title: Lipoxygenase inhibitory constituents from rhubarb.
abstract: Phytochemical study on the ethanol extract of rhubarb led to the isolation of fifteen compounds, including five anthraquinones: chrysophanol (1), physcion (2), emodin (7), chrysophanol-8-O-beta-D: -glucopyranoside (9) and emodin-8-O-beta-D: -glucopyranoside (15), and ten stilbenes: desoxyrhaponticin (3), rhaponticin (4), resveratrol (5), desoxyrhapotigenin (6), rhapontigenin (8), piceatannol-3'-O-beta-D: -glucopyranoside (10), piceid (11), epsilon-viniferin (12), ampelopsin B (13) and isorhaponticin (14). Their structures were identified by comparing the physicochemical data with those of published papers. Among the isolated compounds, stilbene derivatives (3-6, 8 and 10-14) showed remarkable inhibitory effect on lipoxygenase with IC(50) values ranging from 6.7 to 74.1 microM. The inhibition kinetics analyzed by Lineweaver-Burk plots found that they were competitive inhibitors with the linoleic acid at the active site of lipoxygenase. In addition, stilbenes exhibited significantly free radical scavenging activity against ABTS(.+) with trolox equivalent activity capacity (TEAC) values ranging from 1.16 to 4.64. Whereas, anthraquinone derivatives (1-2, 7, 9 and 15) neither inhibited lipoxygenase nor scavenged free radical ABTS(.+). These results indicated that stilbene derivatives were considerate to be mainly lipoxygenase inhibitor and free radical scavenger constituents of rhubarb.
authors.affiliation: College of Pharmacy, Chungnam National University, Daejeon, 305-764, Korea.
authors.forename: Tran Minh
authors.initials: TM
authors.lastname: Ngoc
authors.forename: Pham Thi Hong
authors.initials: PT
authors.lastname: Minh
authors.forename: Tran Manh
authors.initials: TM
authors.lastname: Hung
authors.forename: Phuong Thien
authors.initials: PT
authors.lastname: Thuong
authors.forename: IkSoo
authors.initials: I
authors.lastname: Lee
authors.forename: Byung-Sun
authors.initials: BS
authors.lastname: Min
authors.forename: KiHwan
authors.initials: K
authors.lastname: Bae
mesh_terms: D000880:Anthraquinones / Q000737:chemistry / Q000302:isolation & purification*; D016166:Free Radical Scavengers / Q000737:chemistry / Q000302:isolation & purification; D016859:Lipoxygenase Inhibitors / Q000737:chemistry / Q000302:isolation & purification*; D010936:Plant Extracts / Q000737:chemistry; D012250:Rheum; D013267:Stilbenes / Q000737:chemistry / Q000302:isolation & purification*
chemical_list: D000880:Anthraquinones; D016166:Free Radical Scavengers; D016859:Lipoxygenase Inhibitors; D010936:Plant Extracts; D013267:Stilbenes