Cancer chemopreventive activity of phenylpropanoids and phytoquinoids from Illicium plants

In our joint project involving search of anti-tumor promoters from natural plant sources, six phenylpropanoids and seven phytoquinoids isolated from three Illicium plants (Illiciaceae) were tested for their inhibitory activities against Epstein–Barr virus early antigen (EBV-EA) activation induced by 12-O-tetradecanoylphorbol-13-acetate in Raji cells. All tested compounds showed inhibitory activity against the EBV-EA activation even at 1×10 mol ratio, and the inhibitory activity of their compounds was found to be more than that of β-carotene. Two phenylpropanoids having prenyl group, 4-allyl-2-methoxy-6-(3-methyl-2-butenyl)phenol (3) and 4-allyl-2,6-dimethoxy-3-(3-methyl-2-butenyl)phenol (4), showed more potent activities as anti-tumor promoters (IC50 224 and 217 mol ratio/TPA, respectively). The presence of a prenyl moiety in the phenylpropanoids plays an important role in anti-tumor promoting activity as xanthone, coumarin and flavonoid previously reported. This investigation indicated that prenylated phenylpropanoids might be valuable as potential cancer chemopreventive agents.