Aqueous extracts of Crinum latifolium (L.) and Camellia sinensis show immunomodulatory properties in human peripheral blood mononuclear cells.

In Vietnamese and Chinese traditional medicine, hot aqueous extract of Crinum latifolium is used because of its antitumor activity. The genus Crinum is thought to possess antiviral and immunostimulative properties. Green and black tea derived from Camellia sinensis have similar qualities. A growing body of evidence suggests that moderate consumption of green and black tea may protect, e.g., against several forms of cancer, cardiovascular diseases, and bacterial infections. In this study, the immunomodulatory property of C. latifolium (L.) extracts should further be investigated and compared to those of black and green tea. Human peripheral mononuclear cells were cultured in the presence of tea extracts with or without mitogens or interferon-gamma. The effect of plant extracts on cultured cells was assayed by neopterin production, a sensitive marker reflecting the activation of cell-mediated immunity. Our experiments showed that extracts of C. latifolium (L.) slightly enhance neopterin production in unstimulated peripheral mononuclear cells, whereas an effective reduction of neopterin formation in cells stimulated with concanavalin A (Con A), phytohemagglutinin (PHA), or interferon-gamma (IFN-gamma) was observed. Green and black tea extracts displayed similar immunomodulatory properties in our in vitro system, whereas C. latifolium (L.) extracts seemed to be more effective in reducing neopterin formation in stimulated cells.