Isoscutellarein and hypolaetin 8-glucuronides from the liverwort Marchantia berteroana

The major flavonoid of Marchantia berteroana is hypolaetin 8-O-β-d-glucuronide. This is accompanied by apigenin and luteolin, isoscutellarein (8-hydroxyapigenin) 8-O-β-d-glucuronide, the 7-O-β-d-glucuronide and -galacturonide of apigenin and luteolin, luteolin 3′-O-β-d-glucuronide and -galacturonide, luteolin 7,3′-di-O-β-d-glucuronide and -galacturonide, luteolin 3′,4′-di-O-β-d-glucuronide and -galacturonide, luteolin 7,4′-di-O-β-d-glucuronide, and hypolaetin 8,4′-di-O-β-d-glucuronide. The isoscutellarein and hypolaetin glucuronides, and the galacturonide flavones are all new natural products.     

Luteolin 3′,4′-di-O-β-d-glucuronide and luteolin 3′-O-β-d-glucuronide from Lunularia cruciata

Luteolin 3′,4′-di-O-β-d-glucuronide is the major flavonoid in the liverwort Lunularia cruciata. It is accompanied by small amounts of luteolin 3′-O-β-d-glucuronide. Both are new natural products and the former appears to be a unique example of a 3′,4′-diglycosylated flavonoid. Luteolin 4′-O-β-d-glucuronide was isolated as a hydrolysis product of the diglucuronide.     

Flavonoid variation in the liverwort Conocephalum conicum: Evidence for geographic races

The flavonoids of 2 samples of Conocephalum conicum gametophyte tissue have been studied, one from U.S.A. and the other from Germany. Common to both samples were vicenin-2, lucenin-2, the 7-O-glucuronides of apigenin, chrysoeriol and luteolin and the previously unknown 7-O-glucuronide 4′-O-rhamnosides of apigenin, chrysoeriol and luteolin. Additionally the German sample contained the 7,4′-di-O-glucuronides of apigenin and luteolin and a new compound, apigenin 7-O-diglucuronide 4′-O-glucuronide. The North American sample contained, additionally, luteolin 7,3′-di-O-glucuronide, luteolin 7-O-glucuronide 3′,4′-di-O-rhamnoside (a new triglycoside) and 2 further derivatives of luteolin 7-O-glucuronide. Evidence is presented for the existence of geographic faces of C. conicum and for the qualitative invariability of the flavonoid patterns with changing season or environment.     

Evidence of biosynthetic simplicity in the flavonoid chemistry of the ricciaceae

The major flavonoids in Riccia crystallina are naringenin and its 7-O-glucoside, apigenin 7-O-glucoside and apigenin 7-O-glucuronide and derivatives. Ricciocarpus natans is a rich source of luteolin 7,3′-di-O-glucuronide and also contains the 7-O-glucuronides of apigenin and luteolin and the 3′-O-glucuronide of luteolin. A parallel between the production of biosynthetically simple flavonoids and reduced morphology is evident among these liverworts.     

Two luteolin o-glucuronides from primary leaves of Secale cereale

Two luteolin O-glucuronides have been located exclusively in the photosynthetically active mesophyll of primary leaves of rye (Secale cereale). Their structures have been elucidated as luteolin 7-O-[β-d-glucuronosyl (1 → 2)β-d-glucuronide]-4′-O-β-d-glucuronide and luteolin 7-O-[β-d-glucuronosyl (1 → 2)β-d-glucuronide]. The former glycoside is a new natural compound.     

