ACTIVATION AND INHIBITION OF BENZO(A)PYRENE AND AFLATOXIN-B1 METABOLISM IN HUMAN-LIVER MICROSOMES BY NATURALLY-OCCURRING FLAVONOIDS

  • 1 January 1981
    • journal article
    • research article
    • Vol. 41  (1) , 67-72
Abstract
The effects of several naturally occurring and synthetic flavonoids on the metabolism of [the carcinogens] benzo(a)pyrene and aflatoxin B1 were evaluated. The addition of apigenin, chrysin, fisetin, flavanone, galangin, hesperitin, kaempferol, morin, myricetin, naringenin or quercetin to human liver microsomes inhibited the hydroxylation of benzo(a)pyrene. The addition of flavone, nobiletin, tangeretin or 7,8-benzoflavone to human liver microsomes caused a many-fold stimulation in the hydroxylation of benzo(a)pyrene, the metabolism of aflatoxin B1 to 2,3-dihydro-2,3-dihydroxyaflatoxin B1 and the metabolic activation of aflatoxin B1 to mutagenic products. Quercetin, morin and kaempferol inhibited cytochrome c (P-450) reductase in human liver microsomes; flavone and 7,8-benzoflavone had no effect. The inhibitory effects of quercetin, morin and kaempferol on monooxygenase activity may be caused at least in part by an inhibition in the reduction of cytochrome P-450. All of the 12 flavonoid inhibitors possessed hydroxyl groups; the flavonoid activators were less polar molecules that lacked hydroxyl groups.

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