| Fagopyrum tataricum(tartary buckwheat)is a kind of small annual rain fed crops and flavonoids are the most important characteristics.There are abundant types of tartary buckwheat resources in China,but high-quality tartary buckwheat varieties and the main active components,flavonoids,have not been fully developed and utilized.In recent years,metabolomics technology has been increasingly applied as an assistant breeding method in crop research.This research optimized the flavonoids extraction method by ultrasonic in tartary buckwheat seeds and explored the relationship between total flavonoid content(TFC)and antioxidant activity.Besides,the research used metabolomics methods to screen differential flavonoids and identify metabolic markers,providing a basis for the breeding of tartary buckwheat varieties with high flavonoid content and strong antioxidant activity.The results are as follows:1.The ultrasonic assisted extraction method was used to extract flavonoids in tartary buckwheat seeds.The effects of different soaking time,extraction temperature,extraction time,ethanol concentration,and solid-liquid ratio on the total flavonoid yield were analyzed through single factor experiments.Combined with the Box Behnken response surface experiment,the optimal extraction conditions for flavonoids from tartary buckwheat seeds were obtained as follows: extraction temperature 60°C,extraction time 35 minutes,ethanol concentration 75%,and solid-liquid ratio 1:83(0.012).Under this condition,the actual flavonoid yield can reach7.453%;2.The seed coat color,aspect ratio,thousand grain weight,TFC,1,1-Diphenyl-2-picrylhydrazyl radical 2,2-Diphenyl-1-(2,4,6-trinitrophenyl)hydrazyl(DPPH)radical scavenging ability,terric reducing antioxidant power(FRAP),and cupric reducing antioxidant capacity(CUPRAC))of 167 tartary buckwheat germplasm resources in China were studied,and the relationship between the indicators was analyzed.It was found that there was a significant positive correlation between TFC and three antioxidant activity indicators.Based on TFC and antioxidant activity,,167 tartary buckwheat were cluster analyzed and ultimately divided into 3 categories.Among them,T107,T113,T129,and T130 clustered into Class I with higher TFC and stronger antioxidant activity,while varieties T023,T064,T076,T100,T102,and T111 clustered into Class III with lower TFC and weaker antioxidant activity;3.Using liquid chromatography triple quadrupole mass spectrum(LC-QQQ-MS)technology,flavonoid metabolomics analysis was conducted on 10 selected varieties with significant differences in TFC and antioxidant activity.A total of 58 flavonoid compounds were screened and divided into 6 categories.Among them,the number of compounds belonging to flavonol is the largest,with 41 compounds,accounting for 70.69% of all kinds,followed by flavanol(18.97%),while flavanone(5.17%),anthocyanin(1.72%),isoflavone(1.72%)and flavone(1.72%)are less.Meanwhile,the relative contents of all compounds were compared.Among the 10 varieties,the proportion of flavonol content was more than 91%,the proportion of flavanol was 3.15%-7.92%,and the proportion of flavanone in the 10 varieties was close(0.06%-0.12%).The proportions of anthocyanins,isoflavones,and flavonoid glycosides were all below 0.01%.Compounds 25(rutin),31(kaempferol 3-O-rutoside),29(quercetin O-hexoside deoxyhexoside),50(kaempferol),and 52(kaempferol(isomer))Compound 25(rutin)had higher contents in flavonol,accounting for over 9.80% in each variety.4.Using principal component analysism(PCA),orthogonal partial least squarediscriminant analysis(OPLS-DA),volcanic maps,etc,8 differential flavonoid compounds were further analyzed and screened,including compounds 36(kaempferol 3-O-glucoside),37(kaempferol 7-O-glucoside),38(kaempferol 7-O-glucoside(isomer)),43(quercetin Ohexoside),44(quercetin O-deoxyhexoside),and 47(quercetin-7-O-β-D-glucopyranoside)and55(Jaceosidin)in high TFC and strong antioxidant activity varieties were higher than those in low TFC and weak antioxidant activity varieties,while flavonoid metabolite 13(naringin Oglucoside)was the opposite,and these 8 differential metabolites were positively correlated with TFC and antioxidant activity.5、Analyzing the correlation between 8 differential metabolites,TFC and antioxidant activity of varieties,6 compounds(compounds 13,36,37,38,43,and 47)showed significant correlation with TFC and antioxidant activity,which can be used as biomarkers for screening high flavonoid content and strong antioxidant function tartary buckwheat varieties. |
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