The disposition of a new potential
antineoplastic drug dimefluron after an
oral administration to rats was investigated.
Dimefluron, 3,9-dimethoxy-5-(2-dimethylaminoethoxy)-7H-benzo[c]fluoren-7-one hydrochloride, was administered in a single oral dose (250 mg kg(-1) of
body weight) in the form of an aqueous
solution via a gastric probe.
Dimefluron metabolites were being searched for in rat faeces. Synthetic standards of the expected phase I metabolites (the products of O- and N-desmethylation, N-oxidation and carbonyl reduction of
dimefluron) were prepared and used together with
dimefluron and internal standard in the development of two HPLC bioanalytical methods based on different separation principles. The first separation of
dimefluron and the phase I metabolites was tested on a 250 mm x 4 mm chromatographic column with LiChrospher 60 RP-selectB 5 microm (Merck) using an isocratic mobile phase containing 0.01 M nonylamine
buffer (pH 7.4) and
acetonitrile in the 1:2 ratio (v/v). The second separation was performed on a 250 mm x 4 mm chromatographic column Discovery HS F5, 5 microm (Supelco) using a linear gradient mode with the mobile phase containing
acetonitrile and
phosphate buffer (0.05 M KH2PO4,
pH 3). The flow rate was 1 ml min(-1) in both cases. UV detection was performed in the dual wavelength mode, with 317 nm having been used for
dimefluron and all 7H-benzo[c]fluoren-7-one metabolites, 367 nm for 7H-benzo[c]fluoren-7-ol metabolites. A higher homologue of
dimefluron served as an internal standard. The identity of the
dimefluron metabolites in
biological samples was confirmed using HPLC-MS experiments. The elimination study showed that the concentration maximum for
dimefluron and its metabolites in rat faeces was reached 48 h after the administration of the parent
drug. O-Desmethylated derivatives of
dimefluron prevailed among the phase I metabolites.