High-performance liquid chromatographic determination of the 1,4-diketo and 1,4-diketo-2,3-dihydroxy metabolites of lonapalene in rat urine.
Individual high-performance liquid chromatographic (HPLC) methods have been developed for the determination of two major metabolites of lonapalene in rat urine. The highly unstable and polar 1,4-diketo-2,3-dihydroxy metabolite (II) is extracted from urine by two extraction columns (phenyl followed by silica), further purified by means of HPLC with a fully end-capped C18 HPLC column and quantified by an ultraviolet detector at 280 nm. Ascorbic acid is used as an antioxidant during extraction and overnight injection of II. Urine samples for total II (free plus conjugated) determination are incubated with arylsulfatase and beta-glucuronadase prior to extraction. The 1,4-diketo metabolite (III) is extracted from urine with a C18 extraction column, further purified with a C18 HPLC column, and quantified by an ultraviolet detector at 260 nm. The detection limit for both metabolites is 100 ng/ml of urine (signal-to-noise = 2.5). The methods were used to analyze urine samples from a long-term toxicology study of lonapalene in rats and to determine the linearity of dose-concentration relationships for both metabolites.
Kiang
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Department of Analytical and Metabolic Chemistry, Syntex Research, Palo Alto, CA 94304.
Lee
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D000818:Animals; D002851:Chromatography, High Pressure Liquid / Q000295:instrumentation / Q000379:methods*; D009281:Naphthalenes / Q000652:urine*; D051381:Rats
D009281:Naphthalenes; C045954:RS 43179