Determination And Antioxidant Evaluation Of Flavonoids Compounds From Different Citrus Cultivars

Thirty-five citrus cultivars of citrus from Zhejiang province were collected for the investigation of postharvest fruit quality,incluing weight,edible rate,color,total soluble solids(TSS),total phenolics and antioxidant capacity,etc.In addition,the composition and content of flavonoid compounds and their antioxidant activity in different citrus cultivars were studied.The flavanones and polymethoxyflavones were isolated from nine citrus cultivars and their antioxidant activity and oxidative damage activity were evaluated in vitro.The main results are as follows:1.Significant differences were observed in fruit quality indicators among 35 citrus fruit cultivars.Among them,the most red citrus cultivar is 'MTH'(16.75)and the most green citrus cultivar is 'QOG'(-6.97).We found that Pomelo was the most heavied.The edible rate of citrus is among 56.12?85.31%,the highest edible rate of citrus is 'HMR' In addition,The TSS index was evaluated and found that the 35 citrus cultivars have no significant differences(8.42?16.08 ° Brix),'KZJ'have the hightest value.2.Evaluation of total phenolic and antioxidant activity from citrus cultivars showed that the part of citrus fruit have significant differences,The total phenolic content in different citrus fruit part is flavedo>albedo>segment membrane(SM)>juice sacs(JS).The hightest content citrus is'AY30,(27.55 mg GA/g DW).The total phenolic content of albedo is among 10.35?27.15 mg GA/g DW.The total phenolic content of SM and JS were 6.27?12.56 mg GA/g DW,6.27?12.56mg GA/g DW respectively.In our study we select DPPH,FRAP,ORAC,and CUPRAC methods to evaluate the antioxidant activity of citrus cultivars,'AY30','TC','OG' showed high antioxidant activity,'DF','SW','PG,is lower 'CX' have the lowest antioxidant activity.We also found that total phenolic and antioxidant have well correlation.3.Flavonoid compounds were identified from citrus fruit by UPLC,including flavanone_and polymethoxylated flavones.The flavonoids compounds and content in different citrus cultivars have significant differences.Our study showed that flavedo have the most flavoniods,and PMFS only exist in flavedo.'AY30','TC','OG' have many PMFS such as sinensetin,nobiletin,tangeretin and SHPMF.The cultivars which have the highest content of neohesperidin is 'OG'(21.98 mg/g DW),and 'OG'could also identified poncirin.'TC'has the hightest content of Narirutin which is different from other citrus cultivars.The cultivars'HY','PTY','GC'have more flavanone,and in these cultivars we identified eriocitrin,neoeriocitrin which no identified among other cultivars.In addition,the part of citrus fruit have siginifcant difference in the content of total flavonoids,for example 'TC' flavedo content of total flavonoids is 41.24 mg/g DW,albedo,segment membrane(SM),juice sacs(JS)are82.20 mg/g DW,29.98 mg/g DW,6.99 mg/g DW,respectively.4.According to their antioxidant activity we select nine cirus cultivars from thirty-five citrus fruit.The nine citrus cultivars are divided into flavanone and PMFs with the technology of SPE.The antioxidant activity was evaluated in vitro.The result showed that flavanone has the higher antioxidant activity than PMFs.In addition fifteen flavonoids compounds were evaluated by the means of DPPH,FRAP,CUPRAC,ORAC,and found that eriocitrin,neoeriocitrin have the highest antioxidant acitivity,followed by hesperidin,neohesperidin,naringenin,hesperetin.