Ultrahigh-performance liquid chromatography-high-resolution mass spectrometry analysis of phytochemical profiles of kale (brassica oleracea var. sabellica) harvested at different stages of development

Authors: Liu, Zhihao; Chen, Pei; Wang, Thomas; Pham, Quynhchi; YU, LIANGLI (LUCY) - University Of Maryland; Luo, Yaguang; ZHU, XUDONG - US Department Of Agriculture (USDA); Yang, Tianbao; Sun, Jianghao

Submitted to: ACS Food Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/9/2024
Publication Date: 10/20/2024
Citation: Liu, Z., Chen, P., Wang, T.T., Pham, Q., Yu, L., Luo, Y., Zhu, X., Yang, T., Sun, J. 2024. Ultrahigh-performance liquid chromatography-high-resolution mass spectrometry analysis of phytochemical profiles of kale (brassica oleracea var. sabellica) harvested at different stages of development. ACS Food Science and Technology. 4(11):2752-2761. https://doi.org/10.1021/acsfoodscitech.4c00708.
DOI: https://doi.org/10.1021/acsfoodscitech.4c00708

Interpretive Summary: Kale is a nutrient-rich vegetable that has been recognized for its numerous health benefits. Consumption of microgreens or baby green salads has gained popularity as these young plants offer enhanced nutritional value compared to their mature counterparts. Due to the complexity of kale development, understanding the details of nutritional metabolite profile (e.g., polyphenols and glucosinolates) during different growth stages is of interest. In this study, total and individual polyphenols and glucosinolates from different developmental stages (microgreen, kale, mature, and post mature) of kale were determined and compared using high-resolution mass spectrometry (HRMS)-based metabolomics strategy. The findings will provide valuable data for health agencies and consumers to make informed decisions about their choices of fresh kales.

Technical Abstract: Kale (Brassica oleracea var. sabellica) is a rich source of health-promoting phytochemicals. The current study seeks to elucidate dynamic changes in phytochemical profiles during kale maturation. Total and individual polyphenols and glucosinolates (GLs) from different developmental stages (microgreen, kale, mature, and postmature) of kale were determined and compared using a high-resolution mass spectrometry (HRMS)-based metabolomics strategy. A total of 51 polyphenols and 7 GLs were identified in the kale samples. In addition, we observed significant shifts in the metabolite profiles of kale as the plant progressed from microgreens to mature leafy greens with distinct profiles at each growing stage. The total polyphenol levels were highest in the baby kales, while the GL levels were highest in microgreens. Multivariate analysis identifies GLs and specific hydroxycinnamic acyl glycosides as prominent metabolites in microgreens; however, Quercetin (Qn)-glycosides and Qn-hydroxycinnamic acyl glycosides are unique metabolites in the baby kales. Our study provides valuable insights into the changes in kale secondary metabolites that occur during different stages of the vegetable’s production cycle.