CHANGES IN SAPONIN COMPOSITION OF Dioscorea zingiberensis C. H. WIGHT TUBERS UNDER DIFFERENT STORAGE CONDITIONS

Efficient storage of large amounts of fresh Dioscorea zingiberensis C. H. Wright (DZW) tubers with the minimum loss of useful components is important in diosgenin production. In this study, the components changes, in particular the saponins change of DZW tubers during storage in four different conditions were investigated. Saponins were preliminarily identified through liquid chromatograph-mass spectrometer (LC-MS). Results revealed that plant endogenous enzymes, compared with the other factors concerned most significantly affected diosgenin yield by modifying the composition and content of steroidal saponins. Glycosyl transferase, a plant endogenous enzyme, converted furostanol glycoside to its spirostanol type. Some glycosidases further participated in the biodegradation of polysaccharides at the C-3 position to their corresponding secondary glycosides. Moreover, the environmental microbes also played an important role in DZW tuber storage by secreting enzymes with similar functions. It exhibited some synergistic effect with the plant endogenous enzymes in affecting the components of DZW tubers during storage. This work, to the best of our knowledge, presented the first relatively systematic study of the effects of plant endogenous enzymes and environmental microbes on the storage of DZW tubers, and could provide a preliminary theoretical guidance to the volume storage of fresh DZW tubers in industry.