Pharmacokinetics and metabolism of benzophenone 2 in the rat.

Twelve derivatives of benzophenone (BP1-BP12) are widely used as UV-screens to protect industrial products from light induced damage. There is growing public concern about industrially produced chemicals that might interfere with hormonal signalling pathways, thus having potential adverse effects on human health. The derivative 2,2',4,4'-tetrahydroxybenzophenone (BP2) which is used in cosmetic products and in packaging materials, was previously shown to be an estrogenic endocrine active chemical (EAC). While the metabolisation of BP3 has been analyzed in vivo, according to our knowledge little is known about the pharmacokinetics of BP2. Therefore we performed a dose-response experiment with 5 dosages of BP2 which was applied per gavage to adult ovariectomised (ovx) rats for 5 days. Serum samples were analyzed via HPLC. Metabolites were further identified by Helix pomatia glucuronidase treatment and subsequent ion-trap-mass spectrometry. Additionally we analyzed the time dependent metabolisation and excretion of BP2 in a kinetic study. The parent compound BP2 is metabolised to glucuronide - and sulfate-conjugates. In the serum maximum levels of BP2, BP2-glucuronide and BP2-sulfate were observed already 30 min after BP2 application while highest concentrations of BP2 and its metabolites in urine were measured 120 min after treatment. It is suggested that this biotransformation occurs via a first-pass effect in the gut wall or the liver. Despite this rapid metabolisation and excretion, the amount of unconjugated BP2 was sufficient to induce a dose dependent estrogenic effect in the uterotrophic assay.