5-Methyl ether flavone glucosides from the leaves of Bruguiera gymnorrhiza

Two new 5-methyl ether flavone glucosides (7,4′,5′-trihydroxy-5,3′-dimethoxyflavone 7-O-β-D-glucopyranoside and 7,4′-dihydroxy-5-methoxyflavone 7-O-β-D-glucopyranoside) were isolated from the leaves of Thai mangrove Bruguiera gymnorrhiza together with 7,3′,4′,5′-tetrahydroxy-5-methoxyflavone, 7,4′,5′-trihydroxy-5,3′-dimethoxyflavone, luteolin 5-methyl ether 7-O-β-D-glucopyranoside, 7,4′-dihydroxy-5,3′-dimethoxyflavone 7-O-β-D-glucopyranoside, quercetin 3-O-β-D-glucopyranoside, rutin, kaempferol 3-O-rutinoside, myricetin 3-O-rutinoside and an aryl-tetralin lignan rhamnoside. The structure of a lignan rhamnoside was found to be related to racemiside, an isolated compound from Cotoneaster racemiflora, and also discussed. Structure determinations were based on analyses of physical and spectroscopic data including 1D- and 2D-NMR.     

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.     

Flavonoids and the chemotaxonomy of three Sophora species

Sophora microphylla, S. prostrata and S. tetraptera are distinguishable from one another by their leaf flavonoids. S. microphylla is distinguished by the present of rhamnosylvitexin and rhamnosylisovitexin and S. tetraptera by the presence of apigenin-7-O-rhamnosylglucoside-4′-O-glucoside and the 7-O-glucosides of apigenin, 7,4′-dihydroxyflavone, luteolin and 7,3′,4′-trihydroxyflavone. Sophora prostrata lacks all these flavonoids, but has several pigments which are common to all three species.     

Apigenin 4′-O-β-d-glucoside 7-O-β-d)- glucuronide: The copigment in the blue pigment of Centaurea cyanus

The copigment present in the crystalline blue pigment isolated from Blue Boy cornflowers (Centaurea cyanus L.) was identified as apigenin 4′-O-β-glucoside 7-O-β-d-glucuronide. The NMR spectra of aryl glucuronides are discussed.     

Chemophenetics of Azorean Leontodon taxa (Cichorieae,Asteraceae)

The genera Leontodon s.str. and Hedypnois are so far the only known sources of hydroxyhypocretenolides, a rare subclass of guaianolide type sesquiterpene lactones. In this study the three endemic species from the Azorean Archipelago, L. filii, L. hochstetteri, and L. rigens, were analyzed together with L. hispidus and L. × grassiorum, a hybrid originating from L. hispidus and L. hochstetteri. Flowering heads were analyzed by UHPLC-DAD-MS with regards to their phenolics' profiles, establishing qualitatively identical profiles for all taxa. The following phenolics were detected in flowering heads of all investigated taxa: caffeoyltartaric acid, cichoric acid, chlorogenic acid, 3,5-di-O-caffeoylquinic acid, luteolin, luteolin 7-O-β-d-glucopyranoside, luteolin 4′-O-β-d-glucopyranoside, and luteolin 7-O-β-d-glucuronide.In UHPLC-DAD-MS analyses of the rhizomes, no flavonoids were detected. In rhizomes, caffeoyltartaric acid was only detected in L. hispidus. However, in addition to caffeoylquinic acid derivatives already found in the flowering heads, 1,5-di-O-caffeoylquinic acid, 3,4-di-O-caffeoylquinic acid, and 4,5-di-O-caffeoylquinic acid were detected in rhizomes of all investigated taxa.The chemophenetically most interesting group of hydroxyhypocretenolides was detected in rhizomes of all investigated taxa. 11,13β-Dihydro-14-dihydroxyhypocretenolide was detected in L. filii and L. hochstetteri, while 11,13β-dihydro-14-hydroxyhypocretenolide-β-d-glucopyranoside was present in all Azorean taxa. 1,10-Epoxy-14-hydroxyhypocretenolide-β-d-glucopyranoside and 1,10-epoxy-14-hydroxyhypocretenolide-β-d-glucopyranoside-6′-O-p-hydroxyphenylacetic acid ester were restricted to the Azorean taxa and the hybrid L. × grassiorum, while the dimeric sesquiterpenoid 14-hydroxyhypocretenolide-β-d-glucopyranoside-4′,14″-hydroxyhypocretenoate ester was restricted to L. hispidus and L. × grassiorum.     

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.     

