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Struktur und synthese von flavonol-triosiden aus rhamnus-arten
Abstract
By synthesis and 13C-NMR spectroscopic investigations of rhamnocitrin-, rhamnazin- and rhamnetin - 3 - O - [O - α - l - rhamnopyranosyl - (1 → 4) - O - α - l - rhamnopyranosyl - (1 → 6)] β - d - galactopyranosides and of rhamnocitrin - 3 - O - [O - α - l - rhamnopyranosyl - (1 → 3) - O - α - l - rhamnopyranosyl - (1 → 6)] - β - d - galactopyranoside (rhamnocitrin - 3 - O - β - rhamnisoide) it was proved that all naturally occurring flavonoltriosides, so far isolated from different Rhamnus species, contain the sugar-moiety rhamninose. Thus it was shown that catharticin (rhamnocitrin - 3 - O - β - rhamninoside) is identical with alaternin and xanthorhamnin A (rhamnetin - 3 - O - β - rhamninoside) with xanthorhamnin B, whereas xanthorhamnin C is rhamnazin - 3- O - β - rhamninoside. From Rhamnus saxatilis JACQ., ssp. saxat. a new flavonol - acetyl - trioside was isolated and the structure by MS and 13C-NMR spectroscopic means elucidated to be the rhamnetin - 3 - O - [O - α - l - rhamnopyranosyl - (1 → 3) - O - (4 - O - acetyl - ) - α - l - rhamnopyranosyl - (1 → 6)] - β - d - galactopyranoside.
... Rhamnazin 3-rhamninoside (7) was isolated and characterized by analysis of 1D and 2D NMR spectroscopy ( 1 H, 13 C NMR and MS spectra are in Figures S10-S12, Supplementary Materials). Spectroscopic data of rhamnazin 3-rhamninoside (7) were in good agreement with those reported in the literature [28]. Rhamnazin 3-rhamninoside (7) (8), xanthorhamnin B or rhamnetin 3-rhamninoside (9) and kaempferol 3-rhamninoside (10), respectively (Figures 1c and 3). ...
... Flavonol glycosides 8-10 were also isolated and structurally characterized by analysis of 1D and 2D NMR spectroscopy ( 1 H, 13 C NMR and MS spectra are in Figures S13-S21, Supplementary Materials). Spectroscopic data of compounds 8-10 were identical to those published in the literature [28][29][30][31]. Moreover, flavovilloside or quercetin 3-rhamninoside (11) (Figure 3) was also obtained during the isolation of flavonol glycosides 7-10; its 1 H, 13 C NMR and MS spectra are in Figures S22-S24, Supplementary Materials). ...
... Moreover, flavovilloside or quercetin 3-rhamninoside (11) (Figure 3) was also obtained during the isolation of flavonol glycosides 7-10; its 1 H, 13 C NMR and MS spectra are in Figures S22-S24, Supplementary Materials). Spectroscopic data of quercetin 3-rhamninoside (11) were in good agreement with published values [28]. However, quercetin 3-rhamninoside (11) was not detected by LC-MS/MS analysis; therefore, it is not listed in Table 1 and it does not appear in the molecular networking of a cluster B (Figure 1c) in spite of being a derivative of rutin (2). ...
Ventilago denticulata is an herbal medicine for the treatment of wound infection; therefore this plant may rich in antibacterial agents. UHPLC-ESI-QTOF-MS/MS-Based molecular networking guided isolation and dereplication led to the identification of antibacterial and antifungal agents in V. denticulata. Nine antimicrobial agents in V. denticulata were isolated and characterized; they are divided into four groups including (I) flavonoid glycosides, rhamnazin 3-rhamninoside (7), catharticin or rhamnocitrin 3-rhamninoside (8), xanthorhamnin B or rhamnetin 3-rhamninoside (9), kaempferol 3-rhamninoside (10) and flavovilloside or quercetin 3-rhamninoside (11), (II) benzisochromanquinone, ventilatones B (12) and A (15), (III) a naphthopyrone ventilatone C (16) and (IV) a triterpene lupeol (13). Among the isolated compounds, ventilatone C (16) was a new compound. Moreover, kaempferol, chrysoeriol, isopimpinellin, rhamnetin, luteolin, emodin, rhamnocitrin, ventilagodenin A, rhamnazin and mukurozidiol, were tentatively identified as antimicrobial compounds in extracts of V. denticulata by a dereplication method. MS fragmentation of rhamnose-containing compounds gave an oxonium ion, C6H9O3+ at m/z 129, while that of galactose-containing glycosides provided the fragment ion at m/z 163 of C6H11O5+. These fragment ions may be used to confirm the presence of rhamnose or galactose in mass spectrometry-based analysis of natural glycosides or oligosaccharide attached to biomolecules, that is, glycoproteins.
