Lantadenes and their esters as potential antitumor agents.

Lantadenes are pentacyclic triterpenoids of the weed Lantana camara. Five new lantadenes (14-18) and their methyl esters (20-24) were synthesized, characterized, and screened for cytotoxicity against four human cancer cell lines. The parent compound (1) and the four most active compounds (15, 16, 21, and 22) were further studied for their in vivo tumor inhibitory potential on squamous cell carcinogenesis in Swiss albino mice induced by 7,12-dimethylbenz[a]anthracene (DMBA) and promoted by 12-O-tetradecanoylphorbol-13-acetate (TPA). These results were supported by histopathological studies and discussed in terms of structure-activity relationships. The results inferred the importance of the groups attached to C-22 and C-17 in relation to the antitumor activity of these compounds.