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Radiolabelling studies of free radical reactions using muonium (the second hydrogen radioisotope): evidence of a direct antioxidant role for vitamin k in repair of oxidative damage to lipids
Author(s) -
Rhodes Christopher J.,
Dintinger Timothy C.,
Moynihan Humphrey A.,
Reid Ivan D.
Publication year - 2000
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/1097-458x(200008)38:8<646::aid-mrc699>3.0.co;2-w
Subject(s) - chemistry , radical , allylic rearrangement , antioxidant , vitamin e , vitamin , vitamin c , photochemistry , reactivity (psychology) , medicinal chemistry , organic chemistry , biochemistry , catalysis , medicine , alternative medicine , pathology
Following the recent suggestion that oxidative damage to lipids might involve the formation of C‐2 glyceryl radicals, in addition to main‐chain allylic radicals, which are generally thought important, we studied the kinetics of potential ‘repair’ reactions by vitamin E and vitamin K 1 (which are lipophilic and tend to locate in cell membranes) with 1,1,2‐trimethylallyl and 1‐acetoxyprop‐2‐yl radicals as models of, respectively, main‐chain and glyceryl‐type radicals. The second‐order rate constants for the reaction between trimethylallyl radicals and vitamin E and vitamin K 1 are 9.38 × 10 6 and 3.54 × 10 8 l mol −1 s −1 and those between 1‐acetoxyprop‐2‐yl radicals and vitamin E and vitamin K 1 are 1.76 × 10 8 and 2.03 × 10 6 l mol −1 s −1 , respectively. The results suggest that direct scavenging of glyceryl radicals by vitamin E should be an efficient process, and of main‐chain allylic radicals fairly so. Additionally, it appears that vitamin K 1 can act directly as a ‘radical repair agent,’ given its relatively high reactivity with allylic radicals (four times faster than with vitamin E), so prior reduction to the quinol form may be unnecessary. Copyright © 2000 John Wiley & Sons, Ltd.