Phytochemical Composition and Antitumor Activities of New Salad Greens: Rucola (Diplotaxis tenuifolia) and Corn Salad (Valerianella locusta)

D. tenuifolia and V. locusta , two greens, were analyzed for active compounds and antitumor actions on colorectal cancer cells. Phenolics were determined by UHPLC-Orbitrap-MS; carotenoids and glucosinolates by HPLC-MS; and sterols and fatty acids by gas–liquid chromatography (GLC). For antitumor effects, the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) tests were run on HT-29 colorectal cancer cells, and in CCD-18 untransformed enterocyte cells. Six main carotenoids were identified in both vegetables, while total carotenoids accounted for 3520 and 2970 μg · g −1 dry weight in D. tenuifolia and V. locusta , respectively. Six phenolics were detected in D. tenuifolia (68,600 μg · g −1 dry weight) and five in V. locusta (139,000 μg · g −1 dry weight). Three glucosinolates (GSL) were found in D. tenuifolia (1960 μg · g −1 dry wt. total). Low-polarity extracts from V. locusta and D. tenuifolia showed IC 50 ~ 150 and ~200 μg · mL −1 on HT-29 cells, while both plants lacked actions on CCD-18 cells. V. locusta inhibited HT-29 cancer cells viability more efficiently than D. tenuiofolia , but induced less cytotoxicity. This work highlights the importance of functional foods for colorectal cancer prevention.