An acylated flavone apigenin 7-O-β-D-(4″-cis-p-coumaroyl)glucoside from Echinops echinatus

Besides apigenin 7-O-glucoside, a new acylated flavone has been identified in Echinops echinatus as apigenin 7-O-β-D-(4″-cis-p-coumaroyl)glucoside from spectral and chemical analysis.     

Flavonol and secoiridoid glycosides from Coutoubea spicata

Two flavonol glycosides, unusual for the Gentianaceae, clovin and the new quercetin 3-O-rhamnosyl-(1 → 6)-(4″-trans-p-coumaroyl)galactoside 7-O-rhamnoside (4″-trans-p-coumaroylclovin) have been isolated from the aerial parts ofCoutoubea spicata. The bitter principles of C.spicata were identified as gentiopicrin and swertiamarin. Minor polyphenolic glycosides were characterized by high pressure liquid chromatography with photodiode array detection (HPLC-UV/Vis).     

Linkage of p-coumaroyl and feruloyl groups to cell-wall polysaccharides of barley straw

Treatment of cell walls of barley straw with Oxyporus “cellulase” (a mixture of polysaccharide hydrolases) released compounds containing p-coumaroyl and feruloyl groups bound to carbohydrates, two of which were identified as O-[5-O-(trans-p-coumaroyl)-α-l-arabinofuranosyl]-(1→3)-O-β-d-xylopyranosyl-(1→4)-d-xylopyranose (PAXX) and O-[5-O-(trans-feruloyl)-α-l-arabinofuranosyl]-(1→3)-O-β-d-xylopyranosyl-(1→4)-d-xylopyranose (FAXX).     

Flavonoid diversification in different leaf compartments of Primula auricula (Primulaceae)

Populations of Primula auricula L. subsp. auricula from Austrian Alps were studied for flavonoid composition of both farinose exudates and tissue of leaves. The leaf exudate yielded Primula-type flavones, such as unsubstituted flavone and its derivatives, while tissue flavonoids largely consisted of flavonol 3-O-glycosides, based upon kaempferol (3, 4) and isorhamnetin (5–7). Kaempferol 3-O-(2″-O-β-xylopyranosyl-[6″-O-β-xylopyranosyl]-β-glucopyranoside) (3) and isorhamnetin 3-O-(2″-O-β-xylopyranosyl-[6″-O-β-xylopyranosyl]-β-glucopyranoside) (6) are newly reported as natural compounds. Remarkably, two Primula type flavones were also detected in tissues, namely 3′-hydroxyflavone 3′-O-β-glucoside (1) and 3′,4′-dihydroxyflavone 4′-O-β-glucoside (2), of which (1) is reported here for the first time as natural product. All structures were unambiguously identified by NMR and MS data. Earlier reports on the occurrence of 7,2′-dihydroxyflavone 7-O-glucoside (macrophylloside) in this species could not be confirmed. This structure was now shown to correspond to 3′,4′-dihydroxyflavone 4′-O-glucoside (2) by comparison of NMR data. Observed exudate variations might be specific for geographically separated populations. The structural diversification between tissue and exudate flavonoids is assumed to be indicative for different ecological roles in planta.     

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.     

Acylated flavonoid tetraglycoside from Planchonia careya leaves

Phytochemical investigations of the aqueous extract of Planchonia careya leaves revealed two known flavonol glycosides, kaempferol 3-O-gentiobioside (1) and quercetin 3-O-glucoside (isoquercitrin) (2), and a novel acylated kaempferol tetraglycoside, kaempferol 3-O-[α-rhamnopyranosyl(1 → 3)-(2-O-p-coumaroyl)]-β-glucopyranoside, 7-O-[α-rhamnopyranosyl-(1 → 3)-(4-O-p-coumaroyl)]-α-rhamnopyranoside (3). Structural elucidation was achieved using UV, NMR, and mass spectrometry.     

