The Role of Plant-Derived Bioactive Compounds in Modulating Host–Microbe Interactions and Immune Responses

Plant-derived bioactive compounds play a pivotal role in modulating host–microbe interactions and immune responses through their multifaceted biological activities, including antimicrobial, anti-inflammatory, antioxidant, and immunomodulatory effects. These phytochemicals—such as polyphenols, flavonoids, alkaloids, terpenoids, and saponins—not only directly inhibit the growth and virulence of pathogenic microorganisms but also enhance the growth of beneficial gut microbiota, thereby promoting a balanced microbial ecosystem. This modulation of the gut microbiome, in turn, influences systemic immune functions by regulating key signaling pathways, such as NF-κB, MAPK, and JAK/STAT, and by altering the production of cytokines, chemokines, and reactive oxygen species. Furthermore, plant-derived compounds can strengthen epithelial barrier integrity and stimulate the activity of innate and adaptive immune cells, including macrophages, dendritic cells, T cells, and B cells. By restoring microbial homeostasis and modulating immune responses, these natural agents hold significant therapeutic potential for preventing and managing a wide range of inflammatory, infectious, and autoimmune diseases, making them promising candidates for the development of novel nutraceuticals and functional foods.