... Rhamnazin 3-rhamninoside (7) was isolated and characterized by analysis of 1D and 2D NMR spectroscopy ( 1 H, 13 C NMR and MS spectra are in Figures S10-S12, Supplementary Materials). Spectroscopic data of rhamnazin 3-rhamninoside (7) were in good agreement with those reported in the literature [28]. Rhamnazin 3-rhamninoside (7) (8), xanthorhamnin B or rhamnetin 3-rhamninoside (9) and kaempferol 3-rhamninoside (10), respectively (Figures 1c and 3). ...
... Flavonol glycosides 8-10 were also isolated and structurally characterized by analysis of 1D and 2D NMR spectroscopy ( 1 H, 13 C NMR and MS spectra are in Figures S13-S21, Supplementary Materials). Spectroscopic data of compounds 8-10 were identical to those published in the literature [28][29][30][31]. Moreover, flavovilloside or quercetin 3-rhamninoside (11) (Figure 3) was also obtained during the isolation of flavonol glycosides 7-10; its 1 H, 13 C NMR and MS spectra are in Figures S22-S24, Supplementary Materials). ...
... Moreover, flavovilloside or quercetin 3-rhamninoside (11) (Figure 3) was also obtained during the isolation of flavonol glycosides 7-10; its 1 H, 13 C NMR and MS spectra are in Figures S22-S24, Supplementary Materials). Spectroscopic data of quercetin 3-rhamninoside (11) were in good agreement with published values [28]. However, quercetin 3-rhamninoside (11) was not detected by LC-MS/MS analysis; therefore, it is not listed in Table 1 and it does not appear in the molecular networking of a cluster B (Figure 1c) in spite of being a derivative of rutin (2). ...
Ventilago denticulata is an herbal medicine for the treatment of wound infection; therefore this plant may rich in antibacterial agents. UHPLC-ESI-QTOF-MS/MS-Based molecular networking guided isolation and dereplication led to the identification of antibacterial and antifungal agents in V. denticulata. Nine antimicrobial agents in V. denticulata were isolated and characterized; they are divided into four groups including (I) flavonoid glycosides, rhamnazin 3-rhamninoside (7), catharticin or rhamnocitrin 3-rhamninoside (8), xanthorhamnin B or rhamnetin 3-rhamninoside (9), kaempferol 3-rhamninoside (10) and flavovilloside or quercetin 3-rhamninoside (11), (II) benzisochromanquinone, ventilatones B (12) and A (15), (III) a naphthopyrone ventilatone C (16) and (IV) a triterpene lupeol (13). Among the isolated compounds, ventilatone C (16) was a new compound. Moreover, kaempferol, chrysoeriol, isopimpinellin, rhamnetin, luteolin, emodin, rhamnocitrin, ventilagodenin A, rhamnazin and mukurozidiol, were tentatively identified as antimicrobial compounds in extracts of V. denticulata by a dereplication method. MS fragmentation of rhamnose-containing compounds gave an oxonium ion, C6H9O3+ at m/z 129, while that of galactose-containing glycosides provided the fragment ion at m/z 163 of C6H11O5+. These fragment ions may be used to confirm the presence of rhamnose or galactose in mass spectrometry-based analysis of natural glycosides or oligosaccharide attached to biomolecules, that is, glycoproteins.
Keywords: Ventilago denticulata; natural products; antibacterial activity; antifungal activity; dereplication; molecular networking; flavonoid glycosides; mass spectrometry; MS fragmentation of sugar
... Enfin, la quercétine et le kaempférol sont largement présents dans bon nombre de végétaux comme par exemple Lotus corniculatus (Harborne, 1994). Wagner, 1982 ;Wang et al., 1988 ;Harborne, 1994). Le 3-O-rhamninoside de quercétine et 3-O-rhamninoside de kaempférol ont également été observés notamment dans l'espèce Rh. ...
