New C-glycosylflavones from Cerastium arvense

Three C-glycosylflavones isolated from Cerastium arvense have been identified as 6-C-xylosyl-apigenin (cerarvensin), its 7-O-glucoside and isovitexin 7,2″-di-O-glucoside.     

Flavone C-glycosides from Coronilla varia

One new and 5 known flavone C-glycosides were isolated from leaves and stems of Coronilla varia. The new compound was shown to be isoorientin 2″-O-rhamnoside. The known compounds were isovitexin, isoorientin, isovitexin 4′-O-glucoside, isoorientin 4′-O-glucoside, and isoorientin 7-O-glucoside.     

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 phragmites australis flowers

The major flavonoid constituents of Phragmites australis flowers are the C-glycosylflavones swertiajaponin, isoswertiajaponin and two new O-glycosides, the 3′-O-gentiobioside and the 3′-O-glucoside of swertiajaponin. Two unusual flavonol glycosides, rhamnetin 3-O-rutinoside and rhamnetin 3-O-glucoside, were also characterized from the same tissue.     

C-glycosylflavones from Oryza sativa

Eight flavone C-glycosides isolated from rice plant were found to act as probing stimulants for planthoppers. They have been identified as the known compounds schaftoside, neoschaftoside, carlinoside, isoorientin 2″-glucoside and the new constituents neocarlinoside (6-C-β-D-glucopyranosyl-8-C-β-L-arabinopyranosylluteolin), isoscoparin 2″-glucoside (chrysoeriol 6-C-β-D-(2-O-β-D-glucopyranosyl)glucopyranoside) and its 6?-p-coumaric and ferulic acid esters.     

O-glycosylated C-glycosylflavones from Passiflora platyloba

Five C-glycosylflavonoids including two new compounds, isovitexin 7-rhamnosylglucoside and isomollupentin 7-rhamnosylglucoside, were obtained from the leaves of Passiflora platyloba. The known flavonoids were isovitexin, vitexin and isomollupentin (6-C-arabinosylapigenin). In addition, the coumarin esculetin was isolated.     

Flavonoids of Mayaca fluviatilis (Mayacaceae)

Mayaca is an aquatic monocot of the monogeneric family Mayacaceae. The flavonol glycosides quercetin 3-O-glucoside, quercetin 3-O-rutinoside, and kaempferol 3-O-glucoside, and the flavone luteolin 5-O-glucoside were found in methanolic leaf extracts. The presence of flavonol and flavone O-glycosides sets the Mayacaceae apart from the Commelinaceae, which accumulates predominantly flavone C-glycosides.     

The in vivo incorporation of a flavanone into c-glycosylflavones

C-glycosylation, for the biogenesis of C-glycosylflavones, has been demonstrated to occur at the flavanone level for axenically-cultured Spirodela polyrhiza clone 7003. 4′,5,7-Trihydroxy[2-¹⁴C] flavanone (naringenin) was incorporated in a parallel manner into apigenin 7-O-glucoside and apigenin 8-C-glucoside (vitexin) and into luteolin 7-O-glucoside and luteolin 8-C-glucoside (orientin). In addition the data suggests that the enzyme which oxidizes flavanone (chalcone) to flavone is irreversible under the described experimental conditions.     

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.     

The flavonoids of tetragonotheca (compositae)

Fifteen flavonols, five aglycones and ten glucosides were isolated from the four species of Tetragonotheca, T. repanda, T. helianthoides, T. texana and T. ludoviciana. Included among the isolated flavonols are four previously unreported 7-O-glucosides, 6-hydroxykaempferol 7-O-glucoside, 6-hydroxykaempferol 6-methyl ether 7-O-glucoside, quercetagetin 6,3′-dimethyl ether 7-O-glucoside and quercetagetin 3,6-dimethyl ether 7-O-glucoside.     

