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

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• 作者：Thomas A.K. Prescott ; Geoffrey C. Kite ; Elaine A. Porter ; Nigel C. Veitch ; ^{n.veitch@kew.org}
• 关键词：Iberis saxatilis ; Brassicaceae ; Flavonol pentaglycosides ; Isorhamnetin ; Cryoprobe NMR ; H2BC ; MS/MS
• 刊名：Phytochemistry
• 出版年：2013
• 出版时间：April, 2013
• 年：2013
• 卷：88
• 期：Complete
• 页码：85-91
• 全文大小：322 K

文摘

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-¦Â-d-glucopyranosyl-(1 ¡ú 3)-¦Á-l-rhamnopyranosyl-(1 ¡ú 2)[¦Â-d-glucopyranosyl-(1 ¡ú 2)-¦Á-l-rhamnopyranosyl-(1 ¡ú 6)]-¦Â-d-glucopyranoside, 3-O-¦Â-d-glucopyranosyl-(1 ¡ú 3)-¦Á-l-rhamnopyranosyl-(1 ¡ú 2)[¦Á-l-rhamnopyranosyl-(1 ¡ú 6)]-¦Â-d-glucopyranoside, 3-O-(6-O-E-sinapoyl)-¦Â-d-glucopyranosyl-(1 ¡ú 3)-¦Á-l-rhamnopyranosyl-(1 ¡ú 2)[¦Â-d-glucopyranosyl-(1 ¡ú 2)-¦Á-l-rhamnopyranosyl-(1 ¡ú 6)]-¦Â-d-glucopyranoside, and 3-O-(6-O-E-feruloyl)-¦Â-d-glucopyranosyl-(1 ¡ú 3)-¦Á-l-rhamnopyranosyl-(1 ¡ú 2)[¦Â-d-glucopyranosyl-(1 ¡ú 2)-¦Á-l-rhamnopyranosyl-(1 ¡ú 6)]-¦Â-d-glucopyranoside of isorhamnetin (3,5,7,4¡ä-tetrahydroxy-3¡ä-methoxyflavone), respectively. Analysis of ²J_HC correlations detected with the H2BC (heteronuclear two-bond correlation) pulse sequence aided the unambiguous assignment of glycosidic resonances in the ¹H and ¹³C 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.