Proniosomal encapsulation of olive leaf extract for improved delivery of oleuropein: Towards the valorization of an agro-industrial byproduct

Olive leaf, a by-product of the olive oil industry, is rich in bioactive compounds, including the antioxidant and anti-inflammatory oleuropein. Olive leaf extracts have been explored for nutraceutical applications, but oleuropein's low bioavailability and stability limit its use in food and supplements. This work aimed to mitigate these issues by nano-encapsulating the olive leaf extract in proniosomes-free-flowing powders that form niosomes upon hydration. These niosomes can then be further processed into dosage forms or incorporated into functional foods. Proniosomes based on lactose or mannitol were developed and characterized. Hydration of the proniosomes yielded niosomes with high oleuropein loading and antioxidant activity. These niosomes controlled oleuropein release in simulated gastric and intestinal fluids, protecting it from degradation. Furthermore, niosomal encapsulation enhanced protection against oxidative stress in intestinal cells compared to the unformulated extract, suggesting improved intracellular delivery and making this formulation a suitable candidate as a functional food ingredient.