Lipid composition and antioxidant activity of liver oils from ray species living in Tunisian coasts

The proximate composition, fatty acid profiles, physicochemical properties and radical scavenging activities of liver oil from three ray species, Dasyatis pastinaca, Dasyatis violacea and Rhinoptera marginata, were investigated. Lipid contents of D. pastinaca (58.27%) and D. violacea (57.33%) were significantly high compared to those of R. marginata (10.90%). Among minerals, K and Na were the most abundant elements and the highest values were observed for R. marginata (153.7 and 115.86 mg/100 g, respectively). The fatty acid profiles exhibited a dominance of unsaturated fatty acids exceeding 65% of the total fatty acids. C16:0, C18:0 and C14:0 were the major saturated fatty acids. The most abundant monounsaturated fatty acids were C18:1 (10.88-21.98%) and C16:1 (4.47-23.95%). Interestingly, omega-3 polyunsaturated fatty acid profiles exhibited a dominance of eicosapentaenoic acid (3.36-5.51%) and docosahexaenoic acid (9.07-30.50%). D. pastinaca contained the highest carotenoid and total phenolic content accompanied with the strongest free radical scavenging abilities. This study suggests that ray livers which were actually wasted, could be used as new raw material for omega-3 polyunsaturated fatty acid oil production and a good source of carotenoids and phenolic compounds.