Immunostimulating activity of maysin isolated from corn silk in murine RAW 264.7 macrophages

Corn silk (CS) has long been consumed as a traditional herb in Korea. Maysin is a major flavonoid of CS. The effects of maysin on macrophage activation were evaluated, using the murine macrophage RAW 264.7 cells. Maysin was isolated from CS by methanol extraction, and preparative C-18 reverse phase column chromatography. Maysin was nontoxic up to 100 mu g/ml, and dose-dependently increased TNF-alpha secretion and iNOS production by 11.2- and 4.2-fold, respectively, compared to untreated control. The activation and subsequent nuclear translocation of NF-kappa B was substantially enhanced upon treatment with maysin (1-100 mu g/ml). Maysin also stimulated the phosphorylation of Akt and MAPKs (ERK, JNK). These results indicated that maysin activates macrophages to secrete TNF-alpha and induce iNOS expression, via the activation of the Akt, NF-kappa B and MAPKs signaling pathways. These results suggest for the first time that maysin can be a new immunomodulator, enhancing the early innate immunity.