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.     

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.     

Flavone C-glycosides of two Metzgeria species

Six known tricin and apigenin di-C-glycosides, including 2″-O-ferulylisoschaftoside, have been identified in gametophytic material of Metzgeria conjugata. M. leptoneura contains a new di-C-glycoside, tricin 6-C-xyloside-8-C-hexoside. The chemotaxonomic relevance of the flavonoid patterns is briefly discussed.     

Neolignans of Virola carinata bark

Four neolignans, dehydrodieugenol, its monomethylether, carinatone and carinatin have been isolated from the hexane fraction of the bark of Virola carinata. Three new neolignans were separated from the chloroform fraction and examined by spectroscopy and chemical reactions. Their structures were determined as (2S, 3S)-5-allyl- 7-methoxy-3-hydroxymethyl-2-(3′,4′-dimethoxyphenyl)-2,3-dihydrobenzofuran, (2S)- 1-(3′,4′-dimethoxyphenyl)-2-(3″-allyl-5″-methoxy-6″-hydroxyphenyl)propanone(1) ol(3), (1S,2S)-1-(3′,4′-dimethoxyphenyl)-2-(3″-allyl-5″-methoxy-6″-hydroxyphenyl) propanol(1) and called dihydrocarinatinol, carinatonol and carinatol, respectively.     

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.     

The 2″-O-glucosylation of vitexin and isovitexin in petals of Silene alba is catalysed by two different enzymes

Two separate genes, Fg and Vg, which govern the presence of isovitexin 2″-O-glucoside and vitexin 2″-O-glucoside respectively in the petals of Silene alba control different glucosyltransferases. In Vg/Vg,fg/fg plants no isovitexin 2″-O-glucosyltransferase was present and in vg/vg,Fg/Fg plants no vitexin 2″-O-glucosyltransferase activity could be detected. The Fg-controlled UDP-glucose: isovitexin 2″-O-glucosyltransferase has a pH optimum of8.5, while the Vg-controlled vitexin 2″- O-glucosyltransferase has a pH optimum of7.5. Both glucosyltransferases are stimulated by the divalent cations Ca²⁺, Co²⁺, Mn²⁺ and Mg²⁺. For isovitexin 2″-O-glucosylation, however, much higher concentrations are needed than for vitexin 2″-O-glucosylation.For UDP-glucose a ‘true K_m’ value of0.3 mM with the Fg-controlled and of 0.2 mM with the Vg-controlled enzyme was found. For isovitexin and vitexin these values are respectively 0.09 and 0.01 mM.     

Flavonol glycosides from Securidaca diversifolia

Twelve flavonol glycosides have been isolated from the leaves of Securidaca diversifolia. The separation of ten quercetin 3-glycosides and two kaempferol 3-glycosides was achieved by droplet counter-current chromatography (DCCC), preparative reversed-phase chromatography and gel chromatography. The structures were established on the basis of partial and total acid hydrolysis and spectral data (UV, ¹³C NMR, FAB, MS, D/CI MS). The four apiosides: quercetin 3-(2″-β-D-apiofuranosyl-β-D-glucopyranoside), 3-(2″-β-D-apiofuranosyl-β-D-galactoside), 3-(2″-β-D-apiofuranosyl-α-L-arabinopyranoside) and 3-(2″-β-D-apiofuranosyl-β-D-xylopyranoside) are new natural products. The structure of kaempferol 3-(2″-β-D-apiofuranosyl-β-D-glucopyranoside), previously isolated from Cicer arietinum, is confirmed.     

Xanthones and neoflavonoids from two asian species of calophyllum

The stem barks of both Calophyllum macrocarpum and C. walkeri have yielded the known neoflavonoid apetalic acid. In addition, C. walkeri bark gave four 1,3,7-oxygenated xanthones with prenyl substituents at C-2 and C-8. One of the xanthones has been identified as thwaitesixanthone, and the other three as the related novel derivatives thwaitesixanthonol, demethylcalabaxanthone and 2″-isopropenyl-3″-hydroxydihydrofuranodemethylcalabaxanthone.     

