Analysis of nutritious compositions in Rhizoma Dioscoreae from different varieties and antioxidant properties of their water extracts in vitro

Objective:The nutrient composition of different varieties of Rhizoma Dioscoreae was determined to differentiate the difference of its composition,which may provide some basis for the study of nutritional value,reasonable development and utilization of resources and research of varieties. Method:The nutritious compositions of protein,amylum,amino acids,polysaccharide,trace element and flavonoids from different varieties were determined by Kjeldahl nitrogen determination,acid hydrolysis,anthracene copper-vitriol colorimetry,flame atomic absorption spectrometry and so on. Moreover,the water extracts were prepared with three kinds of Rhizoma Dioscoreae as raw materials and the total reducing power,inhibition rate of OH· and DPPH· of water extract were analyzed in vitro,respectively. Results:The results showed that amino acids,protein,amylum,polysaccharide content of D. batatas"Qi"were 1601.7 mg/100 g,10.62%,22.0% and 7.42%,respectively. Trace element content of ferrum,copper,cobalt,kalium and flavonoids was 1.089 mg/g,0.371 mg/g,0.257 mg/g,2.011 mg/g and 2.48%,respectively. Total protein,amino acids and amylum contents were much higher(p<0.05)than those of Dioscorea opposita Thunb.cv.Tiegun and Dioscorea oppostita Thunb. The results showed that amino acids,protein,amylum,polysaccharide,flavonoids content of Dioscorea opposita Thunb.cv.Tiegun were 1058.0 mg/100 g,4.24%,15.2%,9.26%,4.06%,respectively.Trace element content of calcium,zinc,magnesium and sodium was 7.484,0.449,2.067 and 0.359 mg/g,respectively. Thus the polysaccharides and flavonoids was the richest in Dioscorea opposita Thunb.cv.Tiegun. While amino acids,protein,amylum,polysaccharide,trace element phosphorus,flavonoids content of Dioscorea oppostita Thunb were 967.3 mg/100 g,5.76%,18.4%,8.68%,0.457 mg/g,3.80%,respectively. Its nutritious compositions were balanced. Moreover,the different Rhizoma Dioscoreae possess different antioxidant activities. Total reducing power:V_C > D. batatas "Qi" > Dioscorea opposita Thunb.cv.Tiegun > Dioscorea oppostita Thunb. Inhibition rate of OH·:V_C > D.batatas "Qi" > Dioscorea opposita Thunb.cv.Tiegun > Dioscorea oppostita Thunb. Inhibition rate of DPPH·:V_C > Dioscorea opposita Thunb.cv.Tiegun > D.batatas "Qi" > Dioscorea oppostita Thunb. Conclusion:D. batatas"Qi"was a delicious food with characteristics of high contents of protein and amylum. Dioscorea opposita Thunb.cv.Tiegun could be used as medicine due to its high contents of polysaccharide and flavonoids. Dioscorea oppostita Thunb could be food as well as medicine due to its balanced nutrition. The water extracts of three kinds of Rhizoma Dioscoreae had certain antioxidant effect in vitro.