| Buckwheat is one kind of crop for medicine food homology.Its seeds are rich in resistant starch.The glycemic index is low after eating.It is a perfect food for the patients with diabetes and cardiovascular and cerebrovascular diseases;Its flowers,leaves,and brans are rich in the flavonoids which display good antioxidant effects and the inhibition of appropriate glucosidase,amylase and lipase.In this era of abundant products,the consumption of healthy foods has made buckwheat popular.The growth in demand for buckwheat is not only limited to the seeds,but also the young leaves,sprouts,and extracts.In Asia,young leaves and sprouts are often used as vegetables,and powders of leaves are used as additives or natural practical pigments.Some wild buckwheat was used as feed for cattle in Nepal and Bhutan.However,the researchers found that there was a phototoxic substance in the buckwheat-Fagopyrins,which we call Fagopyrins.As a large country for the production and consumption of buckwheat,it is very necessary to evaluate the safety of buckwheat,especially plants and sprouts,and to study the biological function of Fagopyrins,however,there are only few reports in China.The Fagopyrins in buckwheat leaves was extracted by 90% acetone,methanol,60% glacial acetic acid,and 80% tetrahydrofuran,respectively.The ultraviolet spectra and content in the Fagopyrins extract was analyzed by UV-vis spectrophotometry and HPLC,respectively.90% acetone was used as the extractant,and UV-vis spectrophotometry was the simple and fast analytical method.Fagopyrins in the 90% acetone extract were identified by electrospray ionization mass spectrometry,and the extract was mainly Fagopyrin F and contained a small amount of Fagopyrin D and/or Fagopyrin E.The Fagopyrins content was used as a reference index,and the process conditions for Fagopyrins extraction were optimized by single factor and orthogonal experiments.The optimum conditions for extraction were as follows: 1.5 h of extraction time,85% acetone,55 ℃ of extraction temperature,and 105:3(mg:m L)of solid-liquid ratio.Under this condition,the content of Fagopyrins in buckwheat leaves was 785.63 μ g/g.The method was used to determine the content of Fagopyrins in different varieties,different parts of plants and different growth stages.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 1 638.44 μg/g.The difference between the latter two was not obvious,and the content was between 1 049.34~1 391.60 μg/g and 972.39~1 343.69 μ g/g,respectively.The Fagopyrins content of 8varieties of common buckwheat flowers,leaves and groats were 818.67~1834.46 μg/g,483.20~1 282.44 μg/g and 54.83~98.30 μg/g,respectively.Except for the common buckwheat Xiangtian No.2,the Fagopyrins content of the flowers was the highest.On the whole,the content of Fagopyrins in the flowers was about 1 time higher than that of the leaves,while the Fagopyrins content of the buckwheat groats was extremely low.The Fagopyrins content of buckwheat leaves at different growth stages showed that the Fagopyrins content was the highest at the early stage of plant growth,which was 966.86~1 347.70 μg/g.It decreased slightly in the middle stage.The lowest level of Fagopyrins in the late stage was only 310.50~540.66μg/g,only 1/2~1/3 of the early stage.Buckwheat Fagopyrins is a double-edged sword.It can be used as photodynamic therapy,and possesses anti-cancer,anti-bacterial and other effects.But at the same time,Fagopyrins are phototoxic.After eating,under the light condition,the skin will have dermatitis reaction such as itching and redness.For the drawback of Fagopyrins,this study explored the phototoxic effects of buckwheat Fagopyrins by animal experiments.The Kunming mouse were divided into 5 groups: blank control group,licifugal and high dose group,light and low,medium,high dose group.During the whole experiment,there was no significant difference between the blank control group and the licifugal high-dose group(P>0.05), indicating that Fagopyrins did not cause phototoxicity in mouse under the condition of darkness.Skin epidermal observation and sectioning results showed that 10 g of body weight mouse consumed 15 g of fresh sprouts daily to produce a photosensitivity reaction.The levels of epidermal growth factor,tumor necrosis factor-α,interleukin-1β,interleukin-8 and interleukin-10 in serum were determined by enzyme-linked immunosorbent assay.The phototoxicity of oral buckwheat sprouts on mouse skin was further evaluated.The same results as the section observation were obtained,and the biochemical factors of the low,medium and high dose groups were significantly reduced.Analysis of blood routine and organ coefficient showed that the indicators in the low-dose group were basically normal.Some blood indexes,spleen and thymus coefficients in the middle and high-dose groups were significantly changed.In summary,the light and low-dose group can produce photosensitivity and skin inflammation.As the amount of sprouts increases,some blood indexes,spleen and thymus coefficients are also significantly affected. |
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