Immunostimulatory effect of sweet potato peel-based plant mixture on RAW264.7 macrophages

This study aimed to investigate the immunostimulatory effect of a sweet potato peel-based plant mixture, including Platycodon grandiflorum, Codonopsis lanceolata and corn silk, on RAW264.7 macrophages. We tested the immunostimulatory effect of 12 plant extracts, individually, in terms of nitric oxide (NO) production in RAW264.7 macrophages. NO production of Platycodon grandiflorum, Codonopsis lanceolata, and corn silk extracts (PG, CL, CS) in RAW264.7 macrophages was significantly higher than that of other plant extracts (p<0.05). The cytotoxicity and production of NO and cytokines by PG, CL, CS, and weet potato peel extract (SP) in RAW264.7 macrophages were determined. The production of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6 in PG, CL or CS-treated RAW264.7 macrophages was significantly higher than that of SP-treated ones (p<0.05). Immunostimulatory effect of the extract from plant mixture containing Platycodon grandiflorum, Codonopsis lanceolata, corn silk, and sweet potato peel in the ratio 1:1:0.5:3 (w/w) was significantly higher than that of SP extract alone, and was similar or higher than that of PG, CL, and CS, on RAW264.7 macrophages (p<0.05). Therefore, the extract from plant mixture may be considered as a potential candidate for the development of functional food materials for enhancing immune activity.