The content of soyasaponin and soyasapogenol in soy foods and their estimated intake in the Japanese

Soyasaponins have been reported to promote various health functions. However, the total soyasaponin and soyasapogenol content in soy products and the daily intake remain to be fully elucidated. We developed a high-performance liquid chromatography coupled with tandem mass spectrometric (HPLC-MS/MS) method to evaluate the content of group A and B soyasaponins and soyasapogenols. The total soyasaponin content was measured after pretreatment converted soyasaponins to soyasapogenols. The total soyasaponin content in soy foods was 200-1800 nmol g(-1), although that of soy sauce was 2-7 nmol g(-1). The soyasapogenol to total soyasaponin ratio was 30-50% in long-term matured miso. The majority of the soyasapogenol detected was soyasapogenol B rather than soyasapogenol A, resulting in speculation that further steps are required to liberate aglycones from glycoside-conjugated soyasaponins in soyasapogenol A. We estimated the daily intake of total soyasaponins and soyasapogenols by the Japanese, which was 50.3 and 0.59 μmol, respectively. The soyasapogenol content and the soyasapogenol to total soyasaponin ratio was considerably low in most soy products, except for long-term maturated miso. The major source of the daily intake of soyasaponins and soyasapogenols were tofu and miso, respectively.