... ! "#! ! "#! du sucre sur le composé aglycone qui peut être en position 3 ou 4' (Riess-Maurer et Wagner, 1982 ;Satake et al., 1993). Les sites de glycosylation peuvent être déterminés par l'étude du spectre UV/Visible. ...
... Le rhamninoside monoacétylé est également présent dans le genre Rhamnus : il est nommé O-acétyl-rhamninose ou O-!-L-rhamnopyranosyl-(1"3)-(4-O-acétyl)-O-!-Lrhamnopyranosyl-(1"6)-O-#-D-galactopyranoside(Figure 2.9). Les composés, identifiés notamment dans Rh. saxatilis (Riess-Maurer etWagner, 1982) et Rh. thymifolius(Satake et al., 1993), sont le 3-O-acétyl-rhamninoside de rhamnétine ainsi que le 3Structure chimique de l'acétyl-rhamninose(Satake et al., 1993).De manière plus secondaire, on note la présence d'un autre trisaccharide :l'isorhamninoside ou !-L-rhamnopyranosyl-(1"4)-O-!-L-rhamnopyranosyl-(1"6)-O-#-Dgalactopyranoside. ...
This work concerns the study of three tinctorial plants: madder, buckthorn and weld. These plant species produced many cultures in Provence and represented the principal raw material in red and yellow dyes for dyers and artists. An optimisation of extraction conditions for madder dyes, using ultrasounds, was carried out with a statistical model. This easy, fast and effective extraction process was compared with two other conventional techniques. A cytohistological study on madder roots permits to examine effects produced by the different extraction processes. Cells reveal, after ultrasonic extraction, profound structural alterations, explaining the high yield in extracted dyes in comparison with classical methods. A fundamental study on the dyes identification extracted from Rhamnus species green fruits was carried out. A chromatographic approach using HPLC-UV-MS permits to identify the flavonol fraction. It is mainly composed of glycosiled compounds where the rhamninosid part is linked in position 3 or 4' on the flavonol nucleus. 3-O-acetyl-rhamninosid derivatives were also characterised and they are specific to Rh. saxatilis species. Ripe fruits contained anthraquinonic compounds that were separated from flavonols and concentrated using Solid Phase Extraction (SPE). After NMR analyse, acetyl rhamnosid and arabinosid derivatives of émodine, never described in the specialised literature, were identified as emodin-6-O-(3',4'-diacetyl)-arabinopyranosid and emodin-6-O-(2',3',4' triacetyl)-arabinopyranosid were only present in Rh. alaternus. Yellow dyes of weld (Reseda luteola) were analysed by capillary electrophoresis. In comparison with HPLC, a reduced run time was observed while preserving a suitable separation. These experimental results were successfully applied to the study of ancient samples belonging from museums and including "indiennes" of the XIXth century. Finally, dying tests were carried out, in collaboration with Les Olivades society, in the aim to develop textiles containing natural dyes
... Previous studies showed that Rhamnus genus contains glycosylated flavonols, the aglycone part being constituted by kaempferol, kaempferide, quercetin, rhamnetin, isorhamnetin, rhamnocitrin and rhamnazin [11,[13][14][15]. The glycosidic part is composed by a rhamninoside (α-L-rhamnopyranosyl-(1 → 3)-O-α-L-rhamnopyranosyl-(1 → 6)-O-β-D-galactopyranoside) which can be linked either in position 3 or 4′ on the aglycone [12,13,[16][17][18] (Fig. 1). Another glycosidic part has been identified in R. catharticus by Romani et al. [12], as an O-rhamnoside (and not a rhamninoside), linked in position 3 on quercetin skeleton and commonly named quercitrin. ...
... Several preliminary studies were conducted to develop an LC method for the separation of heterosidic and aglycone compounds (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18) in Rhamnus green fruit extracts. The chromatographic separation conditions of the analytes were optimized by systematically adjusting acetonitrile and bidistilled water (0.01% ...
