Stilbenoids from the Melinjo (Gnetum gnemon L.) Fruit Modulate Cytokine Production in Murine Peyer's Patch Cells Ex Vivo

Melinjo fruit (Gnetum gnemon L.) has been used as a food in Southeast Asia. To investigate if this fruit has regulatory actions on ileal immune responses, we measured T-helper (Th) cytokine production, i.e., interleukin-2 (IL-2), IL-4, IL-5, and interferon-gamma (IFN-γ), in cultured Peyer's patch (PP) cells from mice orally treated with a methanol extract of melinjo fruit. Oral administration of the 50% ethanol extract at 100 mg/kg/ day significantly enhanced the production of the Th1 cytokines IL-2 and IFN-γ irrespective of concanavalin-A stimulation, whereas the production of the Th2 cytokines IL-4 and IL-5 was not affected. We also isolated seven active constituents accompanied with two new stilbenoids from the ethylacetate fraction of the extracts. The structure of the new stilbene glucosides gnemonoside L (5) and gnemonoside M (7) was determined by 1D and 2D NMR and MS analyses. Five known stilbenoids were identified as resveratrol (1), isorhapontigenin (2), gnemonoside D (4), gnetins C (3) and E (6). Among these tested compounds, only new stilbenoid 7 strongly enhanced Th1 cytokine production in cultured PP cells at 10 mg/kg/day. These results indicated that this melinjo extract and its active constituent 7 potentiated T-cell-dependent immune responses in the ileal mucosa.