Methylated anthocyanidin glycosides from flowers of Canna indica

Methylated anthocyanin glycosides were isolated from red Canna indica flower and identified as malvidin 3-O-(6-O-acetyl-β-d-glucopyranoside)-5-O-β-d-glucopyranoside (1), malvidin 3,5-O-β-d-diglucopyranoside (2), cyanidin-3-O-(6″-O-α-rhamnopyranosyl-β-glucopyranoside (3), cyanidin-3-O-(6″-O-α-rhamnopyranosyl)-β-galactopyranoside (4), cyanidin-3-O-β-glucopyranoside (5) and cyanidin-O-β-galactopyranoside (6) by HPLC-PDA. Their structures were subsequently determined on the basis of spectroscopic analyses, that is, ¹H NMR, ¹³C NMR, HMQC, HMBC, ESI-MS, and UV-vis. Compounds (1-4) were found to be in major quantity while compounds (5-6) were in minor quantity.     

Flavones and flavone glycosides from Halophila johnsonii

Halophila johnsonii Eiseman is a shallow-water marine angiosperm which contains UV-absorbing metabolites. Studies on methanol extracts of H. johnsonii by means of HPLC-UV, NMR, HPLC-MS resulted in isolation and identification of seven previously unknown flavone glycosides: 5,6,7,3′,4′,5′-hexahydroxyflavone-7-O-β-glucopyranoside (1), 5,6,7,3′,4′,5′-hexahydroxyflavone-7-O-(6″-O-acetyl)-β-glucopyranoside (2), 6-hydroxyluteolin-7-O-(6″-O-acetyl)-β-glucopyranoside (3), 6-hydroxyapigenin-7-O-(6″-O-acetyl)-β-glucopyranoside (4), 6-hydroxyapigenin-7-O-(6″-O-[E]-coumaroyl)-β-glucopyranoside (5), 6-hydroxyapigenin-7-O-(6″-O-[E]-caffeoyl)-β-glucopyranoside (6) and 6-hydroxyluteolin-7-O-(6″-O-[E]-coumaroyl)-β-glucopyranoside (7). Also isolated were three known flavone glycosides, 6-hydroxyluteolin 7-O-β-glucopyranoside (8), scutellarein-7-O-β-glucopyranoside (9), and spicoside (10), and five known flavones, pedalitin (11), ladanetin (12), luteolin (13), apegenin (14) and myricetin (15). Qualitative comparison of the flavonoid distribution in the leaf and rhizome-root portions of the plant was also investigated, with the aim of establishing the UV-protecting roles that flavonoids played in the sea grass.     

Chemical constituents of Picea neoveitchii

Four flavonoids, 5,7,4′-trihydroxy-3,8,-dimethoxy-6-C-methylflavone (1), 5,8,4′-trihydroxy-3,7-dimethoxy-6-C-methylflavone (2), 7-methoxy-6-C-methylkaempferol (3) and kaempferol-7-O-(2″-E-p-coumaroyl)-α-l-arabinofuranoside (4), together with 15 known compounds, were isolated from the twigs and leaves of Picea neoveitchii Mast. Their structures were elucidated on the basis of analyses of spectroscopic data. Compound 4 showed strong anti-fungal activity against Fusarium oxysporum whereas compounds 1-4 were all active against Rhizoctonia solani.     

Iridoid glycosides from Gardeniae Fructus for treatment of ankle sprain

The iridoid glycosides, genipin 1-O-β-d-isomaltoside (1) and genipin 1,10-di-O-β-d-glucopyranoside (2), together with six known iridoid glycosides, genipin 1-O-β-d-gentiobioside (3), geniposide (4), scandoside methyl ester (5), deacetylasperulosidic acid methyl ester (6), 6-O-methyldeacetylasperulosidic acid methyl ester (7), and gardenoside (8) were isolated from an EtOH extract of Gardeniae Fructus. The structures and relative stereochemistries of the metabolites were elucidated on the basis of 1D- and 2D-NMR spectroscopic techniques, high-resolution mass spectrometry, and chemical evidence. Geniposide (4), one of the main compounds of Gardeniae Fructus, was tested for treatment of ankle sprain using an ankle sprain model in rats. From the second to fifth day, the geniposide (4) (100 mg/ml) treated group exhibited significant differences (p < 0.01) with ∼21-34% reduction in swelling ratio compared with those of the vehicle treated control group. This indicated the potential effect of geniposide (4) for the treatment of disorders such as ankle sprain.     