Flavonoids of Helichrysum chasmolycicum and its antioxidant and antimicrobial activities

From the aerial parts of Helichrysum chasmolycicum P.H Davis, which is an endemic species in Turkey, the flavonoids apigenin, luteolin, kaempferol, 3,5-dihydroxy-6,7,8-trimethoxyflavone, 3,5-dihydroxy-6,7,8,4′-tetramethoxyflavone, apigenin 7-O-glucoside, apigenin 4′-O-glucoside, luteolin 4′-O-glucoside, luteolin 4′,7-O-diglucoside, kaempferol 3-O-glucoside, kaempferol 7-O-glucoside and quercetin 3-O-glucoside were isolated. The methanol extract of the aerial parts of H. chasmolycicum showed antioxidant activity by DPPH method (IC₅₀ 0.92 mg/mL). Antimicrobial activity test was performed on the B, D, E extracts and also 3,5-dihydroxy-6,7,8-trimethoxyflavone and kaempferol 3-O-glucoside which were the major flavonoid compounds obtained from aerial parts of H. chasmolycicum by microbroth dilutions technique. The E (ethanol-ethyl acetate) extract showed moderate antimicrobial activity against Pseudomonas aeruginosa, B (petroleum ether-60% ethanol-chloroform) extract and 3,5-dihydroxy-6,7,8-trimethoxyflavone showed moderate antifungal activity against Candida albicans.     

C-glycosylanthocyanidins synthesized from C-glycosylflavones

Nine C-glycosyldeoxyanthocyanidins, 6-C-β-glucopyranosyl-7-O-methylapigeninidin, 6-C-β-glucopyranosyl-7-O-methylluteolinidin, 6-C-β-(2″-O-β-glucopyranosylglucopyranosyl)-7-O-methylapigeninidin, 6-C-β-(2″-O-β-glucopyranosylglucopyranosyl)-7,4′-di-O-methylapigeninidin, 8-C-β-glucopyranosylapigeninidin, 8-C-β-(2″-O-α-rhamnopyranosylglucopyranosyl)apigeninidin, 8-C-β-(2″-O-α-(4″′-O-acetylrhamnopyranosyl)glucopyranosyl)apigeninidin, 6,8-di-C-β-glucopyranosylapigeninidin (8), 6,8-di-C-β-glucopyranosyl-4′-O-methylluteolinidin (9), have been synthesized from their respective C-glycosylflavones (yields between 14% and 32%) by the Clemmensen reduction reaction using zinc-amalgam. The various precursors (C-glycosylflavones) of the C-glycosylanthocyanidins were isolated from either flowers of Iris sibirica L., leaves of Hawthorn ‘Crataegi Folium Cum Flore’, or lemons and oranges. This is the first time C-glycosylanthocyanidins have been synthesized. The structures of all flavonoids including the flavone rotamers were elucidated by 2D NMR techniques and high-resolution electrospray MS. The distribution of the various structural forms of 8 and 9 are different at pH 1.1, 4.5, and 7.0, however, the two pigments undergoes similar structural transformations at the various pH values. Pigments 8 and 9 with C-C linkages between the sugar moieties and the aglycone, were found to be far more stable towards acid hydrolysis than pelargonidin 3-O-glucoside, which has the typical anthocyanidin C-O linkage between the sugar and aglycone. This stability may extend the present use of anthocyanins as nutraceuticals, pharmaceuticals or colorants.     

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.     

Tyrosine O-glucoside and dopamine 3-O-glucoside in seeds of Entada pursaetha

l-Tyrosine O-glucoside (I) and dopamine-3-O-glucoside (II) have been isolated from seeds of Entada pursaetha DC. The structures have been established by spectroscopic methods, identification of hydrolysis products and comparison with synthetic material. Syntheses are described of II, dopamine 4-glucoside and tyramine-O-glucoside.     

Flavonoids from the leaves and flowers of the Himalayan Cathcartia villosa (Papaveraceae)

Five flavonols, four flavones and one C-glycosylflavone were isolated from the leaves of Cathcartia villosa which is growing in the Himalayan Mountains. They were characterized as quercetin 3-O-vicianoside (1), quercetin 7,4′-di-O-glucoside (3), quercetin 3-O-rutinoside (4), quercetin 3-O-glucoside (5), quercetin 3-O-arabinosylarabinosylglucoside (6) (flavonols), luteolin (7), luteolin 7-O-glucoside (8), apigenin (9), chrysoeriol (10) (flavones), and vicenin-2 (11) (C-glycosylflavone) by UV, LC-MS, acid hydrolysis, NMR and/or HPLC and TLC comparisons with authentic samples. On the other hand, two flavonols 1 and kaempferol 3-O-vicianoside (2) were isolated and identified from the flowers of the species. Flavonoids were reported from the genus Cathcartia in this survey for the first time. Their chemical characters were chemotaxonomically compared with those of related Papaveraceous genera, Meconopsis and Papaver.     

