Profiling of Polyphenols and Glucosinolates in Kale and Broccoli Microgreens Grown under Chamber and Windowsill Conditions by Ultrahigh-Performance Liquid Chromatography High-Resolution Mass Spectrometry

Abstract

Vegetables from the Brassica family are rich in many health-beneficial components, including high levels of polyphenols and glucosinolates (GSLs). However, their exact metabolite compositions are highly affected by cultivating and environmental conditions. Here, we provide the first report of polyphenol and GSL composition of kale and broccoli microgreens grown in growth chamber and windowsill environments. The samples were harvested 10 days after sowing and analyzed using ultrahigh-performance liquid chromatography high-resolution mass spectrometry. Principal component analysis was performed to visualize group clustering, trends, and discriminative ion features. Flavonol derivatives (21 in kale and 7 in broccoli) and hydroxycinnamic acid derivatives (14 in kale and 22 in broccoli) were identified under both growing conditions. Additionally, GSLs, including 7 in kale and 9 in broccoli, were detected. The results demonstrated a clear variation in secondary metabolites between the two growing conditions. The discriminative ion features were hydroxycinnamic acid esters of flavonols and indolic GSLs. Compared to chamber conditions, hydroxycinnamic acid esters of flavonols such as kaempferol-3-disinapoyl-triglucoside-7-diglucoside, kaempferol-3-disinpapoyl-triglucoside-7-glucoside, and kaempferol-3-disinpapoyl-diglucoside-7-glucoside were found to be greater in the windowsill-grown vegetables. The contents of 4-methoxyglucobrassicin and neoglucobrassicin, on the other hand, were greater in the chamber-grown ones. The results suggest that kale and broccoli microgreens grown under commercial- and in-home-grown conditions have different secondary metabolite compositions.