Potential uses of Tunisian pomegranate seed waste: investigation of bioactive compounds and antioxidant activities

The purpose of this study was to evaluate and compare the chemical composition, the bioactive compounds as well as the antioxidant activities of the cold-pressed seed oils of seventeen leading varieties of pomegranate grown in Tunisia. Regardless of variety, Tunisian Pomegranate seed oils showed a significant polyunsaturated fatty acids content (80.64–93.28%) with a notable presence of conjugated linolenic acid and isomers (55.60–85.26%). Punicic acid was the most abundant fatty acid, especially in the Jebali pomegranate seed oil (61.30%). Also, Tocopherols analysis highlighted that pomegranate seed oils can be an interesting source of α-tocopherol (1064.45–1897.00 mg/kg) and γ-tocopherol (592.30–1156.25 mg/kg). Gabsi and Beldi pomegranate seed oils, in particular, demonstrated a high level of vitamin E (p > 0.05). Besides, the oils were found to be abundant in β-sitosterol, β- carotene, and phosphatidylethanolamine. The seventeen pomegranate seed oils also depicted considerable levels of polyphenols (70.65–125.67 mg/g of oil). A total of 10 polyphenols were identified, of which gallic acid was the most prevalent. The in vitro assessment of the antioxidant activity showed that pomegranate seed oils exhibit important radical scavenging activity against DPPH and ABTS⁺ radicals. As a result, this investigation can help pomegranate producers select the best variety based on its ultimate application.