Comparison of starches from five plants of Sect. Stenophora Uline and Sect. Lasiophyton Uline of Dioscorea grown in China.

BACKGROUND: Dioscorea resources with vital medicinal and functional values are abundant in south-west regions of China, especially in Sichuan Province. However, the resource in this region has received less attention compared with that of the north. D. zingiberensis, D. collettii, D. kamoonensis cv. Emei and Jinfo, and D. melanophyma from Sichuan Province and Chongqing City were studied with regard to the most abundant carbohydrate (starch) to search for new medicinal and food resources. RESULTS: The starches were small round granules or small oval granules and large elongated granules, except D. zingiberensis starch granules, which were disc-like in shape. D. zingiberensis and D. collettii starches showed higher values in total starch content, water-binding capacity and infrared ratio of absorbance bands at 1047/1035 and 1047/1022 cm⁻¹. Differential scanning calorimetry analysis demonstrated a higher gelatinisation temperature required more energy during the gelatinisation process. D. zingiberensis and D. collettii starches showed higher resistant starch content of 724.0 and 693.2 g kg⁻¹, respectively, with lower hydrolysis index and estimation of glycaemic index. All the starches exhibited an A-type pattern except D. melanophyma starch, which showed a C-type pattern evaluated by X-ray diffraction. CONCLUSION: These results showed that the starches with their low hydrolysis index values possessed potential values as healthy food.

Fusarium Species and Fusarium oxysporum Species Complex Genotypes Associated With Yam Wilt in South-Central China.

Chinese yam (Dioscorea polystachya Thunb.) is an important root crop. Wilt caused by Fusarium is among the most important emerging diseases on yams. However, there is currently limited information on the molecular epidemiology of Fusarium causing yam wilt. Here, we investigated wilted yam samples from six regions in South-Central China. A total of 117 Fusarium isolates were obtained from diseased tissues of 37 wilted yam plants. These yam plants belonged to two varieties characterized by white and purple fleshy tubers, respectively. Analyses of ef1-α sequences identified that these 117 Fusarium isolates belonged to 11 putative species, with F. aff. commune being the most common (31.6%), followed by F. aff. cugenangense (29.1%), a potential undescribed species Fusarium aff. sp. (11.1%), F. aff. gossypinum (9.4%), F. aff. fujikuroi (8.5%), F. aff. nirenbergiae (6%), and one isolate each (0.85%) of F. aff. asiaticum, F. aff. curvatum, F. aff. odoratissimum, F. aff. solani, and F. aff. verticillioides. Six of these species were recently described as new species within the Fusarium oxysporum species complex (FOSC). Interestingly, 18 of the 37 yam plants were infected by two or more Fusarium species each and there was evidence for differential Fusarium species distributions based on geographic location and/or yam host variety. Multilocus microsatellite genotyping of the 67 FOSC isolates revealed that isolates of the same species from the same diseased plants often belonged to different genotypes. Interestingly, several FOSC microsatellite genotypes were shared among distinct geographic regions, consistent with long-distance dispersal. However, population genetic analyses revealed significant contributions of geographic separation to the overall genetic variation of FOSC with several pairs of geographic populations showing significant genetic differentiations, consistent with differential geographic distribution of the species within FOSC. The implications of our results to the managements of Fusarium wilt in yams were discussed.

A new indole alkaloid from bulbils of Dioscorea opposite Thunb / 药学学报

This study was designed to study the chemical constituents from bulbil of Dioscorea opposite Thunb.. Four compounds were isolated by silica gel column chromatography. On the basis of physic-chemical characters and spectroscopic data analysis, these compounds were identified as lyzalkaloid (3,4-dihydro-6-hydroxy-4-methyl-6H-pyrido[6,5-b]indol-5(1H)-one) (1), anoectochine (2), ginsenine (3), and 2-hydroxy-3-(1H-indol-3-yl) propanoic acid methyl ester (4). Compound 1 is a new indole alkaloid, named as lyzalkaloid. Compounds 2-4 were isolated from this plant for the first time. The cytotoxic activities were assessed by MTT assay. All compounds exhibited the cytotoxic activity against HepG2 and MDA-231 with IC50 values of over 100 μmol·L-1, respectively. All compounds show no significant cytotoxic activities against HepG2, MDA-231 cancer cell.

Simultaneous Determination of Four Major Steroidal Saponins in seven species of Dioscorea L.By HPLC-ELSD / 中草药·英文版

Objective To control the quality of the species in Dioscorea L. better. Methods An HPLC-ELSD method was developed for the first time to simultaneously determine four bioactive ingredients:dioscin gracillin,protoneodioscin, and protoneogracillin in 31 samples belonging to seven species of Dioscorea L. from different areas. The column was an Inertsil HILIC (250mmx4.6 mm,5pm). The separation was carried out with a gradient program. The mobile phase was acetonitrile-water at a flow rate of 0.8 mL/min. Results The standard curve was rectilinear in the range of 0.464-12.97 gg (r=0.9969) for dioscin, 0.310-7.09 ltg (r = 0.9953) for gracillin, 0.469-11.66 gg (r=0.9970) for protoneodioscin, and 0.276-6.87 gg (r＝0.9992) for protoneogracillin. The recoveries of the markers were 98.1%, 100.1%, 97.2%, and 96.4%, respectively. The contents of the four components were quite different among the seven species of Dioscorea L. Conclusion The proposed HPLC-ELSD method is convenient,fast, accurate, and applicable for simultaneous analysis of multiple bioactive components of species in Dioscorea L.for quality control, which could facilitate discovering new natural resources of steroidal saponin.