Original research articleSeeds of pomegranate, tomato and grapes: An underestimated source of natural bioactive molecules and antioxidants from agri-food by-products

•Pomegranate, tomato and grape seeds were biochemically characterized.•Seeds were extracted by supercritical CO2 to prepare high-value vegetable oils.•Oils were assayed for isoprenoids, fatty acids and antioxidant activity.•Seeds are useful sources of phenolics, tocochromanols and unsaturated fatty acids.•Carefully designed oil blends can meet specific dietary requirements of customers.

Pomegranate, tomato and grape seeds are quantitatively relevant agri-food by-products rich in molecules beneficial to human health. To valorize this resource, the composition and antioxidant activity of seeds and deriving supercritical CO2 (SC-CO2) extracted oleoresins were evaluated. Grape seeds showed the highest content of total phenolic compounds (33.9 mg GAE/g), flavonoids (15.6 mg CE/g) and condensed tannins (14.0 mg CE/g), while tomato seeds presented the highest content of tocochromanols (159.6 μg/g). Grape seeds showed the highest total antioxidant activity (178.2 μmol TE/g), as evaluated by TEAC assay, followed by pomegranate (19.8 μmol TE/g) and tomato (9.8 μmol TE/g). Oleoresin yields obtained by SC-CO2 extraction from the seeds ranged between 3.1 (pomegranate) to 7.8 (tomato) g oleoresin/100 g. Total tocochromanols were abundant in pomegranate (2008 μg/g) and tomato (1769 μg/g) oleoresins; a relatively low amount was instead detected in the oleoresin extracted from grape seeds (636 μg/g). Carotenoids were not detected in all oleoresins. Pomegranate oleoresin had a higher antioxidant activity than the others. Mono- and polyunsaturated fatty acids were more abundant than saturated in all oleoresins, with the highest percentage of unsaturated fatty acids detected in pomegranate seed oleoresin (∼90%), mainly due to punicic acid (∼70%).