Inhibition of lipid peroxidation by anthocyanins, anthocyanidins and their phenolic degradation products

Food components that delay or prevent biomolecule oxidation may be relevant in shelf life extension as well as disease prevention. Anthocyanins are a potentially important group of compounds, but they are prone to degradation both in vitro and in vivo, producing simple phenols. In this study, eight structurally related (poly)phenols [anthocyan(id)ins and phenolic acids] were examined for their ability to inhibit lipid oxidation at physiologically relevant concentrations (100-1000nM) using the Cu2+-mediated low-density lipoprotein oxidation model. Interaction between each (poly)phenol and Cu2+ ions was also investigated. (Poly)phenols with an ortho-dihydroxy group arrangement, i.e. cyanidin-3-glucoside, cyanidin and protocatechuic acid, were the most effective within their class, extending the lag phase to oxidation by 137, 255 and 402%, respectively (at 1000 nM). At the same concentration, trihydroxy-substituted compounds (delphinidin and gallic acid) were of intermediate efficacy, extending the lag phase by 175 and 38%, respectively. Compounds with the 4'-hydroxy-3',5'-methoxy arrangement (i.e. malvidin-3-glucoside and malvidin) were the least effective (3 and 58% extension, respectively), while syringic acid (4-hydroxy-3,5-dihydroxy benzoic acid) was pro-oxidant (lag phase shortened by 31%). (Poly)phenols with the orthodihydroxy arrangement chelated Cu2+ ions, which in part explains their greater efficacy over the other (poly)phenols in this model oxidation system. However, differences in their hydrogen-donating properties and their partitioning between lipid and hydrophilic phases are also relevant in explaining these structure-activity relationships.