Highly glycosylated flavonoids from the pods of Bobgunnia madagascariensis

✍ Scribed by Philip C. Stevenson; Stephen P. Nyirenda; Nigel C. Veitch

• Publisher: Elsevier Science
• Year: 2010
• Tongue: French
• Weight: 205 KB
• Volume: 51
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/j.tetlet.2010.07.013

✦ Synopsis

Methanolic extracts of the pods of Bobgunnia madagascariensis (Leguminosae) yielded four pentaglycosylated flavonoids, including the 3-O-a-L-rhamnopyranosyl(1?3)-a-L-rhamnopyranosyl(1?2)[a-L-rhamnopyranosyl(1?6)]-b-D-glucopyranoside-7-O-a-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 b-D-galactopyranosyl isomers, and two saponins. Conformational isomerism of quercetin 3-O-a-L-rhamnopyranosyl(1?3)-a-L-rhamnopyranosyl(1?2)[a-L-rhamnopyranosyl(1?6)]-b-D-glucopyranoside-7-O-a-L-rhamnopyranoside was detected in solution by NMR, a phenomenon previously associated only with C-glycosylflavonoids.