Phytochemical Composition and Functional Properties of Brassicaceae Microgreens: Impact of In Vitro Digestion

The aim of this study was to compare the concentration of phenolic compounds, glucosinolates, proteins, sugars and vitamin C between kohlrabi (Brassica oleracea var. acephala gongylodes), Savoy cabbage (B. oleracea sabauda), Brussels sprouts (B. oleracea gemmifera), cauliflower (B. oleracea botrytis), radish (Raphanus sativus) and garden cress (Lepidium sativum) microgreens for their antioxidant and hypoglycemic potential. In addition, we applied an in vitro-simulated system of human digestion in order to track the bioaccessibility of the selected phenolic representatives, and the stability of the microgreens' antioxidant and hypoglycemic potential in terms of α-amylase and α-glucosidase inhibition after each digestion phase. Using spectrophotometric and RP-HPLC methods with statistical analyses, we found that garden cress had the lowest soluble sugar content, while Savoy cabbage and Brussels sprouts had the highest glucosinolate levels (76.21 ± 4.17 mg SinE/g dm and 77.73 ± 3.33 mg SinE/g dm, respectively). Brussels sprouts were the most effective at inhibiting protein glycation (37.98 ± 2.30% inhibition). A very high positive correlation (r = 0.830) between antiglycation potential and conjugated sinapic acid was recorded. For the first time, the antidiabetic potential of microgreens after in vitro digestion was studied. Kohlrabi microgreens best inhibited α-amylase in both initial and intestinal digestion (60.51 ± 3.65% inhibition and 62.96 ± 3.39% inhibition, respectively), and also showed the strongest inhibition of α-glucosidase post-digestion (19.22 ± 0.08% inhibition). Brussels sprouts, cauliflower, and radish had less stable α-glucosidase than α-amylase inhibitors during digestion. Kohlrabi, Savoy cabbage, and garden cress retained inhibition of both enzymes after digestion. Kohlrabi antioxidant capacity remained unchanged after digestion. The greatest variability was seen in the original samples, while the intestinal phase resulted in the most convergence, indicating that digestion reduced differences between the samples. In conclusion, this study highlights the potential of various microgreens as sources of bioactive compounds with antidiabetic and antiglycation properties. Notably, kohlrabi microgreens demonstrated significant enzyme inhibition after digestion, suggesting their promise in managing carbohydrate metabolism and supporting metabolic health.