Antioxidant effects of phenolic rye (Secale cereale L.) extracts, monomeric hydroxycinnamates, and ferulic acid dehydrodimers on human low-density lipoproteins

Dietary antioxidants that protect low-density lipoprotein (LDL) from oxidat ion may help to prevent atherosclerosis and coronary heart disease. The ant ioxidant activities of purified monomeric and dimeric hydroxycinnamates and of phenolic extracts from rye (whole grain, bran, and flour) were investig ated using an in vitro copper-catalyzed human LDL oxidation assay. The most abundant ferulic acid dehydrodimer (diFA) found in rye, 8-O-4-diFA, was a slightly better antioxidant than ferulic acid and p-coumaric acid. The anti oxidant activity of the 8-5-diFA was comparable to that of ferulic acid, bu t neither 5-5-diFA nor 8-5-benzofuran-diFA inhibited LDL oxidation when add ed at 10-40 muM. The antioxidant activity of the monomeric hydroxycinnamate s decreased in the following order: caffeic acid > sinapic acid > ferulic a cid > p-coumaric acid. The antioxidant activity of rye extracts was signifi cantly correlated with their total content of monomeric and dimeric hydroxy cinnamates, and the rye bran extract was the most potent. The data suggest that especially rye bran provides a source of dietary phenolic antioxidants that may have potential health effects.