C-methylated dihydrochalcones from Myrica gale L: Effects as antioxidants and as scavengers of 1,1-diphenyl-2-picrylhydrazyl

A number of isomeric or chemically closely related C-methylated dihydrochalcones, which is a rare substance class, has been isolated from the fruit exudate of Myrica gale L. and subjected to the following tests: 1) inhibition of lipid peroxidation induced by tert-butyl hydroperoxide or bromotrichloromethane in isolated rat hepatocytes, 2) inhibition of peroxidation induced by Fe2+ ions in a cell free system with linolenic acid as substrate, 3) scavenging activity against the diphenylpicrylhydrazyl radical, and 4) inhibition of enzymatic lipid peroxidation in linoleic acid by soybean 15-lipoxy-genase. One of the compounds (myrigalone B = MyB; 2',6'-dihydroxy-4'-methoxy-3',5'-dimethyldihydrochalcone) showed good activity in all tests, whereas the others were inactive or slightly active, except that myrigalone A (MyA; 3-(1-oxo-3-phenylpropyl)-1,1,5-trimethylcyclohexane like its synthetic analogue MyA* (the polar part of MyA) was nearly as active as MyB in 4). The antioxidant properties of MyB are probably due to its radical scavenging activity and may be related to its conformation, which differs from that of the other compounds.