Degradation of ethyl docosahexaenoate by gamma-ray irradiation and suppression of this degradation by antioxidants.

Ethyl 4,7,10,13,16,19-docosahexaenoate (DHA-Et) dissolved in an ethanol solution or embedded in liposomes was degraded by irradiating with gamma rays in a dose-dependent manner. The degradation rate of DHA-Et embedded in liposomes was higher than that of DHA-Et dissolved in ethanol. Antioxidants suppressed the degradation of DHA-Et embedded in liposomes, the order of activity of the antioxidants being luteolin>fisetin>kaempferol>quercetin>rutin. These results suggest that the hydrophobicity (logP) of an antioxidant is one of determinants for antioxidative activity, but that a vicinal diol structure in the B ring is not favorable for the antioxidative activity.