Immunomodulatory Effects of Thai Medicinal Plants on the Mitogen Stimulated Proliferation of Human Peripheral Blood Mononuclear Cells in Vitro

The immunomodulatory effects of Thai medicinal plants, including Murdannia loriformis, Cymbopogon citratus, Momornica charantia, Centella asiatica, Allium sativum, Carthamus tinctorius, Eclipta alba, Cyperus rotundus, lotus pollen (Dee-Buo), and plant embryos in seeds of the lotus (Ke-Sorn-Buo), on the mitogen stimulated proliferation of human peripheral blood mononuclear cells (PBMCs) were investigated. The results obtained from this study indicated that only water extracts from C. asiatica had an immunostimulating effect on mitogen-stimulated proliferation of human PBMCs. In contrast, the ethanol extract from this plant showed immunosuppressive activity. Moreover, the water and ethanol extracts of Ke-Sorn-Buo, Dee-Buo, C. rotundus and E. alba had immunosuppressive effects. These extracts strongly decreased PBMC proliferation in a dose-dependent manner. Ethanol extract of C. tinctorius also showed immunosuppressive activity at a high concentration. Other medicinal plants did not show any mitogenic responses. This in vitro study revealed various effects of Thai medicinal plant extracts on non-specific cellular immune responses. Further investigation should be considered on the effect of extracts on other immune parameters such as macrophage activity, NK cell activity including cell signaling and cytokine production. Chiang Mai Med Bull 2005;44(1):1-12.