Antioxidative effects of quercetin-glycosides isolated from the flower buds of Tussilago farfara L.
A bioassay-guided fractionation of the ethylacetate soluble fraction from the flower buds of Tussilago farfara L. (Compositae) yielded two flavonoids, quercetin 3-O-beta-L-arabinopyranoside and quercetin 3-O-beta-D-glucopyranoside. These two sugar conjugates of quercetin exhibited higher antioxidative activity than their aglycone, quercetin by NBT superoxide scavenging assay. Moreover, treatment with quercetin 3-O-beta-L-arabinopyranoside significantly increased the total glutathione (GSH) contents and the protein level of gamma-glutamylcysteine ligase (gamma-GCL), a key enzyme required for glutathione (GSH) synthesis in a rat hepatocyte cell line. Subcellular fractionation and reporter gene analysis using antioxidant response element (ARE) construct revealed that quercetin 3-O-beta-L-arabinopyranoside increased the level of nuclear Nrf2 and reporter activity, and that these were associated with the induction of the gamma-GCL gene. After 24 h incubation of cells with quercetin 3-O-beta-L-arabinopyranoside, 23% of the glycoside was converted to its aglycone, quercetin, but gamma-GCL was not induced by 7 microM (23%) quercetin. These results suggest that the two quercetin-glycosides isolated from T. farfara L. have direct antioxidative properties, and that quercetin 3-O-beta-L-arabinopyranoside increases the cellular GSH level by inducing the gamma-GCL gene. These novel effects of quercetin-glycosides are suggestive to underlie the potential putative chemopreventive effects of T. farfara L.
Kim
Mi-Ran
MR
Research Center for Proteineous Materials, Chosun University, Gwangju 501-759, South Korea.
Lee
Jeong Yong
JY
Lee
Hyang-Hee
HH
Aryal
Dipendra Kuma
DK
Kim
Yoon Gyoon
YG
Kim
Sang Kyum
SK
Woo
Eun-Rhan
ER
Kang
Keon Wook
KW
D000818:Animals; D002460:Cell Line; D004790:Enzyme Induction / Q000502:physiology; D005419:Flavonoids / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology*; D035264:Flowers / Q000737:chemistry; D016166:Free Radical Scavengers / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D005721:Glutamate-Cysteine Ligase / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D005982:Glutathione Transferase / Q000096:biosynthesis / Q000378:metabolism; D006027:Glycosides / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology*; D022781:Hepatocytes; D008968:Molecular Conformation; D051267:NF-E2-Related Factor 2 / Q000378:metabolism; D009580:Nitroblue Tetrazolium / Q000737:chemistry; D019906:Nuclear Magnetic Resonance, Biomolecular; D051381:Rats; D013481:Superoxides / Q000378:metabolism; D015533:Transcriptional Activation / Q000187:drug effects; D031207:Tussilago / Q000737:chemistry*
D005419:Flavonoids; D016166:Free Radical Scavengers; D006027:Glycosides; D051267:NF-E2-Related Factor 2; C495636:Nfe2l2 protein, mouse; D013481:Superoxides; D009580:Nitroblue Tetrazolium; D005982:Glutathione Transferase; D005721:Glutamate-Cysteine Ligase; D005978:Glutathione