Tissue-Specific Accumulation and Isomerization of Valuable Phenylethanoid Glycosides from Plantago and Forsythia Plants.

Zoltán Mucsi,Zoltán Kis,Tim Ausbüttel,Moritz Zürn,Kata Horváti,Szilvia Bősze,Béla Noszál,Gergő Tóth,Magdolna Sütöri-Diószegi,Imre Boldizsár,Bernadett Pályi

doi:10.3390/ijms22083880

Abstract

A comparative phytochemical study on the phenylethanoid glycoside (PhEG) composition of the underground organs of three Plantago species (P. lanceolata, P. major, and P. media) and that of the fruit wall and seed parts of Forsythia suspensa and F. europaea fruits was performed. The leaves of these Forsythia species and six cultivars of the hybrid F. × intermedia were also analyzed, demonstrating the tissue-specific accumulation and decomposition of PhEGs. Our analyses confirmed the significance of selected tissues as new and abundant sources of these valuable natural compounds. The optimized heat treatment of tissues containing high amounts of the PhEG plantamajoside (PM) or forsythoside A (FA), which was performed in distilled water, resulted in their characteristic isomerizations. In addition to PM and FA, high amounts of the isomerization products could also be isolated after heat treatment. The isomerization mechanisms were elucidated by molecular modeling, and the structures of PhEGs were identified by nuclear magnetic resonance spectroscopy (NMR) and high-resolution mass spectrometry (HR-MS) techniques, also confirming the possibility of discriminating regioisomeric PhEGs by tandem MS. The PhEGs showed no cytostatic activity in non-human primate Vero E6 cells, supporting their safe use as natural medicines and allowing their antiviral potency to be tested.

Highlights

To determine the novel plant sources of valuable phenylethanoid glycosides (PhEGs) showing no cytotoxicity against normal cells [1], we investigated various tissues of Plantago and Forsythia species
P. lanceolata and P. major are widely distributed around the world, while P. media is common in Europe and Asia and locally in the USA [2]
Since AO and IsoAO are already readily available, we focused on the analysis and isolation of PM, IsoPM, forsythoside A (FA), FH, and FI being present in Plantago and Forythia plants

Summary

Introduction

To determine the novel plant sources of valuable phenylethanoid glycosides (PhEGs) showing no cytotoxicity against normal cells [1], we investigated various tissues of Plantago and Forsythia species.From the large genus of Plantago (order Lamiales, family Plantaginaceae), comprising about 200 species, Plantago lanceolata L. (ribwort plantain), P. major L. (broadleaf plantain), and P. media L. (hoary plantain) were involved in this study. P. lanceolata and P. major are widely distributed around the world, while P. media is common in Europe and Asia and locally in the USA [2]. These herbaceous perennial plants develop an underground rhizome that bears roots, a solitary, erect flower stem, and leaves forming a rosette [3]. Among these three plant species, P. lanceolata and P. major are amongst the most.

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