Encyclopedia of Ayurvedic Medicinal Plants

    
     In Ayurvedic system of medicine, materials from different sources, viz., plants, animals, metals and minerals, are used to prepare the formulations. While the processes of preparing metal-based Ayurvedic formulations are well-specified, little is known about the form in which metal exists in the final product or its mechanism of action. Such knowledge is very much imperative not only for advancement of drug research but also for enhancing the effectiveness of Ayurvedic drugs and for improving their preparation.

Metal-based formulations have been in use since time immemorial. Rigveda mentions the use of gold, silver, copper and bronze in the treatment of disease. Similarly, Charaka and Sushruta, two of the founding fathers of Ayurveda, describe the tonic value of a number of minerals. Nagarjuna, considered to be the father of Rasa Shastra, endeavoured to free the entire world from disease by using processed mercury. According to the Rasa Sharstra the metals, referred to as Dhatu and Updhatu, supplement several essential, disease-preventing elements in the tissues of human body. The metal-based formulations are particularly effective in curing diseases related to organs where such metals are naturally present (Rasatarangini and Rsaratnasamuchaya).

In metal-based preparations of Ayurveda, the metal is not used as it is, but after subjecting it along with herbs, to an involved series of processing steps. The output of such a process is a fine powder, called Bhasma, which is used either alone as a drug or in combination with other herbs (herbo-mineral preparations, e.g., Chandraprabha vati).

Preparation process

Preparation of Bhasma, as mentioned above, is an elaborate process involving Sodhana and Bhasmikaran. The classical texts of Ayurveda prescribe in great detail the way the above processes need to be performed. Metals are first purified through a process called Sodhana, during which the metal is repeatedly heated and then cooled in herbal extracts. This is followed by Bhasmikaran where, the sodhit metal is repeatedly triturated with herbs (bhavana) and calcined in closed earthen crucibles in a pit, by burning cow dung cakes (a process called puta), to obtain Bhasma. The size of the pit, the number of cow dung cakes to be used to obtain a specific temperature and the duration of heating are specified in detail. This process is repeated as many times as prescribed in the classical texts for each preparation. Hence we have dasa puta (10 cycles), shatha puta (100 cycles), sahastra puta (1000 cycles), etc. To ensure that the Bhasma is properly prepared, a set of tests are also specified (Ayurvedic Formulary of India, 2003).

Though Bhasma preparations are widely used in Ayurveda, practically nothing is known as to what happens to the metal when it is subjected to bhavana with herbs and the subsequent calcination process. The traditional texts also do not throw any light on the changes undergone by a metal during the above processes.

It is interesting to note that same metal is processed (i.e. given bhavana) with different sets of herbs, to be used for different indications. In this context, it is all the more interesting to study as to what changes the metal goes through during the different steps of bhavana and subsequently during the calcination process that it acquires a non-toxic, therapeutically efficacious form. Bhasma are known to be effective in very small doses, usually a few milligrams. Shelf-life of Bhasma is believed to be infinite.

New technologies for analyzing the composition of drugs can help answer the above questions, at least partly. Atomic absorption spectroscopy and flame photometry studies have their limitations as they only reveal the presence of the specific metal and the quantity of the metal in a preparation. Earlier, there used to be a view that metal oxides/sulphates and other salts are formed during the process of puta. However, a recent study showed that the formation of metal oxide is an intermediate change; and that the metal subsequently takes a new, hitherto unknown, form that still needs to be characterized (Tripathi et al, 2003).

With the advent of nano-technology, the current belief is that during bhasmikaran the metal acquires nano particle size, which is responsible for its enhanced bioavailability and activity and hence the dose is small. Even if it is so, it remains to be answered as to why the same metal is given bhavana with different set of herbs to be used in different disease conditions. There has to be much more to the elaborate process involved in the preparation of Bhasma than simply imparting nano size to the metal particles. If we understand this, we may be able to reduce the number of steps, especially for satha puta (100 cycles) and sahastra puta (1000 cycles), using modern technologies and equipment available, including grinding machines (for bhavana) and muffle furnace to ash, etc. It may also throw some light on the mechanism of action of Bhasma and open new avenues for understanding disease, and cure using Bhasma.

Recently, doubts have been raised on the safety of the Ayurvedic preparations using Bhasma and concern is expressed regarding the metal toxicity of traditional preparations containing Bhasmas. Ayurveda fraternity argues that toxicity can arise only from a metal in its free form, and that a Bhasma prepared according to the classical methods never contains a metal in free form. It is difficult to resolve this dispute. Ayurvedic practioners themselves admit that due to commercialization of ayurvedic preparations, some of the manufacturers are resorting to shortcuts in the preparation of Bhasma, because of which there is a chance of the presence of free metal.

Though the study as to what happens to the metal during process of preparation of Bhasma is of academic and research interest, it is essential to ensure that there is no toxicity due to the metals added in large quantities in herbo-mineral preparations of Ayurveda, as they are incorporated in the formulations for their specific therapeutic role. To derive benefit from such preparations, it is imperative to prepare the Bhasmas as per the classical methods and subject them to toxicity testing and thereby ensuring their efficacy and safety.