13C nuclear magnetic resonance spectroscopic analysis of seed oils containing conjugated unsaturated acids

¹³C Nuclear magnetic resonance spectroscopy has been used in a nondestructive investigation of conjugated unsaturated acids in seed oil triacylglycerols. Spectra of seven seed oils, fromPunica granatum, Cucurbita palmata, Jacaranda mimosifolia, Centranthus ruber, Catalpa bignonioides, Chilopsis linearis andCalendula officinalis, containing among them six isomeric trienoic acids,cis,trans,cis- andtrans,trans,cis-8,10,12-,cis,trans,cis-, cis,trans,trans-, trans,trans,cis- andtrans,trans,trans-9,11,13-octadecatrienoic acids, and of the oil ofImpatiens balsamina containingcis,trans,trans,cis-9,11,13,15-octadecatetraenoic acid, have been examined. Structures of component acids were derived from shifts of double bond carbons and of carbons close to the double bond systems. Compositions of the oils were obtained from signal intensities. Results were similar to those obtained by older methods. Only oil ofCentranthus ruber contained more than one major conjugated acid; bothcis,trans,trans- andtrans,trans,trans-9,11,13-octadecatrienoic acids were found. The latter acid is now thought to occur naturally. Presented in part at the International Society for Fat Research/American Oil Chemists' Society World Congress, New York, 1980. NRCC no. 20405.