9-oxooctadeca-10,12-dienoic acids as acetyl-CoA carboxylase inhibitors from red pepper (Capsicum annuum L.)

A methanol extract of fed pepper showed potent acetyl-CoA carboxylase inhibitory activity. The active principles were isolated and identified as (E, E)- and (E, Z)-9-oxooctadeca-10,12-dienoic acids by instrumental analyses. The IC50 values of the compounds were 1.4 x 10(-6) and 1.5 x 10(-6) M, respectively, their activity being nearly sixty-times higher than that of the common fatty acids themselves. A comparative study of the structure-activity relationship among their related compounds showed that the inhibitory activity was influenced neither by the position and species of the oxygen functional group in the middle of the alkyl chain nor by the configurations of the double bonds. However, it was found that the presence of double bonds between the terminal carboxyl and the mid-chain oxygen functional group lowered the inhibitory activity which could be recovered by hydrogenation of the double bonds.