Enhanced antioxidant performance of phlorotannin compounds from brown seaweed Sargassum tenerrimum via nanoliposomal encapsulation

• Phlorotannin extract exhibited antioxidant and free radical-scavenging activities. • Increasing the surface-to-volume ratio of nanoliposomes (NLs) enhances their efficacy. • Chitosan-alginate biopolymer (CH-AL-BP) coating enhanced the stability and delivery. • CH-AL-BP-coated NLs significantly improved the oxidative protection of phlorotannins. Seaweeds contain natural antioxidants, known as phlorotannins; however, their direct use in food is limited. Nanoliposomes (NLs) have small, uniform particle sizes (20 nm), a high entrapment efficiency (90 %), and good stability. The unencapsulated extract contained 43.98 mg/g of phenols and 13.94 mg/g of phlorotannins, which increased significantly to 163.64 mg/g and 91.72 mg/g, respectively, after encapsulation in NLs. Additionally, total antioxidant activity, free radical scavenging, and iron reduction improved significantly ( p < 0.05) due to the large surface area and high antioxidant load capacity of NLs. NLs exhibit stronger antioxidant effects than alginate-chitosan-coated NLs, likely because the coating delays release. Overall, encapsulating phlorotannins in nanoliposomes enhanced their antioxidant effects, making them promising for use in food and nutraceutical applications.