Immunomodulation effects of polyphenols from thinned peach treated by different drying methods on RAW264.7 cells through the NF-κB and Nrf2 pathways.

Thinned peach is abundant in polyphenols, and has been shown to exhibit various bioactivities. In this study, we evaluated the underlying immunomodulatory activity of polyphenol extracts of thinned peach (PETP) via the NF-κB and Nrf2 signaling pathways in RAW264.7 macrophages. The results demonstrated that the PETP efficiently activated the nuclear translocation of NF-κB and Nrf2, as well as downstream cytokines (IL-1β, IL-6, TNF-α and IFN-γ), SOD activity and ROS levels in RAW264.7 cells. Specifically, the PETP of natural drying and hot air drying exhibited less efficacy than that of freeze drying in NF-κB pathway. Interestingly, the PETP of hot air drying at 50 °C was more effective than freeze-dried PETP in activating Nrf2 nuclear translocation. Additionally, 50 µg/mL PETP enhanced immune responses, whereas 800 µg/mL PETP inhibited inflammatory development in macrophages. These findings indicated that different PETP affected the immunomodulation effects differently, which associated with the drying methods and incubation concentrations.