Cytotoxic activities and anti-tumor-promoting effects of microbial transformation products of prenylated chalcones from Angelica keiskei.

Three prenylated chalcones, 4-hydroxyderricin (1), xanthoangelol (2), and xanthoangelol F (3), isolated from Angelica keiskei, were transformed by the fungus Aspergillus saitoi. These chalcones were converted to flavanones (i.e., 4, 8, and 12), and prenyl-chain-hydrated (i.e., 5, 7, 9-11, and 13) and ring-B-hydroxylated (i.e., 6) chalcones. The structures of three new metabolites, 7, 9, and 13, were established as 2″,3″-dihydro-4,3″-dihydroxyderricin, 6″,7″-dihydro-7″-hydroxyxanthoangelol, and 6″,7″-dihydro-7″-hydroxyxanthoangelol F, respectively. Upon evaluation of cytotoxic activities of compounds 1-13, the metabolite 7 exhibited potent cytotoxicity against HL60 cells, and this cell death was revealed to be mostly due to apoptosis. In addition, compounds 1-4, 7-10, 12, and 13 were examined for their inhibitory effects on the induction of Epstein-Barr virus early antigen (EBV-EA) by 12-O-tetradecanoylphorbol-13-acetate (TPA) in Raji cells. All compounds tested showed inhibitory effects against EBV-EA activation with potencies higher than that of β-carotene. Furthermore, the metabolite 13 exhibited inhibitory effect on skin tumor promotion in an in vivo two-stage mouse skin carcinogenesis test based on 7,12-dimethylbenz[a]anthracene (DMBA) as initiator, and with TPA as promoter.