Study On Extraction And Antioxidant Capacity Of Phenolic Compounds In Leaves Of Different Blueberry Cultivars

Blueberry leaves are rich in phenols,which have the functions of anti-oxidation,anti-virus,anti-inflammation,prevention of cardiovascular disease,anti-tumor and antidiabetes.However,the lack of utilization of blueberry leaves results in waste of resources.In this paper,six cultivars of blueberry leaves were used as materials and four phenolic extraction solvents were used to seek for suitable solvents for extraction,blueberry cultivars with high phenolic content and strong antioxidant capacity,and an optimized extraction process of phenolic compounds in blueberry leaves.Identification and quantification of flavonoids in blueberry leaves by UPLC-MS/MS was used to explore the changes of phenolic compounds and antioxidant activity in different growth stages of blueberry leaves.The results of this study provide a theoretical basis for the development and utilization of phenolic compounds especially flavonoids in blueberry leaves,and are of great significance for the value improvement of blueberry products,increasing economic benefits,and reducing resource waste.(1)Four kinds of extraction solvents were used to extract the phenolic compounds in six cultivars of blueberry leaves.The results showed that there were significant differences(P<0.05)between four solvents in the extraction of phenols from blueberry leaves,and the order from high to low was:DESs2(choline chlorideglycerol),acidified ethanol,DESs1(choline chloride-oxalic acid),water.There were significant differences in the content of phenolic compounds in the leaves of different cultivars of blueberry(P<0.05).The total phenolic content was in the order of’Legacy’,’Gardenblue’,’Britewell ’,’Primadonna,’,’Emerald’,’Bluegold’,The order of total flavonoid content was s ’Gardenblue ’,’ Britewell’,’Legacy’,’Primadonna,’Bluegold’ and ’Emerald ’.(2)The antioxidant activities(DPPH,ABTS,FRAP)of extracts from six blueberry cultivars using four solvents were determined by UV-Vis spectrometer.The results showed that the antioxidant activity of extract by DESs2 was significantly higher than that of acidified ethanol,DESs1 and water.There were significant differences in antioxidant activity among different cultivars of blueberry leaves(P<0.05).The antioxidant activity in the extract of ’Legacy ’was significantly higher than that of’Gardenblue’,’Britewell’,’Primadonna,’Bluegold’ and ’Emerald ’.(3)The correlation of total phenolic content,total flavonoid content and antioxidant activities(DPPH,ABTS and FRAP)was analyzed.The results showed that there was a significant positive correlation between total phenolic content,total flavonoid content and DPPH,ABTS,FRAP in extracts from blueberry leaves(P<0.05).(4)The leaves of ’Legacy ’blueberry were used as materials to extract phenols by DESs2 solvent,and the main extraction process parameters were optimized by response surface analysis.The optimum extraction process was as follows:water content 16.80%,solid-liquid ratio 1：50 g/mL,extraction times 1.73,ultrasonic time 50.00 min.The total phenolics and total flavonoids were 198.30 mg GAE/g DW and 315.56 mg RE/g DW,respectively.The quadratic multiple regression model of total phenols and total flavonoids in blueberry leaves was established.(5)With ’Legacy’ and ’Gardenblue ’as experimental materials,the leaves were extracted by the optimized extraction process,and the phenolic content and antioxidant activity of blueberry leaves at different growth stages were determined.The results showed that the phenolic content and antioxidant activity of the old leaves of ’Legacy’ and ’Gardenblue’ blueberries were significantly higher than those of mature leaves and young leaves.(6)The flavonoid compounds in blueberry leaves were isolated and identified by ultra-high performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS).The results showed that the main components of flavonoids in blueberry leaves were flavonols and anthocyanins.