Abstract
To examine the seasonal changes of the sapogenins contained in Dioscorea tokoro MAKINO, third-year plants were cultivated on an experimental farm. Rhizome weight started to increase at the end of August, when rapid shoot growth was arrested. Rhizome enlargement was not observed in female plants. The concentrations and quantities of the sapogenins differed with the morphological part of the plant and the month of harvest. Yonogenin quantities in leaves and flowers continued to increase until the end of summer, after which its concentration was maintained in the leaves but decreased rapidly in the flowers. Most of the yonogenin in the aerial parts was degraded or transformed into other substances during September and November. Tokorogenin was present at much lower concentrations in all parts and at all times. Diosgenin was generally found in the rhizome as sugar-bound saponins, and at markedly high levels during August and October. However, four of the 84 plants used contained large quantities of diosgenin in the leaves and flowers.
