Time-resolved fluoroimmunoassay for plasma enterolactone

We present a method for the determination of the lignan enterolactone in pl asma (serum), This compound, produced by intestinal bacteria from matairesi nol and secoisolariciresinol in fiber-rich food, is a biomarker related to the intake of a healthy diet. The method is based on time-resolved fluoroim munoassay using a europium chelate as a label. After synthesis of 5'-O-carb oxymethoxy-enterolactone the compound is coupled to bovine serum albumin an d then used as antigen in immunization of rabbits, The tracer with the euro pium chelate is synthesized using the same 5'-derivative of enterolactone, After enzymatic hydrolysis and ether extraction the immunoassay is carried out using the VICTOR 1420 multilabel counter (Wallac Oy, Turku, Finland). N o antiserum cross-reactivity with available lignans, isoflavonoids, or flav onoids could be detected. The intraassay and interassay coefficients of var iation at different concentrations vary 4.6-6.0 and 5.5-9.9, respectively. The working range of the assay is 1.5-540 nmol/liter. We measured enterolac tone in serum/plasma of 224 Finnish subjects: 98.8% of the subjects had val ues <100 nmol/liter, 38.0% had 20-39.9 nmol/liter, and 34.4% had <20 nmol/l iter. (C) 1998 Academic Press.