Structurally different flavonol glycosides and hydroxycinnamic acid derivatives respond differently to moderate UV-B radiation exposure

• Published in: Physiologia plantarum 2012-08, Vol.145 (4), p.582-593
• Main Authors: Neugart, Susanne, Zietz, Michaela, Schreiner, Monika, Rohn, Sascha, Kroh, Lothar W., Krumbein, Angelika
• Format: Article
• Language: English
• Subjects: Acetylation; Brassica - chemistry; Brassica - radiation effects; Chromatography, High Pressure Liquid; Coumaric Acids - chemistry; Coumaric Acids - metabolism; Flavonols - chemistry; Flavonols - metabolism; Glycosides - chemistry; Glycosides - metabolism; Spectrometry, Mass, Electrospray Ionization; Ultraviolet Rays
• ISSN: 0031-9317; 1399-3054
• DOI: 10.1111/j.1399-3054.2012.01567.x

The aim of this study was to investigate the modifying influence of moderate ultraviolet‐B (UV‐B) radiation exposure on structurally different flavonol glycosides and hydroxycinnamic acid derivatives during pre‐harvest 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 (1 day), moderate UV‐B radiation [0.22–0.88 kJ m−2 day−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 day−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.