title: Rapid dimerization of quercetin through an oxidative mechanism in the presence of serum albumin decreases its ability to induce cytotoxicity in MDA-MB-231 cells.
abstract: Quercetin is a member of the flavonoid family and has been previously shown to have a variety of anti-cancer activities. We and others have reported anti-proliferation, cell cycle arrest, and induction of apoptosis of cancer cells after treatment with quercetin. Quercetin has also been shown to undergo oxidation. However, it is unclear if quercetin or one of its oxidized forms is responsible for cell death. Here we report that quercetin rapidly oxidized in cell culture media to form a dimer. The quercetin dimer is identical to a dimer that is naturally produced by onions. The quercetin dimer and quercetin-3-O-glucopyranoside are unable to cross the cell membrane and do not kill MDA-MB-231 cells. Finally, supplementing the media with ascorbic acid increases quercetin's ability to induce cell death probably by reduction oxidative dimerization. Our results suggest that an unmodified quercetin is the compound that elicits cell death.
authors.affiliation: Department of Biological Sciences, San José State University, San José, CA 95192-0100, USA.
authors.forename: Anh
authors.initials: A
authors.lastname: Pham
authors.forename: Anthony
authors.initials: A
authors.lastname: Bortolazzo
authors.forename: J Brandon
authors.initials: JB
authors.lastname: White
mesh_terms: D000970:Antineoplastic Agents / Q000032:analysis / Q000737:chemistry* / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000737:chemistry; D019281:Dimerization; D005960:Glucosides / Q000737:chemistry / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D010084:Oxidation-Reduction; D011794:Quercetin / Q000031:analogs & derivatives / Q000032:analysis / Q000737:chemistry* / Q000494:pharmacology*; D012709:Serum Albumin / Q000737:chemistry
chemical_list: D000970:Antineoplastic Agents; D005960:Glucosides; D012709:Serum Albumin; D011794:Quercetin; C110309:quercetin 3-O-glucopyranoside