The cinnamic and benzoic acids present in Gaultheria procumbens could be separated by a combination of thin layer, paper, silicic acid, and gas chromatography. After administration of cinnamic-, o-coumaric-, and p-coumaric acid-[3-14C] to this plant, the amount of radioactivity in salicylic, p-hydroxybenzoic, gentisic, protocatechuic, and vanillic acid was quantitatively compared. Whereas all five of the latter acids were radioactive with cinnamic acid as the precursor, onky salicylic and gentisic acid contained radioactivity after administration of o-coumaric acid and only p-hydroxybenzoic, protocatechuic, and vanillic acid were radioactive with p-coumaric acid as the precursor. The results show that the hydroxylation pattern of the benzoic acids can be determined at the cinnamic acid stage.
Acetate-[1-14C] and cinnamic acid-[3-14C] were administered to young leaves of Gaultheria procumbens L. The methylsalicylate isolated from the essential oil was radioactive only with cinnamic acid-[3-14C] as the precursor. Decarboxylation of the salicylic acid showed that the total radioactivity was located in the carboxyl group. Salicylic acid must therefore be regarded as a metabolite of cinnamic acid.
Further investigations on the biosynthesis of benzoic acids in Gaultheria procumbens L. have shown that besides salicylic acid all the other benzoic acids (gentisinic acid, p-hydroxybenzoic acid, protocatechuic acid, o-pyrocatechuic acid(?), syringic acid and vanillinic acid) can be formed from cinnamic acid. In the case of vanillinic acid it was proved that the total activity is located in the carboxyl group when cinnamic acid-[3-14C] is the precursor.
Formiat-14C is incorporated into the methylester group of methylsalicylate.