Highly glycosylated flavonoids from the pods of Bobgunnia madagascariensis |
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Authors: | Philip C Stevenson Stephen P Nyirenda |
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Institution: | a Jodrell Laboratory, Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AB, UK b Natural Resources Institute, University of Greenwich, Chatham Maritime, Kent ME4 4TB, UK c Department of Agricultural Research Services, PO Box 59, Mzuzu, Malawi |
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Abstract: | Methanolic extracts of the pods of Bobgunnia madagascariensis (Leguminosae) yielded four pentaglycosylated flavonoids, including the 3-O-α-l-rhamnopyranosyl(1→3)-α-l-rhamnopyranosyl(1→2)α-l-rhamnopyranosyl(1→6)]-β-d-glucopyranoside-7-O-α-l-rhamnopyranosides of 3,5,7-trihydroxy-2-(4-hydroxyphenyl)-4H-benzopyran-4-one (kaempferol) and 3,5,7-trihydroxy-2-(3,4-dihydroxyphenyl)-4H-benzopyran-4-one (quercetin), which were characterized by a novel O-linked branched tetrasaccharide. Spectroscopic and chemical methods were used to determine the structures of the latter, which co-occurred with the corresponding β-d-galactopyranosyl isomers, and two saponins. Conformational isomerism of quercetin 3-O-α-l-rhamnopyranosyl(1→3)-α-l-rhamnopyranosyl(1→2)α-l-rhamnopyranosyl(1→6)]-β-d-glucopyranoside-7-O-α-l-rhamnopyranoside was detected in solution by NMR, a phenomenon previously associated only with C-glycosylflavonoids. |
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Keywords: | Bobgunnia Swartzia Tribe Swartzieae Leguminosae flavonol pentaglycosides saponins |
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