Phenolic profile and antioxidant properties of dried buckwheat leaf and flower extracts
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Due to a high content of rutin (2-10%), dried buckwheat leaf and flower (DBLF) formulations were shown to be efficient in the treatment of vascular diseases. In order to find a cost effective way for the extraction of antioxidants, the effects of ethanol/water ratio and temperature on the extraction efficiency of phenolic compounds and the mechanisms of antioxidant action of the extracts were tested. Extraction with ethanol/water mixture (80:20, v/v) for 24 h at room temperature, after the mixture was just brought to boil was demonstrated to be an efficient and cheap way for obtaining a high yield of rutin (49.94±0.623 mg/g DBLF). The most abundant phenolic compounds in DBLF extracts were rutin and chlorogenic acid. Flavonoids, especially rutin, were shown to be the most responsible for the antioxidant activity in all investigated lipid model systems, acting as free radical scavengers, electron-donating substances and chelators of iron ions. In β-carotene bleaching tests, the extracts with the highest activity were as efficient as BHT (butylated hydroxytoluole). Regarding the results of antihemolytic and Schaal oven tests, the extracts demonstrated remarkable ability to inhibit the oxidative destruction of erythrocytes and to prolong the beginning of the oxidation process in sunflower oil.