RADIOIMMUNOASSAY FOR A NOVEL LIGNAN-RELATED HYPOCHOLESTEROLEMIC AGENT, S-8921, IN HUMAN PLASMA AFTER HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHYPURIFICATION AND IN HUMAN URINE AFTER IMMUNOAFFINITY EXTRACTION

The novel compound ylvaleryl)-4-hydroxy-6,7,8-trimethoxy-2-naphthoate (S-8921) has hypocholesterolemic activity in animals and is expected t o exhibit a similar activity in human. Reversed-phase high-performance liquid chromatography (HPLC) separation followed by radioimmunoassay (RIA) for human plasma samples (HPLC-RIA) and immunoaffinity extractio n (IAE) followed by RIA for human urine samples (IAE-RIA) were develop ed for investigation of S-8921 behavior in clinical studies. For the R IA, antisera from rabbit and a radioiodine-labelled S-8921 were prepar ed by immunizing a conjugate of S-8921 with bovine serum albumin and b y the Bolton and Hunter method, respectively. HPLC-RIA using a semi-mi cro column was very sensitive, that is a 0.05 ng/ml limit of quantitat ion in human plasma, and specific for unchanged form of S-8921. IAE-RI A using a centrifugal filtration tube completely eliminated the matrix effect of human urine, and was very feasible. The limit of quantitati on was 0.10 ng/ml. RIA detection following HPLC or IAE proved to be ve ry useful for the pharmaceutical analysis of extremely low drug concen trations in body fluids. (C) 1997 Elsevier Science B.V.