Pharmacokinetics in mice and metabolism in murine and human liver fractions of the putative cancer chemopreventive agents 3',4',5',5,7-pentamethoxyflavone and tricin (4',5,7-trihydroxy-3',5'-dimethoxyflavone).
OBJECTIVE
The flavones tricin (4',5,7-trihydroxy-3',5'-dimethoxyflavone) and 3',4',5',5,7-pentamethoxyflavone (PMF) are under development as potential colorectal cancer chemopreventive agents as they reduced adenoma development in the Apc(Min) mouse model of intestinal carcinogenesis. Here, the pharmacokinetic properties and metabolism of these flavones after oral administration were compared in mice.


METHODS
C57BL/6 J mice received an oral bolus of PMF or tricin (807 μmol/kg). Parent flavone and metabolites were analyzed by HPLC/UV in plasma, liver and gastrointestinal tissues. Flavones were incubated with mouse or human hepatic microsomes or 9000xg supernatant (S9), both fortified with a NADPH-generating system and either uridine 5'-diphosphoglucuronic acid (UDPGA, microsomes) or 3'-phosphoadenosine-5'-phosphosulfate (PAPS, S9). Disappearance of substrate was assessed by HPLC/UV, metabolites were characterized by HPLC/MS/MS.


RESULTS
Plasma concentrations and area under the plasma concentration versus time curve for PMF were higher than those for tricin. A mono-O-desmethyl PMF and several isomeric mono-O-desmethyl PMF glucuronides and sulfonates were major PMF metabolites in murine plasma, liver and intestinal tissue. In murine and human liver fractions, in vitro metabolic removal of tricin was faster than that of PMF. On kinetic analysis of metabolite generation in these incubations, apparent maximal velocity (V(max)) values for the generation of tricin O-glucuronide or O-sulfonate were consistently several fold higher than those characterizing the production of mono-O-desmethyl PMF glucuronides or sulfonates via the intermediacy of O-desmethyl PMF.


CONCLUSIONS
The results suggest that inclusion of methoxy moieties confers metabolic stability onto the flavone scaffold.
Cai
Hong
H
Cancer Biomarkers and Prevention Group, Department of Cancer Studies and Molecular Medicine, University of Leicester, LRI, RKCSB, Leicester LE2 7LX, UK.
Sale
Stewart
S
Britton
Robert G
RG
Brown
Karen
K
Steward
William P
WP
Gescher
Andreas J
AJ
D000328:Adult; D000818:Animals; D019540:Area Under Curve; D001190:Arylsulfonates / Q000378:metabolism; D055162:Biocatalysis; D001769:Blood / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism*; D005260:Female; D047309:Flavones / Q000378:metabolism; D005419:Flavonoids / Q000008:administration & dosage / Q000097:blood / Q000378:metabolism* / Q000493:pharmacokinetics*; D005965:Glucuronates / Q000378:metabolism; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008862:Microsomes, Liver / Q000378:metabolism*; D008875:Middle Aged; D055815:Young Adult
C488726:5,7,3',4',5'-pentamethoxyflavone; D001190:Arylsulfonates; D047309:Flavones; D005419:Flavonoids; D005965:Glucuronates; C017769:tricin