Evaluation Of Medicinal Quality Of Leaves From 53 Mulberry Germplasm Resources

Mulberry leaf is the leaf of Morus alba L.,belonging to Morus L.of Moraceae,containing rich nutrients and a variety of bioactive ingredients,such as proteins,mineral elements,vitamins,polysaccharides,polyphenols,flavonoids,alkaloids and so on,with the effect of reducing blood sugar,reducing blood fat,anti-aging,resisting virus and inhibiting the growth of pathogenic bacteria,and is classified as a Chinese herbal medicine with the properties of medicine and food by the Health Ministry.Modern pharmacological researches show that mulberry leaves have obvious pharmacological effects,and polysaccharides,alkaloids and flavonoids in mulberry leaves are the three main medicinal ingredients.In order to meet the demand for the specialized medicinal mulberry varieties during its diversified development,in this study we determined the content of polysaccharides,DNJ(1-deoxynojirimycin,the most main medicinal ingredients among the alkaloids)and flavonoids in the leaves of 51 mulberry varieties from the mulberry germplasm resources library of Southwestern University and 2 mulberry varieties from the Hetian Sericultural Research Institute of Xinjiang Uygur Autonomous Region,and then obtained separately the superior resources of every medicinal ingredient.Furthermore,subordinate function method was applied to make a comprehensive evaluation of the medicinal quality of leaves from 53 mulberry germplasm resources and varieties to screen the specialized leaf-medicinal mulberry varieties in this study.Our results also provided the materials and laid the theoretical foundation for selecting or breeding special medicinal mulberry varieties.The details are as follows.1、Determination and analysis of the content of polysaccharide from mulberry leavesIn this experiment,we converted the water-soluble sugar and total sugar in mulberry leaves into reducing sugar by hydrolysis reaction of hydrochloric acid,determined the content of reducing sugar,water-soluble sugar and total sugar of experimental mulberry leaves with DNS colorimetry,and calculated the content of mulberry leaf polysaccharides by the formula,which is ―mulberry leaves polysaccharide(%)= [mulberry leaves total sugar(%)-mulberry leaves water-soluble sugar(%)] × 0.9‖.The results showed that in leaves from 53 mulberry germplasm resources,the reducing sugar content varied from 1.58 % to 7.16 %,the highest content was Laowo;the water-soluble sugar content varied from 3.99 % to 17.44 %,the highest content was Xiqing 3;the total sugar content varied from 17.30 % to 37.19 %,the highest content was Zhenzhubai(2n=56);mulberry leaves polysaccharide content varied from 7.87 % to 23.35 %,the highest content was Zhenzhubai(2n=56).2、Determination and analysis of the content of DNJ from mulberry leavesIn this experiment,we used 0.05 mol/L HCl solution as the solvent,on the basis of 1:50 solid-liquid ratio,and extracted mulberry leaf DNJ by ultrasound assisted.The temperature of ultrasound was 30 ℃,the time was 10 min,the power was 500 W,and we extracted 2 times.After deriving,the content of mulberry leaf DNJ have been determined by UPLC-TUV according to established conditions of mulberry leaf DNJ determination by Pu Junsong.The results showed that in leaves from 53 mulberry germplasm resources,the DNJ content of Morus nigra L.was the highest,up to 3.19 mg/g,and Lunjiao 40 was the lowest which was 0.44 mg/g,and the difference was nearly 7 times between them.3、Determination and analysis of the content of total flavonoids from mulberry leavesIn this experiment,we used 70% ethanol as solvent,on the basis of 1:20 solid-liquid ratio,extracted mulberry leaf total flavonoids by ultrasound assisted,the temperature of ultrasound was 70 ℃,the time was 10 min,the power was 200 W,and we extracted 3 times,then the content was determined by colorimetric method of sodium nitrite and aluminum nitrate.The results showed that the content of mulberry leaves total flavonoids varied from 2.38 % to 5.79 % except for Morus wittiorum Hand.-Mazz.,which was the highest,and up to 8.04 % of leaves from 53 mulberry germplasm resources.4、Establishment of a comprehensive evaluation system of mulberry leaf medicinal quality and screening of dominant medicinal mulberry resourcesThe above results and analysis showed that not only the same medicinal compositions from the different resources had a significant difference,but also the different medicinal compositions from the same resource were different.It also showed that screening the special medicinal mulberry was necessary and valuable,and it provided an important database for screening the special medicinal mulberry.Referring to the methods used by Zhang Lili,Tian and Cao,we standardized mulberry leaf polysaccharide,DNJ and total flavonoids content by subordinate function,carried out a comprehensive evaluation of the medicinal quality of mulberry leaves based on the sum of the subordinate function values of the different medicinal ingredients,and then screened out superior varieties combined with cluster analysis,variance analysis and multiple comparison.Screening results showed that in the experimental mulberry leaves,Zhenzhubai(2n=56)and Jianpuzhai were superior varieties with the highest content of polysaccharide,Morus nigra L.was a superior variety with the highest content of DNJ,Morus wittiorum Hand.-Mazz.was a superior variety with the highest content of total flavonoids.The comprehensive evaluation results of the top 6 higher medicinal quality of mulberry leaves were Morus wittiorum Hand.-Mazz.,Jianpuzhai,Zhenzhubai(2n=56),Jialing 16,Morus nigra L.and Morus laevigata Wall.,and Jialing 16 was a triploid mulberry variety among them,which was a suitable candidate for a specialized leaf-medicinal mulberry variety,however the other 5 mulberries were superior varieties of medicinal mulberry resources,providing materials for selecting or breeding high-yield,good-quality and medicinal mulberry varieties.In this study,we established a comprehensive evaluation system of mulberry leaf medicinal quality by the method of medicinal quality evaluation of the traditional Chinese medicine,and provided a theoretical basis for the development of medicinal quality evaluation of mulberry resources.Then we screened out 6 dominant medicinal mulberry resources,and provided the materials for selecting or breeding special medicinal mulberry varieties further.These are of great significance to promote diversified development and utilization of mulberry,especially in medicine.