Flavonoids from the flower of Rhododendron yedoense var. poukhanense and their antioxidant activities.
Antioxidant flavonoids have been isolated from the flower of Rhododendron yedoense var. poukhanense. One new flavonoid and three known flavonoids, quercetin-5-O-beta-D-glucopyranoside (1), quercetin (3), and quercitrin (4), were isolated from the butanol and ethyl acetate extracts of the plant. The new flavonoid was identified as myricitrin-5-methyl ether (2). The isolation of these flavonoids from this plant, for the first time, is a valuable finding. The flavonoids were evaluated for their antioxidant activities using 1,1-diphenyl-2-picrylhydrazyl free radical (DPPH), TBARS (thiobarbituric acid reactive substance) and superoxide anion radical (O2-) in the xanthine/xanthine oxidase assay system. In the DPPH scavenging assay, the IC50 values were 4.5 +/- 0.48 microM for compound 2 and 9.7 +/- 0.29 microM for compound 3, which showed an antioxidant activity approximately 1.5-2 times higher than the antioxidant activity of alpha-tocopherol (9.8 +/- 0.94 microM). Additionally, the antioxidant activities of myricitrin-5-methyl ether (2) (IC50 = 1.7 +/- 0.22 microM) and quercetrin (4) (IC50 = 1.9 +/- 0.63 microM) were higher than that of L-ascorbic acid (IC50 = 7.4 +/- 0.63 microM) when evaluated using a TBARS assay. Compound 2 showed high activity in both the inhibition of xanthine oxidase (1.1 +/- 0.21 mM) and in the activation of superoxide scavenging.
Jung
Sung Je
SJ
Graduate School of Biotechnology & Plant Metabolism Research Center, Kyung Hee University, Suwon 449-701, Korea.
Kim
Dong-Hyun
DH
Hong
Yoon-Hee
YH
Lee
Jin-Hee
JH
Song
Hyo-Nam
HN
Rho
Young-Deok
YD
Baek
Nam-In
NI
D001713:Biphenyl Compounds / Q000737:chemistry; D005419:Flavonoids / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D035264:Flowers / Q000737:chemistry; D016166:Free Radical Scavengers / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D005609:Free Radicals / Q000737:chemistry*; D006834:Hydrazines / Q000737:chemistry; D015394:Molecular Structure; D010084:Oxidation-Reduction; D010851:Picrates; D029793:Rhododendron / Q000737:chemistry*; D013329:Structure-Activity Relationship; D013481:Superoxides / Q000737:chemistry; D017392:Thiobarbituric Acid Reactive Substances / Q000737:chemistry; D014969:Xanthine Oxidase / Q000737:chemistry
D001713:Biphenyl Compounds; D005419:Flavonoids; D016166:Free Radical Scavengers; D005609:Free Radicals; D006834:Hydrazines; D010851:Picrates; D017392:Thiobarbituric Acid Reactive Substances; D013481:Superoxides; C004931:1,1-diphenyl-2-picrylhydrazyl; D014969:Xanthine Oxidase