S25 - Session O3 - Mass-spectrometric determination of phyllobilins in leaves of medicinal plants and their application forms

Authors: Lisa Marie Gorfer *, Valentina Grigoletto, Manuel Pramsohler, Peter Robatscher, Michael Oberhuber

Phyllobilins (PBs) are the main products of chlorophyll degradation in plants and algae via the pheophorbide-A oxygenase (PaO)/PB pathway, leading to nonfluorescent chlorophyll catabolites (NCCs), yellow chlorophyll catabolites (YCCs) and the nonfluorescent dioxobilane type NCCs (DNCCs). Diverse pharmacological activities have been described for PBs, including anti-inflammatory and anti-oxidative properties, COX inhibition, ROS scavenging and cell cycle arrest in G2/M, with actin as target. Additionally, PBs inhibit cell proliferation and induce apoptosis, and have therefore been proposed as anti-cancer agents. The aim of this study was to analyse PBs in methanolic extracts of leaves in two physiological stages (green and senescent) and in tea preparations of the following plants: Urtica dioica (common nettle), Echinacea purpurea (purple coneflower) and Fagopyrum esculentum (buckwheat) using liquid chromatography coupled to high-resolution mass spectrometry (UHPLC-HR-Q-TOF-MS). Qualitative analysis was performed in data-dependent MS/MS-mode, applying an in-house database including all known catabolites and analysing typical fragmentation patterns and adduct formations. Fullscan mode was applied for semi-quantification. In leaf samples, the highest number of catabolites (18 PBs) was found in senescent coneflower, whereas the highest content (2,18 µg/cm 2 ) was found in senescent nettle leaves. Buckwheat leaves contained lower contents (0,09 µg/cm 2 ) and diversity (6 PBs) but showed a special class of catabolites with a bridged glycosylation motif. As expected, elevated contents of YCCs were found in senescent leaves of all three species, but were already detected in green leaves of coneflower, albeit in lower concentrations. In tea infusions of green leaves, the highest PB concentrations were found in nettle species with 190.44 µg/L, followed by coneflower tea with 121.28 µg/L and buckwheat tea with an amount of only 19.16 µg/L. In conclusion, this study showed that a remarkable content and diversity of PBs are present in herbal species, which should be further investigated for their potential in food supplements or pharmaceutical applications.