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

Abstract

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, from Punica granatum, Cucurbita palmata, Jacaranda mimosifolia, Centranthus ruber, Catalpa bignonioides, Chilopsis linearis and Calendula officinalis, containing among them six isomeric trienoic acids, cis,trans,cis- and trans,trans,cis-8,10,12-, cis,trans,cis-, cis,trans,trans-, trans,trans,cis- and trans,trans,trans-9,11,13-octadecatrienoic acids, and of the oil of Impatiens balsamina containing cis,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 of Centranthus ruber contained more than one major conjugated acid; both cis,trans,trans- and trans,trans,trans-9,11,13-octadecatrienoic acids were found. The latter acid is now thought to occur naturally. © 1982 American Oil Chemists' Society.