Secondary metabolites of Rubus caesius (Rosaceae)

The European dewberry (Rubus caesius) is a perennial shrub that is widely distributed in Europe but can also be found in North America. In folk medicine, the European dewberry is used to treat hyperglycaemia, diarrhoea and inflammation. LC-MS analysis of the European dewberry confirmed the presence of 35 compounds, mostly flavonoids, phenolic acids and derivatives of ellagic acid. Phytochemical analysis of R. caesius leaves led to the isolation of nine phenolics, namely: quercetin 3-O-β-D-rutinoside (1), kaempferol 3-O-β-D-glucuronide (2), quercetin 3-O-β-D-glucuronide (3), methyl brevifolincarboxylate (4), kaempferol 3-O-β-D-(6″-O-(E)-p-coumaroyl)-glucoside (5), kaempferol (6), quercetin (7), pedunculagin (8), and ellagic acid (9). Compounds 1–8 were isolated from this species for the first time. The chemophenetic significance was discussed.     

Anti-inflammatory activity of flavonoids from Chrozophora tinctoria

Chemical investigation of Chrozophora tinctoria (L.) A. Juss. growing in Saudi Arabia revealed the isolation of two new acylated flavonoids identified as acacetin-7-O-β-d-[α-l-rhamnosyl(1 → 6)]3″-E-p-coumaroyl glucopyranoside (4) and apigenin-7-O-(6″-Z-p-coumaroyl)-β-d-glucopyranoside (5), in addition to amentoflavone (1), apigenin-7-O-β-d-glucopyranoside (2), apigenin-7-O-6″-E-p-coumaroyl-β-d-glucopyranoside (3) and rutin (6). The structures of isolated compounds were established by 1D, 2D NMR and HRESIMS spectral data, in addition to comparison with literature data. The anti-inflammatory activities of isolated compounds were assessed by measuring the levels of IL-1β, IL-6, TNF-α and PGE₂ in the supernatant media of human peripheral blood mononuclear cells (PBMCs) stimulated by phytohaemagglutinin (PHA). At a concentration of 100 μM, compounds 1, 2, 4 and 6 significantly decreased Il-1β, Il-6 and PGE₂ to nearly normal values. All tested compounds caused a dose-dependent decrease in TNF-α level but failed to reach that of the control values.     

Studies on the probing stimulants for the white-backed planthopper,Sogatella furcifera (Homoptera: Delphacidae) in rice plant (Oryza sativa L.)

To elucidate the probing stimulants in rice plants for the white-backed planthopper, Sogatella furcifera, bioassay-guided separations were conducted, which led to the isolation of four active compounds. Using NMR and LC-MS spectra, their structures were determined as isoorientin 2″-O-(6?-(E)-feruloyl)glucoside, isoorientin 2″-O-(6?-(E)-p-coumaroyl)glucoside, tricin 5-O-glucoside, and isoscoparin 2″-O-(6?-(E)-feruloyl)glucoside.     

Flavonoids from phlomis lychnitys

The new naturally occurring acylated flavone glucoside chrysoeriol-7-β-D-(3″-E-p-coumaroyl)glucoside and other flavonoids have been isolated from the aerial parts of Phlomis lychnitys, and identified by spectral techniques. Relationships between flavonoid pattern, phylogeny and geography in Phlomis are discussed.     

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.     

New trans- and cis-p-coumaroyl flavonol tetraglycosides from the leaves of Mitragyna rotundifolia

