Effect of harvest time on saponins in yam (Dioscorea pseudojaponica Yamamoto)

Steroidal saponins including furostanol and spirostanol glycosides are the important bioactive compounds in yams. In the study, the content of individual saponin in varied organs of yam (Dioscorea pseudojaponica Yamamoto) harvested from November to March of the next year (the harvest season) were determined. Results showed that total saponin levels in yam organs (except rhizophor) harvested at various time were in the order: January > December > February > November > March. Saponin contents in rhizophor gathered in December were higher than those obtained in January. The highest total amounts of saponins among various organs were in the order: tuber cortex (619.79 μg/g dw) > tuber flesh (247.84 μg/g dw) > rhizophor (32.19 μg/g dw) > leaf (26.57 μg/g dw) > vine (25.06 μg/g dw).