Immunomodulatory principles of Dichrocephala bicolor.

From the ethanolic extract of Dichrocephala bicolor eight compounds-4,5-dicaffeoyl quinic acid (1); 3,4-dicaffeoyl quinic acid (2); 3,5-dicaffeoyl quinic acid (3); ethyl 4,5-dicaffeoyl quinate (4); methyl 3,5-dicaffeoyl quinate (5); 5-caffeoyl quinic acid (6); caffeic acid (7); and quercetin-3-O-rutinoside (8)-were isolated and identified. All of them were selected for immunopharmacological activity testing. Human mononuclear cells (HMNC) were used as target cells. Cell proliferation was determined by 3H-thymidine uptake. Compounds 2 and 6 potently enhanced HMNC proliferation and interferon-gamma production. Enhancement mechanisms may involve the increase of cytokines production.