Nor-hopanes from Zanha africana root bark with toxicity to bruchid beetles.

Zanha africana (Radlk.) Exell (Sapindaceae) root bark is used by farmers throughout sub-Saharan Africa to protect stored grain from bruchid beetles, such as Callosobruchus maculatus. Chloroform, methanol and water extracts of Z. africana root bark inhibited oviposition and caused significantly higher mortality of C. maculatus at a rate of application equivalent to that applied by farmers compared to control insects. The chloroform extract contained nor-hopanes rarely found in plants of which seven were isolated, one of which was previously known. Two of the most abundant nor-hopanes 3ß,6ß-dihydroxy-7ß-[(4-hydroxybenzoyl)oxy]-21αH-24-norhopa-4(23),22(29)-diene and 3ß,6ß-dihydroxy-7ß-[(4-hydroxybenzoyl)oxy]-24-norhopa-4(23),17(21)-diene were toxic to and reduced oviposition of C. maculatus in a dose dependent manner. Z. africana root bark is rich in insecticidal compounds that account for its effective use by smallholder farmers as an alternative to conventional insecticides.

Phenylethanoid glycosides in tepals of Magnolia salicifolia and their occurrence in flowers of Magnoliaceae.

Phenylethanoid glycosides were among the major UV-absorbing components in 80% aq. CH3OH extracts of the tepals of Magnolia salicifolia (Siebold & Zucc.) Maxim. (Magnoliaceae; Magnolia subgenus Yulania). Structural characterisation of isolated compounds by spectroscopic and chemical methods revealed three previously unrecorded examples, yulanoside A, yulanoside B and 2'-rhamnoechinacoside, and the known compounds echinacoside and crassifolioside; chromatographic methods also identified verbascoside in the tepal extract. Yulanoside A is the first reported example of a phenylethanoid pentaglycoside, namely hydroxytyrosol 1-O-{ß-D-glucopyranosyl-(1→4)-ß-D-glucopyranosyl-(1→6)-[3,4-dihydroxycinnamoyl-(→4)][α-L-rhamnopyranosyl-(1→3)][α-L-rhamnopyranosyl-(1→2)]-ß-D-glucopyranoside}. A survey of Magnolia sensu lato and Liriodendron (the two genera of Magnoliaceae) suggested that yulanoside A and its deglucosyl derivative (yulanoside B) were a feature of the tepal chemistry of Magnolia subgenus Yulania (except Magnolia acuminata, the sole member of section Tulipastrum, which did not accumulate phenylethanoid glycosides). The two species of Liriodendron and examined examples of Magnolia subgenus Magnolia sections Magnolia and Rytidospermum (subsection Oyama) also accumulated phenylethanoid glycosides in their tepals and in these species, and in subgenus Yulania, the major compounds were one or more of echinacoside, 2'-rhamnoechinacoside, crassifolioside and verbascoside. Levels of phenylethanoid glycosides were found to be much lower in species studied from Magnolia sections Gwillimia, Macrophylla and Rytidospermum (subsection Rytidospermum), although yulanoside A was detectable in M. macrophylla and this may have some bearing on the placement of section Macrophylla, which is currently uncertain. In the isolates of yulanoside B and echinacoside, minor phenylethanoid glycosides were determined to be analogues of these compounds with ß-D-xylose at C-3' of the primary glucose rather than α-L-rhamnose.

Monomethyl ethers of 4,5-dihydroxypipecolic acid from Petaladenium urceoliferum: Enigmatic chemistry of an enigmatic legume.

Leaves of Petaladenium (Leguminosae), an Amazonian monospecific genus recently revealed as a member of the Amburaneae clade among the earliest-diverging papilionoid legumes, were found to accumulate three monomethyl ethers of 4,5-dihydroxypipecolic acids. These were characterised by spectroscopic means as the (2S,4S,5R) and (2S,4R,5S) epimers of 5-hydroxy-4-methoxypipecolic acid and (2S,4R,5R)-4-hydroxy-5-methoxypipecolic acid. These compounds were not detected in any other genera in the Amburaneae clade or the wider Angylocalyceae-Dipterygeae-Amburaneae (ADA) clade of papilionoid legumes. Hydroxypipecolic acids, however, were detected in leaves of Myrocarpus and Myroxylon (sister genera in the Amburaneae clade), Angylocalyx and Xanthocercis (sister genera in the Angylocalyceae clade) and Monopteryx (Dipterygeae clade), and were also present in Petaladenium. Iminosugars, known to be accumulated by all four genera in the Angylocalyceae clade (Alexa, Angylocalyx, Castanospermum and Xanthocercis), were found to be characteristic of this group within the ADA clade.

