Immunosuppressive effect of medicinal plants of Kolli hills on mitogen-stimulated proliferation of the human peripheral blood mononuclear cells <i>in vitro</i>

Four medicinal plant species were collected from the Kolli hills of Tamil Nadu and were screened for their immunosuppressive effect. The plants were shade dried and extracted with methanol. The crude methanol extracts were tested for inhibition of lymphocyte proliferation via lymphocyte proliferation assay by ³thymidine uptake. The test plants were Justicia gendarussa, Plumbago indica, Aloe vera, and Aegle marmelos. Among the plants tested J. gendarussa (100 µg/ml) showed the highest lymphocyte inhibition (84%). Sequential extraction of J. gendarussa in various solvents (n-hexane, benzene, ethyl acetate, chloroform, acetone, ethanol, and water) confirmed that all of the above extracts at 50 µg/ml, aqueous extract inhibited lymphocyte proliferation. Further, 17 high performance liquid chromatography fractions were collected for the aqueous extract and fraction no. 15 showed maximum inhibition of lymphocyte proliferation. The present study indicates that these extracts should be investigated further for the possible presence of immunosuppressive components.