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.     

Iridoids from Gentiana loureirii

Iridoid glycosides, 2′,3′,6′-tri-O-acetyl-4′-O-trans-p-(O-β-d-glucopyranosyl)coumaroyl-7-ketologanin (1), 2′-O-caffeoylloganic acid (2), 2′-O-p-hydroxybenzoylloganic acid (3), 2′-O-trans-p-coumaroylloganic acid (4), and 2′-O-cis-p-coumaroylloganic acid (5), were isolated from whole plants of Gentiana loureirii along with six known iridoids, 7-ketologanin (6), loganin (7), loganic acid (8), sweroside, boonein, and isoboonein, and three other known compounds. Their structures were elucidated by spectroscopic means and chemical correlations. The isolated iridoids were evaluated for antibacterial and antioxidant activities, but were either inactive or very weakly active.     

Phenolic glycosides from Agrimonia pilosa

Phytochemical investigation of the methanolic extract from the aerial parts of Agrimonia pilosa led to the isolation of three compounds, (−)-aromadendrin 3-O-β-d-glucopyranoside (1), desmethylagrimonolide 6-O-β-d-glucopyranoside (2), and 5,7-dihydroxy-2-propylchromone 7-O-β-d-glucopyranoside (3), together with nine known compounds, agrimonolide 6-O-glucoside, takanechromone C, astragalin, afzelin, tiliroside, luteolin, quercetin, isoquercetrin, and quercitrin. Their structures were determined by various spectroscopic analysis and chemical transformations.     

Absolute configuration of (+)-pinoresinol 4-O-[6″-O-galloyl]-β-d-glucopyranoside, macarangiosides E, and F isolated from the leaves of Macarangatanarius

A lignan glucoside, (+)-pinoresinol 4-O-[6″-O-galloyl]-β-d-glucopyranoside (1), and two megastigmane glucosides, named macarangiosides E and F (2,3), together with 15 known compounds (4-18) were isolated from leaves of Macarangatanarius (L.) Müll.-Arg. (Euphorbiaceae). Their structures were elucidated by spectroscopic and chemical analyses. In addition, the absolute stereochemistry of macarangiosides B and C isolated previously from the same plant was also determined for the first time. Compounds 1 and 2 were galloylated on glucose and possessed potent DPPH radical-scavenging activity.     

Four new steroidal glycosides from Solanum torvum and their cytotoxic activities

Two novel C-22 steroidal lactone saponins, namely solanolactosides A, B (1, 2) and two new spirostanol glycosides, namely torvosides M, N (3, 4) were isolated from ethanol extract of aerial parts of Solanum torvum. Their structures were characterized as solanolide 6-O-[α-l-rhamnopyranosyl-(1 → 3)-O-β-d-quinovopyranoside] (1), solanolide 6-O-[β-d-xylopyranosyl-(1 → 3)-O-β-d-quinovopyranoside] (2), yamogenin 3-O-[β-d-glucopyranosyl-(1 → 6)-O-β-d-glucopyranoside] (3) and neochlorogenin 3-O-[β-d-glucopyranosyl-(1 → 6)-O-β-d-glucopyranoside] (4) on the basis of spectroscopic analysis. The cytotoxicities of the saponins (1-4) were evaluated in vitro against a panel of human cancer cell lines. Compounds 3 and 4 showed significant cytotoxic activity with the cell lines.     