... However isorhamnetin (14) and rhamnazin (17) are detected in small proportion (traces) in R. alaternus and R. catharticus (Fig. 3, Table 3). At 350 nm in the UV chromatogram, the difference peak areas of kaempferol (15) and rhamnetin (16) also permits to differentiate the three species: in R. saxatilis, the proportion of these two compounds is very similar about 30%, whereas in R. alaternus and R. catharticus, the proportion of kaempferol is greater than those in rhamnetin about 80% and less than 1% respectively (Fig. 3, Table 3). So if we reasonably assume a similar molar absorption coefficient for both the species at 350 nm, we can conclude that in R. saxatilis, the kaempferol (15) and rhamnetin (16) amount ratios are very close to one. ...
Flavonol compounds present in green fruits of Rhamnus species (Rhamnus saxatilis, Rhamnus alaternus and Rhamnus catharticus) were studied. The objective is to compare the chemical composition of the three Rhamnus species in order to distinguish them. Liquid chromatography was employed for the separation of the analytes and the detector is an ion trap mass spectrometer in positive ESI mode. The aglycones part was constituted by usual flavonols as quercetin, kaempferol, isorhamnetin, rhamnetin, rhamnocitrin and rhamnazin while heterosidic part was an O-rhamninoside or O-acetyl-rhamninoside linked in position 3 or 4′ on flavonol skeleton. The UV/Visible spectroscopy has permitted to determine the glycosylation site on the flavonol, and liquid chromatography was used to confirm the glycoside sequence and aglycone part. Each Rhamnus species was characterized by leading compounds as O-acetyl-rhamninoside derivatives for R. saxatilis, 4′-O-rhamninoside for R. alaternus and R. catharticus. Quercetin-4′-O-rhamninoside is only present in R. alaternus species permitting to discriminate it.
... All the observed effects of the aqueous extract of O. rosea also could be related to the presence and the synergism of other phenolic compounds identified by LC-MS/MS studies (Table 2), such as 5,7,2′-trihydroxyflavone (18) and 5,7,2′,5′-tetramethoxyflavanone (26); as well as some alkaloids such as Lepidine B (22) and C (27), and Latifoline (21), which are secondary metabolites of flowering plants and are in part responsible of their anti-inflammatory activity, especially the ones that derivate from isoquinolenes [74,75]. Similarly, we detect the presence of 6-C-Methylkaempferol (24) and Kaempferol 3-(2′′,4′′-diacetylrhamnoside) (10) a flavonoid that previously has been identified in other species with anti-inflammatory, gastroprotective, analgesic, antipyretic and anticarcinogenic properties, such as Zingiber zerumbet (L.) Roscoe ex Sm. [76]. ...
Oenothera rosea L´Hér. ex Ait is a species traditionally used in the treatment of inflammation, headache, stomach pain, infections, among others. The aim of this study was evaluating the acute anti-inflammatory activity of the aqueous extract of O. rosea by 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis. Rats were randomized into six groups: (I) Sham; (II) EtOH; (III) TNBS; and (IV–VI) 250, 500 and 750 mg/Kg, respectively. The colonic injury was induced (groups III–VI) by intrarectal instillation of 0.25 mL of TNBS (10 mg) in 50% ethanol. Groups I and II received an enema (0.25 mL) of physiological saline solution or 50% ethanol, respectively. Treatments were administered by oral gavage 48, 24 and 1 h prior, and 24 h after the induction. The inflammatory response was assessed considering the macroscopic and microscopic damage, the serum nitric oxide (NO), the colonic IL-1β levels, and the myeloperoxidase (MPO) activity. Moreover, we performed an LC–MS-based metabolite profiling, and a docking on the MPO. Doses of 500 and 750 mg/Kg showed a protective effect in the TNBS-induced colonic damage. This activity was related to the downregulation of evaluated parameters. Also, considering previous reports, 29 metabolites of 91 detected were selected for the docking, of which Isolimonic acid (29) and Kaempferol 3-(2′′,4′′-diacetylrhamnoside) (10) showed the highest affinity to MPO. The aqueous extract of O. rosea protected the TNBS-induced colonic damage in rats, an effect that could be associated with the presence of polyphenolic compounds, alkaloids, and terpenes; as well as their ability to down-regulate MPO activity.
