A number of naturally occurring products from vegetables and herbs exert chemopreventive properties against
carcinogenesis. In this paper, two such compounds, isolated from garlic and from a traditional Chinese medicinal herb, are described for review.
Elemene, isolated from the Chinese medicinal herb Rhizoma zedoariae, was shown to exhibit antitumor activity in human and murine
tumor cells in vitro and in vivo. This novel
antineoplastic agent has substantial clinical activity against various
tumors. The in vitro effect of
elemene on the growth of
leukemia cells was evaluated by MTT assay. The IC50 values of
elemene for promyelocytic
leukemia HL-60 cells and
erythroleukemia K562 cells were 27.5 micrograms/mL and 81 micrograms/mL, respectively, while IC50 for peripheral blood leukocytes (PBL) was 254.3 micrograms/mL. The inhibitory effect of
elemene on proliferation of HL-60 cells was associated with cell cycle arrest from S to G2M phase transition and with induction of apoptosis. The apoptosis of
tumor cells was confirmed by
DNA ladder formation on gel electrophoresis and characteristic ultrastructural alterations. The results also demonstrated that inhibitory effects of
allicin, a natural organosulfide from garlic, on proliferation of
tumor cells were associated with the cell cycle blockage of S/G2M boundary phase and induction of apoptosis. These findings suggest that induction of apoptosis may contribute to the mechanisms of antitumor activity of
elemene and
allicin, which merit investigation as potential
chemoprevention agents in humans.