New monoterpene glycosides and phenolic compounds from Distylium racemosum and their inhibitory activity against ribonuclease H

Two new monoterpene glycosides, distyloside A-B (1-2), and a new megastigmane glucoside, iso-dihydrodendranthemoside A (3) were isolated from twigs and leaves of Distylium racemosum, along with five known phenolic compounds (4-8). The structures were established via spectroscopic techniques and chemical transformations, and the absolute stereochemistry of 3 was determined by Mosher’s esterification. A homogeneous fluorescence resonance energy transfer (FRET) quenching assay was used to determine the inhibitory activity of isolates (1-8) on the ribonuclease H enzymes from HIV-1, 2, human, and Escherichia coli. Among them, 6″-O-galloylsalidroside (6) showed potent inhibitory effects with an IC₅₀ value of 3.5 μM on HIV-2, and 1.7 μM on human RNase H, respectively.     

Antibacterial phenolic components from Eriocaulon buergerianum

Five phenolic components, 1,3,6-trihydroxy-2,5,7-trimethoxyxanthone (1), 7,3′-dihydroxy-5,4′,5′-trimethoxyisoflavone (2), toralactone-9-O-β-d-glucopyranoside (3), patuletin-3-O-[2-O-E-feruloyl-β-d-glucopyranosyl-(1 → 6)-β-d-glucopyranoside] (4), patuletin-3-O-[β-d-glucopyranosyl-(1 → 3)-2-O-E-caffeoyl-β-d-glucopyranosyl-(1 → 6)-β-d-glucopyranoside] (5), along with 19 known compounds were isolated from Eriocaulon buergerianum (Eriocaulaceae). Their structures were determined by spectroscopic and chemical methods. All 24 isolated compounds were tested against the pathogenic bacteria Staphylococcus aureus (ATCC 25923); as a result, 10 compounds were found to exhibit antibacterial activity with MICs ranging from 32 to 256 μg/ml.     

Cycloartane glycosides from Astragalus campylosema Boiss. ssp. campylosema

Four cycloartane glycosides, 3-O-[α-l-arabinopyranosyl-(1 → 2)-β-d-xylopyranosyl]-3β,6α,16β,23α,25-pentahydroxy-20(R),24(S)-epoxycycloartane (1), 3-O-[α-l-arabinopyranosyl-(1 → 2)-β-d-xylopyranosyl]-16-O-hydroxyacetoxy-23-O-acetoxy-3β,6α,25-trihydroxy-20(R),24(S)-epoxycycloartane (2), 3-O-[α-l-arabinopyranosyl-(1 → 2)-β-d-xylopyranosyl]-3β,6α,23α,25-tetrahydroxy-20(R),24(R)-16β,24;20,24-diepoxycycloartane (3), 3-O-[α-l-arabinopyranosyl-(1 → 2)-β-d-xylopyranosyl]-25-O-β-d-glucopyranosyl-3β,6α,16β,25-tetrahydroxy-20(R),24(S)-epoxycycloartane (4), along with three known cycloartane glycosides were isolated from the MeOH extract of the roots of Astragalus campylosema ssp. campylosema. Their structures were established by the extensive use of 1D- and 2D-NMR experiments along with ESIMS and HRMS analysis. The occurrence of the hydroxyl function at position 23 (1-2) and of the ketalic function at C-24 (3) are very unusual findings in the cycloartane class.     

Isolation and structure elucidation of 5′-O-β-d-glucopyranosyl-dihydroascorbigen from Cardamine diphylla rhizome

From the methanol extract of Cardamine diphylla rhizome, 5′-O-β-d-glucopyranosyl-dihydroascorbigen (1) and 6-hydroxyindole-3-carboxylic acid 6-O-β-d-glucopyranoside (2) were isolated. The structures of the compounds were elucidated using spectroscopic methods. This is the second report on the presence of a glucosylated indole ascorbigen in plants.     

