Effect of salinity stress on phenolic compounds and carotenoids in buckwheat (Fagopyrum esculentum M.) sprout

The effect of salinity stress on the nutritional quality of buckwheat sprouts cultivated for 1, 3, 5, and 7 d was investigated by analysis of the antioxidant activity and levels of phenolic compounds and carotenoids. Treatment with various concentrations of NaCl (10, 50, 100, and 200 mM) resulted in an increase in the amount of phenolic compounds and carotenoids in the sprouts compared with the control (0 mM). The phenolic contents of sprouts treated with 10, 50, and 100 mM after 7 d of cultivation were 57%, 121%, and 153%, respectively, higher than that of the control (0 mM NaCl). Moreover, the accumulation of phenolic compounds was primarily caused by an increase in the levels of 4 compounds: isoorientin, orientin, rutin, and vitexin. The carotenoid content of sprouts treated with 50 and 100 mM NaCl was twice higher than that of the control. In addition, the antioxidant activity of ethanol extracts of the sprouts was increased by NaCl treatment. Although the growth rate of sprouts decreased with >50 mM NaCl, these results suggest that treatment of an appropriate concentration of NaCl improves the nutritional quality of sprouts, including the level of phenolic compounds, carotenoids, and antioxidant activity.