(±)11-HDHA is an autoxidation product of DHA in vitro.{7479,7491} It is also produced from incubations of DHA in rat liver, brain, and intestinal microsomes.{7480,7490,7492} DHA is metabolized to 11(S)-HDHA by human platelets and canine retina.{7483,7486,7484,7492} In addition to 11(S)-HDHA, 14(S)-HDHA is also produced by platelets.{7483,7484,7492} 11(S)-HDHA is an inhibitor of U-46619-induced human platelet aggregation and rabbit and rat aortic smooth muscle contraction with IC50 values of about 50, 4.7, and 7.5 μM, respectively.{7484,7481} (±)11-HDHA is a potential marker of oxidative stress in brain and retina where DHA is an abundant PUFA.