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Effects of Noni (Morinda citrifolia) Fruit on Cell-Mediated Immunity
Morinda citrifolia, commonly known as noni, is a traditional natural medicine in French Polynesia and Hawaii. Previous studies have been performed to elucidate its pharmacological activities. In one such study, noni exhibited anti-tumor activity through immune system activation. However, the underlying mechanism was not studied in detail. In the current study, the picryl chloride-induced contact dermatitis (PC-CD) model was used to evaluate the effect of noni fruit flesh extract (MCF-ext) on cell-mediated immunity (CMI). MCF-ext was administered orally to mice for 1 week. Afterwards, CMI suppressive substance from Ehrlich carcinoma-bearing mice (EC-sup) was injected intraperitoneally. MCF-ext treated mice recovered from CMI suppression. Activity guided fractionation led to the isolation of an iridoid glucoside, deacetylasperulosidic acid (DAA), as an active compound. The effects of MCF-ext and DAA on the production of selected cytokines and lymphocyte subsets (CD3+, CD4+, CD8+, B220+ and CD49b+) in splenocytes were also evaluated. MCF-ext and DAA aided recovery from EC-sup induced IL-2 reduction but did not influence cell populations. Furthermore, MCF-ext and DAA enhanced natural killer (NK) cell activity against Yac-1 (murine lymphoma) cells. These results suggest MCF-ext and DAA possess immunomodulatory properties and control CMI by normalizing cytokine production and/or activating NK cells.