The haploinsufficiency profile of α-hederin suggests a caspofungin-like antifungal mode of action.

The leaves of common ivy (Hedera helix) contain the cytotoxic saponin α-hederin, which is inhibitory to Candida albicans at low concentrations. To investigate the mode of action of α-hederin, a haploinsufficiency screen was carried out using a library of 1152 Saccharomyces cerevisiae deletion strains. An ethanol ivy extract containing α-hederin was used in the initial screen to reduce the amount of compound required. Strains exhibiting disproportionately low growth were then examined in more detail by comparing growth curves in the presence and absence of α-hederin. This approach identified three hypersensitive strains carrying gene deletions for components of the transcription related proteins SWI/SNF, RNA polymerase II and the RSC complex. Saponin cytotoxicity is often attributed to membrane damage, however α-hederin did not induce hypersensitivity with an aminophospholipid translocase deletion strain that is frequently hypersensitive to membrane damaging agents. The haploinsufficiency profile of α-hederin is most similar to that reported for drugs such as caspofungin that inhibit synthesis of the fungal cell wall. Screening with plant extracts rather than isolated compounds, provides a valuable shortcut in haploinsufficiency screening provided hypersensitive strains are then confirmed as such using purified active principles.

A yeast chemical genetics approach identifies the compound 3,4,5-trimethoxybenzyl isothiocyanate as a calcineurin inhibitor.

The phosphatase enzyme calcineurin controls gene expression in a variety of biological contexts however few potent inhibitors are currently available. A screen of 360 plant extracts for inhibition of calcineurin-dependent gene expression in the model organism Saccharomyces cerevisiae identified the compound 3,4,5-trimethoxybenzyl isothiocyanate as an inhibitor. The compound was subsequently shown to inhibit human calcineurin via a mixed inhibition mechanism. To gain further mechanistic insight a yeast haploinsufficiency screen of 1152 deletion strains was carried out using a novel liquid medium screening method. The resulting haploinsufficiency profile is similar to that reported for the known calcineurin inhibitor FK506.

Isoflavonoids of the leguminosae.

This account describes 275 new isoflavonoids published between 2008 and 2011 as constituents of the Leguminosae, commenting on their source, identification, biological activity, synthesis, and ecological or chemosystematic significance. Applications of hyphenated analytical techniques to the characterisation of Leguminosae isoflavonoids are also reviewed, together with advances in biosynthetic studies. A checklist of new compounds by species is given, and 226 references are cited.

Enhanced profiling of flavonol glycosides in the fruits of sea buckthorn (Hippophae rhamnoides).

Use of enhanced LC-MS/MS methods to identify common glycosyl groups of flavonoid glycosides enabled better characterization of the flavonoids in fruits of sea buckthorn (Hippophae rhamnoides). The saccharide moieties of 48 flavonol O-glycosides detected in a methanol extract were identified by these methods. Several of the flavonol glycosides were acylated, two of which were isolated and found to be new compounds. Their structures were determined using spectroscopic and chemical methods as isorhamnetin 3-O-(6-O-E-sinapoyl-ß-D-glucopyranosyl)-(1→2)-ß-D-glucopyranoside-7-O-α-L-rhamnopyranoside (24) and isorhamnetin 3-O-(6-O-E-feruloyl-ß-D-glucopyranosyl)-(1→2)-ß-D-glucopyranoside-7-O-α-L-rhamnopyranoside (30). Analysis of the acylated glycosyl groups of 24 and 30 by serial mass spectrometry provided evidence to suggest the acylation position of 11 other minor flavonol glycosides acylated with hydroxycinnamic or hydroxybenzoic acids. The nitric oxide scavenging activities of 24 and 30 were compared with those of other flavonoids and with ascorbic acid and the potassium salt of 2-(4-carboxyphenyl)-4,5-dihydro-4,4,5,5-tetramethyl-1H-imidazolyl-1-oxy-3-oxide (carboxy-PTIO).

