Flavone C-glycosides of Apometzgeria pubescens

Eleven flavone di-C-glycosides, including nine which are new, have been identified in gametophytic material of Apometzgeria pubescens. Tricetin 6,8-di-C-glucoside and tricin 6-C-arabinoside-8-C-pentoside are the major compounds. Another identified was ferulylisoschaftoside. The chemotaxonomic relevance of the flavonoid pattern of Apometzgeria pubescens is briefly discussed.     

Structure of a 6,8-di-C-pentosylapigenin from Mollugo pentaphylla

One of the di-C-pentosylflavones isolated from Mollugo pentaphylla was identified as 6-C-β-d-xylopyranosyl-8-C-α-l-arabinop     

Flavonoids of Plagiochila asplenioides

Besides an apigenin- and a luteolin-di-C-glycoside, 5 previously unknown di-C-glycosides of tricetin were identified in the gametophytic and sporophytic tissues of Plagiochila asplenioides. Two of them were new 6,8-di-C-hexopyranosyltricetins, and two were new 6-C- hexopyranosyl-8-C-pentopyranosyltricetins. 6-C-Hexopyranosyl-8-C-pentopyranosyltricetin-5′-methyl ether was also found.     

Nouvelles C-glycosylflavones extraites de Spergularia rubra

Three 6,8-di-C-glucosylflavones: 6,8-di-C-β-d-glucopyranosylapigenin, luteolin and chrysoeriol were isolated from the whole plant of Spergularia rubra. Two new compounds, 7,2″-di-O-β-d-glucopyranosyl-6-C-α-l-arabinopyranosylapigenin and 6-C-α-l-arabinopyranosylapigenin (isomollupentin), were also characterized. Structural assignments were based on ¹H NMR and MS spectra and on comparison with synthetic samples. MS fragmentation patterns of the new di-O-glucosyl compound PM derivative and of its acid hydrolysis product are given.     

The flavonoids of Trichophorum cespitosum

Fifteen flavonoids were isolated from Trichophorum cespitosum, including two new di-C-glycosylflavones, 6-C -arabinosyl-8-C-glucosylchr     

Flavonoids of the liverwort Marchantia foliacea

The major flavonoids of Marchantia follacea are the 7-O-β-d-glucuronides of apigenin, chrysoeriol and tricin, and apigenin-6,8-di-C-glucoside (vicenin-2). Minor constituents include the rhamnosylglucuronides of the above flavones. Apparent isomerization of the glucuronides on hydrolysis (MeOH-HCl) proved to be due to methylation of the sugar carboxyl group.     

Flavonoid pattern and systematics of the genus Leucocyclus

The flavonoid pattern of the monotypic Turkish genus Leucocyclus consists of C-glycosylflavones (isovitexin; isoorientin and derivatives; several di-C-glycosylapigenins; schaftoside, isoschaftoside and vicenin-3; lucenin-2), of flavonol 3-O-glycosides (quercetin and kaempferol 3-O-rhamnoglucoside) and trace amounts of luteolin 7-O-rhamnoglucoside. The systematic significance of the flavonoid diversification within Leucocyclus as well as possible relationships to other genera of the Anthemideae are discussed.     

Isocarlinoside,a di-C-glycosylflavone from Lespedeza capitata

Six di-C-glycosylflavones isolated from Lespedeza capitata leaves were identified as schaftoside, neoschaftoside, isoschaftoside, carlinoside, neocarlinoside and a new natural compound: isocarlinoside (6-C-α-l-arabinopyranosyl-8-C-β-d-glucopyranosylluteolin).     

Flavonoid variation in the genus briza

During a survey of 6 Eurasian and 10 South American Briza species for leaf flavonoids, 27 components were found. Twelve of these were identified: tricin 5-glucoside, tricin 7-glucoside, quercetin 3-glucoside, kaempferol 3-glucoside, vitexin, isovitexin, orientin, iso-orientin, and the 4′-O-glucoside of all 4 glycoflavones, 3 of which are reported for the first time. The Eurasian species, with the exception of Briza maxima, are remarkably uniform in their flavonoid pattern, accumulating mainly vitexin and isovitexin; whereas the South American species are characterized by the presence of orientin, iso-orientin and 9 unidentified flavonoids. In Briza media and the South American species, ploidy level is shown to play a large part in flavonoid variation. Examination of 12 diploid and 8 autotetraploid plants of B. media revealed that diploids accumulate vitexin and isovitexin, whereas tetraploids accumulate orientin and iso-orientin, autotetraploidy having apparently upset regulatory genes in the formation of the flavone C-glycosides. Mild alkaline treatment of both isovitexin and iso-orientin was found to give 100% conversion to the corresponding 8-C-glucoside.     

