting during the whole flower anthesis. Studies on the local distribution of 19 flavonols across the petals confirmed that the majority are concentrated in the basal part of the ray flower. However, in contrast to the earlier studies, eupatolitin 3-O-glucoside (6,7-dimethoxyquercetin 3-O-glucoside) was present in both the basal and apical parts of the petals, whereas eupatolin (6,7-dimethoxyquercetin 3-O-rhamnoside) was exclusively found in the apical parts. The enzymes involved in the formation of the flavonols in R. hirta were demonstrated for the first time. These include a rare flavonol 6-hydroxylase, which was identified as cytochrome P450-dependent monooxygenase and did not accept any methylated flavonol as substrate. All enzymes were present in the basal and apical parts of the petals, although some of them clearly showed higher activities in the basal part. This indicates that the local accumulation of flavonols in R. hirta is not achieved by a locally restricted presence of the enzymes involved in flavonol formation.     

Change of supercooling capability in solutions containing different kinds of ice nucleators by flavonol glycosides from deep supercooling xylem parenchyma cells in trees

Deep supercooling xylem parenchyma cells (XPCs) in Katsura tree contain flavonol glycosides with high supercooling-facilitating capability in solutions containing the ice nucleation bacterium (INB) Erwinia ananas, which is thought to have an important role in deep supercooling of XPCs. The present study, in order to further clarify the roles of these flavonol glycosides in deep supercooling of XPCs, the effects of these supercooling-facilitating (anti-ice nucleating) flavonol glycosides, kaempferol 3-O-β-d-glucopyranoside (K3Glc), kaempferol 7-O-β-d-glucopyranoside (K7Glc) and quercetin 3-O-β-d-glucopyranoside (Q3Glc), in buffered Milli-Q water (BMQW) containing different kinds of ice nucleators, including INB Xanthomonas campestris, silver iodide and phloroglucinol, were examined by a droplet freezing assay. The results showed that all of the flavonol glycosides promoted supercooling in all solutions containing different kinds of ice nucleators, although the magnitudes of supercooling capability of each flavonol glycoside changed in solutions containing different kinds of ice nucleators. On the other hand, these flavonol glycosides exhibited complicated nucleating reactions in BMQW, which did not contain identified ice nucleators but contained only unidentified airborne impurities. Q3Glc exhibited both supercooling-facilitating and ice nucleating capabilities depending on the concentrations in such water. Both K3Glc and K7Glc exhibited only ice nucleation capability in such water. It was also shown by an emulsion freezing assay in BMQW that K3Glc and Q3Glc had no effect on homogeneous ice nucleation temperature, whereas K7Glc increased ice nucleation temperature. The results indicated that each flavonol glycoside affected ice nucleation by very complicated and varied reactions. More studies are necessary to determine the exact roles of these flavonol glycosides in deep supercooling of XPCs in which unidentified heterogeneous ice nucleators may exist.     

Identification and characterization of a rhamnosyltransferase involved in rutin biosynthesis in Fagopyrum esculentum (common buckwheat)

Rutin, a 3-rutinosyl quercetin, is a representative flavonoid distributed in many plant species, and is highlighted for its therapeutic potential. In this study, we purified uridine diphosphate-rhamnose: quercetin 3-O-glucoside 6″-O-rhamnosyltransferase and isolated the corresponding cDNA (FeF3G6″RhaT) from seedlings of common buckwheat (Fagopyrum esculentum). The recombinant FeF3G6″RhaT enzyme expressed in Escherichia coli exhibited 6″-O-rhamnosylation activity against flavonol 3-O-glucoside and flavonol 3-O-galactoside as substrates, but showed only faint activity against flavonoid 7-O-glucosides. Tobacco cells expressing FeF3G6″RhaT converted the administered quercetin into rutin, suggesting that FeF3G6″RhaT can function as a rhamnosyltransferase in planta. Quantitative PCR analysis on several organs of common buckwheat revealed that accumulation of FeF3G6″RhaT began during the early developmental stages of rutin-accumulating organs, such as flowers, leaves, and cotyledons. These results suggest that FeF3G6″RhaT is involved in rutin biosynthesis in common buckwheat.     