Acyl spermidines in inflorescence extracts of elder (Sambucus nigra L., Adoxaceae) and elderflower drinks.

LC-UV-MS analyses of inflorescence extracts of Sambucus nigra L. (elder, Adoxaceae) revealed the presence of numerous acyl spermidines, with isomers of N,N-diferuloylspermidine and N-acetyl-N,N-diferuloylspermidine being most abundant. Pollen was the main source of the acyl spermidines in the inflorescence. Three of the major acyl spermidines were isolated and their structures determined by NMR spectroscopy as N5,N¹°-di-(E,E)-feruloylspermidine and the new compounds N¹-acetyl-N5,N¹°-di-(Z,E)-feruloylspermidine and N¹-acetyl-N5,N¹°-di-(E,E)-feruloylspermidine. An isomer of N,N,N-triferuloylspermidine was also obtained and identified as N¹,N5,N¹°-tri-(E,E,E)-feruloylspermidine. In addition to stereoisomers of the isolated acyl spermidines, other acyl spermidines detected by the positive ion LC-UV-MS were isomers of N-caffeoyl-N,N-diferuloylspermidine, N-coumaroyl-N,N-diferuloylspermidine, N-caffeoyl-N-feruloylspermidine, N-coumaroyl-N-feruloylspermidine, N-acetyl-N-caffeoyl-N-feruloylspermidine, and N-acetyl-N-coumaroyl-N-feruloylspermidine. Analysis of commercial elderflower drinks showed that acyl spermidines were persistent in these processed elderflower products. Examination of inflorescence extracts from Sambucus canadensis L. (American elder) revealed the presence of acyl spermidines that were different from those of S. nigra.

Generic detection of basic taxoids in wood of European Yew (Taxus baccata) by liquid chromatography-ion trap mass spectrometry.

The occurrence of the cardiotoxin taxine (comprising taxine B and several other basic taxoids) in leaves of Taxus baccata L. (European yew) is well known and has led to public concerns about the safety of eating or drinking from utensils crafted from the wood of this poisonous species. The occurrence of basic taxoids in the heartwood of T. baccata had not been examined in detail, although the bark is known to contain 2'ß-deacetoxyaustrospicatine. Initial examination of heartwood extracts for 2'ß-deacetoxyaustrospicatine by liquid chromatography-mass spectrometry (LC-MS) revealed the presence of this basic taxoid at about 0.0007% dry weight, using a standard isolated from bark. Analyses for taxine B, however, proved negative at the extract concentration analysed. Observing other basic taxoids within the heartwood extracts was facilitated by developing generic LC-MS methods that utilised a fragment arising from the N-containing acyl group of basic taxoids as a reporter ion. Of the various MS strategies available on a hybrid ion trap-orbitrap instrument that allowed observation of this reporter ion, combining all-ion collisions with high resolution ion filtering by the orbitrap was most effective, both in terms of the number of basic taxoids detected and sensitivity. Numerous basic taxoids, in addition to 2'ß-deacetoxyaustrospicatine, were revealed by this method in heartwood extracts of T. baccata. Red wine readily extracted the basic taxoids from heartwood while coffee extracted them less efficiently. Contamination with basic taxoids could also be detected in soft cheese that had been spread onto wood. The generic LC-MS method for detecting basic taxoids complements specific methods for detecting taxine B when investigating yew poisoning cases in which the analysis of complex extracts may be required or taxine B has not been detected.

Highly glycosylated flavonols with an O-linked branched pentasaccharide from Iberis saxatilis (Brassicaceae).

