Zein-Pectin Nanoparticles for Luteolin Delivery: Physicochemical Characterization, Antioxidant Activity, and...

Luteolin (LUT) is a hydrophobic flavonoid with relevant antioxidant potential; however, its application in food and nutraceutical systems is limited by poor aqueous solubility, low dispersibility, and restricted gastrointestinal availability. In this study, luteolin-loaded zein-pectin nanoparticles (ZPEC/LUT NP) were developed by antisolvent precipitation using pectin as the sole stabilizing polysaccharide. ZPEC/LUT NP showed a mean diameter of 345 ± 4 nm, polydispersity index (PDI) of 0.206 ± 0.019, negative zeta potential (-27± 1 mV), and high encapsulation efficiency (87% ± 11%). The similarity between unloaded and loaded nanoparticles indicated that LUT incorporation did not markedly alter particle size, morphology, or surface charge. Fourier Transform Infrared (FTIR), x-ray diffraction (XRD), and thermal analyses supported physical encapsulation of LUT within the zein-pectin matrix, with LUT present mainly in an amorphous or molecularly dispersed state. Short-term colloidal stability studies showed that ZPEC/LUT NP maintained nanometric dimensions and acceptable PDI values during 60 days of storage at room temperature and 10°C. During simulated gastrointestinal digestion, LUT was gradually transferred into soluble fractions, reaching an apparent bioaccessibility of approximately 16% after 6 h. In the ABTS assay, ZPEC/LUT NP exhibited higher apparent radical scavenging activity than free LUT, with IC₅₀ values of approximately 12.5 and 22.5 µg/mL, respectively. Unloaded nanoparticles showed only limited antioxidant contribution. Overall, zein-pectin nanoparticles represent a promising food-grade platform for improving the physicochemical performance and apparent antioxidant activity of hydrophobic flavonoids, although further studies are required to evaluate long-term stability and biological performance under physiological conditions.