Phytochemical Characterization, Taxonomic Insights, and Immunomodulatory Mechanisms of Echinacea purpurea: A Comprehensive Review on Its Role in Enhancing Host Defences Against Viral and Bacterial Pathogens

Background: Echinacea purpurea (L.) Moench, commonly known as purple coneflower, has been traditionally employed in North American and European herbal medicine for its immune-enhancing properties. In the context of increasing antimicrobial resistance and recurrent viral outbreaks, interest in botanicals with immunomodulatory potential has grown substantially. Objective: To provide a comprehensive synthesis of the phytochemical profile, taxonomic attributes, immunomodulatory mechanisms, and antimicrobial activities of E. purpurea, while identifying research gaps and future directions. Methods: A narrative review was conducted using peer-reviewed literature from databases such as PubMed, Scopus, and Web of Science, focusing on studies published between 1980 and 2025. Key inclusion criteria encompassed original research and reviews reporting on phytochemistry,taxonomy, immune modulation, antiviral and antibacterial activity, and clinical relevance. Results: E. purpurea contains diverse bioactive compounds, including alkamides, caffeic acid derivatives (e.g., cichoric acid), flavonoids, and polysaccharides. These constituents act via modulation of cytokine production, activation of macrophages, enhancement of natural killer (NK) cell function, and regulation of oxidative stress pathways. The plant exhibits notable antiviral effects against respiratory viruses (e.g., influenza, coronaviruses) and antibacterial activity against Gram-positive and Gram-negative species. However, variability in phytochemical content due to cultivation conditions, extraction methods, and plant part used limits reproducibility across studies. Conclusion: The integration of phytochemistry, taxonomy, and mechanistic evidence highlights E. purpurea as a promising adjunct in infection prevention and immune health. Standardized extract formulations, omics-based mechanistic studies, and high-quality clinical trials are needed to translate these findings into consistent therapeutic applications.