Four flavonol glycosides isolated from non-flowering leafy shoots of Iberis saxatilis (Brassicaceae) were characterised by spectroscopic and chemical methods as saxatilisins A-D, the 3-O-ß-D-glucopyranosyl-(1→3)-α-L-rhamnopyranosyl-(1→2)[ß-D-glucopyranosyl-(1→2)-α-L-rhamnopyranosyl-(1→6)]-ß-D-glucopyranoside, 3-O-ß-D-glucopyranosyl-(1→3)-α-L-rhamnopyranosyl-(1→2)[α-L-rhamnopyranosyl-(1→6)]-ß-D-glucopyranoside, 3-O-(6-O-E-sinapoyl)-ß-D-glucopyranosyl-(1→3)-α-L-rhamnopyranosyl-(1→2)[ß-D-glucopyranosyl-(1→2)-α-L-rhamnopyranosyl-(1→6)]-ß-D-glucopyranoside, and 3-O-(6-O-E-feruloyl)-ß-D-glucopyranosyl-(1→3)-α-L-rhamnopyranosyl-(1→2)[ß-D-glucopyranosyl-(1→2)-α-L-rhamnopyranosyl-(1→6)]-ß-D-glucopyranoside of isorhamnetin (3,5,7,4'-tetrahydroxy-3'-methoxyflavone), respectively. Analysis of (2)J(HC) correlations detected with the H2BC (heteronuclear two-bond correlation) pulse sequence aided the unambiguous assignment of glycosidic resonances in the (1)H and (13)C NMR spectra of these compounds. Saxatilisins A, C, and D, are the first flavonol glycosides to be described with a pentasaccharide chain at a single glycosylation site. Several pentaglycosides of kaempferol and quercetin, tentatively assigned as saxatilisin analogues from LC-MS/MS analyses, were present as minor constituents of the extracts.

Amides and an alkaloid from Portulaca oleracea.

A total of 16 phenolic compounds, including one new and five known N-cinnamoyl phenylethylamides, one new pyrrole alkaloid named portulacaldehyde, five phenylpropanoid acids and amides, and derivatives of benzaldehyde and benzoic acid, were isolated and identified from a polar fraction of an extract of Portulaca oleracea. Their structures were determined through spectroscopic analyses.

Flavonol glycosides acylated with 3-hydroxy-3-methylglutaric acid as systematic characters in Rosa.

LC-UV-MS/MS analysis of leaf extracts from 146 accessions of 71 species of Rosa revealed that some taxa accumulated flavonol O-glycosides acylated with 3-hydroxy-3-methylglutaric acid, which are relatively uncommon in plants. The structures of two previously unrecorded examples isolated from Rosa spinosissima L. (syn. Rosa pimpinellifolia L.) were elucidated using spectroscopic and chemical methods as the 3-O-α-L-rhamnopyranosyl-(1→2)-[6-O-(3-hydroxy-3-methylglutaryl)-ß-D-galactopyranosides] of kaempferol (3,5,7,4'-tetrahydroxyflavone) and quercetin (3,5,7,3',4'-pentahydroxyflavone). The corresponding 3-O-[6-O-(3-hydroxy-3-methylglutaryl)-ß-D-galactopyranoside] of quercetin was also present in R. spinosissima, but at lower levels, together with 17 other flavonol O-glycosides for which structures were assigned using LC-UV-MS/MS. The distribution of flavonol 3-hydroxy-3-methylglutarylgalactosides in Rosa was limited to some species of subgenus Rosa section Pimpinellifoliae and Rosa roxburghii Sw. of the monotypic subgenus Platyrhodon, indicating that this character could be of value in phylogenetic analyses of the genus.

Distinct chemotypes of Tephrosia vogelii and implications for their use in pest control and soil enrichment.

