Study On Structural Identification And Stability Of Polyphenols From Daylily

Polyphenol is an important functional compound in daylily,which has a great influence on its nutritional and sensory quality during processing and storage.In this paper,fresh daylily was used as raw material,and the polyphenols of daylily were separated and purified by ultrasonic-assisted ethanol solution extraction and macroporous resin adsorption-desorption,and the structure of daylily polyphenols was identified by triple quadrupole LC/MS technique.On this basis,the stability of polyphenols during dry storage and under different physical and chemical conditions was studied.The results are as follows:(1)Using fresh daylily as raw material,the effects of ultrasonic time,ethanol concentration,solid-liquid ratio and ultrasonic temperature on the yield of polyphenols in daylily were investigated by single factor test and response surface test.The effects of temperature and ethanol concentration on the yield of polyphenols reached a significant level.The order of the influence of various factors on the yield of polyphenols in daylily was solid-liquid ratio > ultrasonic temperature > ethanol concentration > ultrasonic time;solid-liquid ratio and temperature,time and ethanol The interaction between the concentrations has an impact on the yield of polyphenols;the optimal conditions for ultrasonic-assisted extraction of polyphenols from daylily are ethanol concentration of 66%,ultrasonic time of 22 min,ultrasonic temperature of43 ℃,solid-liquid ratio of 1:12,polyphenols The yield was 2.318%.(2)The macroporous resin was used to separate and purify the polyphenols of daylily.The research showed that the HPD600 macroporous resin had better adsorption effect on the polyphenols of daylily.The effects of adsorption time,adsorption pH and adsorption temperature on adsorption rate were discussed by single factor test and orthogonal test.The optimum adsorption conditions were determined as the adsorption temperature of 50 ℃,the pH of the adsorption solution of 6,the adsorption time of 3 h,and the average adsorption rate was 28.76%.The experiment further used ethanol to desorb the polyphenolic compounds of daylily.The effects of desorption temperature,ethanol concentration,desorption pH and desorption time on the desorption rate were discussed through single factor experiments and orthogonal experiments.The results showed that the influence of various factors on the desorption rate was greatly The order is ethanol concentration>desorption temperature>desorption pH>desorption time.And the optimal desorption conditions were determined as ethanol concentration 100%,temperature 60 ℃,pH 6,adsorption time 3 h,and the average desorption rate was78.94%.(3)The structure of the purified daylily polyphenols was identified,and the three compounds of daylily polyphenols were rutin,chlorogenic acid and quercetin were analyzed by liquid chromatography-mass spectrometry.(4)The content of polyphenol monomers in fresh daylily was analyzed from high to low by HPLC/ESI-TQTOF-MS: rutin,chlorogenic acid,and quercetin;the contents of three polyphenols in four different samples were significantly different(p<0.05),the polyphenol content of daylily was significantly reduced after steam blanching,one-year storage and two-year storage.During heat treatment and storage,all three polyphenols were lost,and the most serious one was quercetin.Different pH,temperature,light,oxidant and other physical and chemical factors have significant effects on the stability of daylily polyphenols.