Abstract: The Fagopyrins in buckwheat leaves was extracted by 90% acetone,methanol,60% glacial acetic acid and 80% tetrahydrofuran respectively.The Fagopyrins ultraviolet spectrum and content in the extract was analyzed by UV-vis spectrophotometry and HPLC,and identified Fagopyrins of 90% acetone extract by electrospray ionization mass spectrometry.Then,90% acetone was used as the best extractant and UV-vis spectrophotometry was the simple and fast analytical method,the extract is mainly Fagopyrin F and contains a small amount of Fagopyrin D and/or Fagopyrin E.The Fagopyrins content was used as a reference index,and the process conditions of Fagopyrins extraction were optimized by single factor and orthogonal experiments.The optimum extraction conditions were as follows:1.5 h of extraction time,85% acetone,55 ℃ of extraction temperature,and 105∶3 (mg∶mL) of material liquid ratio.Under this condition,the content of Fagopyrins in buckwheat leaves was 786 μg/g.The method was used to determine the content of Fagopyrins in 20 varieties of 3 species buckwheat and different parts of the buckwheat.The results showed that the content of Fagopyrins in cymosum buckwheat leaves was higher than that of common buckwheat and tartary buckwheat,and the highest content was 1 638 μg/g.The difference between the latter two was not obvious,and the content was between 1 049-1 392 μg/g and 972-1 344 μg/g respectively.The Fagopyrins content of 8 varieties of common buckwheat flowers and leaves were 818-1 834 μg/g and 483-1 282 μg/g,respectively.Except for the Xiang common buckwheat No.2,the Fagopyrins content of the flowers was the highest.On the whole,the content of Fagopyrins in the flowers was nearly 1 time higher than that of the leaves,while the Fagopyrins content of the buckwheat groats was extremely low,only 55-98 μg/g.We analyzed the correlation of buckwheat leaves between flavonoids and Fagopyrins content.For content of flavonoids,cymosum buckwheat was the highest,followed by tartary buckwheat,and the lowest was common buckwheat.The content of flavonoids in buckwheat leaves was positively correlated with the content of Fagopyrins.However,from the ratio of flavonoids to Fagopyrins,tartary buckwheat leaves were significantly higher than common buckwheat leaves.Above research provided the basis for the selection of buckwheat excellent varieties and also laid a foundation for the research on the safety evaluation of buckwheat.

Key words: fagopyrins, extract, UV-vis spectrophotometry, HPLC, flavonoids and fagopyrins content