The insufficient intake of selenium in the diet of humans and domesticated animals can lead to various and severe health issues, including the degeneration of organs and tissues, thyroid gland disorders and reproductive decline. The selenium intake in human body primarily comes from dietary sources, whereas selenium in food mainly originates from the soil where edible plants and feed crops are grown. Agronomic selenium-enrichment of vegetable and feed crops offers an effective solution to increase selenium intake through diet, as plants can convert inorganic selenium into more bioavailable forms, such as selenoproteins. Moreover, recent studies have evidenced that Se biofortification can also affect synthesis and accumulation of other bioactive compounds, including phenolic compounds, chlorophylls and carotenoids.
This communication reports the results of a study aimed at investigating the influence of selenium biofortification of Chinese cabbage (Brassica rapa L. ssp. pekinensis) on the biosynthesis and accumulation of phytochemicals with various health-promoting effects, such as phenolic compounds (PCs) and glucosinonolates (GSLs). GSLs are secondary plant metabolites containing nitrogen and sulfur atoms that mainly occur in the Brassicaceae family, including the Chinese cabbage, a leafy vegetable cultivated worldwide. The study is conducted in the framework of the EU-funded Project Pathfood, which is aimed at developing modern agronomic techniques to produce selenium-enriched edible plants and food supplements with improved bioavailability of selenium and phytonutrients. Selenium biofortification in field-grown Chinese cabbage was conducted by applying three types of bacteria cocktails, containing selenium in the form of selenite (Se[IV]) and selenate (Se[VI]). Leaves of treated and untreated cabbage were harvested at maturity in peripheral and central parts of the plant and then frozen at -80 °C, prior to their lyophilization. The lyophilized leaves were powdered and stored at -20°C. GSLs and PCs were then extracted with 70% (v/v) methanol-water in a water bath at 70 °C for 15 min. Their occurrence and amount in the samples were investigated by RP-HPLC using a Phenomenex Synergy C18 column, which was eluted by a binary gradient elution system of increasing concentration of acetonitrile in water containing 0.1% (v/v) formic acid. All chromatograms were recorded at two different wavelengths (227nm and 330 nm) to generate specific chromatographic fingerprints for glucosinolates and phenolic compounds, respectively. The RP-HPLC method was then employed to perform untargeted and targeted chromatographic fingerprinting of PCs and GSLs, selectively extracted from both selenium-enriched and control plants, grown under otherwise identical conditions, serving as a baseline for comparison.