Four isoflavanones from the stem bark of Platycelphium voënse

From the stem bark of Platycelphium voënse (Leguminosae) four new isoflavanones were isolated and characterized as (S)-5,7-dihydroxy-2′,4′-dimethoxy-3′-(3″-methylbut-2″-enyl)-isoflavanone (trivial name platyisoflavanone A), (±)-5,7,2′-trihydroxy-4′-methoxy-3′-(3″-methylbut-2″-enyl)-isoflavanone (platyisoflavanone B), 5,7-dihydroxy-4′-methoxy-2″-(2?-hydroxyisopropyl)-dihydrofurano-[4″,5″:3′,2′]-isoflavanone (platyisoflavanone C) and 5,7,2′,3″-tetrahydroxy-2″,2″-dimethyldihydropyrano-[5″,6″:3′,4′]-isoflavanone (platyisoflavanone D). In addition, the known isoflavanones, sophoraisoflavanone A and glyasperin F; the isoflavone, formononetin; two flavones, kumatakenin and isokaempferide; as well as two triterpenes, betulin and β-amyrin were identified. The structures were elucidated on the basis of spectroscopic evidence. Platyisoflavanone A showed antibacterial activity against Mycobacterium tuberculosis in the microplate alamar blue assay (MABA) with MIC = 23.7 μM, but also showed cytotoxicity (IC₅₀ = 21.1 μM) in the vero cell test.     

Acylflavonoid C-glycosides from Eleusine coracana

Chromatographic fractionation of the methanolic extract of the shoots of Eleusine coracana led to the identification of three novel acylflavonoid glycosides, 6″-O-3-hydroxy-3-methylglutaroylorientin (1), 6″-O-malonylvitexin (2), and 4″-O-3-hydroxy-3-methylglutaroylvitexin (3) as well as five known flavonoid glycosides, orientin (4), isoorientin (5), vitexin (6), isovitexin (7), and 6″-O-3-hydroxy-3-methylglutaroylvitexin (8). The structures of these compounds were established on the basis of NMR and mass spectral data.     

Coumarin sulphates of Seseli libanotis

Three new sulphate ester salts derived from known coumarin alcohols–one of them tertiary–have been obtained from roots of Seseli libanotis subsp. eu-libanotis. Their structures were established as (2′S)-rutaretin-1″-sulphate, (3′R)-lomatin-3′-sulphate and (3′R,4′R)-khellactone-3′-sulphate. They were together with their parent alcohols characterized by ¹³C NMR spectroscopy. It is the first report on coumarin sulphates in plants.     

Xanthones from Tovomita pyrifolium

The wood of Tovomita pyrifolium (Guttiferae) contains the novel tovopyrifolins A [1,6-dihydroxy-7-methoxy-5-prenyl-6′,6′-dimethylpyrano (2′,3′:3,2)xanthone], B (1,5-dihydroxy-3,4-dimethoxyxanthone) and C (1,3,5-trihydroxy-2-methoxyxanthone) and also the known tovophyllins A and B [structure revised to 1,6-dihydroxy-5-prenyl-6′, 6′-dimethylpyrano(2′,3′:3,2)-6″,6″-dimethylpyrano(2″,3″:7,8)xanthone].     

Structural confirmation of dihydrocinnamic acids from Adiscanthus fusciflorus by 13C NMR

In the wood of Adiscanthus fusciflorus six known alkaloids 4-methoxy-2-quinolone, 1-methyl-4-methoxy-2-quinolone, dictamine, skimmianine, γ-fagarine and N-methylflindersine and two new dihydrocinnamic acids 3-[2′,6′-dimethoxy-6″,6″-dimethylpyrano(2″,3″:4′, 3′)phenyl]-propionic acid and its methyl ester were identified. The structures of the dihydrocinnamic acid derivatives were confirmed by ¹³C NMR.     

