Abstract
The phagocyte–microbe interactions in the immune system is a defense mechanism but when excessively or inappropriately deployed can harm host tissues and participate in the development of different non-immune and immune chronic inflammatory diseases such as autoimmune problems, allergies, some rheumatoid disorders, cancers and others. Immunodrugs include organic synthetics, biological agents such as cytokines and antibodies acting on single targets or pathways have been used to treat immune-related diseases but with limited success. Most of immunostimulants and immunosuppressants in clinical use are the cytotoxic drugs which possess serious side effects. There is a growing interest to use herbal medicines as multi-component agents to modulate the complex immune system in the prevention of infections rather than treating the immune-related diseases. Many therapeutic effects of plant extracts have been suggested to be due to their wide array of immunomodulatory effects and influence on the immune system of the human body. Phytochemicals such as flavonoids, polysaccharides, lactones, alkaloids, diterpenoids and glycosides, present in several plants, have been reported to be responsible for the plants immunomodulating properties. Thus the search for natural products of plant origin as new leads for development of potent and safe immunosuppressant and immunostimulant agents is gaining much major research interest. The present review will give an overview of widely investigated plant-derived compounds (curcumin, resveratrol, epigallocatechol-3-gallate, quercetin, colchicine, capsaicin, andrographolide, and genistein) which have exhibited potent effects on cellular and humoral immune functions in pre-clinical investigations and will highlight their clinical potential.
Highlights
Immunity is the body’s natural defense system against various infectious diseases
Natural products and folklore medicines are the main contributors of the leads in the design and development of therapeutic agents
Numerous illnesses can be alternatively treated by immunomodulation using medicinal plants, instead of chemotherapy
Summary
Immunity is the body’s natural defense system against various infectious diseases. The factors which trigger immunity include previous infection, immunization, and various external stimuli (Baxter, 2007). Natural immunomodulators with clinical potential specific cells and mediators against strange substances constitutes the immune response (Baxter, 2007). The plant-based compounds that served as FIGURE 1 | Cells of innate and adaptive immune response. Innovative technologies and the excessive research on immunomodulatory natural products, plants, their extracts, and their active moieties with immunomodulatory potential, may provide us with valuable entities to develop as novel immunomodulatory agents to supplement the present chemotherapies. The potential use as immunomodulatory agents, modes of action and plant origin of numerous important plant-based lead compounds has been comprehensively discussed (Figure 2). Beside these compounds, other phytochemicals including essential oils, steroids, terpenoids, phenolics, pigments, flavonoids, and alkaloids, etc. The medicinal benefits of curcumin have been known since centuries
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