... The only studies referring to R. saxatilis were reported more than 30 years ago and comprised merely a structure determination and synthesis of flavonol triosides (Riess-Maurer and Wagner, 1982), or extraction and isolation of L-bornesitol from the title plant (Plouvier, 1958). ...
Several species belonging to the genus Rhamnus (Rhamnaceae), comprising ones among which are found the most typical plants of the Italian flora, are known to contain biologically active anthraquinone secondary metabolites. Although several Rhamnus species were so far investigated, no information is available concerning the content and relative abundances of anthraquinones in R. saxatilis. In this study we used a simple, reliable, and accurate analytical method to determine the anthraquinones in bark of R. saxatilis. This allowed us also to trace a comparative study on the efficacy of different extraction solvents in ultrasonication time dependent assays. Separation and quantification of anthraquinones were accomplished using a C18 column with the mobile phase of H2O:methanol (40:60, v/v, 1% formic acid) at a flow rate of 0.7mL/min and a detection wavelength of 254nm, while the qualitative analyses were also achieved at a wavelength of 435nm.Finally, the described HPLC method, was used to obtain a specific chemical fingerprint for this species in comparison with other species from the same family.
In the last five decades study on plant secondary metabolites have been increasing. Higher plants with a wide range of secondary metabolites have been very important in the search of new therapeutic agents. In this study secondary metabolites of Lathyrus armenus (Boiss. & Huet) which are endemic in Turkey, were studied. Flavonol glycosides (Rhamnocitrin-3-O-rhamninoside, Rhamnetin-3-O-rhamninoside, Rhamnazin-3-O-rhamninoside, kaempferol3-O-rhamninoside and, kaempferol-3-O-glucosyl (1→2) rhamnoside) were isolated by different chromatographic methods and identified by 1 H, 13 C NMR, as well as 2D NMR and Mass spectroscopy techniques from ethyl acetate and aqueous fractions of L. armenus's methanolic extract. This is the first study about secondary metabolites of Turkish Lathyrus species.
Es wurden intensiv weiterbearbeitet: Polyphenole, Anthrachinone und biogenetisch verwandte Körper, Alkaloide und Saponine und Sapogenine. Über Nutzpflanzen (mit zahlreichen Synonymen) vgl. S. 829–835, 1882 von Rudolf Mansfelds Kulturpflanzen-Verzeichnis (vide Ref. [1], S. 372 in Bd. VIII) und für Ziziphus (= Zizyphus)-Arten Ref. [2]). Eine schöne Arbeit mit zahlreichen blattanatomischen Abbildungen (Haare, Gerbstoffzellen, Drusen von Calciumoxalat) wurde der nordamerikanischen (Süd-Canada bis Guatemala) Gattung Ceanothus gewidmet (3).
A new flavonol glycoside i.e., 7-O-methylkaempferol-3-O-α-L-rhamno- pyranosyl-(1®6)-O-b-D-galactopyranoside (1) together with a known flavonol glycoside; kaempferol-14-O-α-L-rhamnopyranosyl-(1®3)-O-α-L- rhamnopyranosyl-(1®6)-O-β-D-galactopyranoside (2) were isolated from methanolic fraction of leaves of Kalanchoe pinnata. Their structures were determined with the help of chemical method and concerted use of 1D and 2D NMR spectroscopy.
By 1975, some 360 flavone and flavonol glycosides were known to occur in the plant kingdom (Harborne and Williams, 1975). In the following five years, this number doubled so that some 720 structures were listed in our first supplement (Harborne and Williams, 1982). The pace of discovery during 1981–1985 has not slowed down and we now list at the end of this book nearly a thousand substances. This is a conservative estimate in the sense that a number of partly characterized glycosides, which probably differ in mode of linkage or in the type of sugar configuration from those reported here, have been described but are not included in our lists. It is to be regretted that some investigators still do not characterize their glycosides with the necessary rigour to establish the structures unambiguously. As before, the term ‘glycoside’ is used in its widest sense and we include here flavones and flavonols which are acylated and sulphated as well as glycosylated.
