RasayanaRasayana, a Sanskrit word (with literal meaning: Path (ayana) of the Juice (rasa), or Elixir vitae), is used to describe chemistry and alchemy, and chemistry is generally called Rasayan Shastra in Sanskrit, Marathi, Hindi, Kannada and several other Indian languages. Ancient rasayana texts center around the use of prepared forms of mercury (see samskaras), as do occidental alchemical texts. However, there is also ample mention of the preparation of medical tinctures in the ancient science of rasayana; rasayana is in fact a part of Ayurveda.
Ayurveda, the oldest health science has eight branches. Rasayana (rejuvenation) is one of them. Rasa has different meanings like "taste“, “essence", "flavor”, ”juice”, or “emotion", but is not limited to any of these. In therapeutic process Rasa is concerned with the conservation, transformation, and revitalization of energy. Rasa nourishes our body, boosts immunity and helps to keep the body and mind in best of health. Rasayana describes an herbal preparation that promotes a youthful state of physical and mental health and expands happiness. Rasayana herbs have high levels of both safety for daily use and effectiveness. They are given to small children as tonics, and are also taken by the middle-aged and elderly to increase longevity.
Rasayana herbs and formulas are often confused with the categories of adaptogens, amphoterics, alteratives and tonics, although they are not identical. Rasayanas affect the body in a general way, i.e . they may affect the immune system rather than the lungs. They are nontoxic in normal doses and are amphoteric, in that they won't over-tonify the body. Tonics will build up or stimulate the body towards normal health but can be over-tonifying. Alteratives will help normalize physiology, but do it through gentle eliminative functions that tend to focus on one or more organs, so are quite different. Amphoteric herbs seem to have a built in buffer that will help the body achieve homeostatic or allostatic balance, building or eliminating to achieve physiological equilibrium. While all rasayanas are amphoteric, some amphoteric herbs can be specific to an organ and are thus not rasayanas. Both rasayanas and adaptogens are nontoxic, and amphoteric, but adaptogens tend to work on a body-wide basis, by stimulating the HPA axis and the neuroendocrine system. Some rasayanas do not stimulate the HPA axis or may focus somewhat more narrowly on major systems of the body such as the digestive or immune systems. However the categories tend to overlap and many herbs belong to both categories.