Cultivation, Collection of Crude drugs

Cultivation, Collection of Crude drugs

AS per PCI Syllabus

(S. Y.  B. Pharm Sem IV) Unit -I

Cultivation of crude drugs:

Cultivation of medicinal plants requires intensive care and management.

The conditions and duration of cultivation required vary depending on the quality of medicinal plant materials required.

Methods of Propagation

A. Vegetative Propagation (Asexual Propagation)

Vegetative propagation can be defined as regeneration or formation of a new individual from any vegetative part of the plant body. The method of vegetative propagation involves separation of a part of plant body, which develops into a new plant.

Methods of Vegetative Propagation

They are two types:

1. Methods of Natural Vegetative Propagation

2. Methods of Artificial Vegetative Propagation.

1. Methods of Natural Vegetative Propagation

Vegetative Propagation by Stem

Examples

  Runner  :  peppermint.

  Bulb  :  Allium,  Squill.

  Corms  : Colchicum.

  Tuber  : Potato, aconite.

  Offset  : Valerian.

  Rhizome  : Ginger and haldi.

2. Methods of Artificial Vegetative Propagation

1. Cutting

These are the parts of the plant (stem, root or leaf) which, if grown under suitable' conditions, develop new plants.

Stem cutting are generally used to obtained new plants.

Examples: Sugar cane and rose, etc.

2. Layering

Roots are induced on the stem while it is still attached to the parent plant. This part of stem is later detached from the parent plant and grown into a new plant.

3. Grafting

New variety is produced by joining parts of two different plants. The rooted shoot of one plant, call.

stock, is joined with a piece of shoot of another plant known as scion.

Examples: Rose, citrus, rubber, etc.

4. Micro propagation

This method consists of growing cell, tissue and organ in culture. Small pieces of plant organs or tissues are grown in a container with suitable nutrient medium, under sterilized conditions.

The tissue grows into a mass of undifferentiated cells called callus which later differentiates into plantlets. These are then transferred into pots or nursery beds and allowed to grow into full plants.

Importance of Asexual Propagation

1. It is a cheaper, easier and rapid method of multiplication. Many fruit trees usually require 4-5 years to bear the fruits when developed from seeds. The plants developed by vegetative methods take only a year to bear fruits.

2. Plants like roses and chrysanthemum, etc do not form viable seeds. Thus, vegetative propagation is the only method of propagation is the only method of reproduction and continuation of species in such plants.

3. All the plants developed by these methods will be generally similar to the parent plant.

4. Micro propagation is useful in raising disease free plants, homozygous diploids, and those without viable seeds.

B. Seed Propagation (Sexual Propagation)

The process of sexual propagation:

(i) Micro-sporogenesis

Microspores are formed from microspore mother cells inside the anther.

(ii) Pollination

This is the transfer of pollen grains from the anther to the stigma.

(iii) Micro-gametogenesis

This involves the formation of male gametes from microspore.

(iv) Mega-sporogenesis

This process leads to the formation of megaspores from megaspore mother cell, inside the ovule .

(v) Mega-gametogenesis

The events involving the formation of embryo sac from megaspore are included in this process.

(vi) Fertilization

Fusion of male and female gametes takes place, resulting in the formation of zygote.

(vii) Embryogeny

The process involves development of embryo from zygote.

Collection of crude drugs

For the collection of medicinal plants, a proper time should be selected. Herbs are selected for collection at a stage when they yield maximum amount of chemical constituents Skilled labour should be employed as they are trained to identify and select the herbs at a proper stage.

The age of the plant also plays a vital factor for their selection. Diseased plants should be rejected, Season of collection should also be given due consideration while selecting the plants for collection. 

Harvesting

Medicinal plants should be harvested during the optimal season or time period to ensure the production of medicinal plant materials and finished herbal products of the best possible quality. 

The time of harvest depends on the plant part to be used. 

Detailed information concerning the appropriate timing of harvest is often available in national pharmacopoeias, published standards, official monographs and major reference books.

As Per WHO Guidelines

1.Medicinal plants/herbal drugs should be harvested when they are at the best

possible quality for the proposed use.

2.Damaged plants or parts plants need to be excluded.

