Indian medicinal plants used as immunomodulatory agents: A review

India is a country with rich biodiversity and enormous treasure of medicinal plants and consequently called as medicinal garden of the world, many indigenous systems such as Ayurveda, Yoga, Unani, Homeopathy, Naturopathy, and Siddha are well-known and practiced in India from decades. A large number of Indian medicinal plants have been reported to possess immunostimulant activity and thus can serve as potential source of drug in various immunocompromised states such as AIDS, cancer, and for treatment of various chronic infections. At present, there is much-growing interest in the use of these medicinal plants as modulators of the complex immune system. 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, lactones, alkaloids, and glycosides, present in several plants, have been reported to be responsible for the plant’s immunomodulating properties. Thus, the search for natural products of plant origin as new leads for the development of potent and safe immunosuppressant and immunostimulant agents is gaining much major research interest. Keeping in mind, the tremendous potential of the medicinal plants and their derived drugs, this review also discusses biological screening methods for various plant drugs that focus on revealing the mechanism involved in immunomodulation. This review further focuses on the various medicinal plants available in India used to enhancement and suppresses of impaired immune system under unfavorable conditions.