In the course of a chemotaxonomic study of the genus Actinidia, several new flavonol triglycosides have been characterised by 1H and 13C NMR spectroscopy. These are kaempferol and quercetin, 3-O-[α-rhamnopyranosyl-1-4)-rhamnopyranosyl-(1-6)-β-galactopyranoside, kaempferol 3-O-[α-rhamnopyranosyl-(1-4)-rhamnopyranosyl-(1-6)-β-glucopyranoside], and kaempferol 3-O-[α-rhamnopyranosyl-(1-4)-3‴-O-acetyl-α-rhamnopyranosyl-(1-6)-β-galactopyranoside]. Quercetin and isorhamnetin analogues of the dirhamnosyl glucoside were also detected.
From the fruits of Rhamnus leptophylla, three flavonol glycosides were isolated in high yields and identified as multiflorin A, kaempferol-3-O-β-rhamninoside and alaternin, respectively. The isolation of multiflorin A is significant, since this plant is used as a purgative in China.
Two new flavonoidal C-glycosides provisionally named as pakistoside A (1) and pakistoside B (2) have been isolated from the aerial parts of Abutilon pakistanicum. Their structures have been assigned through detailed spectral analyses including 2D-NMR techniques. In addition kaempferol, kaempferol-3-O-α-L-rhamnopyranoside and luteolin are isolated for the first time from this plant.
The new flavonol glycosides kaempferol-3-O-[alpha-L-rhamnopyranosyl-(1->3)-alpha-L-rhamnopyranosyl-(1->6)-beta-D-glucopyranoside] and kaempferol-3-O-[alpha-L-rhamnopyranosyl-( 1->3)-(4'''-O-acetyl)-alpha-L-rhamnopyranosyl-(1->6)-beta-D-glucopyranoside] have been isolated from China green tea. Kaempferol-3-O-[alpha-L-rhamnopyranosyl-(1->3)-alpha-L- rhamnopyranosyl-(1->3)-alpha-L-rhamnopyranosyl-(1->6)-beta-D-galactopyranoside] was identified for the first time in tea.
The fruits of Rhamnus prinoides yielded the known anthraquinones emodin and physcion, emodinanthrone, prinoidin, the flavonoid rhamnazin and five new pigments identified as acetylated derivatives of emodinanthrone and emodin rhamnopyranoside.
Two new flavonol triglycosides, and a new anthraquinone glycoside, have been isolated from the roots of Rhamnus formosana. These compounds have been characterized as rhamnazin 3-O-[α-l-rhamopyranosyl(1→4)-α-l-rhamnopyranosyl(1→6)-β-d-galactopyranoside (rhamnazin 3-isorhamninoside), rhamnocitrin 3-O-isorhamninoside and 1,6,8-trihydroxy-3-methylanthraquinone 1-O-rhamnosyl(1→2)glucoside, respectively.
Two flavonol glycosides, rhamnetin 3-O-#-neohesperidoside (1) and rhamnocitrin 3-O-#-neohesperidoside (2), which had been isolated from leaves of the African medicinal plant Boscia salicifolia, were synthesized and tested for biological activity. Rhamnetin 3-O-#-neohesperidoside (1) proved to be a weak immunosuppressant.
A pattern recognition technique is demonstrated for grouping data and assigning the carbohydrate structures of four carbohydrate moieties. Using existi
Acer tegmentosum is a type of deciduous tree that grows in Korea. It has been used in traditional medicine for the treatment of hepatic disorders. In this study, chromatography fractionation and isolation have been successfully used to yield 15 compounds, including 10 flavonoids, 4 phenylethyl glycosides, and 1 other glycoside. Their structures were determined on the basis of their physical and spectral properties [(1)H and (13)C nuclear magnetic resonance (NMR) and mass spectrometry (MS)] and by comparison of these results to similar data in the literature. The total peroxyl radical-scavenging capacity of each isolated compound was evaluated. Among them, the most active components belong to the flavonoids. Among these, quercitrin (1), 6-hydroxy-quercetin-3-O-galactose (6), and (+)-catechin (8) showed stronger activity than the positive control Trolox.
From the berries of Rhamnus petiolaris a new acylated flavonol glycoside was isolated and identified as rhamnetin 3-O-[3"-O-(p-coumaroyl)-alpha-L-rhamnopyranosyl(1-->3)- alpha-L-rhamnopyranosyl(1-->6)]-beta-D-galactopyranoside. Additionally, five known flavonol glycosides, rhamnetin, rhamnazin, quercetin and kaempferol 3-rhamninosides, and quercetin 3-rhamnoside were isolated.
