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Chain‐breaking fused heterocyclic antioxidants: Antioxidant activities of 9 H ‐xanthene‐2,7‐diols and α‐tocopherol upon liposomal membranes
Author(s) -
Yamamura Tatsuo,
Ishida Takafumi,
Tatara Hiroyuki,
Nishiyama Tomihiro
Publication year - 1997
Publication title -
journal of the american oil chemists' society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.512
H-Index - 117
eISSN - 1558-9331
pISSN - 0003-021X
DOI - 10.1007/s11746-997-0211-0
Subject(s) - xanthene , chemistry , antioxidant , diol , phosphatidylcholine , organic chemistry , liposome , membrane , phospholipid , biochemistry
We evaluated the antioxidant activities of 9 H ‐xanthene‐2,7‐diols and α‐tocopherol (α‐Toc) upon the oxidation of soybean phosphatidylcholine liposomal membranes, induced by 2,2′‐azobis(2‐amidinopropane) dihydrochloride (AAPH) and 2,2′‐azobis(2,4‐dimethylvaleronitrile (AMVN). The stoichiometric factors of 9 H ‐xanthene‐2,7‐diols, initiated with water‐soluble AAPH and lipid‐soluble AMVN, were 1.9–2.7 and 1.2–1.8‐fold greater than those of α‐Toc, respectively. The consumption profile of the antioxidant confirmed that 9 H ‐xanthene‐2,7‐diol was completely consumed within the induction period ( t inh ) and that the 9 H ‐xanthene‐2,7‐diol oxidation product was formed. When all oxidation product was depleted, t inh was terminated, and rapid oxidation occurred. These results suggested that the antioxidant activities of 9 H ‐xanthene‐2,7‐diol depend not only on the initial hydrogen abstraction from 9 H ‐xanthene‐2,7‐diol but also on a second hydrogen abstraction from the residual phenolic OH group of the oxidation product. Ascorbic acid (AsA) could not scavenge the radicals by itself in the lipid bilayer. However, when 9 H ‐xanthene‐2,7‐diol was located in the lipid bilayer, the addition of AsA into the aqueous phase prolonged t inh and reduced the rate of decay of 9 H ‐xanthene‐2,7‐diol.