Extraction of Se species in buckwheat sprouts grown from seeds soaked in various Se solutions

The transformation of selenium (Se) in buckwheat sprouts grown from seeds soaked in various Se solutions (Se-methionine (10 mg Se L−1), selenate or selenite (5, 10, 20 mg Se L−1)) was investigated. The extraction procedure was optimised by (a) using optimal extraction media (water, phosphate buffer, 0.1, 0.2, 0.3 M HCl, the enzyme protease alone or in combination with cellulase, amylase or lipase), and by (b) optimising the ratio between sample and enzyme. For Se speciation analysis extracts with the highest percentage of soluble Se were analysed, and additionally the stability of the extracts was investigated. The results showed that uptake of Se by sprouts was dependent on the form and concentration of Se in the solution used for soaking. Optimal extraction efficiencies were obtained by hydrolysis with 0.3 M HCl and protease. Selenate (23.7–29.7% from Se(VI) sprouts and in trace amounts from Se(IV) and SeMet sprouts), Se-methionine (2.4–7.9%) and selenite (traces) were detected in all supernatants, regardless of soaking solution.