Tephrosia vogelii Hook. f. (Leguminosae) is being promoted as a pest control and soil enrichment agent for poorly-resourced small-scale farmers in southern and eastern Africa. This study examined plants being cultivated by farmers and found two chemotypes. Chemotype 1 (C1) contained rotenoids, including deguelin, rotenone, sarcolobine, tephrosin and α-toxicarol, required for pest control efficacy. Rotenoids were absent from chemotype 2 (C2), which was characterised by prenylated flavanones, including the previously unrecorded examples (2S)-5,7-dimethoxy-8-(3-hydroxy-3-methylbut-1Z-enyl)flavanone, (2S)-5,7-dimethoxy-8-(3-methylbut-1,3-dienyl)flavanone, (2S)-4'-hydroxy-5-methoxy-6″,6″-dimethylpyrano[2″,3″:7,8]flavanone, (2S)-5-methoxy-6″,6″-dimethyl-4″,5″-dihydrocyclopropa[4″,5″]furano[2″,3″:7,8]flavanone, (2S)-7-hydroxy-5-methoxy-8-prenylflavanone, and (2R,3R)-3-hydroxy-5-methoxy-6″,6″-dimethylpyrano[2″,3″:7,8]flavanone. The known compounds (2S)-5-methoxy-6″,6″-dimethylpyrano[2″,3″:7,8]flavanone (obovatin 5-methyl ether) and 5,7-dimethoxy-8-(3-hydroxy-3-methylbut-1Z-enyl)flavone (Z-tephrostachin) were also found in C2. This chemotype, although designated Tephrosia candida DC. in collections originating from the World Agroforestry Centre (ICRAF), was confirmed to be T. vogelii on the basis of morphological comparison with verified herbarium specimens and DNA sequence analysis. Sampling from 13 locations in Malawi where farmers cultivate Tephrosia species for insecticidal use indicated that almost 1 in 4 plants were T. vogelii C2, and so were unsuitable for this application. Leaf material sourced from a herbarium specimen of T. candida contained most of the flavanones found in T. vogelii C2, but no rotenoids. However, the profile of flavonol glycosides was different to that of T. vogelii C1 and C2, with 6-hydroxy-kaempferol 6-methyl ether as the predominant aglycone rather than kaempferol and quercetin. The structures of four unrecorded flavonol glycosides present in T. candida were determined using cryoprobe NMR spectroscopy and MS as the 3-O-α-rhamnopyranosyl(1→6)-ß-galactopyranoside-7-O-α-rhamnopyranoside, 3-O-α-rhamnopyranosyl(1→2)[α-rhamnopyranosyl(1→6)]-ß-galactopyranoside, 3-O-α-rhamnopyranosyl(1→2)[α-rhamnopyranosyl(1→6)]-ß-galactopyranoside-7-O-α-rhamnopyranoside, and 3-O-α-rhamnopyranosyl(1→2)[(3-O-E-feruloyl)-α-rhamnopyranosyl(1→6)]-ß-galactopyranosides of 6-hydroxykaempferol 6-methyl ether. Tentative structures for a further 37 flavonol glycosides of T. candida were assigned by LC-MS/MS. The correct chemotype of T. vogelii (i.e. C1) needs to be promoted for use by farmers in pest control applications.

Direct inhibition of calcineurin by caffeoyl phenylethanoid glycosides from Teucrium chamaedrys and Nepeta cataria.

ETHNOPHARMACOLOGICAL RELEVANCE: Teucrium chamaedrys L. and Nepeta cataria L. (Lamiaceae) are species with traditional uses that relate to the treatment of inflammation. Extracts of both species were found to inhibit calcineurin; an important regulator of T-cell mediated inflammation that has received little attention in ethnopharmacological research. MATERIALS AND METHODS: Extracts and isolated compounds were tested against calcineurin in its calmodulin-activated and basal un-activated state. Active compounds were isolated using Sephadex LH-20 gel filtration and HPLC then identified using NMR spectroscopy. RESULTS AND CONCLUSIONS: Activity-guided fractionation of Teucrium chamaedrys and Nepeta cataria led to the isolation of the caffeoyl phenylethanoid glycosides teucrioside, verbascoside and lamiuside A (teupolioside). The three compounds inhibited calcineurin both in the presence and absence of calmodulin, suggesting a direct interaction with calcineurin. Calcineurin inhibition should be considered as a potential mode of action when investigating the immunomodulatory activity of caffeoyl phenylethanoid glycoside containing plants.

Leaf chemistry and foliage avoidance by the thrips Frankliniella occidentalis and Heliothrips haemorrhoidalis in glasshouse collections.

