Effect of Tilia x viridis flower extract on the proliferation of a lymphoma cell line and on normal murine lymphocytes: contribution of monoterpenes, especially limonene.

Tilia species are widely used in Europe as medicinal plants. The selective antiproliferative activity of a Tilia cordata flower dichloromethane extract (DME) on a lymphoma cell line has been reported previously and in order to extend this to other unstudied Tilia species, the effect of Tilia x viridis DME on the proliferation of tumor and normal murine lymphocytes was investigated. The bioguided fractionation of DME yielded a fraction rich in limonene (L), alpha-pinene and beta-pinene, which presented a selective antiproliferative action on tumor lymphocytes (EC(50) on tumor cells: 3.8 +/- 0.2 microg/mL; EC(50) on normal cells: 205 +/- 1.8 microg/mL). While all monoterpenes exhibited this activity, limonene proved to be the most active (EC(50) on tumor cells: 35 +/- 2.0 microg/mL; EC(50) on normal cells: 72 +/- 5.0 microg/mL) also exerting a stimulatory effect on non-mitogen stimulated lymphocytes proliferation (% of stimulation respect to control) (mean +/- SEM): L 10 microg/mL: 25 +/- 1.0%; 20 microg/mL: 38.5 +/- 2.5%; L 40 microg/mL: 41 +/- 0.9%; L 60 microg/mL: 58.5 +/- 3%. T. x viridis may thus constitute a potential source of monoterpenes with immunomodulatory activity.