Flavone di-C-glycosides from Scutellaria baicalensis

From the roots of Scutellaria baicalensis two new di-C-glycosylflavones have been isolated. Their structures have been established on the basis of mass, ¹H and ¹³C NMR spectroscopy as chrysin 6-C-glucoside-8-C-arabinoside and chrysin 6-C-arabinoside-8-C-glucoside.     

Corymboside,nouvelle di-C-glycosylflavone des racines de Carlina corymbosa

Corymboside, a new di-C-glycosylflavone from Carlina corymbosa roots, was shown to be 6-C-α-l-arabinopyranosyl-8-C-β-d-galactopyranosylapigenin by MS, CD, ¹H and ¹³C NMR.     

New flavone-di-C-glycosides from the seeds of Egyptian lupin (Lupinus termis)

Raw lupin seeds flour is increasingly used as a food ingredient because of its nutritional and functional values. This study is considered to be the first phytochemical investigation of the flavonoids of the methanol (MeOH) fraction of Lupinus termis seeds. The study led to the isolation of two new di-C-glycoside flavones, apigenin-6-C-β-d-glucopyranosyl-8-C-[β-d-apiofuranosyl-(1 → 2)]-β-glucopyranoside (1), apigenin-6-C-β-d-glucopyranosyl-8-C-[α-l-rhamnopyranosyl-(1 → 2)]-β-glucopyranoside (2), together with one known flavone di-C-glycoside, apigenin-7-O-β-d-apiofuranosyl-6,8-di-C-β-glucopyranoside (3). These compounds are considered to have potential functional properties. The isolated compounds may contribute to the yellow color of raw lupin seeds flour-based products. It may also be used as natural yellow color in food or pharmaceutical products and as a dietary supplement product. These rare flavones were purified by using semi-preparative HPLC. The structures of the isolated compounds were elucidated on the basis of extensive spectroscopic methods, 1D and 2D nuclear magnetic resonance techniques, FAB (Fast Atom Bombardment) – mass spectrometry and acid hydrolysis.     

(+)-Pinpollitol: A di-O-methyl d-(+)-chiro-inositol from Pinus radiata

(+)-Pinpollitol, a new cyclitol recently isolated from the pollen of Pinus radiata, was found in the needles of this species. (+)-Pinpollitol was found to be a di-O-methyl ether Of d-(+)-chiro-inositol, and tentative isomeric structures have been proposed for the cyclitol. (+)-Pinpollitol is the first di-O-methyl inositol to be found in a gymnosperm and is one of only three di-O-methyl inositols yet found in nature.     

Negatively charged flavones and tricin as chemosystematic markers in the palmae

A survey of 125 species of the Palmae revealed a complex pattern of flavonoids in the leaf. C-Glycosylflavones, leucoanthocyanins and tricin, luteolin and quercetin glycosides were common, being present in 84, 66, 51, 30 and 24% of the species respectively. Apigenin and kaempferol were recorded in only a few species and isorhamnetin only once. Eighteen flavonoids were identified: the 7-glucoside, 7-diglucoside and 7-rutinoside of both luteolin and tricin, tricin 5-glucoside, apigenin 7-rutinoside, quercetin 3-rutinoside-7-galactoside, isorhamnetin 7-rutinoside, orientin, iso-orientin, vitexin, isovitexin and vitexin 7-O-glucoside. Many of the C- and O-flavonoid glycosides were present as the potassium bisulphate salts and negatively charged compounds were detected in 50% of the species. The distribution patterns are correlated with the taxonomy of the family in several ways. Thus, the Phoenicoideae and Caryotoideae have distinctive flavonoid patterns, there is evidence to support the separation of the subfamilies Phytelephantoideae and Nypoideae, and tricin is a useful marker at tribal level. At the generic level, Cocos is clearly separated from Butia, and other Cocoseae and Mascarena and Chamaedorea form well defined groups within the Arecoideae. A numerical analysis of these biochemical data, together with morphological characters, produces a new classification which suggests that the flavonoid data may have more systematic value than is indicated when they are applied to the traditional classification.     

