Inhibitory Effect of Cryptoporic Acid E, a Product from Fungus Cryptoporus volvatus, on Colon Carcinogenesis Induced with N‐Methyl‐N‐Nitrosourea in Rats and with 1,2‐Dimethylhydrazine in Mice

The antitumorigenic effect of cryptoporic acid E (CPA‐E), a dimeric drimane sesquiterpenoid isolated from the fungus Cryptoporus volvatus, on colon carcinogenesis was investigated. Female F344 rats given an intrarectal instillation of 2 mg of N‐methyl‐N‐nitrosourea 3 times weekly in weeks 1 and 2 were fed diet containing 0.2% CPA‐E from week 3. Femal ICR mice given 15 weekly intraperitoneal injections of 10 mg of 1,2‐dimethylhydrazine/kg body weight during weeks 1 to 15 were fed diet containing 0.06% CPA‐E from week 1. The experiment was terminated at week 35 for rats and at week 25 for mice. The incidence and the number of tumors per animal were reduced in CPA‐E‐fed animals compared to the controls: 31% vs. 75% (P<0.05) and 0.4±0.2 (SEM) vs. 0.9 ± 0.2 (0.1> P>0.05) in rats, and 31% vs. 63% (0.1>P>0.05) and 0.4±0.2 vs. 2.4 ± 0.8 (P<0.05) in mice (16 animals in each group). Intrarectal deoxycholic acid‐induced colonic mucosal ornithine decarboxylase activity was significantly lowered in CPA‐E‐fed animals compared to controls. This shows an antipromoting activity of CPA‐E against colon carcinogenesis. Thus, it was concluded that CPA‐E inhibits colon cancer development in both rats and mice treated with 2 different colon carcinogens.