LC-ESI-FT-MSn Metabolite Profiling of Symphytum officinale L. Roots Leads to Isolation of Comfreyn A, an Unusual Arylnaphthalene Lignan

Preparations of comfrey (Symphytum officinaleL.) roots are used topically to reduce inflammation. Comfrey anti-inflammatory and analgesic properties have been proven in clinical studies. However, the bioactive compounds associated with these therapeutic activities are yet to be identified. An LC-ESI-Orbitrap-MS(n)metabolite profile of a hydroalcoholic extract of comfrey root guided the identification of 20 compounds, including a new arylnaphthalene lignan bearing a rare delta-lactone ring, named comfreyn A. Its structure was determined using extensive 2D NMR and ESI-MS experiments. Additionally, the occurrence of malaxinic acid, caffeic acid ethyl ester, along with the lignans ternifoliuslignan D, 3-carboxy-6,7-dihydroxy-1-(3 ',4 '-dihydroxyphenyl) -naphthalene, globoidnan A and B, and rabdosiin was reported inS. officinalefor the first time. These results helped to redefine the metabolite profile of this medicinal plant. Finally, caffeic acid ethyl ester and comfreyn A were found to significantly inhibit E-selectin expression in IL-1 beta stimulated human umbilical vein endothelial cells (HUVEC), with EC values of 64 and 50 mu M, respectively.