Synthesis of (±)-7,3′- and 7,4′-di-O-methyleriodictyol and of velutin and pilloin

Synthetic 2′-hydroxy-3,4′,6′-trimethoxy-4-benzyloxychalcone (I) affords (±)-7,3′-di-O-methyleriodictyol (II) and 7,3′-di-O-methylluteolin (or velutin, VII) identical with natural samples. Similarly synthetic 2′-hydroxy-4,4′,6′-trimethoxy-3-benzyloxychalcone (X) gives natural (±)-7,4′-di-O-methyleriodictyol (XI) and 7,4′-di-O-methylluteolin (or pilloin, IX). However, attempts to partially etherify II with one mole of prenyl bromide to obtain the natural prenyl ether failed; only the corresponding diprenyloxychalcone (IV) was obtained.     

The taxonomic position of Sphaerocarpos and Riella as indicated by their flavonoid chemistry

The major flavonoid glycosides of Sphaerocarpos texanus are luteolin 7-O-glucuronide and 7,4′-di-O-glucuronide. Riella americana and R. affinis both contain apigenin, chrysoeriol and luteolin 7-O-glucuronides but R. americana additionally contains luteolin 3′-O-glucuronide. This finding supports the inclusion of Sphaerocarpaceae and Riellaceae in the order Marchantiales rather than their separation into another order.     

New water soluble flavone and xanthone glycosides from Hypericum canariense L.

The water soluble portion of the aerial parts of Hypericum canariense L. yielded after acetylation the 5,7,3′4′-tetra- and 7,3′4′-triacetates of a new flavonoid 5,7,3′,4′-tetrahydroxy-3-O-β-d-(methyl 2,3,4-triacetoxypyranuronyl)-quercetin, the 3′-acetate of a new flavonoid 3′-hydroxy-5,7,4′-trimethoxy-3-O-β-d-(methyl 2,3,4-triacetoxypyranuronyl)-quercetin, the 3′-acetate and the 3′5′-diacetate of the new flavonoid 5,3′dihydroxy-7,4′-dimethoxy-3-β-d-(methyl 2,3,4-triacetoxypyranuronyl)-quercetin, the xanthone derivative mangiferin 2′,3′,4′,6′-tetraacetate and the latter's new 1,3,6,7′-tetramethoxy, 1,3,6-trimethoxy-4-acetoxy and 1,7-diacetoxy-3,6-dimethoxy analogs.     

Two further acylated flavone glucosides from Anisomeles ovata

The structures of two new acylated apigenin glucosides are reported from the aerial parts of Anisomeles ovata. They were separated as their acetates and identified as apigenin 7-O-β-d-(2″,6″-di-O-p-coumaroyl)glucoside and apigenin 7-O-β-d-(4″,6′-di-O-p-coumaroyl)glucoside by ¹H NMR study of the acetates and by chemical degradative methods. The allocation of the p-coumaroyl moieties is also supported by a study of the ¹³C NMR spectrum of the inseparable mixture of glucosides.     

Unique flavonoid glycosides from the new zealand white pine, Dacrycarpus dacrydioides

A number of new flavonoid glycosides have been isolated from foliage of the New Zealand white pine, Dacrycarpus dacrydioides. These include tricetin 3′,5′-di-O-β-glucopyranoside; the 3′-O-β-xylopyranoside, 7-O-α-rhamnopyranoside and 7-O-α-rhamnopyranoside-3′-O-β-xylopyranoside of 3-O-methylmyricetin; the 3′-O-β-xylopyranoside, 7-O-α-rhamnopyranoside and 7-O-α-rhamnopyranoside-3′-O-β-xylopyranoside of 3-O-methyl-quercetin, and the 3′-O-β-xylopyranoside and 7-O-α-rhamnopyranoside-3′-O-β-xylopyranoside of 3,4′-di-O-methylmyricetin. The accumulation of 3-methoxyflavones and B-ring trioxygenated flavonoids appears to distinguish D. dacrydioides from all other New Zealand members of the classical genus Podocarpus. Support for De Laubenfels' proposed separation of Dacrycarpus from this genus is seen in the present work.     

