Immunotherapeutic agents have become important addition to the list of anticancer treatments and one of
strategies being developed is to improve the therapeutic index of cytokines so that better anticancer effects
can be elicited with less toxicity. Some types of natural products have the ability to stimulate the immune
system such as a potent stimulator of natural killer cells and macrophages [5,6]. Activated Natural Killer
(NK) cells are potent anti-tumor effector cells and play an important role in immunosurveillance [7]. The
lytic activity of NK cells can be augmented by exposure to interferons [8] and interleukin-2 [9].