| Tartary buckwheat contains starch,protein,fat,vitamins and other nutrients,also contains rutin,quercetin,gallic acid,chlorogenic acid,2,3,4-trihydroxybenzoic acid and other phenolic compounds.Previous studies have revealed that Tartary buckwheat has anti-oxidation,anti-cancer,regulate blood sugar level and other health functions,these health functions mainly attributed to phenolic compounds.It is a necessary process for food to enter the body that gastrointestinal digestion,which may change the structure and properties of phenolic compounds in food,as well as the way of combining with other components,thus affecting the release of phenolic compounds,and thus affecting their bioavailability.Therefore,on the basis of optimization evaluation phenolic compounds and antioxidant activities of Tartary buckwheat,this paper analyzed the phenolic compounds of Tartary buckwheat by using germination model,and revealed the enzymes related to the synthesis and decomposition of phenolic compounds and their activity changes.A simulated digestion in vitro model was established with ?-amylase,pepsin and pancreatin as digestive enzymes,which was used to elucidate the release and bioavailability of phenolic compounds of Tartary buckwheat,these results provide scientific basis for functional evaluation and intensive processing of Tartary buckwheat.(1)A three-solvents extracting method was established,which consist of 80 % acetone,ethyl acetate and 70 % ethanol,by this method,80 % acetone extracts,ethyl acetate extracts and 70 % ethanol extracts were prepared of Tartary buckwheat.The phenolic compounds were analyzed by high performance liquid chromatography(HPLC),and the antioxidant activities were analyzed by DPPH,ABTS and FRAP of the extracts.The results show that the contents of total phenolics and flavonoids of 70 % ethanol extracts were 1746.8 ± 29.3 ? 2092.3 ± 39.1mg GAE/100 g DW and 2116.7 ± 32.3 ? 2834.3 ± 21.3 mg RE/100 g DW,respectively,which were higher than the corresponding amount of 80 %acetone extracts and ethyl acetate extracts.The DPPH,ABTS and FRAP values of 70 % ethanol extracts were 2683.3 ± 79.9 ? 3091.7 ± 19.6,10130 ± 368 ? 12380 ± 171 and 2906.8 ± 30.3 ? 3779.9 ± 38.2 mg TE/100 g DW,respectively,which were higher than the corresponding values of 80 % acetone extracts and ethyl acetate extracts.70 % ethanol extracts contain important components of phenolic compounds of Tartary buckwheat,the results showed of phenolic compounds composition that the accumulation was the highest of single phenolic compounds in 70 %ethanol extract,mainly rutin and quercetin,and the content of rutin was1902.0 ± 14.2 ? 2402.8 ± 19.5 mg/100 g DW.Gallic acid,chlorogenic acid and 2,3,4-trihydroxybenzoic acid were detected in 80 % acetone extracts,and the content of gallic acid was the highest,which ranged from 164.57 ± 23.71 ? 521.97 ± 30.81 mg/100 g DW.The ethyl acetate extracts only contain 2,3,4-trihydroxybenzoic acid.These results indicated that the three-solvents extracting method could comprehensively extract phenolic acids and flavonoids of Tartary buckwheat,and the method could be used for the composition analysis and functional properties evaluation of phenolic compounds from Tartary buckwheat.(2)A germination model of Tartary buckwheat was established at25 ? for 10 d,the phenolic compounds and antioxidant activity of the samples were analyzed for each 12 h or 24 h germination interval,and the changes of phenolic compounds and antioxidant activity were analyzed during the germination process of Tartary buckwheat,and the changes were revealed that of enzymes related to the synthesis and decomposition of phenolic compounds and their activities during the germination of Tartary buckwheat.The results showed that total phenolics,total flavonoids and antioxidant activities showed an upward trend in the process of germination,and the maximum values were 2964.8 ± 13.9 mg GAE/100 g DW,5514.5 ± 110.7 mg RE /100 g DW and 5935.8 ± 98.1mg TE /100 g DW,respectively.Gallic acid,chlorogenic acid and2,3,4-trihydroxybenzoic acid showed an upward trend during germination,and the maximum values were 449.12 ± 5.26,105.33 ± 0.23 and 50.442 ±1.477 mg/100 g DW,respectively,while rutin showed a trend of decreasing first and then rising,the maximum value was 2663.4 ± 61.1mg/100 g DW,and there was no significant change that the content of quercetin during the whole germination process.The study of enzymatic reaction kinetics showed that the activities of PAL and CHI,the key enzymes of flavonoid synthesis,were consistent with the phenolics contents,while the activities of RDEs were opposite to the rutin contents.These results indicated that germination could activate the activities of key enzymes in flavonoid synthesis such as PAL and CHI,and inhibit the activities of RDEs,thus increasing the contents of phenolic compounds in Tartary buckwheat.The results could provide guidance for the intensive processing and the development of functional products of Tartary buckwheat.In addition,rutin degrading enzyme is an important endogenous enzyme of Tartary buckwheat,which shows strong degrading activity for rutin.Therefore,the regulation of this enzyme activity is of great significance to the evaluation and processing of functional properties of Tartary buckwheat.(3)A simulated digestion in vitro model was established that based on digestive enzymes and an intestinal absorption model based on dialysis membrane,the release rules and bioavailability of phenolic compounds in Tartary buckwheat were explained by using the digestion model in vitro combined with the intestinal absorption model.The results showed that the small intestine was the main site for the release of phenolic compounds from Tartary buckwheat.The main phenolic compounds were rutin,quercetin,3,4-dihydroxybenzoic acid,2,3,4-trihydroxybenzoic acid and chlorogenic acid by digestion release in vitro.The release amount of 2,3,4-trihydroxybenzoic acid and chlorogenic acid during simulated digestion in vitro were 54.780 ± 0.117mg/100 g DW and 8.9445 ± 2.5720 mg/100 g DW,respectively,which were 253.5 % and 112.1 % of the corresponding chemical extraction amount,68.6 % of 2,3,4-trihydroxybenzoic acid and 100 % of chlorogenic acid were absorbed.The release amount was 81.914 ± 0.573mg/100 g DW of 3,4-dihydroxybenzoic acid during simulated digestion in vitro,which 73.7 % was absorbed,and the compound was not detected in chemical extraction.Rutin,quercetin and kaempferol are less effective during simulated digestion in vitro,and which may end up in the colon,where they are released by fermentation.The amount of quercetin entering colon was 620.14 ± 8.41 mg/100 g,which was 3.6 times of that of chemical extraction.These results indicated that simulated oral,stomach and small intestine digestion in vitro promoted the release of3,4-dihydroxybenzoic acid,2,3,4-trihydroxybenzoic acid and chlorogenic acid of Tartary buckwheat,and thus improved the bioavailability of phenolic compounds in Tartary buckwheat. |
PDF Full Text Request