No abstract

This paper is available online at http://dmd.aspetjournals.org ABSTRACT:The nonsteroidal anti-inflammatory drug naproxen is primarily metabolized in humans by acyl glucuronidation to form naproxen acyl glucuronide and by O-dealkylation to form 6-O-desmethylnaproxen (DMN). DMN contains both carboxy and phenolic groups and has been shown to form acyl glucuronide and sulfate conjugates. This project aimed to investigate whether DMN formed a phenolic glucuronide and diglucuronide(s) (with both the carboxy and phenolic groups glucuronidated). Male Sprague-Dawley rats (300-350 g) with exteriorized bile flow were dosed i.v. with DMN at 50 mg/kg. Four major DMN-related peaks were detected in bile by high-performance liquid chromatography (HPLC) analysis at 225 nm, including the known acyl glucuronide and sulfate conjugates. Selective hydrolyses using acidic and alkaline conditions and digestion with ␤-glucuronidase allowed tentative identification of the two unknown peaks as the phenolic glucuronide of DMN and a novel acyl glucuronide-sulfate diconjugate of DMN (i.e., formed by sulfonation of the phenolic group and glucuronidation of the carboxy group). The identities were confirmed by liquid chromatography-tandem mass spectrometry analysis of individual HPLC fractions. Total recovery of the DMN dose was approximately 80%, with the sulfate conjugate (50%) and unchanged DMN (10%) being excreted predominantly in urine and the acyl glucuronide (10%), phenolic glucuronide (6%), and acyl glucuronide-sulfate diconjugate (4%) being excreted predominantly or exclusively in bile. No evidence for a diglucuronide metabolite of DMN was found in either bile or urine of the DMN-dosed rats.The salicylate derivative diflunisal, a nonsteroidal anti-inflammatory drug (NSAID 1 ), has both carboxy and phenolic functional groups and forms acyl glucuronide, phenolic glucuronide, and sulfate monoconjugates as major metabolites in humans and animals (Tocco et al., 1975;Lin et al., 1985;Loewen et al., 1986;Dickinson et al., 1989). In previous work, we have reported the additional formation of small quantities of quasi "diglucuronides" of diflunisal in the rat and the perfused rat liver (King and Dickinson, 1991;Wang and Dickinson, 1998). The yield of diglucuronides was greater if the preformed biosynthetic acyl glucuronide was administered and much greater again when the acyl migration rearrangement isomers were administered. By contrast, no diglucuronides were formed after administration of the phenolic glucuronide of diflunisal. Interestingly, the mixture of diglucuronides appeared to comprise the phenolic glucuronides of the 2-, 3-, and possibly 4-O-positional isomers of the acyl glucuronides (King and Dickinson, 1991). Whether any "real" diglucuronide (i.e., the phenolic glucuronide of the biosynthetic acyl glucuronide) was formed was equivocal. These results brought forth interesting questions about the presence of recognition/transport/metabolism processes pertaining to real (i.e., biosynthetic) acyl glucuronides versus "look-alikes" (i.e...

The observed dual inhibition of both LOX- and COX-metabolic pathways may offer an explanation for the reported clinical efficacy and the favorable gastrointestinal tolerability of the original remedy Zeel comp. N.

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In the abstract the correct dose in the sentence ''Microvesicular steatosis was found in rats treated with [500 lg/kg body weight cimicifuga extract.'' should be 1,000 mg/kg body weight (instead of [500 lg/kg). The corresponding dose in the results part of the article is cited correctly.The authors apologize for this error and any confusion it may have caused.The online version of the original article can be found under