Phenolic glucosides from Olea europaea subs. africana

Two new lignan glucosides, (+)-1-acetoxypinoresinol 4″-methyl ether 4′-β-d-glucoside and (+)-1-hydroxypinoresinol 4′-β-d-glucoside, together with three known glucosides, (+)-1-acetoxypinoresinol 4′-β-d-glucoside, esculin and oleuropein, were isolated from the bark of Olea europaea subs africana.     

Biflavones from the leaves of Araucaria excelsa

Eight biflavones have been isolated from the leaf extracts of Araucaria excelsa. 7″-O-Methylamento-flavone, 7,7″-di-O-methylamentoflavone, 4′ or 4″', 7-di-O-methylcupressuflavone, 7,7″,4″'-tri-O-methyl agathisflavone and 7,4′,7″-tri-O-methylamentoflavone are new compounds and are being reported for the first time. The others are 7,7″-di-O-methylagathisflavone,7,4′,7″,4″'-tetra-O-methylamentoflavone and 7,4′,7″,4″'-tetra-O-methyl-cupressuflavone. Mass and NMR spectral studies are used for structural elucidation. In addition, the presence of several other biflavones has been indicated by TLC examination of methylated products.     

An alkaloid from Haplophyllum tuberculatum

A new alkaloid (+)-tuberine was isolated from Haplophyllum tuberculatum. Physicochemical and spectral evidence established its structure and stereochemistry as N- benzoyl-4′-[(2″S,3″S,6″S)-(+)-7″-acetoxy-2″-hydroxy-3″,7″-dimethyl-3″,6″-epoxyoctyloxy]phenethylamine.     

Lignans from Nectandra turbacensis

Bark and wood of Nectandra turbacensis (Lauraceae) contain, besides the known furofuran lignans (+)-sesamin, (+)-demethoxyexcelsin and (+)-piperitol, the novel (1R,5R,2S,6S)-2-(3′-methoxy-4′,5′-methylenedioxyphenyl)-6-(4″-hydroxy-3″-methoxyphenyl)-3,7-dioxabicyclo[3.3.0]octane [(+)-methoxypiperitol] and (1R,2S,5R)-2-(3′-methoxy-4′,5′-methylenedioxyphenyl)-3,7-dioxa-6-oxobicyclo[3.3.0]octane.     

Diarylpropanes from the wood of Iryanthera grandis

Trunk wood of Iryanthera grandis contains 1(2′-hydroxy-4′,6′-dimethoxyphenyl)-3-(3″,4″-methylenedioxyphenyl)-propane and 1(2′-hydroxy-4′,6′-dimethoxyphenyl)-3-(3″-methoxy-4″-hydroxyphenyl)-propane, as well as three additional known diarylpropanes, a new flavan (±)-5,7-dimethoxy-4′-hydroxyflavan and the known (±)-7,4′-dihydroxy-3′-methoxyflavan.     

New C-glycosylflavones from Mollugo distica

Four C-glycosylflavones isolated from Mollugo distica were identified as 8-C-β-d-glucopyranosyl-genkwanin, 8-C-α-l-arabinopyranosylgenkwanin and their 2″-rhamnosides.     

Lucidafuranocoumarins B and C from the twigs of Feroniella lucida: Absolute configurations of lucidafuranocoumarin C

Two new furanocoumarins, lucidafuranocoumarins B (1) and C (2), were isolated from the twigs of Feroniella lucida, together with five known compounds (3–7). The structures of these compounds were identified on the basis of extensive spectroscopic methods. The absolute configurations of lucidafuranocoumarin C at C-2″ and C-5″ were established as R- and S-configurations, respectively, by applying Mosher's method. Some isolates were also evaluated for their cytotoxicity against KB, MCF-7 and NCI-H187 cell lines.