Collection of Crude Drugs


Collection of crude drugs influenced by various factors like season, time, age of plants etc. Hence it is important to collect the crude drug during appropriate season or time period to get the maximum quality product from the source materials. The quantitative and qualitative concentration of active chemical constituent varies with the stages of plant growth and development. The best time for collection of crude drugs is determined on the basis of quality and quantity of active chemical constituent of targeted medicinal plant. For example, digitalis have highest level of total glycoside in first year of leaves, but glycoside which is medicinally important reach highest level in second year of plants. We will look best time period for collection of some plant parts.

Collection of some important plant parts


Leaves are collected when flowering is just started or reach its height. They should be collected in dry weather as wet weather deteriorate their quality. The leaves collected in weather shows discoloration on drying. It is preferred to collect leaves along with stem and then separate them. For example, coca leaves collected when they are ready to fall from stem.


Flowers collection is preferred in dry weather when they are fully expanded. The flowers collected in wet weather show discoloration on drying. For example, clove is collected when in bud and kousso flower is collected after pollination and fertilization.


Fruits collected when are fully grown, but they may be fully ripe or half ripe. For example, fennel and dill collected when they are fully ripe. Cardamom is just collected before the dehiscence.


Barks are preferably collected in autumn (after fall of leaves) or spring (before development of the leaves). Bark like cinnamon is collected in rainy season and wild cherry bark is collected in autumn, because during this season the concentration of active chemical constituent is high.

There are three methods of bark collection, felling, uprooting and coppicing. In felling tree is cut near to the ground level. Branches and stem are removed from the bark. In uprooting method, trees which are 10-15 years old are cut and root is dug up. The bark is removed from root, branches and trunk. In coppicing method stems are cut down at short distance from the ground, then bark is removed from trunk and branches.

The underground drugs

The underground organs of plants such as roots and rhizomes are preferably collected in autumn. In autumn their tissues are fully stored with reserve foods and the concentration of active chemical constituents is abundant. These parts should be freed from soil by shaking or brushing the drug.

After collection of parts of medicinal plants, these parts go through preliminary process like, elimination of contaminants and undesirable materials, washing, sorting and cutting. The collected crude drugs should be protected from insects, birds, pests, rodents and domestic animals. Different plant species and parts should be stored separately to protect from contamination.


Harvesting is an important procedure in collection of crude drugs. While harvesting it is important to give attention to type of plant and their chemical standards desired. Harvesting is done by skilled workers. Genuine drug is separated from the similar looking drugs.

The underground drugs (roots, rhizomes, etc.) are harvested with the help of mechanical device like diggers or lifters. These drugs are washed with water to remove earthy matter. Drugs constituting all aerial parts harvested with the help of binders. Flowers, seeds and small fruits harvested with the help seed striper. Fennel, coriander and carraway uprooted and dried. Harvesting of clove is done by beating plant with bamboos. Seaweeds producing agar are harvested with the help of long handled forks.

WHO guidelines for harvesting

  • Drugs should be harvested when reach best quality.
  • Damaged plants or parts should be separated.
  • Drugs should be harvested in best conditions, avoiding wet soil, rain and high humidity. If harvesting is done in wet conditions adverse effects should be counteracted.
  • Cutting devices should be adjusted such a way to minimise soil contamination.
  • The harvested drug should not come into direct contact with soil.
  • Care should be taken to avoid mixing of toxic weeds.
  • Containers should be free from contamination from previous harvests. Containers must be kept in dry conditions free from pests and inaccessible to rodents, livestock and domestic animals.
  • Mechanical damage must be avoided.
  • Freshly harvested drugs should be transported as quickly as possible to avoid thermal degradation.


Drying of crude drug is important to improve its quality make it resistant to microbial growth. Drying also reduces moisture content and inhibits partially enzymatic reaction. They are two types of methods for drying, natural drying (sun drying) and artificial drying.

Natural drying

In this method drug is dried under direct sunlight. For example, seeds and fruits. Drugs containing volatile oils and natural colours are dried in shade, to retain the chemical constituent. For example, peppermint, digitalis, clove, senna, etc.

Artificial drying

Artificial drying includes, tray dryers, vacuum dryers and spray dryers.

Try dryers (oven): This method is suitable for drugs which do not contain volatile oils and are quite stable to heat. In this method hot air of desired temperature is circulated through dryers. For example, belladonna roots, cinchona barks, tea.

Vacuum dryers: Heat sensitive drugs are dried using vacuum dryers. For example, tannic acid and digitalis leaves.

Spray dryers: Drugs which are highly sensitive to atmospheric conditions and heat are dried by spray dryers. This technique is used for quick drying of economically important plant constituents. For example, papaya latex, pectin, tannins, milk, etc.

Dressing (garbling)

In this process unwanted particles like sand, dirt and foreign organic parts of the same plant are removed. In case of lobelia and stramonium excessive stems needed to be removed. Pieces of irons present in castor seeds must be removed before crushing.


  • Storage site for medicinal material should be well ventilated, dry and protected from light (amber coloured container).
  • Floor should be tidy, without cracks and easy to clean.
  • Processed medicinal plant material should be packaged in clean, dry boxes, bags or other containers.
  • Materials used for packaging should be non-polluting, clean, dry and in undamaged condition.
  • Wooden boxes and paper bags should not be used for storage of crude drugs.
  • Drugs containing volatile oil should be stored in dry, well aerated building with limited temperature fluctuations.


Crude drugs are collected when they contain maximum concentration of active chemical constituents. After collection crude drugs are required to be processed before marketing. Collection involves processes like harvesting, drying, packing and storage. Collection is important process to maintain good quality crude drugs.

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