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.     

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.     

Distribution of charged flavones and caffeylshikimic acid in Palmae

Identification of the phenolic constituents in flowers of nine palm species has revealed that charged C-glycosylflavones and caffeylshikimic acid are characteristically present. Flavonol glycosides are also common; the 3-glucosides, 3-rutinosides and 3,4′-diglucosides of quercetin and isorhamnetin and the 7-glucoside and 3,7-diglucoside of quercetin are all variously present. Tricin 7-glucoside, luteolin 7-rutinoside and several unchanged C-glycosylflavones were also detected. Male flowers of Phoenix canariensis differ from female flowers in having flavonol glycosides. As expected, in most species studied, flavonoid patterns in the flowers vary considerably from those found in the leaves.     

Flavonoid diversification in Achillea ptarmica and allied taxa

More than 50 collections of 12 species forming the A. ptarmica group have been analysed for their leaf flavonoids. C-Glycosylflavones (iso-orientin and derivatives, vicenins and lucenins) were found to be the main components, whereas flavonol 3-O-glycosides (based on quercetin and kaempferol) and flavone 7-O-glycosides (based on luteolin and diosmetin) were of restricted distribution. Infraspecific variability regarding C-glycosylflavones was observed in most of the taxa investigated. By contrast, flavonol 3-O-glycosides appeared to be stable characters and were sometimes accumulated instead of C-glycosylflavones. In addition to the flavonoids, the geographical distribution patterns and the possible origin of the A. sibirica in Eastern Asia are briefly discussed.     

Structural determination of C-glycosylflavones by mass spectrometry of their permethyl ethers: O-glycosyl-6-C-glycosylflavones

Permethylated O-glycosyl-C-glycosylflavones give well defined MS including an important molecular peak. Permethyl 6-C-glycosylflavones O-glycosylated on a phenolic hydroxyl group are easily distinguished from the isomeric permethyl 6-C-diholosylflavones. In both types, the position of the O-glycosidic bond can be deduced from the MS, eventually after acid hydrolysis. 2″-O-glycosyl-6-C-glycosylflavones can be differentiated from their 8-C isomers.     

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.     

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.     

Flavonoids in the leaves of Hillebrandia and Begonia species (Begoniaceae)

The fresh leaves of Hillebrandia sandwicensis and 126 Begonia taxa were chemotaxonomically surveyed for flavonoids. Of their taxa, H. sandwicensis and 119 species, one variety and three hybrids were analyzed for flavonoids for the first time. Ten flavonols and eleven C-glycosylflavones were isolated and characterized as quercetin 3-O-rutinoside (1), kaempferol 3-O-rutinoside (2), isorhamnetin 3-O-rutinoside (3), quercetin 3-O-glucoside (4), quercetin 3-methyl ether 7-O-rhamnosylglucoside (5), quercetin 3,3'-dimethyl ether 7-O-rhamnosylglucoside (6), quercetin glycoside (13), quercetin glycoside (acylated) (14), kaempferol glycoside (17) and quercetin 3-O-rhamnoside (18) as flavonols, and isovitexin (7), vitexin (8), isoorientin (9), orientin (10), luteolin 6-C-pentoside (11), luteolin 8-C-pentoside (12), schaftoside (15), isoschaftoside (16), chrysoeriol 6,8-di-C-pentoside (19), apigenin 6,8-di-C-arabinoside (20) and isovitexin 2''-O-glucoside (21) as C-glycosylflavones. Quercetin 3-O-rutinoside (1) alone was isolated from H. sandwicensis endemic to Hawaii. Major flavonoids of almost Begonia species was also 1. Begonia species were divided into two chemotypes, i.e. flavonol containing type and C-glycosylflavone containing type. Of 14 section of the Begonia, almost species of many section, i.e. sect. Augustia, Coelocentrum, Doratometra, Leprosae, Loasibegonia, Monopteron and Ruizoperonia, were flavonol types. On the other hand, C-glycosyflavone type was comparatively most in sect. Platycentrum.     

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.     

