Inhibition of the Tumor-promoting Action of 12-O-Tetradecanoylphorbol-13-acetate by Some Oleanane-type Triterpenoid Compounds

Since glycyrrhetinic acid was proved to suppress tumor promoter effects, several oleanane-type triterpenes which were chemically derived from oleanolic acid and hederagenin were tested in vitro and in vivo against the action of tumor promoter, 12-O-tetradecanoylphorbol 13-acetate.

By in vitro experiment monitoring with 12 - O - tetradecanoylphorbol-13-acetate-induced stimulation of ³²P₁ incorporation into phospholipids and an in vivo test on skin tumor formation in mice initiated with 7,12-dimethylbenz[a]anthracene and promoted with 12-O-tetradecanoylphorbol-13-acetate, 18β-olean-12-ene-3β,28-diol, (=erythrodiol), 18β-olean-12-ene-3β,23,28-triol, 18α-olean-12-ene-3β,28-diol, and 18α-olean-12-ene-3β,23,28-triol showed remarkable suppressive effects. Especially 18α-oleanane derivatives having a CH₂OH grouping converted from the COOH group initially allocated at C-17 were 100 times more effective than glycyrrhetinic acid both in vitro and in vivo.