A crude drug is any naturally occurring, unrefined substance derived from organic or inorganic sources such as plant, animal, bacteria, organs or whole organisms intended for use in the diagnosis, cure, mitigation, treatment, or prevention of disease in man or other animals.
Crude drugs are unrefined medications in their raw or natural forms. Prior to the 1950s, every pharmacy student learned about crude drugs in pharmacognosy class. Pharmacognosy is the study of the proper horticulture, harvesting and uses of the raw medications found in nature.
Raising, harvesting and selling crude drugs was how many large pharmaceutical companies started out. Companies such as Eli Lilly and Company sold crude drugs to pharmacists to save them time and money, but the early pharmacy graduate would know how to raise their own crude drugs if need be.
1. Collecting of medicinal plants
A. Suitable time for collection
The amount of a constituent is usually not constant throughout the life of a plant. The stage at which a plant is collected or harvested is, therefore, very important for maximizing the yield of the desired constituent. The differences are sometimes not only quantitative but also qualitative.
B. Rules for collection
The following general rules are based on assuming that the material is best collected when the organ in question has reached its optimal state of development:
1.Roots and rhizomes are collected at the end of the vegetation period, i.e. usually in the autumn. In most cases they must be washed free of adhering soil and sand.
2.Bark is collected in the spring.
3.Leaves and herbs are collected at the flowering stage.
4.Flowers are usually gathered when fully developed.
5.Fruits and seeds are collected when fully ripe.
C. Methods of collection
Medicinal plants must be largely collected by hand. This is especially true in the case of wild plants.With cultivation on a large scale, it may be possible to use modern agricultural harvesters, but in many cases, e.g. barks, manual collection is unavoidable. Thus, the cost of drug production is largely the cost of the labor involved.
2. Preservation of plant material
The plant material must first be preserved so that the active compounds will remain unchanged during transport and storage. The cells of living plants contain not only low molecular-weight compounds and enzymes, but they also have many kinds of barriers that keep these constituents apart. When the plant dies, the barriers are quickly broken down and the enzymes then get the opportunity to promote various chemical changes in the other cell constituents, e.g. by oxidation or hydrolysis. Preservation aims at limiting these processes as far as possible.
•The most common method for preserving plant material is drying.
•Enzymic processes take place in aqueous solution. Rapid removal of the water from the cell will, therefore, largely prevent degradation of the cell constituents.
•Drying also decreases the risk of external attack, e.g. by moulds.
•Living plant material has a high water content: leaves may contain 60-90% water, roots and rhizomes 70-85%, and wood 40-50%. The lowest percentage, often no more than 5-10%, is found in seeds.
•To stop the enzymic processes, the water content must be brought down to about 10 %.
•Drying must be done quickly, in other words at raised temperatures and with rapid and efficient removal of the water vapor.
•The most efficient drying is achieved in large driers of the tunnel type. The plant material is spread out on shallow trays, which are placed on mobile racks and passed into a tunnel where they meet a stream of warm air.
•The air temperature is kept at 20-40 °C for thin materials such as leaves, but is often raised to 60-70 °C for plant parts that are harder to dry, e.g. roots and barks.
•When the crude drug has been collected under primitive conditions, without access to a drier, it must be...