Effect of natural light periods on rutin, free amino acid and vitamin C contents in the sprouts of common (Fagopyrum esculentum Moench) and tartary (F. tataricum Gaertn.) buckwheats

Contents of rutin, free amino acids and vitamin C were measured with the sprouts of common buckwheat (Fagopyrum esculentum Moench, FE) and tartary buckwheat (F. tataricum Gaertn., FT), cultivated in darkness and/or under natural light conditions. Flavonoids, including rutin and quercetin were isolated from the sprouts of FE and FT by using HPLC and quantified with their authentic standard compounds. In FE sprouts, rutin content placed under natural light conditions was higher than from plants grown in darkness. In contrast, in FT sprouts rutin content was significantly affected both by days after seeding (DAS) and by lighting. On average, rutin content (55mg/g dry weight) of FT sprouts was 2.2-fold higher than that of FE sprouts. In both species, free amino acids levels were increased with increased natural light periods, and vitamin C content of the sprouts cultivated in darkness in both species was significantly lower than that of light-grown sprouts. Based on these characteristics, we concluded that the green sprouts of FT are a superior source of rutin, free amino acids and vitamin C. They could therefore be used as ‘functional foods’ fresh vegetables and freeze-dried powder.