ABSTRACT
Forsyqinlingines C (1) and D (2), two C9 -monoterpenoid alkaloids bearing a rare skeleton, were isolated from the ripe fruits of Forsythia suspensa. Their structures, including absolute configurations, were fully elucidated by extensive spectroscopic data and ECD experiments. The plausible biogenetic pathway for compounds 1 and 2 was also proposed. In vitro, two C9 -monoterpenoid alkaloids showed anti-inflammatory activity performed by the inhibitory effect on the release of ß-glucuronidase in rat polymorphonuclear leukocytes (PMNs), as well as antiviral activity against influenza A (H1N1) virus and respiratory syncytial virus (RSV).
Subject(s)
Alkaloids/chemistry , Anti-Inflammatory Agents/chemistry , Antiviral Agents/chemistry , Forsythia/chemistry , Monoterpenes/chemistry , Alkaloids/isolation & purification , Alkaloids/pharmacology , Animals , Anti-Inflammatory Agents/isolation & purification , Anti-Inflammatory Agents/pharmacology , Antiviral Agents/isolation & purification , Antiviral Agents/pharmacology , Forsythia/metabolism , Fruit/chemistry , Fruit/metabolism , Glucuronidase/metabolism , Influenza A Virus, H1N1 Subtype/drug effects , Magnetic Resonance Spectroscopy , Molecular Conformation , Neutrophils/cytology , Neutrophils/drug effects , Neutrophils/metabolism , Platelet Activating Factor/pharmacology , Rats , Respiratory Syncytial Viruses/drug effectsABSTRACT
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.