TY - JOUR T1 - Absolute Oral Bioavailability and Metabolic Turnover of β-Sitosterol in Healthy Subjects JF - Drug Metabolism and Disposition JO - Drug Metab Dispos SP - 2026 LP - 2030 DO - 10.1124/dmd.112.046623 VL - 40 IS - 10 AU - Guus Duchateau AU - Brett Cochrane AU - Sam Windebank AU - Justyna Herudzinska AU - Davindera Sanghera AU - Angela Burian AU - Markus Müller AU - Markus Zeitlinger AU - Graham Lappin Y1 - 2012/10/01 UR - http://dmd.aspetjournals.org/content/40/10/2026.abstract N2 - The metabolic turnover, absolute oral bioavailability, clearance, and volume of distribution for β-sitosterol were measured in healthy subjects. [14C]β-Sitosterol was used as an isotopic tracer to distinguish pulse doses from dietary sources and was administered by both oral and intravenous routes. The administered doses of [14C]β-sitosterol were in the region of 3 to 4 μg, sufficiently low as not to perturb the kinetics of β-sitosterol derived from the diet. Because the plasma concentrations of [14C]β-sitosterol arising from such low doses were anticipated to be very low, the ultrasensitive isotope ratio analytical method of accelerator mass spectrometry was used. The limit of quantification for [14C]β-sitosterol was approximately 0.1 pg/ml, the oral absolute bioavailability was just 0.41%, clearance was 85 ml/h, volume of distribution was 46 L, and the turnover was 5.8 mg/day. Given the steady-state concentrations of β-sitosterol (2.83 μg/ml), then the dietary load was calculated to be approximately 1400 mg/day. ER -