Flavonoid chemistry ofBlennospermatinae, a trans-Pacific disjunct subtribe ofSenecioneae (Asteraceae)

The flavonoid profiles of seven species ofAbrotanella and one species ofIschnea have been shown to be based upon kaempferol 3- and quercetin 3-O-glycosides and a delphinidin glycoside. Glucosides, glucuronides, arabinosides, diglucosides, and rutinosides of the flavonols were identified. The profile ofIschnea consisted solely of quercetin 3-O-glucoside and 3-O-arabinoside whereas the profiles of theAbrotanella species were more varied. Although infraspecific variation was not investigated in this study, the flavonoid chemistry of the two genera is in accordance with the flavonoid variation described for other members ofSenecioneae which are primarily flavonol producers. Based on the known phylogeny and biogeography, the flavonoid distribution from the perspective of long-distance dispersals across the Pacific is discussed. Such events should lead to genetic bottle-neck situations and depauperate flavonoid profiles. A summary of current flavonoid knowledge in theSenecioneae is supplied.     

Spatiotemporal metabolic regulation of anthocyanin and related compounds during the development of marginal picotee petals in <Emphasis Type="Italic">Petunia hybrida</Emphasis> (Solanaceae)

Structures and levels of anthocyanin-related compounds were analyzed during the development of marginal picotee petals in white-center and white-marginal cultivars of Petunia hybrida. In the white site of a white-center cultivar, higher concentrations of quercetin derivatives possessing 7-O-glucoside and/or 3′-O-glucoside occurred than in the colored site, suggesting that these two quercetin glycosylation steps are site-specifically regulated. The boundary areas of petal coloration were composed of cells showing various color densities, whose uniformity among adjacent cells varied between these cultivars. These results indicate diversity in spatiotemporal regulation of anthocyanin biosynthesis and flavonol glycosylations between Petunia cultivars during marginal picotee formation. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Leaf flavonoid glycosides as chemosystematic characters in Ocimum

Thirty-one accessions of nine species belonging to three subgenera of Ocimum (basil, family Lamiaceae) were surveyed for flavonoid glycosides. Substantial infraspecific differences in flavonoid profiles of the leaves were found only in O. americanum, where var. pilosum accumulated the flavone C-glycoside, vicenin-2, which only occurred in trace amounts in var. americanum and was not detected in cv. Sacred. The major flavonoids in var. americanum and cv. Sacred, and also in all other species investigated for subgenus Ocimum, were flavonol 3-O-glucosides and 3-O-rutinosides. Many species in subgenus Ocimum also produced the more unusual compound, quercetin 3-O-(6″-O-malonyl)glucoside, and small amounts of flavone O-glycosides. The level of flavonol glycosides produced was reduced significantly in glasshouse-grown plants, but levels of flavone glycosides were unaffected. A single species investigated from subgenus Nautochilus, O. lamiifolium, had a different flavonoid glycoside profile, although the major compound was also a flavonol O-glycoside. This was identified as quercetin 3-O-xylosyl(1‴→2″)galactoside, using NMR spectroscopy. The species investigated from subgenus Gymnocimum, O. tenuiflorum (=O. sanctum), was characterised by the accumulation of flavone O-glycosides. These were isolated, and identified as the 7-O-glucuronides of luteolin and apigenin. Luteolin 5-O-glucoside was found in all nine species of Ocimum studied, and is considered to be a key character for the genus.     

Acylated flavonol diglucosides from Lotus polyphyllos

Three acylated flavonol diglucosides, kaempferol 3-O-β-(6″-O-E-p-coumaroylglucoside)-7-O-β-glucoside; quercetin 3-O-β-(6″-O-E-p-coumaroylglucoside)-7-O-β-glucoside; isorhamnetin 3-O-β-(6″-O-E-p-coumaroylglucoside)-7-O-β-glucoside were isolated from the whole plant aqueous alcohol extract of Lotus polyphyllos. The known 3,7-di-O-glucosides of the aglycones kaempferol, quercetin and isorhamnetin were also characterized. All structures were established on the basis of chemical and spectral evidence.     

