Free Sterol Content of Brassica Microgreens, Microleaves and Baby Leaves: A Quantitative Study by RPLC-APCI-HRMS

In recent years, innovative edible vegetal products, obtained by harvesting in the early stages of plant development, have emerged for their potential as sources of nutraceuticals. Phytosterols, which play important structural and regulatory roles in plant growth and membrane remodeling, are included among vegetable-related nutraceuticals due to their beneficial effects on human health. For this reason, the present study was focused on the use of RPLC-APCI-HRMS to assess, for the first time, the free sterol (FS) profiles of two edible Brassicaceae plants, namely kale (Brassica oleracea var. acephala) and broccoli raab (Brassica rapa subsp. sylvestris var. esculenta), harvested at the stages of microgreens, microleaves and baby leaves. A comparison with the respective adult forms, conventionally used as edible products upon cooking, was also performed. β-sitosterol was the prevailing FS in all products (>75%), followed by campesterol (8–15%) and isofucosterol (<3%). Total FS concentrations ranged between 13 and 23 mg/100 g fresh weight (FW) for juvenile products of the two plants under study, with the respective highest values being comparable with those found in raw or cooked mature forms (24–26 mg/100 g FW). Interestingly, a more diversified FS profile was observed for juvenile products and an increase in major FS content was observed for microleaves of the two plants cultivated during the winter cycle (January–March), compared to those cultivated in the spring cycle (March–May). These results support the hypothesis that vegetables harvested at early developmental stages may represent promising ready-to-eat alternatives to Brassica plant adult forms, as well as sources of beneficial phytosterols.