Houttuynia cordata–loaded nanophytosomes: Statistical optimization, structural characterization, and enhanced antioxidant performance

Nanophytosomes are lipid-based nanocarrier systems designed to enhance the stability, bioavailability, and functional performance of plant-derived bioactives. In the present study, antioxidant-rich Houttuynia cordata extract was incorporated into phosphatidylcholine–cholesterol bilayers using the thin-film hydration method, followed by factorial design–based optimization. The optimized formulation (HC:PC:CH = 1:2:1.0) produced nanoscale vesicles with a mean particle size of 142.7 ± 2.4 nm , narrow size distribution (PDI: 0.214 ± 0.01), high encapsulation efficiency ( 83.0 ± 1.5% ), and a zeta potential of −32.6 ± 1.1 mV , indicating good colloidal stability. Fourier transform infrared spectroscopy confirmed non-covalent phytoconstituent–lipid interactions, while differential scanning calorimetry and X-ray diffraction analyses demonstrated suppression of crystallinity and molecular dispersion within the lipid matrix. Cholesterol concentration was identified as a key factor governing bilayer packing, membrane rigidity, and encapsulation performance. The optimized nanophytosomal formulation exhibited enhanced antioxidant activity compared to the free extract, with DPPH and ABTS IC₅₀ values of 21.68 ± 0.6 µg/mL and 18.94 ± 0.5 µg/mL , respectively. In vitro release studies revealed a biphasic release pattern with an initial burst followed by sustained release up to 24 h. Kinetic modeling indicated that drug release was best described by the Korsmeyer–Peppas model (R² = 0.978), suggesting a diffusion-controlled mechanism. The formulation demonstrated good physicochemical stability over 90 days under defined storage conditions. Overall, the study establishes a clear relationship between bilayer composition, nanoscale architecture, and functional performance, highlighting the potential of cholesterol-modulated nanophytosomes as effective carriers for enhancing the delivery of plant-derived antioxidants in nutraceutical and biomedical applications.