Enhancing Nutritional and Functional Properties of Broccoli Leaves Through Selenium Biofortification: Potential for Sustainable Agriculture and Bioactive Compound Valorization

Selenium (Se) biofortification is a promising agronomic strategy to enhance dietary intake of this essential micronutrient, while simultaneously adding value to agricultural by-products like Brassica oleracea L. var. italica leaves. This study evaluated the effects of foliar Se biofortification on a fresh-market broccoli cultivar (‘Belstar’) using selenite and selenate salts (1 and 2 mM). Growth performance, biochemical properties, nutraceutical quality, and phytohormone profiles of broccoli leaves were analyzed, highlighting their potential as functional by-products. Multivariate analysis revealed that 2 mM selenite application was the most effective treatment, significantly improving several parameters. Selenium biofortification with 2 mM selenite increased essential nutrient content, including Se, Ca, S, Fe, Mn, Mg, and Mo. It also enhanced soluble protein content (+2.2-fold), phenolic compounds (+1.5-fold), and total antioxidant capacity (+1.4-fold) compared to control plants. In this sense, the nutraceutical quality of broccoli leaves was markedly improved, supporting their use as a source of bioactive ingredients. Additionally, to assess practical applications, water-extracted Se-enriched broccoli leaves demonstrated antifungal activity against the plant pathogen Fusarium solani, attributed to Se-induced alterations in phytohormone profiles. These findings suggest that Se-biofortified broccoli leaves can serve as a sustainable source of essential nutrients and bioactive compounds for the food industry. Furthermore, their antifungal properties position them as potential eco-friendly biopesticides to combat plant pathogenic fungi, thereby promoting sustainable agriculture.