Flavonol glycosides acylated with 3-hydroxy-3-methylglutaric acid as systematic characters in Rosa

LC–UV–MS/MS analysis of leaf extracts from 146 accessions of 71 species of Rosa revealed that some taxa accumulated flavonol O-glycosides acylated with 3-hydroxy-3-methylglutaric acid, which are relatively uncommon in plants. The structures of two previously unrecorded examples isolated from Rosa spinosissima L. (syn. Rosa pimpinellifolia L.) were elucidated using spectroscopic and chemical methods as the 3-O-α-l-rhamnopyranosyl-(1 → 2)-[6-O-(3-hydroxy-3-methylglutaryl)-β-d-galactopyranosides] of kaempferol (3,5,7,4′-tetrahydroxyflavone) and quercetin (3,5,7,3′,4′-pentahydroxyflavone). The corresponding 3-O-[6-O-(3-hydroxy-3-methylglutaryl)-β-d-galactopyranoside] of quercetin was also present in R. spinosissima, but at lower levels, together with 17 other flavonol O-glycosides for which structures were assigned using LC–UV–MS/MS. The distribution of flavonol 3-hydroxy-3-methylglutarylgalactosides in Rosa was limited to some species of subgenus Rosa section Pimpinellifoliae and Rosa roxburghii Sw. of the monotypic subgenus Platyrhodon, indicating that this character could be of value in phylogenetic analyses of the genus.     

Uptake and metabolism of flavonols during in-vitro germination of Petunia hybrida (L.) pollen

Flavonol-deficient petunia pollen [conditionally male fertile (CMF) pollen] is unable to germinate but application of nanomolar concentrations of flavonol aglycones completely restores function (Mo et al. 1992). In this study a chemically synthesized radioactive flavonol, [4′-O-¹⁴C]kaempferide, was used as a model compound to study the metabolism of flavonols during the first few hours of pollen germination. [4′-O-¹⁴C] Kaempferide was as efficient at inducing CMF pollen germination as kaempferol and quercetin, the aglycone form of the endogenous flavonols in petunia pollen. Analysis by high-performance liquid chromatography (HPLC) of extracts from both in-vitro-germinated pollen and the germination medium showed that more than 95% of the applied radioactivity was recovered as three kaempferide 3-O-glycosides and unmetabolized kaempferide; no flavonol catabolites were detected. Only HPLC fractions that contained the aglycone, or produced it upon acid hydrolysis, could induce CMF pollen germination in vitro. Structurally diverse flavonols could be classified according to how efficiently the aglycone was internalized and glycosylated during pollen germination. The ability of an individual flavonol to restore germination correlated with the total uptake of flavonols but not with the amount of glycoside formed in the pollen. Thus this study reinforces the conclusion that flavonol aglycones are the active compound for inducing pollen germination. Received: 4 November 1996/Accepted: 4 December 1996     

Flavonol glycosides from Epimedium sagittatum

Two new flavonol glycosides were isolated from Epimedium sagittatum besides the known flavonol glycosides, icariin and icarisid I. On the basis of spectral analyses, the structures of the compounds were determined to be anhydroicaritin-3-O-α-rhamnoside and icaritin-3-O-α-rhamnoside.     

A flavonol glycoside from Lysimachia Mauritiana

From the whole plant of Lysimachia mauritiana, a new flavonol glycoside (mauritianin) was isolated together with hyperin, kaempferol-3-O-robinobioside and kaempferol-3-O-α-rhamnopyranosyl-(1–2)-β-galactopyranoside. The structure of mauritianin was established as kaempferol-3-O-(2,6-di-O-α-rhamnopyranosyl-β-galactopyranoside).     

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.     

