title: Flavonoid glycosides of the black locust tree, Robinia pseudoacacia (Leguminosae).
abstract: Four flavone glycosides isolated from extracts of the leaves of Robinia pseudoacacia (Leguminosae) were characterised by spectroscopic and chemical methods as the 7-O-beta-d-glucuronopyranosyl-(1-->2)[alpha-l-rhamnopyranosyl-(1-->6)]-beta-d-glucopyranosides of acacetin (5,7-dihydroxy-4'-methoxyflavone), apigenin (5,7,4'-trihydroxyflavone), diosmetin (5,7,3'-trihydroxy-4'-methoxyflavone) and luteolin (5,7,3',4'-tetrahydroxyflavone). Assignment of glycosidic (1)H and (13)C resonances in their NMR spectra was facilitated by (2)J(HC) correlations detected using the H2BC (heteronuclear two-bond correlation) pulse sequence. Spectroscopic analysis of two known triglycosides, acacetin 7-O-beta-d-glucopyranosyl-(1-->2)[alpha-l-rhamnopyranosyl-(1-->6)]-beta-d-glucopyranoside (previously unrecorded from this species) and acacetin 7-O-beta-d-xylopyranosyl-(1-->2)[alpha-l-rhamnopyranosyl-(1-->6)]-beta-d-glucopyranoside ('acacetin trioside'), enabled inconsistencies in the literature relating to these structures to be resolved. Comparison of the flavonoid chemistry of leaves and flowers of R. pseudoacacia using LC-UV and LC-MS showed that flavone 7-O-glycosides, particularly of acacetin, predominated in the former, whereas the latter comprised mainly flavonol 3,7-di-O-glycosides, including several examples new to this species. Tissue dependent differences in flavonoid chemistry were also evident from the glycosylation patterns of the compounds.
authors: Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AB, UK. n.veitch@kew.org
authors: Nigel C
authors: NC
authors: Veitch
authors: Peter C
authors: PC
authors: Elliott
authors: Geoffrey C
authors: GC
authors: Kite
authors: Gwilym P
authors: GP
authors: Lewis
mesh_terms: D002240:Carbohydrate Sequence; D002845:Chromatography; D005419:Flavonoids / Q000737:chemistry*; D035264:Flowers / Q000737:chemistry; D006027:Glycosides / Q000737:chemistry* / Q000302:isolation & purification*; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D031301:Robinia / Q000737:chemistry*
chemical_list: D005419:Flavonoids; D006027:Glycosides