Studies on the anti-tumor-promoting activity of naturally occurring substances. IV. Pd-II [(+)anomalin, (+)praeruptorin B], a seselin-type coumarin, inhibits the promotion of skin tumor formation by 12-O-tetradecanoylphorbol-13-acetate in 7,12-dimethylbenz[a]anthracene-initiated mice.

Since Pd-II [(+)anomalin, (+)praeruptorin B], a seselin-type coumarin, was found to inhibit tumor promoter induced phenomenon in vitro, the effect of Pd-II on the in vivo tumor-promoting action of 12-O-tetradecanoylphorbol-13-acetate (TPA) in 7,12-dimethylbenz[a]anthracene-initiated mouse skin was investigated. Pd-II, applied 40 min before the TPA treatment, at a dose of 10 mumol/painting, completely suppressed tumor formation up to 20 weeks of tumor promotion, without any toxicity. Besides Pd-II, various anti-tumor-promoter coumarins were found in the traditional Chinese medicine Qian-Hu, from which Pd-II was obtained. These coumarins may be useful for the development of an effective method to prevent cancer.