Inhibition of rat liver aryl sulphotransferase by the food additive vanillin

Sulfation of "estrogenic" alkylphenols and 17beta-estradiol by human platelet phenol sulfotransferases

We have investigated the ability of alkylphenols to act as substrates and/or inhibitors of phenol sulfotransferase enzymes in human platelet cytosolic fractions. Our results indicate: (i) straight chain alkylphenols do not interact with the monoamine-sulfating phenol sulfotransferase (SULT1A3); (ii) short chain 4-n-alkylphenols (C < 8) are substrates for the phenol-sulfating enzymes (SULT1A1/2), which exhibit two activity maxima against substrates with alkyl chain lengths of C1-2 and C4-5; (iii) long chain 4-n-substituted alkylphenols (C >/= 8) are poor substrates and act as inhibitors of SULT1A1/2; (iv) human platelets contain two activities, of low and high affinity, capable of sulfating 17beta-estradiol, and 4-n-nonylphenol is a partial mixed inhibitor of the low affinity form of this activity. We conclude that by acting either as substrates or inhibitors of SULT1A1/2, alkylphenols may influence the sulfation, and hence the excretion, of estrogens and other phenol sulfotransferase substrates in humans.

Potentiation of paracetamol and carbon tetrachloride-induced hepatotoxicity in rodents by the food additive vanillin

The potential of vanillin to potentiate the paracetamol and carbon tetrachloride (CCl4)-induced hepatotoxicity was investigated in rats. Vanillin when given alone (15 mg/kg, orally), did not modify liver function in rats as the values of serum enzymes of alkaline phosphatase (ALP) and aminotransaminases (AST and ALT) were found similar to those in the normal animals. However, when given repeatedly before the administration of the subtoxic dose of paracetamol (500 mg/kg) or CCl4 (1 ml/kg), vanillin caused liver damage, as manifested by the significant increase in the serum levels of hepatic enzymes. When tested for its possible interaction with pentobarbital (75 mg/kg, i.p.) and strychnine (0.9 mg/kg, i.p.), it caused reduction in pentobarbital-induced sleep in mice as well as preventing the animals against the lethal effect of strychnine, suggestive of an induction of microsomal drug metabolizing enzymes. These results indicate that vanillin potentiates the hepatotoxic potential of paracetamol and CCl4 in rats probably through an enzyme induction process.

Common food additives are potent inhibitors of human liver 17 alpha-ethinyloestradiol and dopamine sulphotransferases

Interactions between dietary xenobiotics, drugs and biologically active endogenous compounds are a potential source of idiosyncratic adverse pathology. We have examined the inhibition of the sulphation of a number of xenobiotics and endobiotics in human liver cytosol by 15 food additives and constituents. Sulphation of dehydroepiandrosterone was resistant to inhibition by all compounds tested; however, dopamine sulphotransferase (ST) activity was inhibited strongly by (+/-)-catechin, (+)-catechin, octyl gallate, tartrazine and vanillin. Sulphation of the xenobiotic steroid 17 alpha-ethinyloestradiol (EE2) was inhibited by vanillin, erythrosin B and octyl gallate. Of these compounds, only vanillin was found to be sulphated to a significant extent by both human liver and platelets, and vanillin was determined to be a substrate for the monoamine-sulphating isoenzyme of phenolsulphotransferase. Vanillin was found to inhibit 50% of liver EE2 ST activity (IC50) at a concentration of approximately 1.3 microM and the mode of inhibition was non-competitive. The implications of these results for the adverse side effects associated with food additives and oral contraceptives are discussed.