Humulon, a bitter in the hop, inhibits tumor promotion by 12-O-tetradecanoylphorbol-13-acetate in two-stage carcinogenesis in mouse skin.

Humulon, one of the bitters in the hop, was isolated from the female flowers of Humulus lupulus. This component has inhibitory activity against 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced inflammation. At 1 mg/mouse, humulon inhibited markedly the tumor-promoting effect of TPA (1 microgram/mouse) on skin tumor formation following initiation with 7,12-dimethylbenz[a]anthracene (50 micrograms/mouse). Furthermore, humulon inhibited arachidonic acid-induced inflammatory ear edema in mice.