Flavonoid chemistry ofWeigela (Caprifoliaceae) in Korea

Fifteen flavonoids were isolated from flowers and leaves of four species ofWeigela [W. florida (Bunge) A. DC.,W. praecox (Lemoine) Bailey,W. hortensis (Sieb. et Zucc.) K. Koch, andW. subsessilis (Nakai) Bailey] of Korea and one species (W. coraeensis Thunb.) of Japan. The flavonoid data indicated the presence of two distinct chemical groups: the “yellow flower” type producing flavonols and the “red flower” type producing flavonols and flavones. Two cyanidin 3-O-glycosides (glucoside and glucose-xylose) also occurred in all examined taxa. In the floral color-changing species,W. subsessilis, only quercetin glycosides predominated in floral tissue at first, decreasing in number and quantity with time. Instead, cyanidin 3-O-glycosides became present predominantly in flower color changing tissue from yellow to mauve.Weigela florida produced apigenin and luteolin glycosides, along with cyanidin 3-O-glycosides, which were also found inW. subsessilis. Within a relatively limited number of individuals (five),W. hortensis was unique in its production of all flavonols, flavones, and anthocyanins, although two individuals lacked flavone compounds but possessed all flavonols and anthocyanins. In effect, the putative hybrid,W. hortensis of Korea showed additive profiles of the parental marker compounds ofW. subsessilis andW. florida. Pollinator (andrenid bees) non-discrimination betweenWeigela flower-color morphs leading to non-assortive mating was a common, which indicated no breeding barrier among species. This flavonoid study indicated that species of both sections,Weigela andCalysphyrum appeared in each chemical grouping and it was obvious that the arrangement based on flavonoids cut across the sectional treatment of Hara. Floral tissues may be directly involved in the evolutionary strategy of pollination mechanisms and hence, their inherent flavonoids may no longer support taxonomic relationships. The presence of flavone glycosides inWeigela would support that tribe Dievilleae have a closer affinity to tribe Lonicereae within the Family Caprifoliaceae.     

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.     

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.     

Malonyl Isoflavone Glycosides in Soybean Seeds (Glycine max Merrill)

The isoflavone constituents in soybean seeds were investigated, and 9 kinds of isoflavone glycosides were isolated from the hypocotyls of soybean seeds. Three kinds were proved to be malonylated soybean isoflavones named 6″-O-malonyldaidzin, 6″-O-malonylglycitin and 6″-O-malonylgenistin by UV, MS, IR and NMR. The malonylated isoflavone glycosides as major isoflavone constituents in soybean seed were thermally unstable, and were converted into their corresponding isoflavone glycosides. All of the isoflavone components produced intensely undesirable taste effects such as bitter, astringent and dry mouth feeling.     

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.     

Antinociceptive activity of the HPLC- and MS-standardized hydroethanolic extract of Pterodon emarginatus Vogel leaves

Several studies have demonstrated the analgesic and anti-inflammatory effects of fruit and seed extracts from Pterodon emarginatus Vogel (Fabaceae). The objective of this study was to evaluate the antinociceptive activity of the hydroethanolic extract of P. emarginatus leaves in mice and characterize its chemical composition using HPLC coupled to UV–vis diode array detection and mass spectrometry with electrospray ionization. Our results showed that the doses of 500 and 1000 mg/kg produced an antinociceptive effect, as observed in the hot plate test and writhing induced by acetic acid. The chromatographic profile and spectral mass data suggest the presence of di-C-glycosylflavones (e.g., vicenin-2 and schaftoside), C,O-glycosylflavones (e.g., chrysoeriol-8-C-glucosyl-2″-O-glucuronide-6-C-arabinoside) and luteolin-7-O-rutinoside as the main constituents. Lower levels of oleanane-type saponins, such as soyasaponin Bb and Be, and the saponin derivatives hederagenin and aglycone B, which are typical of Fabaceae family, were also found. From this study, it is suggested that the analgesic effect observed is not due to the terpenoids previously reported from fruit and seed extracts, but could be attributed to flavones and the hederagenin derivatives that were identified as main constituents of the hydroethanolic extract from the leaves.     

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.     

Fragmentation pattern of permethyl 6-C-glycosylflavones in electron impact mass spectrometry

A mass spectral fragmentation pattern of permethyl 6-C-glycosylflavones is proposed from the MS data of permethyl derivatives mono-O-deuteriomethylated in the 2″-, 3″-, 4″- or 6″-positions. The synthesis of these compounds via O″-glycosyl-6-C-glucosylflavones is described.     

Isomollupentin-O-glucosides from Cerastium arvense

Eight C-glycosylflavone O-glycosides including three new compounds: isomollupentin 7-O-glucoside, isomollupentin 4′-O-glucoside and isomollupentin 2″-O-glucoside have been isolated from the leaves and flowers of Cerastium arvense. The 27 C-glycosylflavones identified in this plant are tabulated.     

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.     

Structural determination of C-glycosylflavones by mass spectrometry of their permethyl ethers

Permethylated C-glycosylflavones give well defined MS, including in all cases an important molecular peak. The observed fragmentations are characteristic for the nature and position of the sugar. The 6-C and 8-C glycosylated derivatives are clearly differentiated. In dissymmetrical 6,8-di-C-glycosylflavones, the natures of the sugar in both the 6- and 8- positions can be determined. The structures of several natural compounds are discussed.