title: Two new stereoisomers of Tetrahydrofuranoid lignans from the flower buds of Magnolia fargesii.
abstract: Two new stereoisomers of tetrahydrofuranoid lignans, 7S,8R,7'S,8'R- (1) and 7R,8S,7'S,8'R-3,4,3',4'-tetramethoxy-9,7'-dihydroxy-8.8',7.O.9'-lignan (2) along with nine known lignans including tetrahydrofuranoids (3, 4) and tetrahydrofurofuranoids (5-11) were isolated from a CHCl(3)-soluble fraction of the flower buds of Magnolia fargesii. Two tetrahydrofuranoids, magnostellin A (3) and lariciresinol dimethyl ether (4) were isolated from this species for the first time. The structures of these compounds (1-11) were identified by spectroscopic methods as well as by comparison with published values. Absolute configurations of new stereoisomers (1, 2) were determined by the Mosher's esterification method and Circular Dichroism (CD) studies. All the isolates (1-11) were evaluated for their antioxidant activities using modified superoxide radical-scavenging assay. Compounds 5-8 showed the potent superoxide radical-scavenging activities with the ED(50) values of 19.2, 19.2, 16.5, and 27.7 microM, respectively, as compared with standard antioxidants (BHA: 22.8 microM; Trolox: 940 microM).
authors.affiliation: Natural Product Chemistry Laboratory, College of Pharmacy, The Center for Cell Signaling and Drug Discovery Research, Ewha Womans University, Seoul 120-750, Korea.
authors.forename: Jun
authors.initials: J
authors.lastname: Lee
authors.forename: Dongho
authors.initials: D
authors.lastname: Lee
authors.forename: Dae Sik
authors.initials: DS
authors.lastname: Jang
authors.forename: Joo-Won
authors.initials: JW
authors.lastname: Nam
authors.forename: Jong-Pyung
authors.initials: JP
authors.lastname: Kim
authors.forename: Ki Hun
authors.initials: KH
authors.lastname: Park
authors.forename: Min Suk
authors.initials: MS
authors.lastname: Yang
authors.forename: Eun-Kyoung
authors.initials: EK
authors.lastname: Seo
mesh_terms: D002942:Circular Dichroism; D035264:Flowers / Q000737:chemistry*; D017705:Lignans / Q000737:chemistry* / Q000302:isolation & purification; D009682:Magnetic Resonance Spectroscopy; D031566:Magnolia / Q000737:chemistry*; D015394:Molecular Structure; D021241:Spectrometry, Mass, Electrospray Ionization; D013055:Spectrophotometry, Infrared; D013237:Stereoisomerism
chemical_list: D017705:Lignans