Undescribed Alkamides From Echinacea purpurea and Echinacea angustifolia: Chemical Composition and Anti-inflammatory...

Echinacea products are among the most widely used herbal supplements in the United States, primarily valued for their purported alleviation of common cold symptoms. Herein, we report the isolation and characterization of eight alkamides including two new ones (1 and 2) from the roots of two Echinacea species: E. purpurea (1, 3, and 4) and E. angustifolia (2, and 5‒8). This study provides the first comprehensive ¹³C nuclear magnetic resonance assignments of all isolated alkamides. The absolute configuration of 1 was established using Diastereomeric Parameter 4 plus probability analysis and specific rotation. The anti-inflammatory activity of the purified compounds and extracts was evaluated by measuring the inhibition of inducible nitric oxide synthase in lipopolysaccharide-stimulated mouse macrophages (RAW264.7), alongside cytotoxicity assessments. The purified alkamides and the crude extracts exhibited modest anti-inflammatory effects. The current study provides an understanding of the chemical composition of Echinacea and identifies potential markers for distinguishing E. purpurea from E. angustifolia.