An analysis of flavonoid compounds in leaves of Japonolirion (Petrosaviaceae)

Japonolirion, comprising Japonolirion osense Nakai, which occurs on serpentinite at two widely separated localities in Japan, has been considered as an isolated taxon, but more recently has been proved by molecular evidence to be a sister group to an achlorophyllous, mycoheterotrophic genus, Petrosavia. In an effort to research possible characters linking these groups, we analyzed the flavonoid compounds obtained from leaves of Japonolirion using UV spectra, mass spectrometry and ¹H and ¹³C nuclear magnetic resonance, and acid hydrolysis of the original glycosides as well as direct thin layer chromatography and high performance liquid chromatography comparisons with authentic specimens. As a result, we identified seven flavonoids, of which two were major components identified as 6-C-glucosylquercetin 3-O-glucoside and isoorientin. The remaining five were minor components identified as 6-C-glucosylkaempferol 3-O-glucoside, quercetin 3-O-glucoside, quercetin 3-O-arabinoside, vicenin-2 and orientin. Both 6-C-glucosylquercetin 3-O-glucoside and 6-C-glucosylkaempferol 3-O-glucoside were recorded for the first time in nature. Because of their restricted occurrence in angiosperms, both C-glycosylflavonols and 3-O-glycosides of C-glycosylflavonols may be significant chemical markers for assessing relationships of J. osense.     

A C-glucosylated 5-methylchromone from Kenya aloe

A new bitter C-glucoside, aloeresin D, was isolated from a commercial sample of Kenya aloe. Its structure was assigned as 8-C-β-d-[2-O-(E)-p-coumaroyl]glucopyranosyl-2-[(R)-2-hydroxy]propyl-7-methoxy-5-methyl-chromone by spectral data and chemical transformations.     

Flavonoids and xanthones from the leaves of Amorphophallus titanum (Araceae)

The flavonoids and xanthones in the leaves of Amorphophallus titanum, which has the largest inflorescence among all Araceous species, were surveyed. Eight C-glycosylflavones, five flavonols, one flavone O-glycoside and two xanthones were isolated and characterized as vitexin, isovitexin, orientin, isoorientin, schaftoside, isoschaftoside, vicenin-2 and lucenin-2 (C-glycosylflavones), kaempferol 3-O-robinobioside, 3-O-rutinoside and 3-O-rhamnosylarabinoside, and quercetin 3-O-robinobioside and 3-O-rutinoside (flavonols), luteolin 7-O-glucoside (flavone), and mangiferin and isomangiferin (xanthones). Although the inflorescence of this species has been surveyed for flavonoids, those of the leaves were reported for the first time.     

Anthocyanins and flavonols from the flowers of Amherstia nobilis endemic to Myanmar

Three anthocyanins (1–3) and eight flavonols (4–11) were isolated from the flowers of Amherstia nobilis endemic to Myanmar. Anthocyanins were identified as cyanidin 3-O-glucoside (1), 3-O-xyloside (2), and peonidin 3-O-glucoside (3). On the other hand, flavonols were identified as isorhamnetin 3-O-glucoside (4), 7-O-glucoside (5), 3,7-di-O-glucoside (6) and 3-O-rutinoside (7), quercetin 3-O-rutinoside (8) and 3-O-glucoside (9), and kaempferol 3-O-rutinoside (10) and 3-O-glucoside (11). Although an anthocyanin, pelargonidin 3-O-pentoside, has been reported from the flowers of A. nobilis, it was not found in this survey. The presence of flavonols in A. nobilis was reported in this survey for the first time. Flavonoid composition of Amherstia was chemotaxonomically compared with those of phylogenetically related genera Cynometra and Brownea.     

Apigenin and amentoflavone glycosides in the psilotaceae and their phylogenetic significance

Documentation of amentoflavone O-glucosides as the predominant flavonoid glycosides in both genera of the Psilotaceae clearly distinguishes this family from all other families of vascular plants. Psilotum and Tmesipteris also possess apigenin C- and O-glycosides as common flavonoid types. Apigenin 7-O-rhamnoglucoside occurs in both genera and the previously undocumented apigenin 7-O-rhamnoglucoside-4′-O-glucoside, although identified only in Tmesipteris, may also be present in Psilotum. The existence of flavone C-glycosides in both genera may provide a phytochemical relationship between the Psilotaceae and some ferns. The phylogenetic significance of these results is discussed.