Studies On The Starch Characterization And Modification Isolated From Medicinal Plants In Dioscorea Linn.

There are about60kinds of plants in Dioscorea Linn.(Dioscoreaceae). Amongthese plants, most of them possessed essential medicinal and economic values. Themain active ingredients in the medicinal part-rhizome are saponins, polysaccharides,protein, crude fiber and so on. However, starch, accounting for20%~60%of the dryweight, received little attention. Therefore, starch in medicinal plant became a hotpoint in Pharmacognosy and Natural Product Chemistry area. In addition, there aremany plants with the same common name but possessed different lartin name andmore plants discovered in recently years both resulted in confusion in medicinal plantapplication. Starch research on plant relationship could provide valuable evidence formorphological taxonomy, chemotaxonomy and molecular biology taxonomy. In orderto make full use of the medicinal plants and expanse utilization of the starch, differentvarieties and species were collected and hydrolyzed starches were prepared andinvestigated.For the first time, starch from14kinds of plants (Commom name: yam) of Sect.Enantiophyllum in Dioscorea L. were collected and compared in its properties andcharacterisations. It was found that the yam starches from Sichuan and GuangxiProvince displayed B-type pattern from XRD results. Acoording to cluster analysis,the plants were separated into two parts based on properties including thephysio-chemical properties, microstructure, thermal properties, crystalline properties,starch nutrition, hydrolysis index and glycemic index. Then, starches of15kinds frommedicinal plants of Sect. Stenophora Uline, Sect. Combilium Prain et Burkill, Sect.Lasiophyton Uline and Sect. Opsophyton Uline were compared on the properties andcharacterization. From the results of XRD, A-type pattern is common in Sect.Stenophora Uline except D. septemloba Thunb. starch. C-type starch is commom inSect. Combilium Prain et Burkill and Sect. Opsophyton Uline, while A-type starch iscommon in Sect. Stenophora Uline. The results of preliminary cluster analysis wasconsistent with Dioscorea plants evolutionary based on chromosome karyotype. Afterthe alkaline and glucoamylase treatment, C-type starch displayed the same hydrolysismode, degradating from interior to exterior. B-type polymorphs in the core of C-typestructure was gradually degraded with peak at17°2θ split into two small peaks, which was the typical characteristic of A-type starch. Moreover, adhesion amongsome of the starch granules was observed after alkali-treatment for30days in D.zingiberensis and D. opposita starches. Study on starches from Dioscorea plantsprovide the new resouces for starch, filling a gap in medicinal plants. The results alsoprovide evidence from macromolecules for plants relationaship.