The occurrence and characterisation of phenolic compounds in Camelina sativa seed, cake and oil

In this study, the antioxidant activities of Camelina sativa methanolic extracts were evaluated by different chemical assays: reducing power, 2,2-diphenyl-1-picrylhydrazyl (DPPH·) assay, the β-carotene bleaching method and the metal chelating activity assay. An LC–MS profiling method was used for a comprehensive study of the phenolic compounds and their representation in camelina seeds, cake and oil. For this purpose, 4-vinyl derivatives of hydroxycinnamic acids were synthesized by thermal decarboxylation of the corresponding phenolic acids and sinapine was isolated from kale (Brassica oleracea) applying a new method and confirmed by NMR. The results revealed that besides the total phenolic content and antioxidant activity, seeds and cake also possess a similar phenolic profile. In addition to sinapine and 4-vinyl derivatives, other antioxidants were successfully identified: ellagic acid, protocatechuic acid, p-hydroxybenzoic acid, sinapic acid, salicylic acid, catechin, rutin, quercetin and quercetin glucoside. Since after oil pressing most of the phenolic compounds remain in the seed residues, only a few compounds were identified in the oil. Camelina cake was found to have the best reducing power and radical scavenging activity, whereas camelina oil, with a relatively low phenolic content, exhibited the highest iron-chelating capacity and the best inhibitory action against β-carotene discolouration in an emulsified system.