Clarification of the role of quercetin hydroxyl groups in superoxide generation and cell apoptosis by chemical modification.
Accumulated data have suggested that the hydroxyl groups of flavonoids are important for their bioactive function. To directly demonstrate the role of hydroxyl groups, we synthesized a derivative of quercetin, 3,7,3',4'-O-tetrabenzylquercetin (4Bn-Q) that substituted the hydroxyl groups of quercetin with benzyl groups, and then evaluated the ability to inhibit cell proliferation and cause apoptosis in human leukemia (HL-60) cells. The results reveal that quercetin, but not 4Bn-Q, inhibited cell proliferation and induced apoptosis as characterized by DNA fragmentation, activation of caspase-3, and PARP cleavage. Treatment with 4Bn-Q reduced the intracellular level of quercetin-induced superoxide, and the scavenger of superoxide, Mn (III) tetrakis (4-benzoic acid) porphyrin chloride (MnTBAP), reduced the superoxide level and apoptosis induced by quercetin. These findings directly demonstrate that the hydroxyl groups of quercetin contributed to the generation of intracellular superoxide, consequently inhibiting proliferation and inducing apoptosis in HL-60 cells.
Sakao
Kozue
K
Course of Biological Science and Technology, United Graduate School of Agricultural Sciences, Kagoshima University, 1-21-24 Korimoto, Kagoshima 890-0065, Japan.
Fujii
Makoto
M
Hou
De-Xing
DX
D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D049109:Cell Proliferation / Q000187:drug effects; D005434:Flow Cytometry; D016166:Free Radical Scavengers / Q000494:pharmacology; D018922:HL-60 Cells; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008665:Metalloporphyrins / Q000494:pharmacology; D011794:Quercetin / Q000737:chemistry / Q000494:pharmacology*; D013481:Superoxides / Q000378:metabolism*
D016166:Free Radical Scavengers; D008665:Metalloporphyrins; C097284:manganese(III)-tetrakis(4-benzoic acid)porphyrin; D013481:Superoxides; D011794:Quercetin