Showing papers by "Nigel C. Veitch published in 2011"

Cardenolides from Gomphocarpus sinaicus and Pergularia tomentosa (Apocynaceae: Asclepiadoideae) deter the feeding of Spodoptera littoralis

Abstract: Methanol extracts of Gomphocarpus sinaicus, Pergularia tomentosa and Cynanchum acutum (Apocynaceae, sub-family Asclepiadoideae) deterred feeding of Spodoptera littoralis in a binary-choice bioassay. Analyses of extracts using high-performance liquid chromatography with photodiode array detection indicated that methanol extracts of P. tomentosa and G. sinaicus contained cardenolides, while these compounds were not detected in extracts of C. acutum. Activity-guided fractionation of the methanol extracts of G. sinaicus and P. tomentosa resulted in the isolation of six cardenolides: 7,8-dehydrocalotropin, calotropin and coroglaucigenin 3-(6-deoxy-β-allopyranoside)-19-acetate (frugoside 19-acetate) from G. sinaicus, and coroglaucigenin, 16α-acetoxycalotropin and calactin from P. tomentosa. The isolation of 16α-acetoxycalotropin was a new report from P. tomentosa. Each of the 6 cardenolides deterred feeding by S. littoralis, while two cardenolide standards, digoxin and digitoxin, did not affect feeding. Differences among cardenolides in their effect on feeding were associated with specific structural features. C. acutum is the only one of the three species tested that is known to support the development of S. littoralis, although the development of larvae was delayed. The observed feeding deterrent activity of the cardenolide-free methanol extract of C. acutum would suggest that compounds other than cardenolides are responsible for the deterrent activity. These compounds, although deterrent in a short-term feeding assay, might not prevent long term feeding, thus allowing the larvae to develop on the plant.

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

Abstract: 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. Copyright © 2011 John Wiley & Sons, Ltd.

Metabolites from roots of Colubrina greggii var. yucatanensis and evaluation of their antiprotozoan, cytotoxic and antiproliferative activities

Abstract: A purificacao do extrato da raiz de Colubrina greggii var. yucatanensis levou ao isolamento e identificacao do acido 3- O-acetil ceanotico, um novo triterpeno natural, juntamente com os metabolitos ja descritos: acido ceanotico, acido cenotenico, acido betulinico, discarina B e crisofaneina. Os produtos naturais e os derivados semi-sinteticos ester de acetil dimetil ceanotato, dimetil ceanotato e peracetato de crisofaneina mostraram moderada a baixa atividade leishmanicida e tripanocida. Nenhum dos metabolitos mostrou ser citotoxicos ou ter atividade antiproliferativa. Os resultados tambem sugerem que o acido betulinico contribui para a atividade antiplasmodica inicialmente detectada na raiz do extrato bruto de C. greggii var. yucatanensis. Purification of the root extract of Colubrina greggii var. yucatanensis resulted in the isolation and identification of 3- O-acetyl ceanothic acid as a new natural ceanothane triterpene, together with the known metabolites ceanothic acid, cenothenic acid, betulinic acid, discarine B and chrysophanein. The natural products and the semisynthetic esters acetyl dimethyl ceanothate, dimethyl ceanothate and chrysophanein peracetate showed moderate to low leishmanicidal and trypanocidal activities. None of the metabolites showed cytotoxic or antiproliferative effects. The results also suggested that betulinic acid contributes to the antiplasmodial activity originally detected in the crude root extract of C. greggii var. yucatanensis.

Glycosylated constituents of iris fulva and Iris brevicaulis.

Abstract: 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-β-glucopyranosyl)(1‴→2″)-β-glucopyranoside (1) and the new monoterpene glycoside, linalyl-6′-O-(3″-hydroxy-3″-methylglutaroyl)-β-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-β-D-fructofuranosyl-(2↔1′)-[2″,4″,6″-tri-O-acetyl-β-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 β-glucopyranosyl residue of 3a occurred after several hours in solution giving 3-O-(E)-p-coumaroyl-β-D-fructofuranosyl-(2↔1′)-[2″,6″-di-O-acetyl-β-D-glucopyranosyl-(1″→3′)-(2′,6′-di-O-acetyl-4′-O-(E)-p-coumaroyl-α-D-glucopyranoside)] (3b), which subsequently underwent further deacetylation.

Leaf Chemistry and Foliage Avoidance by the Thrips Frankliniella occidentalis and Heliothrips haemorrhoidalis in Glasshouse Collections

Abstract: Observational studies on foliage avoidance by the polyphagous thrips species Frankliniella occidentalis (Pergande) and Heliothrips haemorrhoidalis (Bouche) (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.

Glycosylated Constituents of Iris fulva and Iris brevicaulis.

Abstract: 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-β-glucopyranosyl)(1‴→2″)-β-glucopyranoside (1) and the new monoterpene glycoside, linalyl-6′-O-(3″-hydroxy-3″-methylglutaroyl)-β-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-β-D-fructofuranosyl-(2↔1′)-[2″,4″,6″-tri-O-acetyl-β-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 β-glucopyranosyl residue of 3a occurred after several hours in solution giving 3-O-(E)-p-coumaroyl-β-D-fructofuranosyl-(2↔1′)-[2″,6″-di-O-acetyl-β-D-glucopyranosyl-(1″→3′)-(2′,6′-di-O-acetyl-4′-O-(E)-p-coumaroyl-α-D-glucopyranoside)] (3b), which subsequently underwent further deacetylation.