title: Singlet oxygen oxidation products of biliverdin IXα dimethyl ester.
abstract: Biliverdin IXα is a naturally occurring linear tetrapyrrolic product of the enzymatic oxidative ring cleavage of heme. Evidence is mounting that biliverdin possesses antioxidant properties in mammals but its mode of action is unclear. We present the single crystal X-ray structure analysis of two regioisomeric biladien-1,19-diones-ab that are derived from biliverdin IXα dimethyl ester by addition of two vicinal trans-methoxy groups to the 4,5- or 15,16-double bonds, respectively. The compounds were likely formed by photosensitized singlet oxygen addition, followed by Lewis acid-catalyzed methanol-induced ring-opening of the intermediate epoxide, and OH-to-OMe substitution. We thus present structural evidence for a possible reaction mechanism by which biliverdin can act as an antioxidant.
authors.affiliation: Department of Chemistry, University of Connecticut, Storrs, CT 06269-3060, USA.
authors.forename: Sarina J
authors.initials: SJ
authors.lastname: Dorazio
authors.affiliation: Department of Chemistry, University of Connecticut, Storrs, CT 06269-3060, USA.
authors.forename: Steven
authors.initials: S
authors.lastname: Halepas
authors.affiliation: Institute of Organic Chemistry, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany.
authors.forename: Torsten
authors.initials: T
authors.lastname: Bruhn
authors.affiliation: Department of Chemistry, Youngstown State University, 1 University Plaza, Youngstown, OH 44555, USA.
authors.forename: Kathleen M
authors.initials: KM
authors.lastname: Fleming
authors.affiliation: Department of Chemistry, Youngstown State University, 1 University Plaza, Youngstown, OH 44555, USA.
authors.forename: Matthias
authors.initials: M
authors.lastname: Zeller
authors.affiliation: Department of Chemistry, University of Connecticut, Storrs, CT 06269-3060, USA. Electronic address: c.bruckner@uconn.edu.
authors.forename: Christian
authors.initials: C
authors.lastname: Brückner
mesh_terms: D000975:Antioxidants / Q000737:chemistry / Q000378:metabolism*; D001664:Biliverdine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D010084:Oxidation-Reduction; D026082:Singlet Oxygen / Q000737:chemistry / Q000378:metabolism*
chemical_list: D000975:Antioxidants; D026082:Singlet Oxygen; C022907:biliverdin IX alpha dimethyl ester; D001664:Biliverdine
keywords: Antioxidants; Biliverdin; Epoxidation; Reactive oxygen species; Tetrapyrrolic pigments