Phenolic Profiles and Antioxidant Activity of Buckwheat (Fagopyrum esculentum Mench and Fagopyrum tartaricum L. Gaerth) Hulls, Brans and Flours

The extracts from hulls, brans and flours of Fagopyrum esculentum Mench (FEM, three varieties) and Fagopyrum tartaricum L. Gaerth (FTG, seven varieties) were screened for free and bound phenolic content or total phenolic content (TPC), as well as 1,1 diphenyl-2-picryl hydrazyl (DPPH) free radical scavenging activity and reducing power. Free phenolics were predominant in buckwheat hulls, brans and flours. FEM hulls extract exhibited the highest reducing power and DPPH free radical scavenging activity with the average EC5084.54 μg mL-1and IC5011.54 μg mL-1respectively, FTG brans extract had the highest average TPC (24.87 mg GAE g-1DW), and FEM flours extract showed the lowest TPC, reducing power and radical scavenging activity. Furthermore, the correlations among TPC, DPPH free radical scavenging activity and reducing power of all the samples were investigated. The rank correlation coefficient (rs) between reducing power and DPPH free radical scavenging activity of buckwheat hulls, between TPC and DPPH free radical scavenging activity of buckwheat flours were 0.76 and 0.79, respectively (P<0.05). However, there is no significant correlation between the remaining indexes of hulls and flours, as well as the ten buckwheat brans. This result indicated that some non-phenolic compounds also contributed to the total antioxidant activity in hulls, brans and flours of buckwheats. This study demonstrated that buckwheat hulls and brans, rather than flours, are good source of antioxidants.