The role of plant extracts and Ayurvedic polyherbal preparations in treating various ailments has been acknowledged since time immemorial. Studies based on the effect of these extracts in treatment of different diseases have also been well documented. Indian medicinal literature also emphasizes the synergistic effect of polyherbal drugs in restoring and rejuvenating immune system. This review focuses on the immunomodulatory potential of the polyherbal preparation, Triphala and its three constituents, Terminalia bellerica, Terminalia chebula and Emblica officinalis. The role of Triphala and its extract has been emphasized in stimulating neutrophil function. Under stress condition such as noise, Triphala significantly prevents elevation of IL-4 levels as well as corrects decreased IL-2 and IFN-γ levels. Under the condition of inflammatory stress its immunosuppressive activity is attributed to its inhibitory action on complement system, humoral immunity, cell mediated immunity and mitogen-induced T-lymphocyte proliferation. The aqueous and alcoholic extracts of the individual constituents reportedly enhance especially the macrophage activation due to their free radical scavenging activity and the ability to neutralize reactive oxygen species. This study thus concludes the use of Triphala and its three individual constituents as potential immunostimulants and/or immunosuppressants further suggests them to be a better alternative for allopathic immunomodulators.
Keywords: Emblica officinalis; Immunomodulator; Terminalia bellerica; Terminalia chebula; Triphala.