7,8-Benzoflavone

Inhibitors of cytochromes P-450 may be specific for only one form and SKF 525A, for example, is specific for the phenobarbital inducible form(s), whereas the inhibitor 7, 8-benzoflavone is specific for the polycyclic hydrocarbon-inducible form. 

Benzoflavone (166) is non-planar with a torsion angle of 23° between the phenyl group and the remainder of the molecule, in keeping with the proximity of H-3 and H-2 (80MI22202). However, 5,6-benzoflavone (167) is approximately planar despite similar steric features. It is postulated that interaction between the carbonyl group and H-10 increases the contribution of the canonical form (168), which leads to a more planar structure than would otherwise he exneeteri... 

Ferrera L, Pincin C, Moran O. 2007. Characterization of a 7,8-benzoflavone double effect on CFTR Cl(—) channel activity. J Membr Biol 220 1-9. 

Benzoflavone, therefore, is likewise an anticarcinogenic agent. One may say that 7,8-benzoflavone acts directly, whereas the 5,6-isomer acts indirectly,... 

The conversion of androstenedione to estrone is catalyzed by aromatase. Inhibition of aromatase (human estrogen synthetase) by several naturally occurring flavonoids, including quercetin, chrysin, and apigenin, has been described. The synthetic flavone 7,8-benzoflavone was most active. Aromatization of androstenedione was affected by several flavonoids, of which 7-hydroxy-flavone and 7,4-dihydroxyflavone were the most potent. 

If the metabolism of both substrate and effector are measured, the validity of treating the two processes independently can be tested. For example, we reported that 7,8-benzoflavone dramatically increases the Vm of phenanthrene metabolism by CYP3A4 and that phenanthrene is a partial inhibitor of... 

Two other examples of sigmoidal reactions that are made linear by an activator include a report by Johnson et al. (31), who showed that pregnenolone has a nonlinear double-reciprocal plot that was made linear by the presence of 5 pM 7,8-benzoflavone, and Ueng et al. (23), who showed that aflatoxin B1 has sigmoidal saturation curve that is made more hyperbolic by 7,8-benzoflavone. As with the effect of quinine on carbamazepine metabolism, 7,8-benzoflavone is an activator at low aflatoxin B1 concentrations and an inhibitor at high aflatoxin B1 concentrations. 

An approach for determining the presence of multiple monooxygenases in rat liver microsomes was the use of chemicals that selectively affected certain monooxygenase activities but not others. For example, 7,8-benzoflavone (a-naphthoflavonc) markedly inhibited the hydroxylationofbenzo[a]pyrene by liver microsomes from 3-methylcholanthrene treated rats or by a cytochrome P448-dependent reconstituted enzyme system (68,69), but there was no effect or only a small stimulatory effect of 7,8-benzoflavone on benzo[a]pyrene metabolism in livers from untreated rats (68). 

In mechanistic studies with cholate-solubilized human or rabbit liver microsomes, 7,8-benzoflavone decreased the Km for cytochrome P450 reductase,... 

Fortner JG, Conney AH. 1977. Activation of monooxygenases in human liver by 7,8-benzoflavone. Clin. Pharmacol. Ther. 22 475-85... 

Buening MK, Fortner JG, Kappas A, Conney AH. 1978. 7,8-Benzoflavone stimulates the metabolic activation of aflatoxin B to mutagens by human liver. Biochem. Biophys. Res. Commun. 82 348-55... 

The fungicide (prochloraz), the topical antifungal agent (miconazole) and 7. 8-benzoflavone (a strong inhibitor of cytochrome P-450) limited the conversion of benzo[a]pyrene to a mutagen in S. typhimurium. The order of inhibitory action was 7.8-benzoflavone > prochloraz > miconazole (Antignac et al. 1990). 

Benzoflavone, ciprofoxacin, ellipticine, flavonoids (apigenin, naringenin, quercetin, etc.), fluoxamine, flurafylline, a-naphthoflavone, phenacetin Benzo[a]pyrene, charcoal-broiled beef, cigarette smoke, cruciferous vegetables, dihydralazine, 3-methylcholanthrene... 

Flavonoids are 2-phenyl-l-benzopyran-4-one derivatives which are widely distributed throughout the plant kingdom. Some synthetic flavonoids, notably the 7,8-benzoflavones (a-naphthoflavones (15), lUPAC name 2-arylnaphtho-[ 1,2-l>]pyran-4-ones), chrysin and apigenin, have been shown to act as potent competitive inhibitors of human placental aromatase [135, 136], In this system, 7,8-benzoflavone and chrysin have IC50 values of 70 and 500 nM respectively (androstenedione as substrate). Hydroxylated metabolites of... 

Some sanitizing agents used in the dairy industry contain iodine and nonionic detergent (iodophors). Free iodine can be detected by adding an equal volume of concentrated hydrochloric acid to cold milk followed by a few drops of 2-phenylbenzo(h)chr-omen-4-one(7,8-benzoflavone) solution and a similar quantity of hydrogen peroxide. This is shaken and the presence of iodine is indicated by a lilac or blue colon... 

The contrast and stability of marks fumed with iodine can be improved by secondary treatment with a solution of 7,8-benzoflavone (a-naphthoflavone). This reagent forms a dark-blue charge transfer complex with the absorbed iodine in the fingerprint deposit. 

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