Catabolism of flavonol glucosides in plant cell suspension cultures

Catabolism of flavonol glucosides was investigated in plant cell suspension cultures using kaempferol 3-O-β-d-glucoside and kaempferol 7-O-β-d-glucoside labelled with ¹⁴C either in the glucose or in the flavonol moiety. Catabolic rates of glucosides were compared with those of free glucose and kaempferol. All substrates were degraded efficiently by cell cultures of mungbean, soybean, garbanzo bean and parsley. Based on ¹⁴CO₂-formation, glucose from position 3 of kaempferol is 3–5 times more rapidly metabolized than that from position 7. The flavonol nucleus from both isomers is, however, oxidized to the same extent with a considerable portion of the flavonol being incorporated into insoluble polymeric cell material.     

Flavonoids from Seeds of Camellia semiserrata Chi. and Their Estrogenic Activity

Two new flavonol glycosides and three known flavonoids were isolated from seeds of Camellia semiserrata Chi. The structures of these new flavonol glycosides were established as kaempferol 3-O-[(2'''',3'''',4''''-triacetyl)-α-L-rhamnopyranosyl(1→3)(2''',4'''-diacetyl)-α-L-rhamnopyranosyl (1→6)-β-D-glucopyranoside] and kaempferol 3-O-[(3'''',4''''-diacetyl)-α-L-rhamnopyranosyl(1→3)(2''',4'''-diacetyl)-α-L-rhamnopyranosyl(1→6)-β-D-glucopyranoside] by spectroscopic methods. The estrogenic activity of these compounds was investigated by a recombinant yeast screening assay.     

Detection of 1-O-malylglucose: pelargonidin 3-O-glucose-6'-O-malyltransferase activity in carnation (Dianthus caryophyllus)

Carnations have anthocyanins acylated with malate. Although anthocyanin acyltransferases have been reported in several plant species, anthocyanin malyltransferase (AMalT) activity in carnation has not been identified. Here, an acyl donor substance of AMalT, 1-O-β-d-malylglucose, was extracted and partially purified from the petals of carnation. This was synthesized chemically to analyze AMalT activity in a crude extract from carnation. Changes in the AMalT activity showed close correlation to the accumulation of pelargonidin 3-malylglucoside (Pel 3-malGlc) during the development of red petals of carnation, but neither AMalT activity nor Pel 3-malGlc accumulation was detectable in roots, stems and leaves.     

鸳鸯茉莉开花过程中花青素组成的变化

为了解鸳鸯茉莉(Brunfelsiaacuminata)花色变化的机理,采用高效液相色谱(HPLC)体系检测其开花过程中花青素组成的变化。结果表明,优化的HPLC体系为:流速为0.8 mL min–1,流动相A为7.5%甲酸乙腈,流动相B为7.5%甲酸水,洗脱程序为0 min,8%A;15 min,18%A;25 min,23%A;45 min,40%A;50 min,8%A。利用优化体系检测到鸳鸯茉莉花瓣中含有锦葵色素-3-O-葡萄糖苷、矮牵牛素葡萄糖苷和飞燕草素葡萄糖苷3种花青苷,其中锦葵色素-3-O-葡萄糖苷的含量最高,飞燕草素葡萄糖苷含量最低,且在花色由深变浅的过程中3种花青苷的含量均降低。因此,鸳鸯茉莉的呈色与这3种花青苷有关,且锦葵色素-3-O-葡萄糖苷起主导作用。     

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.     

Flavonol glycosides from Chenopodium foliosum Asch

Three new flavonol glycosides, namely 6-methoxykaempferol-3-O-β-gentiobioside, gomphrenol-3-O-β-gentiobioside and gomphrenol-3-O-α-l-rhamnopyranosyl-(1 → 2)[β-d-glucopyranosyl-(1 → 6)]-β-d-glucopyranoside as well as the known patuletin-3-O-β-gentiobioside and spinacetin-3-O-β-gentiobioside were isolated from the aerial parts of Chenopodium foliosum Asch. The structures of the compounds were determined by means of spectroscopic methods (1D and 2D NMR, UV, IR, and HRMS). DPPH free radical scavenging activity of the new compounds was low or lacking.