Sensitive high-performance liquid chromatographic method for the determination of the lactone form and the lactone plus hydroxy-acid forms of the newcamptothecin derivative DX-8951 in human plasma using fluorescence detection

A sensitive quantitation of the lactone form and the lactone plus hydroxy-a cid forms of DX-8951, a camptothecin derivative, in human plasma has been i nvestigated by high-performance liquid chromatography (HPLC). This assay me thod consisted of two analytical procedures. In Procedure I, the lactone fo rm; was collected by the stepwise separation on a C-18 cartridge. In Proced ure II, the lactone plus hydroxy-acid forms were collected using another ba tch of the plasma sample by co-elution of the two forms from a C-18 cartrid ge with acidic solution. The hydroxy-acid form of DX-8951 was quantitated f rom the difference of the lactone plus hydroxy-acid forms and the lactone f orm. Thereafter, these pre-treated samples were assayed by HPLC under the s ame HPLC conditions with a spectrofluorometer and a reverse-phase ODS colum n. The mobile phase was acetonitrile/0.05 M potassium dihydrogen phosphate (pH 3) (18:82, v/v) at a flow-rate of 1.0 ml/min. For the assay of the lact one form and the lactone plus hydroxy-acid forms of DX-8951 in plasma, anal ytical method were validated over the range 0.2-50 ng/ml. (C) 2000 Elsevier Science B.V. All rights reserved.