Quercetin pentaacetate reacts with methyl iodide or benzyl chloride in dry acetone in the presence of potassium carbonate to give high yields of rhamnetin tetraacetate and 7-O-benzylquercetin tetraacetate, respectively. Further benzylation of 7-O-benzylquercetin tetraacetate in methyl ethyl ketone gives 3,4′,5,7-tetra-O-benzylquercetin monoacetate which yields isorhamnetin when successively deacetylated, methylated and debenzylated. 3,4′,7-Tri-O-benzylquercetin 5-monoacetate and 4′,7-di-O-benzylquercetin triacetate were isolated as by-products in these reactions. From these data it follows that acetyl groups attached to the flavone nucleus may be successively replaced by alkyl groups in the order 7 > 4′ > 3 > 5 > 3′. The constitutions of these new partial benzyl ethers of quercetin were established by recently reported spectrophotometric procedures.
Rhamnocitrin-, rhamnazin- and rhamnetin-3-o-[α-L-rhamnopyranosyl-(1»4)-α-L-rhamnopyranosyl]-(1»6)-β-D-galactopyranosides have been synthesized and the structures of catharticin, xanthorhamnin B and C elucidated by 13C-spectroscopy.
From the fruits of Rhamnus petiolaris two new flavonol-3-O-triosides were isolated and identified as rhamnazin-3-O-[α-l-rhamnopyranosyl (1 → 4)-α-l-rhamnopyranosyl (1 → 6)]-β-d-galactopyranoside and rhamnetin-3-O-α-l-rhamnopyranosyl (1 → 2)-α-l-rhamnopyranosyl (1 → 6)]-β-d-galactopyranoside, respectively.
Various di- and tri-saccharides containing l-rhamnose were synthesized by condensation of 2,3,4-tri-O-acetyl- or 2,3,4-tri-O-benzoyl-α-l-rhamnopyranosyl bromide with an unblocked glycopyranoside. The determination of the anomeric configuration of l-rhamnose saccharides by n.m.r. is difficult because structure has a greater effect on the spectra than does configuration. The α and β configurations and the position of the substitution may be assigned from the chemical shifts of H-5 and CH3. In all the compounds having a β configuration, a shielding of the methyl group and a deshielding of the H-5 proton have been observed as compared to the compounds having an α configuration. The H-5 proton and the methyl group of peracetylated, (1→3)-linked α-l derivatives always resonate at higher fields than the corresponding protons of (1→6)-linked α-l derivatives.RésuméLa synthèse de plusieurs di- et tri-saccharides dans la série du l-rhamnose a été réalisée par condensation du bromure de 2,3,4-tri-O-acétyl- ou 2,3,4-tri-O-benzoyl-α-l-rhamnopyranosyle avec un glycopyranoside non bloqué. L'étude en r.m.n. du proton des différents mono-, di- et tri-saccharides obtenus au cours de ces synthèses a permis de confirmer la difficulté d'attribution de la configuration osidique dans cette série par la valeur du proton anomère, celle-ci étant plus sensible à la substitution qu'à la configuration. La valeur du déplacement chimique du proton H-5 et du groupement méthyle peut servir à préciser la configuration et la position de la substitution. Dans tous les composés de configuration β, on a observé un déblindage du groupement méthyle et un blindage du proton H-5 par rapport aux composés de configuration α. Le proton H-5 et le groupement méthyle dans les dérivés peracétylés des composés α-l-(1→3) résonnent toujours à un champ plus fort que les mêmes protons dans les composés α-l-(1→6).
Condensation of 1,2:3,4-di-O-isopropylidene-α-d-galactopyranose (1) with 2,4-di-O-acetyl-3-O-(2,3,4-tri-O-acetyl-α-l-rhamnopyranosyl)-α-l-rhamnopyranosyl bromide (2), followed by subsequent removal of the isopropylidene and acetyl groups from the product, afforded the first of the title trisaccharides. The reaction of 1 with 3,4-di-O-benzyl-2-O-p-nitrobenzoyl-α-l-rhamnopyranosyl bromide and deacylation of the product gave a disaccharide derivative that was treated with 2,3,4-tri-O-acetyl-α-l-rhamnopyranosyl bromide. Removal of the protecting groups from the product gave the second (15) of the title trisaccharides. The reaction of 1 with the acetobromo derivative of 2-O-α-l-rhamnopyranosyl-l-rhamnose, with subsequent removal of protecting groups from the product, also gave trisaccharide 15.
