(THE VALUABLE GIFT OF NATURE)
According to the World Health Organization (WHO), about three-quarters of the world population relies upon traditional remedies (mainly herbs) for the health care of its people. In fact, herbs and/or plants are the oldest friends of mankind. They not only provided food and shelter but also served to cure different ailments.
Herbal medicine, sometimes called traditional or natural medicine, has always existed in one way or another in different cultures and civilizations, such as Ayurvedic (India), Egyptian, Western, Chinese, Kampo (Japan) and Greco-Arab or Unani-Tibb (south Asia).
Traditional medicine all over the world is currently being revalued through extensive research activity on various plant species and their therapeutic properties
Ethnopharmacological activities in Ayurvedic medicine
Ayurveda stresses the use of plant-based medicines and treatments. Various plants identified in the Indian Ayurvedic system of medicine display a wealth of pharmacological properties. The ayurvedic system of medicine is one of the oldest systems of medicine and includes various ethnopharmacological activities such as immunostimulation, tonic, neurostimulation, anti-ageing, antibacterial, antiviral, antirheumatic, anticancer, adaptogenic, etc.
1 An entire section of the Materia Medica of Ayurveda is devoted to “Rasayana”, drugs reputed to enhance body resistance.
2 Listed as a class in the texts of traditional Indian Medicine literature, Rasayana consists of a number of plants reputed to promote physical and mental health, improve defense mechanisms of the body and enhance longevity. These attributes are similar to the modern concept of adaptogenic agents, which are known to afford protection of the human physiological system against diverse stressors.
3 A number of medicinal plants as Rasayanas have been claimed to possess immunomodulatory activity, e.g., Withania somnifera, Tinospora cordifolia, and Mangifera indica.4, 5 They can depress or potentiate the host’s capacity to resist infection and tumors non-specifically, or react specifically to a foreign substance. Immunomodulators act on the complex network of mechanisms of the immune system in a way not yet fully elucidated
This may be defined as the body’s ability to identify and resist large numbers of infectious and potentially harmful microorganisms, enabling the body to prevent or resist diseases and inhibit organ and tissue damage. The immune system is not confined to any one part of the body. Immune stem cells, formed in the bone marrow, may remain in the bone marrow until maturation or migrate to different body sites for maturation. Subsequently, most immune cells circulate throughout the body, exerting specific effects. The immune system has two distinct but overlapping mechanisms with which to fight invading organisms, the antibody-mediated defense system (humoral immunity) and the cell-mediated defense system (cellular immunity).
6) Immune systems
The basic architecture of the immune system is multilayered, with defenses on several levels. Most obvious and primary is the skin: the first barrier against infection. Another is physiological, where conditions like the temperature and pH of the body provide inappropriate living conditions for foreign organisms. Once pathogens have successfully entered the body, they are addressed by the innate and/or the acquired or adaptive immune system. Both systems consist of a multitude of cells and molecules that interact in a complex manner to detect and eliminate pathogens. Detection and elimination depend upon chemical bonding: surfaces of immune system cells are covered with various receptors, some of which chemically bind to pathogens, while others bind to other immune system cells or molecules to enable the complex signaling system that mediates the immune response.
These are biological or synthetic substances that can stimulate, suppress or modulate any aspect of the immune system including both adaptive and innate arms of the immune system.
Classification of immunomodulators
Clinically, immunomodulators can be classified into the following three categories:
Immunoadjuvants are used to enhance the efficacy of vaccines and therefore could be considered specific immune stimulants. Immunoadjuvants hold the promise of being the true modulators of the immune response. It has been proposed that they be exploited as selectors between cellular and humoral helper T1 (Th1) and helper T2 cells (Th2), immunoprotective, immunodestructive, and reagenic [immunoglobulin E (IgE)] versus IgG type immune responses—posing a real challenge to vaccine designers.
8) Immunostimulants are inherently non-specific as they are envisaged as enhancements to a body’s resistance to infection. They can act through innate as well as adaptive immune responses. In healthy individuals, the immunostimulants are expected to serve as prophylactic and promoter agents, i.e., as immunopotentiators, by enhancing the basic level of immune response. In the individual with impairment of immune response, they are expected to act as immunotherapeutic agents.
9) Immunosuppressants are a structurally and functionally heterogeneous group of drugs, which are often concomitantly administered in combination regimens to treat various types of organ transplant rejection and autoimmune diseases.
10) Correlation of immunomodulators with Ayurveda
Ayurveda is a most ancient and yet currently vital tradition practiced widely in India, Sri Lanka and other countries. It has a sound philosophical and experimental basis. Atharvaveda (around 1200 bc), Charak Samhita and Sushrut Samhita (1000–500 bc) are the main classic reference collections that give a detailed description of over 700 herbs.
Concept of Rasayana
The word Rasayana, a combination of two words (rasa and ayana), refers to nutrition and its transportation throughout the body. Rasayana therapy enhances the qualities of rasa, enriching it with nutrients so one can attain longevity, improved memory and intelligence, freedom from disorder, youthfulness, excellence of hair, complexion and voice, optimum development of physique and sense organs, mastery over phonetics and brilliance. As a dedicated stream of medication for immune promotion, antidegenerative and rejuvenating health care, the Rasayana therapy of Ayurveda is known to prevent the effects of ageing and improve the quality of life for healthy as well as diseased individuals. Rasayana is helpful to improve immunity and is normally advised during the degenerative phase of life, which starts from around 45 years in both males and females.
11) Plants as immunomodulators
Several medicinal plants used in the Indian traditional system known as Rasayana (devoted to enhancement of the body’s resistance) have attracted the attention of scientists world-wide. As discussed below, several medicinal plants exhibit not only immunomodulatory activity but also a wide range of antioxidant, antiasthmatic, antiarrhythmic, anti-inflammatory, hepatoprotective, hypocholesterolemic, antifungal, cardiotonic, diuretic, and other medicinal activitie
Table 1. A brief description of common plant-derived immunomodulators
|Asparagus racemosus Wild. (Liliaceae)||Shatavaari||Roots||Saponins, sitosterols||Ulcer healing agent, nervine tonic, anti-gout.15, 23|
|Tinospora cordifolia Miers. (Menispermiaceae)||Amrita, guduuchii||Entire herb||Alkaloidal constituents such as berberine, tinosporic acid||Hypoglycaemic agent, antipyretic.15, 26|
|entella asiatica Linn. (Umbelliferae),||Brahmi||Herb||Triterpenoid saponins||Immunomodulator.6|
This illustration shows what happens when the immune system is “trained” as an immunomodulator