Preparation and Characterization of Brassica rapa L. Polysaccharide–Zein Nanoparticle Delivery System Loaded with Capsaicin

Capsaicin, a natural bioactive compound, has attracted wide interest for its potential health benefits. However, its rapid metabolism and strong irritancy upon oral administration have greatly limited its further application. To address these issues, this study developed a nanoparticle delivery system using corn Zein and Brassica rapa L. polysaccharide (BP) as carriers, with capsaicin (CAP) as the core. The optimized formulation (BP:Zein = 1:2, Zein:CAP = 2.5:1, mg/mg) produced stable, uniform spherical nanoparticles with an average particle size of 203.05 nm, a polydispersity index (PDI) of 0.138, a zeta potential of −44.9 mV, an encapsulation efficiency of 54.03%, and a drug loading capacity of 184.57 μg/mg. Fourier transform infrared spectroscopy (FTIR), fluorescence spectroscopy (FS), X-Ray diffraction, scanning electron microscope (SEM), and transmission electron microscopy (TEM) analyses confirmed that CAP was successfully encapsulated, forming nanoparticles through hydrogen bonding and hydrophobic interactions between CAP and Zein. The obtained nanoparticles displayed regular spherical morphology and uniform size distribution. Compared with single-layer Zein–CAP nanoparticles, BP–Zein–Capsaicin (BZC) nanoparticles exhibited markedly improved stability under different pH, ionic strength, and storage conditions. In vitro simulated digestion showed a sustained-release profile, with 36.76% of CAP released after 4 h. The anti-inflammatory experiment showed that both the nanoparticle and free capsaicin groups significantly inhibited xylene-induced acute ear edema in mice, with the medium- and high-dose nanoparticle groups exhibiting stronger anti-inflammatory effects than the free capsaicin group. These findings suggest that the nanoparticle delivery system effectively enhances the anti-inflammatory activity of capsaicin, possibly by improving its stability, achieving sustained release, and enhancing its bioavailability in vivo. Overall, capsaicin-loaded Brassica rapa L. polysaccharide–Zein nanoparticles combine small particle size, high drug loading, and excellent stability, providing a promising strategy for functional food development and targeted bioactive delivery.