Two new flavonol tetraglycosides, quercetin 3-O-(4-O-trans-p-coumaroyl)-α-l-rhamnopyranosyl (1→2) [α-l-rhamnopyranosyl (1→6)]-β-d-glucopyranoside-7-O-α-l-rhamnopyranoside (krathummuoside A) and quercetin 3-O-(4-O-cis-p-coumaroyl)-α-l-rhamnopyranosyl (1→2) [α-l-rhamnopyranosyl (1→6)]-β-d-glucopyranoside-7-O-α-l-rhamnopyranoside (krathummuoside B) were isolated from the leaves of Mitragyna rotundifolia in addition to eight known compounds, quercetin 3-O-α-l-rhamnopuranosyl (1→2) [α-l-rhamnopyranosyl (1→6)]-β-d-glucopyranoside-7-O-α-l-rhamnopyranoside, rutin, (−)-epi-catechin, 3,4,5-trimethoxyphenyl β-d-glucopyranoside, (6S, 9R)-roseoside, 3-O-β-d-glucopyranosyl quinovic acid 28-O-β-d-glucopyranosyl ester, (+)-lyoniresinol 3α-O-β-d-glucopyranoside, and (+)-syringaresinol-4-O-β-d-glucopyranoside. The structure elucidation of these compounds was based on analyses of spectroscopic data including 1D- and 2D-NMR.     

Flavonolacyl glucosides from the aril of Schotia brachypetala Sond. and their antioxidant,antibacterial and antimalarial activities

Two new flavonolacyl glucosides, 3-O-methylquercetin 7-O-[β-D-6″-(E-p-coumaroyl) glucopyranoside] (1) and 3,4′-di-O-methylquercetin 7-O-[β-D-6″-(E-p-coumaroyl) glucopyranoside] (2), four known flavonol glycosides (3–5, 7) and one known dihydroflavonolglucoside (6) were isolated from the aril part of Schotia brachypetala with high-speed countercurrent chromatography (HSCCC) as the primary chromatographic technique. The structures of the isolated compounds were elucidated with spectroscopic and spectrometric methods and acid hydrolysis. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) antioxidant, antibacterial and antimalarial activities of selected isolates were evaluated. Strong to moderate antioxidant activity (lowest IC₅₀ of 15.2 μM), moderate to weak antibacterial activity (lowest MIC of 0.13 mg/mL) and moderate antimalarial activity (lowest IC₅₀ of 5.18 μg/mL) compared to the positive controls were observed.     

Four new iridoid glucoside p-coumaroyl esters from Ajuga decumbens

From the methanolic extract of the dried whole plant ofAjuga decumbens, four new iridoid glucosidecis- andtrans-p-coumaroyl esters, decumbeside A (1), B (2), C (7) and D (8) were isolated together with the known reptoside (6) and 8-acetylharpagide (9). The structures of the new compounds have been elucidated on the basis of spectroscopic and chemical evidence.     

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.     

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 constituents of Ephedra alata

Two new flavonol glucosides have been identified in Ephedra alata, namely, herbacetin 8-methyl ether 3-O- glucoside-7-O-rutinoside and herbacetin 7-O-(6″-quinylglucoside). The known flavonoids vicenin II, lucenin III, kaempferol 3-rhamnoside, quercetin 3-rhamnoside and herbacetin 7-glucoside were also found. The structure of the isolated compounds was determined mostly by FABMS and ¹H NMR spectroscopy. The final structure of the new compounds and of herbacetin 7-glucoside was confirmed by ¹³C NMR spectroscopy.     

Anthraquinone,anthrone and phenylpyrone components of Aloe nyeriensis var. kedongensis leaf exudate

The leaf exudate of Aloe nyeriensis var. kedongensis yielded six compounds which were identified on the basis of spectral data and inter-conversions as two groups of three allied compounds. These were (a) 4-methoxy-6(2′,4′-dihydroxy-6′- methylphenyl)-pyran-2-one, its 2′-O-β-D-glucopyranoside (aloenin) and the 2″-O-p-coumaroyl ester of aloenin, (b) the anthracene derivatives l,2,8-trihydroxy- 6-methylanthraquinone (nataloe-emodin), its 2-O-β-D-glucopyranosyl ester and the corresponding 10-C -β-D-glucopyranoside nataloin.     

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.     

Biologically active phenolics from Lilium longiflorum

The new phenolics, the trans-p-coumaroyl and the feruloyl esters of 2,3-dihydroxy-1,2-propanedicarboxylic acid and itaconic acid, were isolated from Lilium longiflorum; the cis-p-coumaroyl ester was also detected. The biological activities of the trans-p-coumaroyl ester are described.