Reaction of hematin with allylic fatty acid hydroperoxides: identification of products and implications for pathways of hydroperoxide-dependent epoxidation of 7,8-dihydroxy-7,8-dihydrobenzo(a)pyrene

Journal Article · Tue Sep 06 00:00:00 EDT 1988 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00418a059· OSTI ID:6464954

Labeque, R; Marnett, L J

Reaction of 10-hydroperoxyoctadec-8-enoic acid (10-OOH-18:1) with hematin in sodium phosphate buffer containing Tween 20 generates 10-oxooctadec-8-enoic acid, 10-oxodec-8-enoic acid (10-oxo-10:1), and 10-hydroxyoctadec-8-enoic acid in relative yields of 79, 4, and 17%, respectively. The product profile and relative distribution are unaffected by 1 mM butylated hydroxyanisole. Approximately 5% of the hydroperoxide isomerizes from the 10- to the 8-position. 10-Oxo-10:1 most likely arises via ..beta..-scission of an intermediate alkoxyl radical to the aldehyde and the n-octyl radical. To test this, 10-hydroperoxyoctadeca-8,12-dienoic acid was reacted with hematin under identical conditions. 10-Oxooctadeca-8,12-dienoic acid, 10-oxodec-8-enoic acid, and 10-hydroxyoctadeca-8,12-dienoic acid are formed in relative yields of 50, 45, and 5%, respectively. The product ratios are constant with time and hydroperoxide to catalysts ratio and unaffected by inclusion of phenolic antioxidants. Two products of reaction of the 2-octenyl radical with O/sub 2/, octenal and octenol, were detected in 10% yield relative to 10-oxo-10:1. Inclusion of 7,8-dihydroxy-7,8-dihydrobenzo(a)pyrene (BP-7,8-diol) led to epoxidation by both 10-OOH-18:1 and 10-OOH-18:2. Studies with isotopically labeled hydroperoxide or O/sub 2/ indicated approximately 65% of the epoxide oxygen was derived from O/sub 2/ and 35% from hydroperoxide oxygen, consistent with the involvement of peroxyl free radicals as the oxidizing agents. The available evidence indicates that hematin reduces the fatty acid hydroperoxides homolytically to alkoxyl radicals that are oxidized to ketones, reduced to alcohols, or under ..beta..-scission to aldehydes. Carbon radicals generated during these reactions couple to O/sub 2/, generating peroxyl free radicals that epoxidize BP-7,8-diol.

• Research Organization: Wayne State Univ., Detroit, MI (USA)
• OSTI ID: 6464954
• Journal Information: Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 27:18; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AROMATICS
BENZOPYRENE
BIOCHEMISTRY
BIOLOGICAL PATHWAYS
CARBON 14 COMPOUNDS
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
CHEMISTRY
CHROMATOGRAPHY
CONDENSED AROMATICS
EPOXIDES
EVEN-EVEN NUCLEI
HEME
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HYDROCARBONS
ISOTOPES
LABELLED COMPOUNDS
LIGHT NUCLEI
LINOLEIC ACID
LIQUID COLUMN CHROMATOGRAPHY
MONOCARBOXYLIC ACIDS
NUCLEI
OLEIC ACID
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
OXIDATION
OXYGEN 18
OXYGEN COMPOUNDS
OXYGEN ISOTOPES
PEROXIDES
PEROXY RADICALS
PIGMENTS
PORPHYRINS
RADICALS
SEPARATION PROCESSES
STABLE ISOTOPES