山药与穿龙薯蓣中尿囊素含量研究

… Significant differences in allantoin contents were observed between interspecific and intraspecific yam varieties, and allantoin contents in the four varieties of D. polystachya were …

Abstract China is an important domestication center of yams, and two main yam species of Dioscorea opposita and D. alata are commonly cultivated in China. However, the differences of nutritional and medicinal characteristics between the two species and their subgroups remain unclear, which would greatly affect the resource conservation and commercial utilization of yams. In this study, typical yam resources including the species of D. opposita (wild and cultivated Ruichang yam from southern China, and Tiegun yam from northern China) and two landraces of D. alata (Longyan yam and Anyuan yam from southern China) were selected as materials. Nutritional traits and medicinal characteristics were determined and analyzed respectively. The results showed that there was no significant differences in the content of most nutrients between D. opposita and D. alata, but most cultivated Ruichang yam of D. opposita showed higher levels of starch, soluble sugar, sucrose, and ascorbate in tuber than that in yam from D. alata. Moreover, an UPLC-MS method was developed for identification and determination of medicinal characteristics in the two species. The results showed that allantoin can be detected in all selected samples. Cultivated Ruichang yam of D. opposita possessed the highest allantoin content among the tested materials, and was significantly different with that in Tiegun yam and D. alata. Dioscin was not detected in D. alata. Overall, there was little difference in nutritional composition between D. opposita and D. alata, but the medicinal quality of D. opposita was better than that of D. alata. Due to the outstanding comprehensive quality, the local variety of cultivated Ruichang yam can be further developed and utilized.

Abstract Wild yams (Dioscorea spp.) are medicinal plants rich in secondary metabolites of pharmacological interest, mostly allantoin and steroidal saponins. Their natural populations are overexploited and endangered. Cultivated yams could represent an alternative source of metabolites if interesting varieties could be selected. The objectives of the present study were to develop an HPTLC protocol for the simultaneous quantification of allantoin and steroidal saponins in dried yam powders, to compare species and varieties originating from distant geographical origins and to assess their potential as a source of secondary metabolites. Overall, 1151 accessions belonging to six cultivated species were analysed (1000 acc. from Nigeria, and 146 acc. from Vanuatu) and were compared to five commercial powders of wild yam (D. villosa). Allantoin, dioscin, gracillin, protodioscin, protogracillin and five unknown saponins were quantified. Dioscorea villosa powders varied in content and composition, with allantoin ranging from 0.23 to 22.35 mg/g (DW) and total saponins from 37.36 to 129.97 mg/g. Allantoin was present in the six species, with highest values in D. bulbifera bulbils (20.38 mg/g) and D. cayenensis tubers (17.12 mg/g). Steroidal saponins were quantified in three species, D. cayenensis, D. esculenta and D. rotundata, but were absent in D. alata, D. bulbifera and D. dumetorum. Mean total saponins contents were 42.15 mg/g in D. cayenensis, 17.65 mg/g in D. esculenta and 17/44 mg/g in D. rotundata, with accessions presenting very high values in D. cayenensis (78.31 mg/g) and D. rotundata (69.65 mg/g). For both allantoin and saponins, variation was observed within tubers and the tuber peel was richer than the flesh. Cultivated yam species represent a sustainable source of allantoin and steroidal saponins which could be further increased through conventional breeding.