28-deacetylbelamcandal, a tumor-promoting triterpenoid from Iris tectorum

A spiroiridal-type triterpenoid, 28-deacetylbelamcandal (1), was isolated f rom the rhizomes of Iris tectorum as an active principle that stimulated di fferentiation of human promyelocytic leukemia (HL-60) cells, a short-term s creening method for 12-O-tetradecanoylphorbol 13-acetate (TPA)-type tumor p romoters. In the same manner as TPA, compound 1 bound to protein kinase C ( PKC) and activated PKC, and induced tumor necrosis factor-a release from HL -60 cells. In an in vivo study, groups treated with 100 mu g 7, 12-dimethyl benz[alpha]anthracene plus 400 nmol of 1 showed 64.3% tumor incidence by we ek 20. It has thus been demonstrated that 1 represents a new structural cla ss of mouse skin-tumor promoters.