Ayurvedic medicinal substances are used to bring about a balance of the tridoshas In traditional Ayurvedic practice, a medicinal formula is always considered as being more than merely the sum of its parts. It is the overall balance or action of a formula that is valued.
Preparation of Ayurvedic drugs follows the general Ayurvedic philosophy that emphasizes the whole; that is, substances are combined in such a way that their natural attributes synergistically enhance the action of the whole formula .Traditional formulas are often named. The name may denote a specific combination of herbs and other products prepared in a prescribed way, or formulas may be named for their major ingredient(s), for the person who first devised the formula, for the therapeutic action, for the part of the plant used, etc, for example Triphala powder is the mixture of powders of three fruits amla, baheda and hirda: Chyavanprash is a semisolid formulation named after a sage ‘Chyavan’ who first devised the formula.
The principles that guide Ayurvedic medicinal formulation are:
synergy, opposition, enhancement, protection, and balance.
Synergy is the enhancement of the effectiveness of herbs and minerals with similar or complementary action, when they combine together.
Opposition is the counterbalancing of an undesirable effect an herb or mineral by adding another ingredient with the opposite action.
Enhancement is the promotion of the efficacy of the main ingredient, by either increasing its activity or its absorption, by the addition of other ingredients to a formulation.
Protection describes when the potential toxicity of a formula is checked by adding mild laxatives or diuretics that promote elimination.
Balance describes when the antagonistic actions of different portions of a formula are considered in balance with each other.
Single drugs are rarely used in Ayurveda. The formulations often contain heterogeneous mixtures of herbs and minerals with a complex process of purification and preparation.
The traditional methods used to prepare Ayurvedic drugs are based on the principles of extraction, concentration, and purification. The choice of preparation method depends on the part of the plant to be used, on its condition (fresh or dried), and on the drug's expected use; for example, cold decoctions are preferred for conditions attributed to an excess of pitta. Plants can also be used whole or as their expressed juice.
A common method for the preparation of an herbal decoction involved 1 part of herb to 16 parts of water. This mixture is then gently heated until it reduced to one-fourth of the original volume. Water is the major solvent used for extraction, but milk, oil, or fermented juices are also used. Both medicinal wine (asava-arishta) and medicinal jams (leha-avaleha) are used in Ayurvedic preparations.
Some substances used in Ayurvedic medicine are toxic in their original form, such as poisonous herbs (aconite) or metals (lead, mercury, arsenic, antimony). Shodhana (purification) is the process by which toxic substances are purified; that is, rendered less toxic. For example, detoxification of mercury involved heating and cooling the mercury salt, grinding it, and then suspending and re-suspending the substance in a variety of liquids. Specific products that facilitate the process are added at each stage of preparation. In addition, the instructions may call for the use of a specific vessel at different stages of preparation, and they may be detailed to the point of stating from which direction the heat is to be applied. It is the experience of Ayurvedic practitioners that at the conclusion of an appropriate purification process, the toxic substances are no longer poisonous but are therapeutic.
The classical Ayurvedic methods of preparation are complex, tedious, and shortcuts in preparation may make a significant difference in the efficacy and safety of the resultant product. Because of this, it may be beyond the scope of the average scientific paper to exactly describe the method in which an herb is prepared, especially if a formula is used. This may create a problem in replicating the results of other researchers.
Properties of Ayurvedic Herbs
Ayurvedic herbs are described and classified according to five major properties: rasa (taste), guna (physicochemical properties), veerya (potency), vipaka (post-digestive effect), and prabhava (unique effect of the drug) .The term rasa, mean taste, can also mean dhatus or tissues.
It is divided into six major tastes: madhura (sweet), amla (sour/acid), lavana (salty), katu (pungent), tikta (bitter), and kashaya (astringent). In Ayurveda, each taste is made of a combination of two of the five basic elements or mahabhutas (earth, water, fire, air, and ether). Each taste has corresponding effects on the three bodily doshas (pitta, vata, and kapha).
It represents the more physical aspects of a medicinal substance. There are five major classes of guna, and each class corresponds to one of the major elements:
heaviness corresponds with earth;
unctuousness with water;
keenness and sharpness with fire;
dryness with air; and
light with ether.
Gunas are generally considered in pairs: light/heavy, wet/dry, etc. There is an extensive subdivision of guna based on combinations with the elements, but its description is beyond the scope of this report
It represents the active principle or potency of a drug.
Factors such as growth conditions, harvesting technique, and storage affect an herb's veerya. Various authorities have different classification systems for this attribute. The simplest system classifies veerya as having properties that range between hot and cold. Substances that heat are pitta dominant; cooling ones are kapha and vata dominant.
It is the quality a substance takes on after it has been acted on by the body. After digestion, the rasas are simplified into three groups corresponding to three vipakas.
It refers to a drug's unique influence on the body. Even though the drugs have the same rasa, guna, veerya, and vipaka they may have different actions in the body. The drug's prabhava accounts for these differences.