Evaluation of the immunomodulatory effects of five herbal plants

A group of medicinal plants including, Silybum marianum, Matricaria chamomi lla, Calendula officinalis, Cichorium intybus and Dracocephalum kotschyi wh ich grow in Iran, were extracted with ethanol 70% and the mitogenic activit y was examined both on human peripheral blood lymphocytes and thymocytes. E ffect of these extracts on proliferative responsiveness of human lymphocyte s to phytohemagglutinin (PHA) and on the mixed lymphocyte reaction (MLR) wa s also investigated. The results obtained indicated that none of the extrac ts had a direct mitogenic effect on human lymphocytes or thymocytes (stimul ation index, SI < 0.07). Among the plants studied, C. intybus and C. offici nalis showed a complete inhibitory effect on the proliferation of lymphocyt es in the presence of PHA (SI range 0.01-0.49). A dose dependent inhibitory effect was obtained in the case of D. kotschyi. Extract of M. chamomilla s howed almost no stimulatory effect. A significant decrease in proliferation assay due to 0.1-10 mu g/ml of S. marianum was observed (SI < 0.46, P < 0. 05). In MLR, a markedly stimulatory effect with some lower concentrations o f all the extracts except Dracocephalum was detected. The highest stimulato ry effect was due to 100 mu g/ml of S. marianum (SI 2.82). Treatment of mix ed lymphocytes with 0.1-10 mu g/ml of C. officinalis (SI range 1.34-1.80) a nd 10 mu g/ml of M. chamomilla and C. intybus (SI 2.18 and 1.70, respective ly) strongly increased the cell proliferation. In conclusion, this in vitro study revealed the capacity of all the extracts except Dracocephalum to en hance the proliferation of lymphocytes after stimulation with the allogenic cells. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.