The synthesis of 4′,6′-diacetamido-4′,6′-dideoxycellobiose hexa-acetate from lactose

Reaction of methyl 4′,6′-di-O-mesyl-β-lactoside pentabenzoate (8), synthesised via the 4′,6′-O-benzylidene derivative (6), with sodium azide in hexamethylphosphoric triamide gave three products. In addition to the required 4′,6′-diazidocellobioside (9), an elimination product, methyl 4-O-(6-azido-2,3-di-O-benzoyl-4,6-dideoxy-α-L-threo-hex-4-enopyranosyl)-2,3,6-tri-O-benzoyl-β-D-glucopyranoside (12), and an unexpected product of interglycosidic cleavage, methyl 2,3,6-tri-O-benzoyl-β-D-glucopyranoside (13), were formed. The origin of the latter product is discussed. The diazide 9 was converted into 4′,6′-diacetamido-4′,6′-dideoxycellobiose hexa-acetate (16) by sequential debenzoylation, catalytic reduction, acetylation, and acetolysis.     

Unprecedented furan-2-carbonyl C-glycosides and phenolic diglycosides from Scleropyrum pentandrum

Five unprecedented furan-2-carbonyl C-glycosides, scleropentasides A–E, and two phenolic diglycosides, 4-hydroxy-3-methoxybenzyl 4-O-β-d-xylopyranosyl-(1 → 6)-β-d-glucopyranoside and 2,6-dimethoxy-p-hydroquinone 1-O-β-d-xylopyranosyl-(1 → 6)-β-d-glucopyranoside, were isolated from leaves and twigs of Scleropyrum pentandrum together with potalioside B, luteolin 6-C-β-d-glucopyranoside (isoorientin), apigenin 8-C-β-d-glucopyranoside (vitexin), apigenin 6,8-di-C-β-d-glucopyranoside (vicenin-2), apigenin 6-C-α-l-arabinopyranosyl-8-C-β-d-glucopyranoside (isoschaftoside), apigenin 6-C-β-d-glucopyranosyl-8-C-β-d-xylopyranoside, adenosine and l-tryptophan. Structure elucidations of these compounds were based on analyses of chemical and spectroscopic data, including 1D and 2D NMR. In addition, the isolated compounds were evaluated for their radical scavenging activities using both DPPH and ORAC assays.     

Chalcone glycosides from aerial parts of Brassica rapa L. ‘hidabeni’, turnip

A phytochemical investigation of the aerial parts of Brassica rapa L. ‘hidabeni’, turnip resulted in the isolation of three new chalcone glycosides, 4′-O-β-d-glucopyranosyl-4-hydroxy-3′-methoxychalcone (1), 4′-O-β-d-glucopyranosyl-3′,4-dimethoxychalcone (2) and 4,4′-di-O-β-d-glucopyranosyl-3′-methoxychalcone (3) along with three known glycosides. The structures of the three newly isolated chalcone glycosides were elucidated on the basis of 1D and 2D NMR and mass spectroscopy.     

Flavonoids and tannins of Acacia species

The heartwoods of Acacia giraffae and A. galpinii were selected from South African Acacias as representative of those with abnormally high and minimal tannin contents respectively. A. galpinii contains amongst other analogues, the first natural (+)-2,3-trans-3,4-trans-teracacidin (7,8,4′-trihydroxy-flavan-3,4-diol and novel 3-O-methyl-, 7,8-di-O-methyl- and 7,8,4′-tri-O-methylflavonol analogues. (−)-2,3-cis-3,4-cis-Melacacidin (7,8,3′,4′-tetrahydroxyflavan-3,4-diol) is also present, but tannins are absent. By contrast, from the large excess of leueofisetinidin tannins which characterizes the wood of A. giraffae, only (+)-catechin, (+)-2,3-trans-3,4-trans-leucofisetinidin (7,3′,4′,trihydroxyflavan-3,4-diol and all-trans-(+)-leueofisetinidin-(+)-catechin could be isolated.