Antioxidant and antiproliferative activities in different maturation stages of broccoli (Brassica oleracea Italica) biofortified with selenium

•We analyse the potential broccoli enriched with selenium to a functional food.•Broccoli has significant antioxidant and antiproliferative activities.•Biofortification increased the amount of phenolic compounds and antioxidant activity.•The activities studied are influenced by the development of broccoli.•The broccoli seedlings had higher antioxidant and anti-proliferative activity. In this work, three different broccoli maturity stages subjected to biofortification with selenium were evaluated for antioxidant and antiproliferative activities. Antioxidant trials have shown that the maturation stages biofortified with selenium had significantly higher amounts of phenolic compounds and antioxidant activity, especially seedlings. Although non-polar extracts of all samples show antiproliferative activity, the extract of broccoli seedlings biofortified with selenium stood out, presenting cytocidal activity for a glioma line (U251, GI50 28.5mgL−1).