title: Bioactivation of the phytoestrogen diosmetin by CYP1 cytochromes P450.
abstract: Breast cancer is a major cause of death worldwide. Amongst the various forms of treatment chemoprevention is favoured and natural products such as the dietary flavonoids have been examined for their cancer preventative activity. In this study we investigated the anticancer activity of the flavonoid diosmetin, as a result of cytochrome P450 CYP1 metabolism. Diosmetin was metabolized to luteolin via an aromatic demethylation reaction on the B-ring from CYP1A1, CYP1B1 and the hepatic isozyme CYP1A2. CYP1A1 and CYP1A2 also produced additional unidentified metabolites. CYP1B1 showed the lowest apparent KM and CYP1A1 the highest apparent Kcat. Diosmetin was also metabolized to luteolin in estrogen receptor positive breast cell-line (MCF-7 cells) preinduced for 24 h with the potent CYP1 inducer 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Treatment of MCF-7 cells with TCDD caused bioactivation of diosmetin enhancing its cytotoxicity. Taken together these data suggest that the flavonoid diosmetin is metabolised to the more active molecule luteolin by CYP1 family enzymes.
authors.affiliation: Leicester School of Pharmacy, De Montfort University, The Gateway, Leicester LE1 9BH, United Kingdom.
authors.forename: Vasilis
authors.initials: V
authors.lastname: Androutsopoulos
authors.forename: Nicola
authors.initials: N
authors.lastname: Wilsher
authors.forename: Randolph R J
authors.initials: RR
authors.lastname: Arroo
authors.forename: Gerry A
authors.initials: GA
authors.lastname: Potter
mesh_terms: D001189:Aryl Hydrocarbon Hydroxylases; D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology; D049109:Cell Proliferation / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid; D019363:Cytochrome P-450 CYP1A1 / Q000378:metabolism*; D019388:Cytochrome P-450 CYP1A2 / Q000378:metabolism*; D065633:Cytochrome P-450 CYP1B1; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D005419:Flavonoids / Q000494:pharmacology*; D006801:Humans; D047311:Luteolin / Q000378:metabolism; D048789:Phytoestrogens / Q000494:pharmacology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured
chemical_list: D005419:Flavonoids; D048789:Phytoestrogens; D012333:RNA, Messenger; D003577:Cytochrome P-450 Enzyme System; D001189:Aryl Hydrocarbon Hydroxylases; C504573:CYP1A2 protein, human; C585496:CYP1B1 protein, human; D019363:Cytochrome P-450 CYP1A1; D019388:Cytochrome P-450 CYP1A2; D065633:Cytochrome P-450 CYP1B1; D047311:Luteolin; C039602:diosmetin