Chapter 17 - Plant-Derived Immunomodulators

Abstract

Human immune system is a complex interplay of numerous dynamic cellular and biochemical components. The dynamicity in immune “homeostasis” is altered by certain exogenous and endogenous factors causing pathophysiological conditions. The states of pathophysiology can be moderated by the immunomodulators to restore normalcy. The restorative and rejuvenating property of the immunomodulators strengthen the body’s defense mechanisms against such maladies. These immunomodulators could either induce stimulation or amplification of the immune response as immunostimulants or suppress the immune response as immunosuppressants or enhance the efficacy of vaccines as immunoadjuvants. The plant-derived immunomodulators are being considered as safer alternatives as most synthetic immunomodulators pose serious toxicity or other side effects. While immunostimulants are used for treating cancer, immunosuppressants can help to treat various autoimmune and hypersensitivity disorders. Several commonly known plants like Acorus calamus, Actinidia macrosperma, Allium sativum, Alpinia galangal, Alternanthera tenella, Andrographis paniculata, Angelica sinensis, Argyreia speciosa, Averrhoa bilimbi, Azadirachta indica, Boerhaavia diffusa, Catharanthus roseus, Centella asiatica, Codonopsis pilosula, Cynodon dactylon, Curcuma longa, Ficus benghalensis, Ganoderma tsugae, Morus alba, Murraya koenigii, Ocimum sanctum, Panax ginseng, Pelargonium graveolens, Phyllanthus emblica, Picrorhiza scrophulariiflora, Senegalia catechu, Terminalia arjuna, Tinospora cordifolia, Tridax procumbens, Withania somnifera, Zingiber officinale, etc. are currently being investigated for their immunomodulatory potentials. On the other hand, many plant-derived bioactive compounds like flavonoids, iridoid glycosides, polysaccharides, saponins, terpenes, cordifolioside A, syringing, curcumin, resveratrol, epigallocatechol-3-gallate, quercetin, colchicine, capsaicin, andrographolide, genistein, flavopiridol, combretastatin, lycopene, dendroside, dendronobilosides, etc. play an immunomodulatory role. Medicinal plants induce a nonspecific widespread modulation of the immune system with effects on various immune cells, namely, macrophages, natural killer cells, and granulocytes. Hence, a better understanding of immunomodulatory roles of plants, their mode of action, and phytoconstituents would enable us to identify lead compounds from natural sources for the development of novel and safe immunomodulators that can fortify current therapies.