Antioxidative properties of buckwheat grain, hull and flours
The cultivation of pseudocereal buckwheat (Fagopyrum esculentum, Moench) has gained raising attention, due to many positive physiological effects. Buckwheat grain contains large amount of proteins, starch, vitamins and does not contain gluten, which classify buckwheat products as functional ones. Also, buckwheat grains have been well known as a plant source of rutin, quercetin, kaempferol-3-rutinoside, and contain trace quantity of flavonol triglycoside. In order to investigate the distribution of these compounds and antioxidant activity in buckwheat, ethanolic extracts of different fractions were prepared and investigated: whole grain, dehulled grain, hull and two types of flours (wholegrain and light). For the purpose of antioxidant screening iron (III) reduction and 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) scavenging activities were applied. Total phenol and flavonoid contents of each extract were also determined.
All investigated samples contained significant quantities of plant phenolics and flavonoids. Among them the ethanolic extract of the hull fraction was the most abundant. It contained 1.18% of flavonoids and 1.43% of phenolics in dry extract, which is almost ten times more then in other investigated extract. Furthermore, hull extract exhibited the best antioxidant activities in both tests applied. Significant correlation was obtained for the results of these tests (0.97, p<0.05). Also, these results strongly correlate with the total phenol and flavonoid contents of the samples.
Regarding the obtained results and the fact that hulls are milling by product, they could be potentially used as a useful source of natural antioxidants.