Histochemical localization and characterization of chalcones on the foliar surface of Zuccagnia punctata Cav. Insights into their physiological role

Dihydroxychalcones as well as other metabolites synthesized via the phenylpropanoid pathway have a wide range of biological activities. Although this class of phenolic compounds is found in very large amounts in some tissues, their physiological significance remains unclear. This approach focused on the chemical analysis of Zuccagnia punctata leaf rinse extract in which dihydroxychalcones (99.25 mu g 2',4'-dihydroxychalcone/cm(2) and 73.38 mu g 2',4'-dihydroxy-3'-methoxychalcone/cm(2)) are the main constituents. Histochemical analysis (fluorescence microscope and emission scanning electron microscope coupled with an energy dispersive X-ray spectrometer) revealed a high flavonoid concentration on the foliar surface. The high accumulation of phenolic compounds, flavonoids or chalcones in the cuticle of Z. punctata leaves would act as defense mechanisms against UV radiation for the protection of photosynthetic tissues against oxidative stress. (C) 2015 Phytochemical Society of Europe. Published by Elsevier B.V. All rights reserved.