Anti-tumor-promoting activities of selected pungent phenolic substances present in ginger

Ginger (Zingiber officinale Roscoe, Zingiberaceae) has been widely used as a dietary spice, as well as in traditional oriental medicine. The rhizome of ginger contains pungent vanillyl ketones, including [6]-gingerol and [6]-paradol, and has been reported to possess a strong anti-inflammatory activity. These pungent substances have a vanilloid structure found in other chemopreventive phytochemicals, including curcumin. In our study, we found anti-tumor-promoting properties of [6]-gingerol and [6]-paradol. Thus, topical application of [6]-gingerol or [6]-paradol 30 min prior to 12-O-tetradecanoyl-phorbol-13-acetate (TPA) attenuated the skin papillomagenesis initiated by 7,12-dimethylbenz[a]anthracene in female ICR mice. These substances also significantly inhibited the tumor-promoter-stimulated inflammation, TNF-alpha production, and activation of epidermal ornithine decarboxylase in mice. In another study, [6]-gingerol and [6]-paradol suppressed the superoxide production stimulated by TPA in differentiated HL-60 cells. Taken together, these findings suggest that pungent vanilloids found in ginger possess potential chemopreventive activities.