Azaphilones inhibit tumor promotion by 12-O-tetradecanoylphorbol-13-acetate in two-stage carcinogenesis in mice.

Monascorubrin (an azaphilone derivative) was isolated from Monascus anka, 'Monascus pigment', a natural pigment of food additivies, was extracted from Monasucs spp., and chaetoviridin A, one of the azaphilones, was isolated from Chaetomium globosum var. flavo-viridae. Application of 1 microgram of 12-O-tetradecanoylphorbol-13-acetate (TPA), a tumor promoting agent, to the mouse ear resulted in induction of inflammation. Among monascorubrin and related compounds assayed, monascorubrin, chaetoviridin A and its related compounds inhibited the inflammatory activity of TPA in mice. The 50% inhibitory dose of these compounds for TPA-induced inflammation was 0.4-1.5 mumol. Furthermore, monascorubrin (2 mumol), chaetoviridin A (2 mumol) and Monascus pigment (1 mg) markedly suppressed the promoting effect of TPA (1 microgram) on skin tumor formation in mice initiated with 7,12-dimethylbenz[a]anthracene (50 micrograms). It is assumed that the inhibition of tumor promotion by monascorubrin, chaetoviridin A and Monascus pigment is due to anti-inflammatory activity.