Determination of dimethyl-4,4 '-dimethoxy-5,6,5 ',6 '-dimethylene dioxybiphenyl-2,2 '-dicarboxylate in human serum by high performance liquid chromatography

Dimethyl-4,4'-dimethoxy-5,6,5',6'-dimethlene dioxybiphenyl-2,2'-dicarboxyla te (DDB) has been shown to improve liver function in chronic hepatitis pati ents. Despite the fact that the oral bioavailability for DDB appears to be low and variable, the intestinal absorption of the drug is not well underst ood because of the lack of sensitivity and inadequate separation of DDB fro m endogenous peaks derived from the serum in previously developed HPLC assa ys. The present study describes a reliable HPLC method for DDB in serum sam ples for normal dose human bioavailability trials. A. deproteinated serum s ample was subjected to a solid-phase extraction procedure. The residue df t he Sep-Pak eluent was reconstituted in acetonitrile and an aliquot was dire ctly injected onto an octadecyl silica column (4 mu m, 250 x 4.5mm I.D.). T he mobile phase consisting of acetonitrile and water (52.5% acetonitrile in water, v/v), was delivered at a now rate of 1ml/min, and DDB elution from the HPLC column was monitored by UV absorption at 278nm. The assay was line ar in the range of 5-100ng DDB/ml serum with inter-day and intra-day variat ion less than 14.3 and 13.2 %, respectively. To determine whether the HPLC assay can be utilized in normal dose bioavailability studies, human serum s amples (1ml each) were obtained from a typical normal dose bioavailability study (oral capsule for DDB; 15 mg as DDB) and analyzed for DDB. The drug w as readily detectable in all samples from 30min to 720min after administrat ion. Therefore, these data indicate that this HPLC assay is readily applica ble to a normal dose pharmacokinetic study of DDB in human subjects.