Observational studies on foliage avoidance by the polyphagous thrips species Frankliniella occidentalis (Pergande) and Heliothrips haemorrhoidalis (Bouché) (Thysanoptera: Thripidae) identified six non-host species (Allagopappus dichotomus (Asteraceae), Gardenia posoquerioides (Rubiaceae), Plectranthus aff. barbatus, Plectranthus strigosus, Plectranthus zuluensis (Lamiaceae), and Sclerochiton harveyanus (Acanthaceae) among plants growing within a major glasshouse botanical collection. The effects of sequentially obtained acetone and aqueous methanol leaf extracts on mortality in first instar Frankliniella occidentalis were assessed. The acetone leaf extract of Sclerochiton harveyanus, which had the highest activity against the thrips, yielded four new iridoids, sclerochitonosides A-C, and sclerochitonoside B 4'-methyl ether. Mortality of F. occidentalis was increased on exposure to all four iridoids, and the most active iridoid was sclerochitonoside A (8-epiloganic acid 4'-hydroxyphenylethyl ester). Choice experiments demonstrated that this compound did not significantly deter H. haemorrhoidalis from treated leaf surfaces. The significance of iridoids in the defense mechanism of plants against thrips is discussed.

Acylated flavonol glycosides from the forage legume, Onobrychis viciifolia (sainfoin).

Ten acylated flavonol glycosides were isolated from aqueous acetone extracts of the aerial parts of the forage legume, Onobrychis viciifolia, and their structures determined using spectroscopic methods. Among these were eight previously unreported examples which comprised either feruloylated or sinapoylated derivatives of 3-O-di- and 3-O-triglycosides of kaempferol (3,5,7,4'-tetrahydroxyflavone) or quercetin (3,5,7,3',4'-pentahydroxyflavone). The diglycosides were acylated at the primary Glc residue of O-α-Rhap(1→6)-ß-Glcp (rutinose), whereas the triglycosides were acylated at the terminal Rha residues of the branched trisaccharides, O-α-Rhap(1→2)[α-Rhap(1→6)]-ß-Galp or O-α-Rhap(1→2)[α-Rhap(1→6)]-ß-Glcp. Identification of the primary 3-O-linked hexose residues as either Gal or Glc was carried out by negative ion electrospray and serial MS, and cryoprobe NMR spectroscopy. Analysis of UV and MS spectra of the acylated flavonol glycosides provided additional diagnostic features relevant to direct characterisation of these compounds in hyphenated analyses. Quantitative analysis of the acylated flavonol glycosides present in different aerial parts of sainfoin revealed that the highest concentrations were in mature leaflets.

Acylated flavonol tri- and tetraglycosides in the flavonoid metabolome of Cladrastis kentukea (Leguminosae).

The foliar metabolome of Cladrastis kentukea (Leguminosae) contains a complex mixture of flavonoids including acylated derivatives of the 3-O-rhamnosyl(1→2)[rhamnosyl(1→6)]-galactosides of kaempferol and quercetin and their 7-O-rhamnosides, together with an array of non-acylated kaempferol and quercetin di-, tri- and tetraglycosides. Thirteen of the acylated flavonoids, 12 of which had not been reported previously, were characterised by spectroscopic and chemical methods. Eight of these were the four isomers of kaempferol 3-O-α-l-rhamnopyranosyl(1→2)[α-l-rhamnopyranosyl(1→6)]-(3/4-O-E/Z-p-coumaroyl-ß-d-galactopyranoside) and their 7-O-α-l-rhamnopyranosides, and three were isomers of quercetin 3-O-α-l-rhamnopyranosyl(1→2)[α-l-rhamnopyranosyl(1→6)]-(3/4-O-E/Z-p-coumaroyl-ß-d-galactopyranoside) - the remaining 4Z isomer was identified by LC-UV-MS analysis of a crude extract. The final two acylated flavonoids characterised by NMR were the 3E and 4E isomers of kaempferol 3-O-α-l-rhamnopyranosyl(1→2)[α-l-rhamnopyranosyl(1→6)]-(3/4-O-E-feruloyl-ß-d-galactopyranoside)-7-O-α-l-rhamnopyranoside while the 3Z and 4Z isomers were again detected by LC-UV-MS. Using the observed fragmentation behaviour of the isolated compounds following a variety of MS experiments, a further 18 acylated flavonoids were given tentative structures by LC-MS analysis of a crude extract. Acylated flavonoids were absent from the flowers of C. kentukea, which contained an array of non-acylated kaempferol and quercetin glycosides. Immature fruits contained kaempferol 3-O-α-rhamnopyranosyl(1→2)[α-rhamnopyranosyl(1→6)]-ß-galactopyranoside and its 7-O-α-rhamnopyranoside as the major flavonoids with acylated flavonoids, different from those in the leaves, only present as minor constituents. The presence of acylated flavonoids distinguishes the foliar flavonoid metabolome of C. kentukea from that of a closely related legume, Styphnolobium japonicum, which contains a similar range of non-acylated flavonoids.