Synthesis of 2,3-anhydro- and 3,4-anhydro-hexopyranosides having a methyl branch on the oxirane ring,and their reactions with some lithium methylcuprate reagents

Three 2,3-anhydroaldohexopyranosides having a 2-C-methyl or 3-C-methyl branch, as well as three 3,4-anhydroaldohexopyranosides having a 3-C-methyl (7) or 4-C-methyl branch, were newly synthesized. The reactions of these, together with those of a known 3-C-methyl epoxide (2), with three kinds of lithium methylcuprate were investigated. Except for 2 and 7, the vicinal monodeoxy di-C-methyl derivatives were obtained by attack of the cuprates at the sterically less-hindered site of the oxirane ring, irrespective of the stereoelectronic effect. Formation of a unique, acyclic 1-enitol derivative from 2, and of a 4-enolone derivative from 7, was ascertained. Differences in the reactivity among the cuprates was also observed.     

Enzymatic synthesis of p-nitrophenyl 35-O-β-N-acetylglucosaminyl|-α-maltopentaoside by lysozyme; a novel substrate for human amylase assay

Transglycosylation from di-N-acetylchitobiose to the 3-position at the nonreducing end glucosyl group of p-nitrophenyl α-maltopentaoside was regioselectively induced through the use of hen egg-white lysozome. The enzyme formed p-nitrophenyl 3⁵-O-β-N-acetylglucosaminyl-α-maltopentaoside (5% of the enzyme-catalyzed net decreased of p-nitrophenyl α-maltopentaoside) from di-N-acetylchitobiose as a donor and p-nitrophenyl α-maltopentaoside as an acceptor. The rate of the transglycosylation depended on the concentration of substrate, the temperature and the pH. The hydrolytic actions of human pancreatic and salivary α-amylase on this derivative were examined. The maltopentaoside derivative was shown to be useful as a substrate for α-amylase assay through a coupled reaction involving α-D-glucosidase and glucoamylase.     

The structures of amentoflavone glycosides isolated from Psilotum nudum

On the basis of new spectroscopic evidence, structures are proposed for three amentoflavone glycosides and an apigenin di-C-glycoside previously isolated from Psilotum nudum. The major glycoside is identified as the 7,4′,4′“-tri-O-β-D-glucopyranoside, minor glycosides as the 4′,4′“-di-O-β-D-glucopyranoside and 7,4′“-di-O-β-D-glucopyranoside, and the apigenin di-C-glycoside as vicenin-2. The amentoflavone glucosides are all new natural products.     

Flavonoid glycoside accumulation trends of Achillea nobilis L. and related species

More than 50 collections of five species forming the Achillea nobilis group were analysed for their leaf flavonoid complement. Major accumulation trends were found to be C-glycosylflavones and flavonol 3-O-glycosides. The most common pattern consisted of the C-8-glycosylfiavones (vitexin and orientin), the C-6-glycosylflavone (isoörientin) together with minor amounts of di-C-glycosylapigenins and quercetin 3-O-glycosides. Additionally, C-6-glycosylflavones (isovitexin) and their 7-methyl ethers swertisin and swertiajaponin were sporadically accumulated, characterizing particularly two subspecies of A. nobilis. Whereas C-glycosylflavone dominated profiles were typical of most species, two taxa exhibited a flavonol dominated profile (A. ligustica; A. virescens p.p.). Regarding the infraspecific and interpopulational variations of flavonoid accumulation trends, their systematic and ecological significance is briefly discussed.     

Comparative flavonoid glycoside biochemistry as a chemotaxonomic tool in the subdivision of the classical ‘genus’ Lycopodium

A wide variety of novel flavone 5-O-glucosides has been isolated from Lycopodium scariosum. The predominance of tricin derivatives in this species is not in accord with earlier proposed chemotaxonomic definitions of the sub-groups within the classical genus Lycopodium L. cernuum is the first lycopod found to contain flavone C-glycosides and its suggested taxonomic separation from other members of the group is thus substantiated. Flavonoid glycosides appear to offer more definitive chemotaxonomic characters than do the previously used aglycones and modification of the chemical definitions of the sub-groups in these terms is necessary.     

Structural determination of 6-C-diglycosyl-8-C-glycosyl-flavones and 6-C-glycosyl-8-C-diglycosylflavones by mass spectrometry of their permethyl ethers

Permethylated 6-C-diglycosyl-8-C-glycosylflavones and 6-C-glycosyl-8-C-diglycosylflavones gave well defined EIMS including the molecular peak and a fragmentation pattern characteristic of the 6-C-glycosyl residue. X″′-O-glycosides (8-C-disaccharides) are thus easily distinguished from X″-O-glycosides (6-C-disaccharides) and, in the latter, the position of the O-glycosidic bond should be deduced from the MS, after acid hydrolysis. Three new C-glycosylflavones have been characterized in this way from Spergularia rubra and Stellaria holostea.