2.10. Oxygen Radical Absorbance Capacity (ORAC) Assay

The antioxidant capacity of AST, free and encapsulated into SLN and SSLN, was measured using ORAC assay. During this test, the decay in fluorescein fluorescence due to peroxyl-radical formation by the peroxyl radical generator AAPH (2,2′-azobis 2- amidinopropane, dihydrochloride) is monitored over time. FL solution containing AAPH was used as the positive control and FL solution without AAPH as negative control. The assay was performed at 37 °C on a VICTOR Wallac 1420 Multilabel Counters fluorimeter (Perkin Elmer, Boston, MA, USA) set with excitation filter 540 nm and emission filter 570 nm. Fluorescein (FL) and AAPH were used at 12 nM and 100 mM, respectively. AST was solubilized in ethanol (12.5 µM), while SLN and SSLN formulations were diluted at the same concentration with phosphate buffer. After adding AAPH, the fluorescence was monitored for 30 h. Trolox was used as reference compound.