INHIBITION OF LIPID-PEROXIDATION IN LOW-DENSITY-LIPOPROTEIN BY THE FLAVONOID MYRIGALONE-B AND ASCORBIC-ACID

Lipid peroxidation in human LDL (0.05 mg protein/mL) incubated with Cu 2+-ions (5 mu M) in vitro was dose-dependently inhibited by the flavon oid myrigalone B (MyB) and by ascorbic acid. MyB at 6 mu M increased t he oxidation lag time by 135 +/- 24 min (approximately 5-fold compared to controls) and reduced the maximum oxidation rate by 46 +/- 5%. Asc orbic acid, at 9 mu M, increased the lag time by 179 +/- 29 min (6-fol d compared to controls) but did not affect the maximum oxidation rate, The increase in lag time induced by MyB was enhanced in the presence o f ascorbic acid. Their effects were additive, except when both were pr esent at the highest concentration tested, when a significant potentia tion, giving an increase in lag time of approximately 2 hr more than t he sum of separate effects, occurred. Concentration-time curves for My B in the absence and presence of ascorbic acid showed that the vitamin protected MyB against deterioration during incubation, and indicated that the net consumption of MyB in the oxidation process was reduced. No differences were observed when ordinary ascorbic acid and Ester-C(R ) a commercial vitamin C product, were compared. In conclusion, MyB an d ascorbic acid seem to interact in a way that further improves the an tioxidant status of the LDL particle relative to each substance separa tely.