Activation of monooxygenases in human liver by 7,8-benzoflavone

Clin Pharmacol Ther. 1977 Oct;22(4):475-84. doi: 10.1002/cpt1977224475.


Addition of 10(-4) M 7,8-benzoflavone to homogenates of human liver samples obtained by autopsy or surgical biopsy increased the rate of benzo[a]pyrene hydroxylation up to 11-fold. 7,8-Benzoflavone also increased the rates of hydroxylation of zoxazolamine and antipyrine at 10(-4) M but inhibited these reactions at 10(-6) M. The effects of 7,8-benzoflavone on the hydroxylation of benzo[a]pyrene and zoxazolamine in microsomes from human liver were similar to those in homogenates. Addition of 7,8-benzoflavone to homogenates of surgical biopsy samples of human liver had little or no effect on the rates of oxidative metabolism of 7-ethoxycoumarin, coumarin, and hexobarbital. Marked individuality for the activating and inhibiting effects of 7,8-benzoflavone was observed in different liver samples. This individuality may result both from the presence of multiple monooxygenases in varying amounts and proportions in the different liver samples and from a selective effect of 7,8-benzoflavone on certain of the monooxygenases.

MeSH terms

  • Adolescent
  • Adult
  • Antipyrine / metabolism
  • Autopsy
  • Benzopyrenes / metabolism
  • Biopsy
  • Coumarins / metabolism
  • Dealkylation
  • Enzyme Activation
  • Female
  • Flavonoids / pharmacology*
  • Hexobarbital / metabolism
  • Humans
  • Hydroxylation
  • In Vitro Techniques
  • Liver / drug effects
  • Liver / enzymology*
  • Male
  • Microsomes, Liver / drug effects
  • Microsomes, Liver / enzymology
  • Middle Aged
  • Oxygenases / metabolism*
  • Zoxazolamine / metabolism


  • Benzopyrenes
  • Coumarins
  • Flavonoids
  • Zoxazolamine
  • Hexobarbital
  • Oxygenases
  • Antipyrine