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Within the past bee an increase in global awareness of environmental issues including the proper usage and preservation of natural resources. Thailand, in an effort to become self-reliant, has strived to fully utilize and protect the existing natural resources including medicinal plants. In solving the country's health problems, the government has resorted to the use of medicinal plants in order to provide basic health card for the people. In spite of the fact that much of the research carried out on Thai medicinal plant has, in the past, been directed towards the isolation of active compounds for use as modern drugs, it is recognized that appropriate modification an development of indigenous drugs are of equal importance.

The intrinsic principles of traditional Thai medicine are propounde on the knowledge of:

1. Drug matters. This concerns the basic knowledge of each drug ingredient which may be derived from plant, animal of mineral. Traditional practitioners must be knowledgeable on the names, description, colour, odour and taste of each drug.

2. Drug attributes. In Thai medicine, drugs are divided into groups according to their pharmacological actions. The tastes ascribed to the formulated drugs are believed to be correlated to their ability to cure certain ailments. For instance, drugs with a cooling taste are said to cure ailments caused by the fire element while those with acrid taste are prescribed for the restoration of the wind element. Individual drugs are recognized as possessing astringent sweet, bitter, acrid, nutty, salty or sour tastes.

3. Drug grouping. To facilitate drug prescription in traditional Thai medicine where a recipe may consist of 30-40 ingredients, a number of drug ingredients are grouped together. These may bi ingredients with similar nature or attributes or they may be different drugs grouped together to form specific entities. Each of these drug groups may consist of two to nine ingredients. An example of these entities is 'the two licorices' comprising Thai licorice (Albizia myriophylla) and Spanish licorice (Glycyrrhiza glabra).

4. Drug dispensing or compounding. In traditional Thai medicine, a drug refers to two or more ingredients mixed together into an appropriate dosage form. The ingredients contained in each recipe may be classified into three main categories, namely the principal drug(s), the adjuvant (s) and the flavouring agents. In general, twenty-five dosage forms are recognized. These include the more common preparations, such as pills, decoctions, alcoholic macerates, snuffs, poultices and suppositories. In addition to these traditional dosage forms, the Ministry of Public Health has permitted two more modern dosage forms for traditional drugs, i.e. tables and capsules. Preservatives are also allowed to be used in traditional drug formulation.

Besides the main principles as outlined above, other factors also have to be taken into consideration. These are:

1. Specific knowledge of drug ingredients. Since more than one drug plant may possess identical common or local names, traditional practitioners must be able to identify the correct species and to differentiate between useful species and poisonous ones. The knowledge on the part or parts of medicinal plants to be used is also essential. Other pertinent information includes the forms in which the drug ingredients are required. Some ingredients are best used fresh while others are used in the dried form. Certain ingredients may need to be detoxified prior to use.

2. Doses. The appropriate amount of each ingredient is usually measured out using the old system of measurements. An example of traditional Thai system of measurement ofr weight is given below.

1 chang (1.200 g)=20tum-lueng
1 tum-lueng(60 g)=4baht
1 baht(15 g)= 4 salueng
1 salueng(3.75 g)=2feung
1 feung (1.875 g)=4 pai
1 pai(0468 g)=2utt

Traditional systems for measuring lengths and capacities also exist.

3. Vehicles. These are liquids used in drug formulation in order to dissolve or to extract active constituents from drug ingredients. In many cases, they may act to potentiate the action of the principal drug. Vehicles used in traditional drug formulation include water, spirit and lime water, for instance. The potency of the elixir may depend on the choice of vehicle used.

4. Methods of preparation. Of the 25 dosage forms previously mentioned, in practice only four or five are in common use and these are briefly described below.

Preparation of Drug Ingredients

All ingredients must first be washed and then cut into small pieces if they are to be used fresh. If dried ingredients are required, fresh ingredients are sliced thinly and sum dried.

Fluid Extracts

Both fresh and dried ingredients may be prepared into the above explanation. The method is suitable for ingredients which are water soluble but may be unappetizing in their crude forms. To prepare an extract, the plant materials are placed into a utensil which may be a clay, an enameled or stainless steel pot. Water is added as stipulated in the recipe or until it just covers the ingredients. The mixture is then boiled for 2-30 minutes depending on the types of ingredients used.

Infusion

A somewhat simpler version of the above procedure, the method entails the addition of boiling water onto finely shredded ingredients contained in a small cup or glass with a lid. The mixture is set aside to brew for 3-5 minutes, after which the clear supernatant is decanted.

Alcoholic Macerates

This method is mostly used for extracting water-insoluble constituents from dried drug ingredients. Air- dried drugs are weighed, wrapped in a piece of muslin and then placed into a glass jar with a tightly fitted lid. Sufficient quantity of spirit (28-40 degree proof) is then added to just cover the ingredients. With daily stirring, the maceration process is usually allowed to proceed of a period of 1-5 weeks.

Pills

To prepare pills, binding agents such as honey or syrup are used. Dried and finely powdered ingredients are placed into a bowl and a small amount of honey is gradually added. This mixture is then kneaded into a large ball. The mixture may be shaped into small round balls by hand or with the aid of a special tool. The finished pills are then sun dried for 1-2 days. The pills produced in this way may be stored in closed jars for up to one month.

As outlined above, the techniques of drug compounding in traditional Thai medicine are, in most cases, kept simple with minimum requirement for sophisticated equipment, so that they could e practiced at household and community levels. With the advancement of today's technology, however, the methods of indigenous drug production could be vastly improved to make the drugs more effective, safer and more acceptable to the modern generation.

Tamarind
Scientific name: Tamarindus indica Linn.
Family:GEGUMINOSAE
Vernacular name:Ma-khaam

The pulp is used as a laxative in traditional Thai medicine while the kernels from roasted ripe seeds are used as an anthelmintic for threadworms in children. The pulp contains 12-15 percent of organic acids including tartaric, citric and lactic acids.

Plaunoi
Scientific name: Croton sublyratus Kurz
Family:DUPHORBIACEA
Vernacular name:Plaunoi

Indian Senna
Scientific name:Cassia angustifolia Vahl
Family:LEGUMINOSAE
Vernacular name:Ma-khaam-khaek

Asiatic Pennywort
Scientific name:Centella asiatica Urban
Family:UMBELLIFERAE
Vernacular name:Bua-bok

Plai
Scientific name:Zingiber cassumunar Roxb.
Family:ZINGIBERACEAE
Vernacular name:Plai

The pressed juice from pounded fresh rhizomes has long been used to relieve sprains. The powder derived from the dried rhizomes is used in traditional medicine as an anti-asthmatic agent.