Chemical Composition, Nutritional Profile, and Bioactive Properties of Diplotaxis tenuifolia, a Health-Promoting Food

Diplotaxis tenuifolia (Brassicaceae), valued for its culinary use and bioactive potential, has not yet been comprehensively characterized in terms of its chemical composition and biological properties. This study investigated the nutritional profile, phytochemical composition, and antioxidant activity of D. tenuifolia cultivated in Portugal. The leaves contain substantial levels of essential minerals, particularly calcium, potassium, magnesium, iron, manganese, and chromium, while heavy metal levels were below regulatory safety limits. The nutritional profile also revealed high dietary fiber content, enriched glutamic and aspartic acids in the protein fraction, and α-linolenic acid as the predominant fatty acid. Phenolic compounds were most efficiently extracted by boiling them in 80% methanol, yielding the highest total phenolic (125.41 mg gallic acid equivalents g−1) and flavonoid contents (3.72 mg quercetin equivalents g−1). HPLC-PDA-ESI-MSn analysis enabled the detailed characterization of phenolic acids, flavonol glycosides, and glucosinolates, highlighting the first report of sulfoglucobrassicin in D. tenuifolia. Additionally, 6-methylsulfonyl-3-oxohexyl-glucosinolate, proline, pipecolic acid, glucaric acid, eicosanoic acid, 9,10,12,13-tetrahydroxy-octadecanoic acid (sativic acid) and 9,12,13-trihydroxyoctadec-10-enoic acid were described for the first time in this species. The extract exhibited also antioxidant activity, with ABTS IC50 57.54 ± 0.18 µg mL−1, DPPH IC50 302.73 ± 2.36 µg mL−1, and FRAP 752.71 ± 4.59 µmol eq. Fe(II) g−1. These findings establish D. tenuifolia as a nutritionally rich plant and a promising source of natural antioxidants for nutraceutical and pharmaceutical applications.