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

Authors: LIU, ZHIHAO - University Of Maryland; SHI, JENNA - Rice University; WAN, JIAWEI - University Of Maryland; Pham, Quynhchi; ZHANG, ZHI - University Of Maryland; Sun, Jianghao; YU, LIANGLI - University Of Maryland; Luo, Yaguang - Sunny; Wang, Thomas - Tom; Chen, Pei

Submitted to: ACS Food Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/2/2021
Publication Date: 12/29/2021
Citation: Liu, Z., Shi, J., Wan, J., Pham, Q., Zhang, Z., Sun, J., Yu, L., Luo, Y., Wang, T.T.Y., Chen, P. 2021. 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. ACS Food Science and Technology. 2(1):101-113. https://doi.org/10.1021/acsfoodscitech.1c00355.
DOI: https://doi.org/10.1021/acsfoodscitech.1c00355

Interpretive Summary: Brassica vegetables are rich sources of glucosinolates (GSLs) and polyphenols, which are two of the most widely investigated secondary metabolites in plants due to their potential health-promoting effects. Kale and broccoli are the most popular and consumed brassica vegetables. The secondary metabolites are also known to be affected by numerous environmental factors. Thus, a metabolomics strategy, based on comparing the composition profiles from chamber and windowsill conditions, was used to identify metabolites unique to each growing condition. The results could provide valuable information for commercial and at-home growers.

Technical Abstract: Brassica vegetables contain many health-enhancing components, such as high levels of polyphenols and glucosinolates (GSLs). Metabolite composition of Brassica vegetables are affected by environmental factors including abiotic and biotic stresses. The purpose of this study was to determine and compare the polyphenol and GSL composition of kale and broccoli microgreens growing under chamber and windowsill environments. The samples were analyzed using ultra-high-performance liquid chromatography high-resolution mass spectrometry (UHPLC-HRMS). Principal component analysis (PCA) was performed on the data 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 in the above samples. Additionally, GSLs, including 7 in kale, and 9 in broccoli, were also detected. The results demonstrated clear variation in secondary metabolism between the two growing conditions. The discriminative ion features were hydroxycinnamic acid esters of flavonols and indolic GSLs. Compared to chamber condition, 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 higher in windowsill condition. Content of 4-methoxyglucobrassicin (4-MGBS) and neoglucobrassicin (NGBS), on the other hand, were higher in chamber condition. The results suggest that kale and broccoli grown under commercial and in home-grown conditions may have a different composition of secondary metabolites.