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. Author manuscript; available in PMC: 2012 May 1.

Published in final edited form as: Free Radic Biol Med. 2011 Mar 4;50(9):1163–1170. doi: 10.1016/j.freeradbiomed.2011.02.001

Scheme 2 — Proposed mechanism of COX-DGLA peroxidation to form DGLA-derived free radicals exclusively via C-8 oxygenation.

Note that in DGLA peroxidation, C-8 oxygenation (addition of the second O₂), after formation of the C-13 radical and C-9/C-11 endoperoxide bridge (addition of the first O₂), corresponds to the formation of carboxyl end carbon-centered radicals and oxygen-centered radicals. The H source needed for β’-scission in this pathway could be hydrophilic Ser-530 and Gly-526 of COX channel residues as well as H₂O [29–30]. The proposed oxygen-centered radicals can be further decomposed to the other products, e.g. C-9 to C-11 elimination to form malonaldehyde.

* In the case of peroxidation of DGLA-methyl ester, m/z 338 and m/z 368 of the POBN adduct of ^•C₈H₁₃O₂ () and ^•C₉H₁₇O₃ () are observed instead of m/z 324 and m/z 354.

Inline graphic — Proposed mechanism of COX-DGLA peroxidation to form DGLA-derived free radicals exclusively via C-8 oxygenation.

Note that in DGLA peroxidation, C-8 oxygenation (addition of the second O₂), after formation of the C-13 radical and C-9/C-11 endoperoxide bridge (addition of the first O₂), corresponds to the formation of carboxyl end carbon-centered radicals and oxygen-centered radicals. The H source needed for β’-scission in this pathway could be hydrophilic Ser-530 and Gly-526 of COX channel residues as well as H₂O [29–30]. The proposed oxygen-centered radicals can be further decomposed to the other products, e.g. C-9 to C-11 elimination to form malonaldehyde.

* In the case of peroxidation of DGLA-methyl ester, m/z 338 and m/z 368 of the POBN adduct of ^•C₈H₁₃O₂ () and ^•C₉H₁₇O₃ () are observed instead of m/z 324 and m/z 354.