Compositions And Biological Activities Of Phenolic Compounds Of Tartary Buckwheat

This article studies the content and composition of phenolic,flavonoids（free phenolic,bound phenolic,free flavonoids,bound flavonoids）,and antioxidant activity in different environments of tartary buckwheat,and also analyzes the dynamic changes ofγ-aminobutyric acid content in tartary buckwheat germination and different growth stages of different organs,that to be able to screen out high-quality tartary buckwheat varieties and rationally use tartary buckwheat resources.The study was to analyze the content of polyphenols and flavonoids,49 Tartary buckwheat varieties planted in the low-elevation regions of the Jianghan Plain of Hubei.The contents of free,bound and total phenolics and flavonoids were determined and the antioxidant activities of their seed extracts were analyzed in vitro using the DPPH free radical,ABTS free radical and iron ion reduction antioxidant（FRAP）assays.And the phenolic compositions of the seed extracts were determined by the high performance liquid chromatography（HPLC）.The contents of free flavonoids and free phenolics were 13.36-34.95 mg/g and 10.10-29.34 mg/g,respectively,accounting for 90.98%and79.44%of the total flavonoids and total phenolics,so polyphenols and flavonoids mainly exist in free form.The phenolic substances in tartary buckwheat grains are mainly composed of rutin,quercetin,epicatechin,kaempferol,kaempferol-3-rutinoside,and quercetin-3-O-rutinoside-3’-O-glucopyranoside It is composed of flavonoids such as glucoside,among which free phenolic is mainly rutin and quercetin,and bound phenolic is mainly epicatechin and rutin.The trend of the three antioxidant activities of49 tartary buckwheat variety extracts was consistent,and the main source of antioxidant activity was the free extract.The bound antioxidant activity was relatively small,and the correlation analysis showed that the tartary buckwheat variety’s antioxidant activity Significantly correlated with the content of polyphenols and flavonoids.Therefore,high-nutrition tartary buckwheat varieties were screened based on the content and composition of polyphenols and flavonoids to meet market food processing and production requirements.Phenolic content and composition and antioxidant activities and dynamics of γ-aminobutyric acid in tartary buckwheat sprouts after germination were investigated by such chemical techniques as high-performance liquid chromatography with the tartary buckwheat variety of Zhaoku 2.The results showed that the content of polyphenols,flavonoids andγ-aminobutyric acid increased significantly during the germination of tartary buckwheat grains to the formation of sprouts,and the contents of total phenolic,total flavonoids andγ-aminobutyric acid increased rapidly during germination 2 to 6 days,reaching 109.27 mg/g,137.73 mg/g,and 6.37 mg/g at the 6th germination day,respectively.Herein,the contents of free phenols and flavonoids tended to vary consistently with the phenol and flavonoid totals,being 4.08 and 4.53times those in tartary buckwheat seeds at the 6^th germination day,respectively and the content ofγ-aminobutyric acid was 4.46 times those in tartary buckwheat seeds at the6^th germination day.The contents of bound phenols and flavonoids were significantly increased in sprouts after germination but were relatively lower than the contents of free phenols and flavonoids in seeds before germination.There were six flavonoids identified in the seed extracts of tartary buckwheat before and after germination by HPLC.The main flavonoids in the free extracts mainly were rutin and quercetin of which the content of rutin slowly increased 6-7 days after seed germination,reaching50.80 mg/g at the 6th germination day,and the content of quercetin was continuously reduced after the 1st germination day.The main flavonoids in the bound extracts were epicatechin and rutin.The DPPH free radical method,ABTS free radical method and iron ion reduction antioxidant method（FRAP）were used to comprehensively evaluate the antioxidant activities of tartary buckwheat extracts at different germination stages.It was found that the free,bound and total antioxidant activities of tartary buckwheat seeds after germination were all significantly increased.It shows that the tartary buckwheat sprouts germinated to the 6th day has wider market application value.The contents of phenolic,flavonoids,γ-aminobutyric acid and antioxidant activities were to study of different organs in different growth stages with tartary buckwheat variety’Zhaoku 2’.Studies have shown that the content of free phenol and free flavonoids were significantly higher than the content of bound phenols and bound flavonoids,accounting for 90.06%and 94.96%of total phenol and total flavonoids content,respectively.The content of free phenol and free flavonoids in tartary buckwheat decreased significantly from flowering to seed maturity,and the content was the highest during flowering.As the leaves matured to the senescence stage,the content of free phenol and free flavonoids continued to decrease.The content of bound phenol and bound flavonoids was relatively small,and the content was higher from the flowering stage to the immature seed,which was significantly higher than other stages.The trends of total phenol and total flavonoid content were consistent with free phenol and free flavonoid.The content ofγ-aminobutyric acid was significantly higher than that of other stages at the stage of seed maturation to S2,and the content ofγ-aminobutyric acid in senescent leaves was the lowest,reaching 0.75 mg/g.Six flavonoid monomers were also identified,of which the content of rutin was the highest.The antioxidant activity of tartary buckwheat extracts in different organs at different growth stages was significantly related to the content of polyphenols and flavonoids,and the content of rutin was also significantly related to the polyphenols,flavonoids,and antioxidant activities.Therefore,the content and composition of tartary buckwheat polyphenols and flavonoids andγ-aminobutyric acid in different growth stages of tartary buckwheat are comprehensively considered in order to make reasonable use of tartary buckwheat resources.