Bilobol, isolated from ginkgo fruit pulp, has been noted to be a strong skin irritant like 12-o-tetradecanoylphorbol-13-acetate (TPA), a tumor-promoter in the skin. A comparative investigation of morphological changes induced by bilobol and TPA induced in the skin of CD-1 mice, and an assessment of the skin tumor promoting potential of bilobol were therefore performed. In experiment I, mice received a single application of 2.5, 50 or 1000 μg of bilobol, or 0.1 or 2.5 μg of TPA on the right ear. The 50 or 1000 μg bilobol and 2.5 μg TPA doses caused ear redness, epidermal thickening and inflammatory infiltration. The dose of 2.5 μg of TPA, which is usually used as tumor promoter in skin carcinogenesis, was equivalent to 50 μg of bilobol in irritant effect. Thus, 50 μg of bilobol was used for the promotion testing (experiment II) in CD-1 mice initiated with 100 μg of 7, 12-dimethylbenz[a]anthracene (DMBA). Treatment with either 10 or 50 μg bilobol twice a week for 30 weeks did not result in any tumor development, thus suggesting that bilobol is not a complete promoter of skin carcinogenesis, despite generation of inflammation.
The Japanese Society of Toxicology Headquarters