Antioxidative effects of lemon oil and its components on copper induced oxidation of low density lipoprotein

Oxidation of low density lipoprotein (LDL) has been implicated in atherogen esis since several years. Therefore many researchers are looking for potent antioxidants which are able to inhibit LDL-oxidation and thus lower the ri sk for atherosclerosis. In particular several flavonoids have been investig ated for their antioxidant capacity and it was shown that many factors Infl uence the ability of flavonoids to retard LDL-oxidation, among others their lipophilic character. Since essentail offs and some of their components wh ich are highly lipophilic, have been shown to possess antioxidant propertie s, their effects on copper-induced LDL-oxidation were analysed. Plasma was incubated with different terpenoid substances and subsequently the LDL was isolated. It could be demonstrated that the terpenoids were enriched in LDL after incubation with plasma. To follow the kinetics of copper induced LDL -oxidation formation of conjugated dienes as well as loss of tryptophan flu orescence were measured. Furthermore the antioxidants alpha -tocopherol, be ta -carotene and lycopene were quantified in LDL. It could be shown that pa rticularly lemon oil and one of its components, gamma -terpinene, are effic iently slowing down the oxidation of LDL. This effect is independent of alp ha -tocopherol stability in LDL, whereas the loss of carotenoids during oxi dation Is strongly retarded.