Mechanistic insights into the antimicrobial activity of plant-based immunomodulators: A narrative review

Abstract

Immunomodulators have been used in combination with other therapeutic modalities as a prophylaxis to prevent or treat various immune-related diseases including infectious diseases. They have been investigated as possible alternative anti-infectives which are less toxic and inexpensive, and less prone to microbial resistance than the contemporary antimicrobials. The mechanisms of antimicrobial activity of these immunomodulators may involve stimulation of secretion of cytokines, enhancing phagocytosis, and producing antimicrobial peptides to effectively assist the immune system to combat infections. In this review, the antimicrobial effects and mechanisms of various plant-based immunomodulators through modulation of immune response were critically analyzed and discussed. Various studies have provided quantitative data on the effectiveness of these immunomodulators including lectins, polysaccharides, alkaloids, flavonoid glycosides, triterpene glycosides, and polyphenols in enhancing the body's defense mechanisms against infections. Among these, lectins and polysaccharides have been much investigated. The compounds were able to trigger the release of soluble mediators that assist in coordinating the immune system against pathogens and modulate the activity of immune cells against bacteria via phagocytosis. However, there is limited investigations on their efficacy as possible alternative anti-infectives. Most studies have been carried out experimentally to elucidate the specific mechanisms underlying the antimicrobial effects of these immunomodulators. Future research on the antimicrobial effects of plant-based immunomodulators in humans is essential to elucidate their mechanisms of action within the human immune system. Furthermore, thorough studies are necessary to evaluate their safety and efficacy for clinical use, ensuring their potential as valuable tools in the fight against infections.