Structurally different flavonol glycosides and hydroxycinnamic acid derivatives respond differently to moderate UV-B radiation exposure.
The aim of this study was to investigate the modifying influence of moderate UV-B radiation exposure on structurally different flavonol glycosides and hydroxycinnamic acid derivatives during preharvest using kale, a leafy Brassica species with a wide spectrum of different non-acylated and acylated flavonol glycosides. Juvenile kale plants were treated with short-term (one day), moderate UV-B radiation (0.22 – 0.88 kJ m-2 d-1 biologically effective UV-B (UV-BBE)). Twenty compounds were quantified, revealing a structure-specific response of flavonol glycosides and hydroxycinnamic acid derivatives to UV-B radiation. A dose- and structure-dependent response of the investigated phenolic compounds to additional UV-B radiation was found. The investigated quercetin glycosides decreased under UV-B; for kaempferol glycosides, however, the amount of sugar moieties and the flavonol glycoside hydoxycinnamic acid residue influenced the response to UV-B. Monoacylated kaempferol tetraglucosides decreased in the investigated UV-B range, whereas the monoacylated kaempferol diglucosides increased strongly with doses of 0.88 kJ m-2 d-1 UV-BBE. The UV-B induced increase in monoacylated kaempferol triglucosides was dependent on the acylation pattern. Furthermore, the hydroxycinnamic acid glycosides disinapoyl-gentiobiose and sinapoyl-feruloyl-gentiobiose were enhanced in a dose-dependent manner under UV-B. While UV-B radiation treatments often focus on flavonol aglycones or total flavonols, our investigations were extended to structurally different non-acylated and acylated glycosides of quercetin and kaempferol.
Neugart, S.; Zietz, M.; Schreiner, M.; Rohn, S.; Kroh, L.W.; Krumbein, A. 2012. Structurally different flavonol glycosides and hydroxycinnamic acid derivatives respond differently to moderate UV-B radiation exposure. Physiologia Plantarum 145 (4), 582-593.