Identification And Determination Of Flavonoids From Different Citrus Cultivars Fruit And Their Antioxidant Activity

Citrus is the world’s largest fruit and also the second largest fruit grown in China.China has a vast territory and a variety of climates suitable for citrus cultivation.Citrus has evolved a rich variety of resources in its long history of cultivation.Flavonoids are widely found in citrus plants.In this paper,23 varieties of citrus fruits were selected as materials,technologies such as LC-MS were used to carry out related research.The main results are as follows:1.Different varieties of citrus differed in single fruit weight,pulp ratio and TSS.The average fruit weight of pomelo was higher,among which’Shatianyou’ has the highest single fruit weight,which was 2315.10 g,and the other class ’Buddha’ was 333.86 g.The pulp ratio is between 56.23%and 84.00%,’Guangpijinju’ was the lowest while ’Xinhuitianju’ was the highest;the TSS of different varieties are distributed at 8.23 °Brix～19.89 °Brix.the highest value was’Guangpijinju’(19.89 0Brix),the lowest value was ’Xinhuitianju’(8.23 °Brix).2.There are significant differences in total phenolic content and antioxidant activity in different parts of citrus’different varieties.Among the 23 citrus varieties,the total phenolic content of the flavedo was significantly higher than that of the albedo,the segment membrane and the juice sacs:the total phenolic content of the flavedo varied from 4.38 mg GAE/g DW to 21.10 mg GAE/g DW,among which the highest value was ’Taoyecheng’,and ’Aiyuan 38’had the lowest value.The total phenolic content in the albedo was distributed in the range of 1.75 mg GAE/g DW～17.37 mg GAE/g DW,and the highest total phenolic content was’ Daidai’ while the lowest variety was’ Buddha’;the total phenolic content of the segment membrane was distributed in the range of 4.86 mg GAE/g DW～11.37 mg GAE/g DW;in the juice sacs,the total phenol content was in the range of 2.73 mg GAE/g DW～7.92 mg GAE/g DW.The antioxidant capacity varied among different varieties of citrus.From the perspective of the composite index of antioxidant capacity,the most resistant varieties of flavedo,albedo,segment membrane and juice sacs were’Bendizao’,’Mashuiju’,Daidai’ and ’Majiayou’;the weakest were’Shatianyou’,’Foshou’,’Xinhuitianju’ and ’Shatangju’.Correlation analysis between total phenolic content and antioxidant capacity showed that total phenol was significantly and positively correlated with antioxidants in flavedo,albedo and segment membrane.3.Using the LC-MS to identify the flavonoids in the fruit of 23 citrus varieties,this experiment identified a total of 53 kinds of flavonoids,including 5 kinds of flavonoid-C-glycoside,4 kinds of flavonoid-O-glycoside,12 kinds of flavanone-O-glycoside,32 kinds of polymethoxyflavone(PMFs).Compared with the existing literature,two flavonoids,phloretin-3’,5’-di-C-glucoside and hesperitin-7-O-rhamonoside,are reported for the first time in citrus.4.Identification and quantification of flavonoids in various parts of 23 citrus varieties,we found out that the content of 37 substances in the flavedo were the higher than other parts.The polymethoxyflavonoids are only detected in the flavedo.The main flavanones contained in the flavedo are eriocitrin,neweriocitrin,narirutin,hesperidin,and didymin.The main polymethoxylflavonoids in the flavedo are nobiletin,tangeretin,5HPMF and sinensetin.5.Using 25 kinds of flavonoids,including neoericitrin,naringin,narirutin,hesperidin,neohesperidin,hesperidin-7-O-glycoside,isosinensetin,senensetin,tangeretin,5HPMFs,monohydroxytetramethoxyflavone,monohydroxytrimethoxyflavone,tricin,pentamethoxyisoflavone,tetramethyl-O-isoscutellarein,Hexa-O-methylgossypetin,tetramethyl-O-scutellarein,5,4’-dihydroxy-3,7,8,3’-tetramethoxyflavone and so on,as character substance,we can classify our collected citrus varieties into Citrus reticulate,Citrus maxima,Citrus sinensis and Citrus hybrid.