New insights into the phenolic constituents and their relationships with antioxidant capacity during the growth of a commonly consumed Asian vegetable, Brassica rapa var. parachinensis (choy sum)

Abstract

Choy sum, a common edible Asian brassica vegetable, was systematically investigated to determine the profile of phenolic compounds (PC) in its three major growth stages (microgreen, seedling and adult), using UHPLC-Q-TOF-MS/MS and LC-QQQ-MS. Among 92 identified PC, 17 new kaempferols containing 7-O-hydroxycinnamoylglucoside were detected. Significant differences in PC profiles were observed during plant growth. Antioxidant capabilities (AOX) were also determined in parallel using TPC, DPPH and ORAC assays. Seedlings, compared to microgreens and adult plants, had the highest antioxidant capability. Further, data revealed that seedlings had more PC varieties, with highest content of various hydroxycinnamic acids and flavonoids than other two stages. Six PC with substantial antioxidant capability were identified, and all were abundant at seedling than at the other two stages. In contrast to various earlier reports that microgreens contained higher plant nutrients, present data suggest seedlings contained more varieties and higher content of PC.