Abstract: Flavonoids from guava fruit were obtained though ultrasonic-assisted extraction and were purified using an AB-8 macroporous resin column before being used to prepare zein-guava flavonoid composite nanoparticles (ZGF) by a solvent evaporation-induced self-assembly method. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) were used to explore the morphology and characteristics of the as-prepared samples. In addition, the cytotoxicity of the flavonoids and the composite nanoparticles was studied by the methyl thiazolyl tetrazolium method and the impact of ZGF on cellular reactive oxygen species (ROS) production was evaluated using the fluorescent probe DCFH-DA. The antioxidant activity of ZGF was evaluated by measuring the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity. The release behavior of ZGF in artificial gastric juice was investigated. The results showed that the purity of the purified flavonoids was 67.0%. The maximum encapsulation efficiency of 93.29% was obtained when the mass ratio of zein to flavonoids was 16:1. The size of the prepared nanoparticles was approximately 500 nm with a spherical structure. ZFG had no obvious cytotoxicity on HepG2 cells in the concentration range of 0.5–5 mg/mL. Moreover, ZFG could protect HepG2 cells from oxidative damage induced by H2O2 in a concentration-dependent manner and could scavenge 86.02% of DPPH radicals at a concentration of 416.67 μg/mL. Furthermore, the cumulative release rate of ZGF in artificial gastric juice was increased from 1 to 6 h of digestion reaching 64.11%, suggesting good release performance. This study provides a theoretical reference for the comprehensive utilization of guava flavonoids.

Key words: guava; flavonoids; zein; composite nanoparticles; antioxidant activity