Basic nutritional investigationComparison of bioavailability (I) between soyasaponins and soyasapogenols, and (II) between group A and B soyasaponins

ObjectiveThe bioavailability and absorption of soyasaponins and soyasapogenols remain unclear; therefore, the aim of this study was to evaluate plasma soyasaponin and soyasapogenol concentrations and absorption characteristics.MethodsSprague-Dawley rats were divided into three groups (n = 6), and each group was orally administered a single dose of each test sample. Blood was collected from the cervical vein and plasma soyasapogenol concentrations were measured. A Caco-2 cell monolayer absorption assay was performed in which both soyasapogenol A and B (10 μmol/L) were added to the apical side, and soyasapogenol concentrations on the apical and basolateral sides were determined. Permeability parameters also were calculated.ResultsAbsorption of soyasapogenol B was better than that of group B soyasaponins. The time needed to reach peak soyasapogenol B concentration in rats administered soyasapogenol B was 1 to 3 h, whereas that in rats administered group B soyasaponins was 8 h. The ratio of plasma soyasapogenol A to plasma soyasapogenol B was lower than the ratio in the test samples administered. The apical-to-basolateral absorption of soyasapogenol B in the Caco-2 human colon cancer monolayer cell model (apparent permeability coefficient [Papp], 5.5 × 10−6 cm/sec) was higher than that of soyasapogenol A (Papp, 1.6 × 10−6 cm/sec).ConclusionThese results suggest that bioavailability of soyasapogenols is better than that of corresponding soyasaponins and that of group B soyasaponins is better than that of group A soyasaponins.