title: Free and bound phenolic compounds in leaves of pak choi (Brassica campestris L. ssp. chinensis var. communis) and Chinese leaf mustard (Brassica juncea Coss).
abstract: Eleven pak choi cultivars and two leaf mustard cultivars grown under field conditions in China were investigated for the free polyphenol content in their outer and inner leaves, as well as in their leaf blades and leaf stalks. In most cases, there were no significant differences between the hydroxycinnamic acid derivative and flavonoid derivative contents in the outer and inner leaves for the 13 cultivars. However, the contents of blades and stalks differed: hydroxycinnamic acids and flavonoids were present in greater amounts in the leaf blade than in the leaf stalk. Trace or small amounts of flavonoids were detected in the pak choi and leaf mustard stalks. Additionally, the bound phenolic contents of two pak choi cultivars and two leaf mustard cultivars were investigated. The concentrations of cell wall-bound phenolic compounds were higher in the leaf blade than in the leaf stalk under field conditions in China. These compounds represent only a minor portion of the total phenolic contents (flavonoids and hydroxycinnamic acids) in leaf stalks (0.81-1.18%) and leaf blades (0.05-0.08%) from fresh plant material. The storage of plant samples from four Chinese cabbage cultivars resulted, in most cases, in an increase of phenolic content, within six days, at 4°C and 20°C. The increase might have been triggered by post-harvest plant stresses, which stimulate the biosynthesis of polyphenols.
authors.affiliation: Department of Food Technology, Institute of Human Nutrition and Food Science, University of Kiel, Heinrich-Hecht-Platz 10, 24118 Kiel, Germany. Electronic address: info@foodtech.uni-kiel.de.
authors.forename: Britta
authors.initials: B
authors.lastname: Harbaum
authors.affiliation: Department of Food Technology, Institute of Human Nutrition and Food Science, University of Kiel, Heinrich-Hecht-Platz 10, 24118 Kiel, Germany.
authors.forename: Eva Maria
authors.initials: EM
authors.lastname: Hubbermann
authors.affiliation: Department of Horticulture, School of Agriculture and Food Science, Zhejiang Forestry University, Lin'an, Hangzhou, Zhejiang 311300, China.
authors.forename: Zhujun
authors.initials: Z
authors.lastname: Zhu
authors.affiliation: Department of Food Technology, Institute of Human Nutrition and Food Science, University of Kiel, Heinrich-Hecht-Platz 10, 24118 Kiel, Germany.
authors.forename: Karin
authors.initials: K
authors.lastname: Schwarz
keywords: Cell wall-bound phenolic compounds; Chinese Brassica vegetables; Chinese leaf mustard; Flavonoids; Hydroxycinnamic acids; Kaempferol; Leaf blade; Leaf stalk; Outer and inner leaf; Pak choi; Storage