Acylated flavonol tetraglycosides from Delphinium gracile

An ethanol extract of the aerial parts of Delphinium gracile DC. yielded five flavonol glycosides quercetin-3-O-{[β-d-xylopyranosyl (1 → 3)-4-O-(E-p-caffeoyl)-α-l-rhamnopyranosyl (1 → 6)][β-d-glucopyranosyl (1 → 2)]}-β-d-glucopyranoside (1), quercetin-3-O-{[β-d-xylopyranosyl (1 → 3)-4-O-(E-p-coumaroyl)-α-l-rhamnopyranosyl (1 → 6)][β-d-glucopyranosyl (1 → 2)]}-β-d-glucopyranoside (2), quercetin-3-O-{[β-d-xylopyranosyl (1 → 3)-4-O-(Z-p-coumaroyl)-α-l-rhamnopyranosyl (1 → 6)][β-d-glucopyranosyl (1 → 2)]}-β-d-glucopyranoside (3), kaempferol-3-O-{[β-d-glucopyranosyl (1 → 3)-4-O-(E-p-coumaroyl)-α-l-rhamnopyranosyl (1 → 6)][β-d-glucopyranoside-7-O-(4-O-acetyl)-α-l-rhamnopyranoside (4) kaempferol-3-O-{[β-d-glucopyranosyl (1 → 3)-4-O-(E-p-coumaroyl)-α-l-rhamnopyranosyl (1 → 6)][β-d-glucopyranoside-7-O-(4-O-acetyl)-α-l-rhamnopyranoside (5) in addition to 4-(β-d-glucopyranosyloxy)-6-methyl-2H-pyran-2-one (6) and rutin. Structures were elucidated by spectroscopic methods.     

Anthocyanins from red flowers of Camellia cultivar 'Dalicha'

Five anthocyanins, cyanidin 3-O-(2-O-β-xylopyranosyl-6-O-(Z)-p-coumaroyl)-β-galactopyranoside (2), cyanidin 3-O-(2-O-β-xylopyranosyl-6-O-(E)-p-coumaroyl)-β-galactopyranoside (3), cyanidin 3-O-(2-O-β-xylopyranosyl-6-O-(E)-caffeoyl)-β-galactopyranoside (4), cyanidin 3-O-(2-O-β-xylopyranosyl-6-O-acetyl)-β-galactopyranoside (5), and cyanidin 3-O-(2-O-β-xylopyranosyl-6-O-acetyl)-β-glucopyranoside (6), together with the known cyanidin 3-O-(2-O-β-xylopyranosyl)-β-galactopyranoside (1), were isolated from red flowers of Camellia cultivar ‘Dalicha’ (Camellia reticulata) by chromatography using open columns. Their structures were subsequently determined on the basis of spectroscopic analyses, i.e., ¹H NMR, ¹³C NMR, HMQC, HMBC, HR ESI-MS and UV-vis.     

Regioselective synthesis of a glycomimetic trisaccharide of Sialyl Lewis (sLe)

Sialyl Lewis (sLe^x) is the smallest naturally occurring carbohydrate ligand that binds to E-Selectin on the activated endothelium. We report here the total synthesis of acetic acid-sLe^x analog (12), for testing as a therapeutic agent. Methoxyethyl 4-O-(3,4-O-isopropylidene-β-d-galactopyranosyl)-β-d-glucopyranoside (3) was prepared starting from the methoxyethyl-β-d-lactoside (2), which was selectively benzoylated to give the methoxyethyl 2,6-di-O-benzoyl-4-O-(2,6-di-O-benzoyl-3,4-O-isopropylidene-β-d-galactopyranosyl)-β-d-glucopyranoside (4). Glycosylation of acceptor 4 with methyl 2,3,4-tri-O-benzyl-1-thio-β-l-fucopyranoside (5) in the presence of cupric bromide and tetrabutylammonium bromide afforded the corresponding methoxyethyl 2,6-di-O-benzyl-3-O-(2,3,4-tri-O-benzyl-α-l-fucopyranosyl)-4-O-(2,6-di-O-benzyl-3,4-O-isopropylidene-β-d-galactopyranosyl)-β-d-glucopyranoside (6). Selective removal of the 4″,6″-O-isopropylidene group from 6 gave the deprotected trisaccharide 7. The regioselective esterification of O-3″ of trisaccharide 8 (obtained from the dibutylstannylene derivative of 7) with benzyl-2-bromoacetate and tetrabutylammonium bromide afforded the 3″-O-carbobenzyloxymethyl trisaccharide derivative 9, which on saponification and hydrogenolysis with palladium-charcoal afforded the target trisaccharide 12 glycomimetic of Sialyl Lewis (sLe^x) trisaccharide omitting the sialic acid moiety.     

