Structure-activity relationships of brassinin in preventing the development of carcinogen-induced mammary lesions in organ culture.

Brassinin, a phytoalexin, is found in Chinese cabbage. Previously, we showed that brassinin significantly inhibited dimethylbenz(a)anthracene (DMBA)-induced mammary lesions in organ culture. Moreover, it was an effective inhibitor against two stage skin carcinogenesis. In the present study, we synthesized several analogs of brassinin and evaluated their effectiveness in the mouse mammary gland organ culture model. Results showed that cyclobrassinin, also a naturally occurring brassinin analog, was more effective than brassinin. Spirobrassinin and N-ethyl-2,3-dihydrobrassinin also significantly inhibited mammary lesion formation. However, none of the methyl substituted analogs were effective. The effects of brassinin may, in part, be mediated by induction of phase II detoxifying enzymes such as quinone reductase.