A convenient method has been developed for the synthesis of all mono- and di-O-benzyl ethers of methyl α-L-rhamnopyranoside applying a new stereoselective method for the hydrogenolytic ring-cleavage of benzylidene acetals. Using the prepared dibenzyl ethers as aglycones, the (1→2)-, (1→3)- and (l→4)-linked rhamnosyl-rhamnose derivatives (13–15) were synthesised. Hydrogenolysis of the latter compounds and subsequent acetylation gave the pentaacetates (16–18) of methyl dirhamnosides, which on saponification furnished the free methyl dirhamnosides (19–21). Acetolysis of 16–18 gave the corresponding dirhamnose-hexaacetates which were transformed into the three disaccharides by saponification. The structure of each product was investigated by 13C-NMR spectroscopy, and for the purpose of 13C-NMR studies the mono-O-methyl ethers of methyl α-L-rhamnopyranoside, the diacetates and di-O-benzyl ethers of the latter compounds, and, also the diacetates of methyl α-L-rhamnopyranoside were synthesised.It has been established that, for 13C-NMR investigations of oligosaccharides, the benzyl ethers of monosaccharides are more suitable model compounds than the currently used monosaccharide methyl ethers.
A general mass spectrometric method is described for the structure elucidation of flavonoid oligosaccharides. Information is obtained from the mass spectra of the perdeuteriomethylated compounds and their hydrolysis products, using GC-MS coupling.The major part of the structures of the flavonoid troisides, xanthorhamnin, alaternin and catharticin has been established by this method.
Die MS-Analyse natürlich vorkommender Flavonoid-mono-, -di- und -tri-O-glykoside in Form ihrer Isopropyliden-Permethylderivative ermöglicht: (1) die massenspektroskopische Unterscheidung zwischen dia-stereoisomeren Zukeranteilen, (2) die Ermittlung der Molekulargewichte und zugleich die Bestimmung intergly-kosidischer Bindungen bei Di- und Triglykosiden mit Hilfe deutlicher M+-Peaks und (3) die Differenzierung zwischen der furanoiden und pyranoiden Form von Zuckern in den genuinen Glykosiden. Es werden die charakteristischen MS-Daten vonüber 20 Flavonoid-O-glykosid-IP-Derivaten tabellarisch angegeben.
Aus den oberirdischen Teilen von Euphorbia esula L. (Euphorbiaceae) wurde ein Flavonglykosid isoliert und als 3.5.7.4′-Tetrahydroxy-flavon(Kämpferol)-3-β-D-glucuronid (8) identifiziert. Seine Struktur wurde durch Kupplung von 7.4′-Dibenzyl-Kämpferol mit α-Acetobromglucuronsäure-methylester, Darstellung des Vollacetats, Entbenzylierung und Verseifung zu 8 bewiesen.
Synthesis of Glucuronides in the Flavonoid-Series, II. Isolation of Kaempferol-3-β-D-glucuronide from Euphorbia esula L.
From the aerial parts of Euphorbia esula L. (Euphorbiaceae) a flavone-glycoside was isolated and identified as 3,5,7,4′-tetrahydroxyflavone(kaempferol)-3-β-D-glucuronide (8). Its structure was confirmed by coupling of 7,4′ -dibenzylkaempferol with methyl(tri-O-acetyl-α-D-glucopyranosyl bromide)-uronate, followed by total acetylation, debenzylation and saponification to 8.
The mass spectra of 13 perdeuteriomethylated flavonoid disaccharides comprising flavones, flavanones, flavonols and an isoflavone are reported. It is shown that their fragmentation pattern allows unequivocal differentiation according to the structural type of the aglycone, the sugar sequence and the position of the interglycosidic linkage. Moreover, information regarding substitution on the aglycone can be obtained. All compounds except one exhibited molecular ion peaks thus allowing direct molecular weight determination.
- Fleury
- Herzig