Inhibition of in vitro microsomal lipid peroxidation by isoflavonoids

In a comparative study the inhibition of microsomal lipid peroxidation induced by an Fe2+-ADP-complex and NADPH by naturally occurring isoflavones and their reduced derivatives (isoflavanones and isoflavans) has been examined. It is found that the isoflavanones are more active than the parent isoflavones and the isoflavans are by far the most potent inhibitors. In our in vitro test system 6,7,4'-trihydroxy- and 6,7-dihydroxy-4'-methoxyisoflavans (IC50 values 1.3 X 10(-6) and 1.1 X 10(-6) mol/l respectively) surpass the inhibitory effect of alpha-tocopherol, (+)-cyanidanol-3 and BHA (butylated hydroxyanisole). In order to establish a structure-activity relationship, a few more isoflavans have been included in the investigation.