Analysis Of Carotenoids In Sweetpotato Leaves

Sweetpotato is cultivated widely in China,and sweetpotato leaves have been used as waste for years.However,a few recent researches showed that important bioactive ingredients-carotenoids exist in the leaves of sweetpotato.In order to guide the cultivation of sweetpotato and make the best use of its leaves,in this paper the method of analysis of lutein in sweetpotato leaves was established,and the parameters for extracting carotenoids was also optimatized.Additionaly,effects of drying method of leaves and different light intensity during the growth of sweetpotato on the content of carotenoids in leaves were also investigated.The results were as follows:(1) Based on the option of the detection wavelength and ingredients of mobile phase, evaluation of the linear relationship,precision and reproducibility,stabilization and recovery experiments,the HPLC analysis method for lutein was established:column:SunFire^TM C₁₈ (150mm×4.6mm,5μm),detection wavelength is 445nm,the mobile phase is methanol:water = 95:5(V/V) and the flow-rate is 0.8mL/min.This method is sensitive,accurate and reliable for lutein determination in sweetpotato leaves.Significant difference in the content of lutein in the leaves of eight sweetpotato breeds was found,and the highest level is found in "Sushu 8".(2) With the combination of ultrasonic extraction and spectroscopic analysis,the optimum extraction conditions for total carotenoids were studied according to the orthogonal design based on the experiment of single factor.The optimum extracting conditions are:the ratio of solid to liquid:1:60,20%methanol,and treating with ultrasonic wave for 40min at 25℃.Significant differences of content of total carotenoids were found in leaves of eight sweetpotato breeds,and the highest level is 336mg/kg DW in "Sushu 8".(3) Vacuum and microwave drying methods are prior to sun,shade and oven drying in avoiding the loss of lutein and the carotenoids in the leaves of sweetpotato.Weakening the light intensity modestly was found to enhance the accumulation of total carotenoids in sweetpotato leaves.