| Buckwheat is a common food and medicine crop in China.It has remarkable positive effects on postprandial blood glucose,blood glucose stabilization and antioxidation.It has been proved that many active substances in buckwheat,such as dietary fiber,phenolic compounds,D-chiro-inositol,D-fagomine are closely related to the bioactive functions.At present,the planting scale of buckwheat is expanding,but its yield per unit area is low,and the grain is still the main consumption part of buckwheat.Buckwheat belongs to infinite inflorescence and has the characteristics of coexisting of flowers and fruits.Therefore,buckwheat plants at harvest time have higher overall utilization value.Dietary fiber(DF)is an important biological macromolecule in buckwheat.It is abundant in buckwheat.Studies have shown that soluble dietary fiber(SDF)has the same effect in regulating postprandial blood glucose level and antioxidant activity.However,at present,the distribution of active substances in buckwheat plants is not clear,and the physical and chemical characteristics of SDF are not comprehensive enough.Therefore,it is very important to maximize the buckwheat plants in order to improve the overall efficiency of buckwheat cultivation.In this study,the distribution of functional factors in buckwheat plants was preliminarily explored by means of HPLC,GC,TEM,XRD etc.The composition,physical and chemical properties of SDF in buckwheat were evaluated.The main contents and results of research are as follows:(1)Buckwheat bran is the most abundant part contianing SDF and D-fagomine.The content of phenols and D-chiro-inositol in buckwheat leaves is the highest.Buckwheat plants and grains were divided into seven parts: root,stem,leaf,hull,bran,crude powder and fine powder.The content of active substances with hypoglycemic function was determined.The results showed that the total dietary fiber(TDF)content of buckwheat plants ranged from 15.36 to 88.69%.The contents of TDF and insoluble dietary fiber(IDF)were in order of root > stem > leaf > hull > bran > crude powder > fine powder,respectively.The contents of SDF and D-fagomine in buckwheat bran were 9.88% and 2.81 mg/kg,respectively.The contents of total phenolic substances and D-chiro-inositol in buckwheat leaves were 8.81 mg/g and 26.93 mg/g respectively.SDF was extracted from stem,hull,bran and flour.(2)The SDF extraction rate and total flavonoids content of bran were the highest.The four SDFs extracted belong to rough DF.The basic components of four kinds of SDF were analyzed by HPLC and GPC.The results showed that the highest extraction rate of SDF from bran and the content of total flavonoids were 12.09% and 2.21 mg/g,and xylose accounted for 65.21% of bran SDF.The purity of four SDFs was 80% and the average molecular weight was 3 kDa,belonging to oligosaccharides.(3)The structure of bran SDF is loose and porous,showing a three-dimensional network structure.The physical structures of four kinds of SDFs were preliminarily analyzed by TEM,AFM and FT-IR.The results showed that the four SDFs were disordered and amorphous,with low crystallinity,characteristic peaks of polysaccharides and bending or stretching vibration peaks of aromatic hydrocarbons.There are many polygonal holes in bran SDF.The powder SDF is spherical.The structure of buckwheat bran SDF and buckwheat flour SDF is loose.Hull SDF is flaky and stem SDF is massive,both of them are closely structured.(4)The bran SDF has strong amylase inhibition ability,glucose adsorption ability and antioxidant ability.The functional properties of four kinds of SDF were analyzed by in vitro.The results showed that hull SDF and bran SDF had high antioxidant capacity,while bran SDF and flour SDF had high amylase inhibition and glucose adsorption capacity.The adsorption capacity and inhibition of amylase of SDF may be related to the physical structure of SDF in water-soluble state.The above results showed that there were significant differences in the composition and content of bioactive substances in different parts of buckwheat.The distribution of TDF and IDF in different tissue of buckwheat plants was regular,and the content of SDF in bran was the highest.SDF in bran had a three-dimensional reticular structure,and had obvious effects in antioxidant,inhibiting amylase activity and adsorbing glucose.The results may clarify the distribution of functional substances in buckwheat and the basic functional properties of SDF in buckwheat stem,hull,bran and flour,providing basis for selective development of buckwheat resources. |
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