title: Flavone C-glycosides from leaves of Oxalis triangularis.
abstract: The flavone C-glycosides luteolin 6-C-(2''-O-beta-xylopyranosyl-beta-glucopyranoside) (1), apigenin 6-C-(2''-O-alpha-rhamnopyranosyl-beta-glucopyranoside) (2), apigenin 6-C-(2''-O-beta-xylopyranosyl-beta-glucopyranoside) (3), apigenin 6-C-(2''-O-(6'''-(E)-caffeoylglucoside)-beta-glucopyranoside) (4), and apigenin 6-C-(2''-O-(6'''-(E)-p-coumaroylglucoside)-beta-glucopyranoside) (5) have been isolated from the purple leaves of Oxalis triangularis. Compound 4 is new, while 5 has previously been isolated from Cucumis sativus after treatment with silicon and infection with Sphaerotheca fuliginea. Signal duplication in the NMR spectra of 2, 4, and 5 revealed the presence of rotameric conformers, created by rotational hindrance at the C(sp3) -C(sp2) glucosyl-flavone linkage in these flavone C-glycosides.
authors.affiliation: Department of Chemistry, University of Bergen, Allégt. 41, N-5007 Bergen, Norway.
authors.forename: Saleh
authors.initials: S
authors.lastname: Rayyan
authors.forename: Torgils
authors.initials: T
authors.lastname: Fossen
authors.forename: Øyvind M
authors.initials: ØM
authors.lastname: Andersen
mesh_terms: D000595:Amino Acid Sequence; D002851:Chromatography, High Pressure Liquid; D006027:Glycosides / Q000737:chemistry* / Q000302:isolation & purification; D008969:Molecular Sequence Data; D018515:Plant Leaves / Q000737:chemistry; D010944:Plants / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet
chemical_list: D006027:Glycosides