Caffeoyl arbutin and related compounds from the buds of Vaccinium dunalianum

Dunalianosides A-I (1-9), esters of arbutin and related phenolic glucosides, were isolated from the buds of Vaccinium dunalianum Wight (Ericaceae) together with 20 known compounds, and their structures were established on the basis of 1- and 2D NMR spectroscopic evidence. Dunalianosides F-H were dimers of p-hydroxyphenyl 6-O-trans-caffeoyl-β-d-glucopyranoside (10). The latter was obtained in extraordinary high yield (22% of dry weight), and dunalianoside I (9) was found to be a conjugate of arbutin with an iridoid glucoside.     

Phenolic compounds and rare polyhydroxylated triterpenoid saponins from Eryngium yuccifolium

Phytochemical investigation on the whole plant of Eryngium yuccifolium resulted in the isolation and identification of three phenolic compounds (1-3) and 12 polyhydroxylated triterpenoid saponins, named eryngiosides A-L (4-15), together with four known compounds kaempferol-3-O-(2,6-di-O-trans-p-coumaroyl)-β-d-glucopyranoside (16), caffeic acid (17), 21β-angeloyloxy-3β-[β-d-glucopyranosyl-(1→2)]-[β-d-xylopyranosyl-(1→3)]-β-d-glucuronopyranosyloxyolean-12-ene-15α,16α,22α,28-tetrol (18), and saniculasaponin III (19). This study reports the isolation of these compounds and their structural elucidation by extensive spectroscopic analyses and chemical degradation.     

Dibenzofuran and pyranone metabolites from Hypericum revolutum ssp. revolutum and Hypericum choisianum

In a project to isolate and characterise anti-staphylococcal compounds from members of the genus Hypericum, a dibenzofuran and a pyranone were isolated from the dichloromethane and hexane extracts of Hypericum revolutum ssp. revolutum Vahl (Guttiferae) and Hypericum choisianum Wall. ex. N. Robson (Guttiferae), respectively. The structures of these compounds were elucidated by 1- and 2D-NMR spectroscopy and mass spectrometry as 3-hydroxy-1,4,7-trimethoxydibenzofuran (1) and 4-(3-O-3″)-3″-methylbutenyl-6-phenyl-pyran-2-one (2). The metabolites were evaluated against a panel of multidrug-resistant strains of Staphylococcus aureus. Compound 1 exhibited a minimum inhibitory concentration (MIC) of 256 μg/ml, whereas compound 2 was inactive at a concentration of 512 μg/ml.     

Unusual withanolides from aeroponically grown Withania somnifera

In an attempt to maximize production and the structural diversity of plant metabolites, the effect of growing the medicinal plant Withania somnifera under soil-less aeroponic conditions on its ability to produce withaferin A and withanolides was investigated. It resulted in the isolation and characterization of two compounds, 3α-(uracil-1-yl)-2,3-dihydrowithaferin A (1) and 3β-(adenin-9-yl)-2,3-dihydrowithaferin A (2), in addition to 10 known withanolides including 2,3-dihydrowithaferin A-3β-O-sulfate. 3β-O-Butyl-2,3-dihydrowithaferin A (3), presumably an artifact formed from withaferin A during the isolation process was also encountered. Reaction of withaferin A with uracil afforded 1 and its epimer, 3β-(uracil-1-yl)-2,3-dihydrowithaferin A (4). The structures of these compounds were elucidated on the basis of their high resolution mass and NMR spectroscopic data.