Glycosylated constituents of iris fulva and Iris brevicaulis.

The major constituents of leaf extracts of Iris fulva KER GAWL. comprised a known flavone C-glycoside, 5,4'-dihydroxy-7-methoxyflavone-6-C-(6‴-O-(E)-p-coumaroyl-ß-glucopyranosyl)(1‴→2″)-ß-glucopyranoside (1) and the new monoterpene glycoside, linalyl-6'-O-(3″-hydroxy-3″-methylglutaroyl)-ß-D-glucopyranoside (2), both of which were prominent components of Iris brevicaulis RAF. leaf extracts. The structure of a new polyacylated sucrose derivative (3a) obtained from the rhizomes of I. fulva was elucidated as 3-O-(E)-p-coumaroyl-ß-D-fructofuranosyl-(2↔1')-[2″,4″,6″-tri-O-acetyl-ß-D-glucopyranosyl-(1″→3')-(2',6'-di-O-acetyl-4'-O-(E)-p-coumaroyl-α-D-glucopyranoside)]. Selective hydrolysis of the 4″-O-acetyl moiety of the terminal ß-glucopyranosyl residue of 3a occurred after several hours in solution giving 3-O-(E)-p-coumaroyl-ß-D-fructofuranosyl-(2↔1')-[2″,6″-di-O-acetyl-ß-D-glucopyranosyl-(1″→3')-(2',6'-di-O-acetyl-4'-O-(E)-p-coumaroyl-α-D-glucopyranoside)] (3b), which subsequently underwent further deacetylation.

Identification of common glycosyl groups of flavonoid O-glycosides by serial mass spectrometry of sodiated species.

Flavonoid O-glycosides are a ubiquitous and important group of plant natural products in which a wide variety of sugars are O-linked to an aglycone. Determining the identity of the sugars, and the manner in which they are linked, by mass spectrometry alone is challenging. To improve the identification of common O-linked di- and trisaccharides when analysing mixtures of flavonoid O-glycosides by liquid chromatography/mass spectrometry (LC/MS), the fragmentation of electrosprayed sodium adducts in an ion trap mass spectrometer was investigated. The sodium adducts [M + Na](+) of kaempferol 3-O-glycosides generated sodiated glycosyl groups by the neutral loss of kaempferol. The product ion spectra of these sodiated glycosyl groups differed between four isomeric kaempferol 3-O-rhamnosylhexosides and four isomeric kaempferol 3-O-glucosylhexosides in which the primary hexose was either glucose or galactose and bore the terminal glucose or rhamnose at either C-2 or C-6. Fragmentation of sodiated glycosyl groups from linear O-triglucosides and branched O-glucosyl-(1 → 2)-[rhamnosyl-(1 → 6)]-hexosides produced sodiated disaccharide residues, and the product ion spectra of these ions assisted the identification of the complete sugar. The product ion spectra of the sodiated glycosyl groups were consistent among flavonoid O-glycosides differing in the position at which the sugar was O-linked to the aglycone, and the nature of the aglycone. The abundance of sodiated species was enhanced by application of a pre-trap collision voltage, without the need to dope with salt, allowing automated LC/MS methods to be used to identify the glycosyl groups of common flavonoid O-glycosides, such as rutinosides, robinobiosides, neohesperidosides, gentiobiosides and sophorosides.