Anti-tumor-initiating effects of phenolic compounds isolated from the bark of Picea jezoensis var. jezoensis.

We have previously reported the isolation of nine phenolic compounds including three new flavonostilbenes, jezonocinols A, B, and C, from the MeOH extract of the bark of Picea jezoensis var. jezoensis. Further investigation of the MeOH extract led to the isolation of three new stilbene-type compounds and one new 1,4-benzodioxane-type compound, together with seven known phenolic compounds. These compounds were tested for their inhibitory effects on the activation of (+/-)-(E)-methyl-2-[(E)-hydroxy-imino]-5-nitro-6-methoxy-3-hexemide (NOR 1), a nitric oxide (NO) donor, as a primary screening test for anti-tumor initiators. All compounds tested exhibited potent inhibitory effects on NOR 1 activation. Furthermore, jezonocinol B, the most potent inhibitor of NOR 1 activation, showed remarkable anti-tumor-initiating activity in the in vivo two-stage mouse skin carcinogenesis test using peroxynitrite (ONOO(-); PN) as the initiator and 12-O-tetradecanoylphorbol-13-acetate (TPA) as the promoter.