Natural Killer (NK) cell activity assay
Peripheral blood mononuclear cells (PBMC) were washed, resuspended and adjusted to 2x106 cells/ml in complete RPMI 1640 containing 10% FBS. PBMC were incubated in the absence or presence of the extracts at the final concentrations of 10 ng/ml, 100 ng/ml, 1 ìg/ml, 10 ìg/ml and 100 ìg/ml at 37oC for 18 hours. After incubation, the cultures were washed and then used as effector cells for the assay of NK cell activity.