Abstract
Selenium (Se) is considered essential for human nutrition as it is involved in the metabolic pathway of selenoproteins and relevant biological functions. Microgreens, defined as tender immature greens, constitute an emerging functional food characterized by overall higher levels of phytonutrients than their mature counterparts. The nutraceutical value of microgreens can be further improved through Se biofortification, delivering Se-enriched foods and potentially an enhanced content of bioactive compounds. The current study defined the effect of sodium selenate applications at three concentrations (0, 8, and 16 μM Se) on the bioactive compounds and mineral content of coriander, green basil, purple basil, and tatsoi microgreens grown in soilless cultivation. Analytical emphasis was dedicated to the identification and quantification of polyphenols by UHPLC-Q-Orbitrap-HRMS, major carotenoids by HPLC-DAD, and macro micro-minerals by ICP-OES. Twenty-seven phenolic compounds were quantified, of which the most abundant were: Chlorogenic acid and rutin in coriander, caffeic acid hexoside and kaempferol-3-O(caffeoyl) sophoroside-7-O-glucoside in tatsoi, and cichoric acid and rosmarinic acid in both green and purple basil. In coriander and tatsoi microgreens, the application of 16 μM Se increased the total phenols content by 21% and 95%, respectively; moreover, it improved the yield by 44% and 18%, respectively. At the same Se dose, the bioactive value of coriander and tatsoi was enhanced by a significant increase in rutin (33%) and kaempferol-3-O(feruloyl)sophoroside-7-O-glucoside (157%), respectively, compared to the control. In green and purple basil microgreens, the 8 μM Se application enhanced the lutein concentration by 7% and 19%, respectively. The same application rate also increased the overall macroelements content by 35% and total polyphenols concentration by 32% but only in the green cultivar. The latter actually had a tripled chicoric acid content compared to the untreated control. All microgreen genotypes exhibited an increase in the Se content in response to the biofortification treatments, thereby satisfying the recommended daily allowance for Se (RDA-Se) from 20% to 133%. The optimal Se dose that guarantees the effectiveness of Se biofortification and improves the content of bioactive compounds was 16 μM in coriander and tatsoi, and 8 μM in green and purple basil.
Highlights
Microgreens have recently increased in popularity by earning the title of “functional food” or “superfood” [1,2]
The growth period of the respective microgreens is comparable with that found in a previous work on the same genotype harvested at the second true leaf stage, in which tatsoi was found to be harvest ready earlier than coriander, green, and purple basil [2]
Our results indicated that selenium doses up to 16 μM significantly enhanced the content of this element without depressing the yield, demonstrating the effectiveness of Se biofortification of microgreens
Summary
Microgreens have recently increased in popularity by earning the title of “functional food” or “superfood” [1,2]. They are defined as tender immature greens produced from seedlings of vegetables, grains, herbs, and wild species, harvested at soil level upon the appearance of a pair of first true leaves, which usually occurs within 7–21 days from sowing, depending on the species [3,4]. Selenium (Se) applications have been shown to have the dual effect of both enriching food with an essential microelement and increasing the overall content of bioactive compounds in microgreens [9,10]
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