Research Of Dioscorea Alata Extract Antioxidant Properties Abstract

Yam (Diosoreaceae Dioscorea), commonly known as Huai Shan or potato, was anefficient cash crop. Yam has great development potential for its nutrient-rich, variety,availability for medicinal, staple or non-staple food. Dioscorea alata was a native Keelungyam of Taiwan Province and its derivatives. The natives love eating Dioscorea alatabecause it is rich in protein, vitamins, starch and minerals. In this paper, Dioscorea alatawas chosen as raw material, the main influence factors during processing were discussed,and its functions were evaluated. The main results were as follows:Dioscorea alata, with high content of water, was rich in microelement and its mainfunctional ingredientts, polysaccharides, saponins and polyphenols, while it was low inprotein, ash, cellulose. The content of water in yam peal and meat was86.02%,80.23%;its protein, fat and fiber content were lower relatively; Yam had high content of potassium,manganese, copper, iron, zinc,which were1.13%、3.55%、2.22%、1.49%、2.48%in peal,and1.02%、3.28%、2.02、1.81%、3.13%in yam meat. The content of polysaccharides was6.22%in peal and3.32%in yam meat, while saponins content was0.11%and0.08%,polyphenols content was3.8%and1.1%, respectively.Ethanol extraction technology of extracting polyphenols from Dioscorea alata wasinvestigated. During the extracting process, three main factors including the concentrationof ethanol, ratio of solid to liquid, exacting time were studied by using single factoranalysis method. Employing response surface methodology (RSM), the optimumtechnological conditions for extracting polyphenols in yam peal were obtained as ethanolvolume fraction of50.07%, solid-liquid ratio of1:10.89, extraction time57.08min, and thecontent of total polyphenols in this condition was4.33±0.26mg/g, while the optimumextraction conditions in yam meat were ethanol volume fraction of51.33%, solid-liquidratio of1:9.01, extraction time59.33min, and the content of total polyphenols in thiscondition was1.28±0.13mg/g.The effects of drying and extraction processes on the antioxidant activities of differentparts of yam were studied. Generally speaking, freeze-dried yam maintained higherantioxidant activities than hot air-dried, the peel had more than the meat. Among three extraction methods,50%ethanol extraction was the best, and room temperature waterextraction is better than hot water extraction. Results showed that heat treatmentsignificantly reduced antioxidant capacity of yam, so yam peal should be kept duringprocessing and avoid high-temperature heating.By HPLC analysis of the composition and content of polyphenols in yam, resultsshowed that the major polyphenols of the extraction was chlorogenic acid.The antibacterial activity of ethanol extracts and its inhibitory effect on intracellularreactive oxygen species generation was tested. It was concluded that extracts can inhibitStaphylococcus aureus and Escherichia coli significantly; minimum inhibitoryconcentration of freeze-dried yam meat against Staphylococcus aureus was0.13%andEscherichia coli was0.03%. And the extract at low concentrations10ppm can significantlyreduce the generation of ROS, had effective antibacterial and antioxidant activity,indicating its value of further development and utilization.