Proniosomal encapsulation and characterization of a hydroxytyrosol-enriched olive leaf liquid extract

This study investigates the encapsulation of the lyophilized extract of fermented olive leaf brine, enriched in hydroxytyrosol, within proniosomal systems to preserve its bioactive properties. Proniosomes are dry, free-flowing precursor structures that spontaneously convert into niosomes upon contact with water. Compared to conventional liposomal and niosomal systems, they offer distinct advantages, including enhanced stability, controlled release, and prolonged shelf-life. These features make proniosomal structures an effective carrier system for thermally and oxidatively sensitive phenolic compounds. The prepared proniosomal formulations were comprehensively analyzed in terms of physicochemical, morphological, and aroma characteristics. XRD results indicated partial amorphization occurring after encapsulation. DSC analyses revealed shifts in endothermic peaks, indicating enhanced thermal stability. SEM and AFM images demonstrated a homogeneous surface morphology and nanoscale particle size distribution (average particle size ~270 ± 15 nm, zeta potential –32 ± 2 mV). Antioxidant activity was evaluated using DPPH and ABTS assays; in the DPPH assay, proniosomal formulations exhibited significantly higher radical scavenging capacity compared to the free extract (p<0.05), whereas ABTS activity did not show a linear relationship with concentration. No significant inhibition was observed in antimicrobial tests. The encapsulation efficiency of proniosomes decreased during the first week of storage and remained stable thereafter.