ANTIOXIDANT ACTION OF VACCINIUM-MYRTILLUS EXTRACT ON HUMAN LOW-DENSITY LIPOPROTEINS IN-VITRO - INITIAL OBSERVATIONS

Oxidative modifications of low density lipoproteins (LDL) are now reco gnised as one of the major processes in atherogenesis. Various drugs, as well as a number of natural products, have been proposed to inhibit such processes. Among the naturally-occurring constituents of plants which appear to possess antioxidant activity are polyphenolic compound s such as flavonoids. The aqueous extract of Vaccinium myrtillus is ri ch in such molecules. In this report, we describe the in vitro antioxi dative potential of this extract on human LDL. The copper-induced oxid ative modification of these lipoproteins was assessed using 1) measure ment of oxidative resistance as determined by the lag-phase preceding conjugated diene formation; 2) quantification of the amount of lipoper oxides and thiobarbituric acid-reactive substances generated, and meas urement of the modification in the net negative electrical charge of t he lipoproteins, over a 7-hour time course experiment. Trace amounts o f V myrtillus extract (15 to 20 mu g/mL) induce statistically signific ant changes in the oxidation behaviour of LDL, which include 1) prolon gation of the lag-phase of conjugated diene production (P < 0.01); 2) reduction in the formation of lipoperoxides and of thiobarbituric acid -reactive substances up to 7 hours and especially between 1 and 5 hour s (P < 0.01); and 3) inhibition of modification in the net negative ch arge of LDL. These results demonstrate that V myrtillus extract exerts potent protective action on LDL particles during in vitro copper-medi ated oxidation. Calculation of IC50 values indicates that, on a molar basis, this extract may indeed be more potent than either ascorbic aci d or butylated hydroxytoluene in the protection of LDL particles from oxidative stress.