3.Medicinal plants should be harvested under the best possible conditions avoiding

wet soil, dew, rain or exceptionally high air humidity. If harvesting occurs in wet

conditions possible adverse effects on the herbal drug due to increased moisture

levels should be counteracted.

4.Cutting devices or harvesters must be adjusted such that contamination from soil

particles is reduced to a minimum.

5.The harvested medicinal plant/herbal drug should not come into direct contact

with the soil. It must be promptly collected and transported in dry, clean

conditions.

6. During harvesting, care should be taken to ensure that no toxic weeds mix with

harvested medicinal plants/herbal drugs.

7. All containers used during harvesting must be clean and free of contamination

from previous harvests. When containers are not in use, they must be kept in dry

conditions free of pests and inaccessible to mice/rodents, livestock and domestic

animals.

8. Mechanical damage and compacting of the harvested medicinal plant/herbal

drug that would result in undesirable quality changes must be avoided. 

In this respect, attention must be paid to

 (a) overfilling of the sacks, (b) Stacking up of sacks.

9. Freshly harvested medicinal plants/herbal drugs must be delivered as quickly as

possible to the processing facility in order to prevent thermal degradation.

Processing of herbal raw materials involves various stages from which the crude

drugs undergo after harvesting. It can be classified into primary and secondary

processing which are further sub categorized as follows.

Garbling (Sorting)

This process helps in ensuring the purity and cleanliness of the harvested

material. Dirt like soil, dust, impurities like insects, dead tissues and residual non

medicinal plants are Separated from the raw material. 

The process depends on the part of the plant to be prepared. The process may

involve procedures such as removing dirt and foreign Substances, discarding

damaged parts, peeling of barks, sieving, trimming, removal of hairs from roots,

removal of seeds from fruits, stripping of leaves from stems. 

This may be done by mechanical means but in some cases it is usually performed

manually by hands.

Drying

In some cases, the plant material should be thoroughly dried after washing in

order to prevent the deterioration and degradation of active constituents. They

must be dried as soon as possible to remove moisture and reduce the damage due

to microbial or mould infestation.

Drying also prevents the activation of certain enzymes which may otherwise

degrade the active ingredients and also facilitate grinding and milling of the raw

material. 

Depending on the drug & nature of ingredients, different drying methods can be

used which are as follows.

I) Natural drying

a) Sun drying:

Most herbal raw material can be dried in open air under direct sunshine provided

the climate is suitable. The duration of drying process depends on the physical

structure of the plant material and weather conditions. The plant material should

be spread out in thin layers, care should be taken to prevent contamination by

diet. impurities. While drying the plant material should also be protected from

insects, Birds, rodents, pests and other domestic animals. 

b) Shade drying: 

Some medicinal plants cannot be directly exposed to sunlight, hence need to be

dried under shade. This drying process is slow but helps in minimizing loss 

of  colour, volatile oils and aromatic components from being evaporated.

II) Artificial drying 

Drying by artificial heat is more rapid than open air drying and is necessary in

rainy season and regions where there is high humidity. The temperature and

equipment used for drying depends on the physical and chemical nature of the

drug and its constituents. Various equipment's such as tray dryers, spray dryers,

vacuum dryers are used. 

Over heating may lead to excessive loss of volatile components as well as

decomposition of chemical constituents. The temperature should be kept below

60 0C wherever possible.

a. Tray dryers (Oven)

The drugs which do not contain volatile oils and are quite stable to heat or which

need deactivation of enzymes are dried in tray dryers.

In this process, hot air of the desired temperature is circulated through the

dryers and this facilitates the removal of water content of the drugs (belladonna

roots, cinchona bark, tea and raspberry leaves and gums are dried by this

method).

b. Vacuum dryers

The drugs which are sensitive to higher temperature are dried by this process,

e.g. Tannic acid and digitalis leaves.

c. Spray dryers

Few drugs which are highly sensitive to atmospheric conditions and also to

temperature of vacuum-drying are dried by spray-drying method. The technique is

followed for quick drying of economically important plant or animal constituents,

rather than the crude drugs.

Example: papaya latex, pectin, tannins, etc.

Secondary processing

The secondary processing differs from one herb to another depending on the

nature of active ingredients as well as therapeutic properties. 

Secondary processing includes techniques such as removal of foreign substances,

prevention of microbial / infestation, enhancing the efficacy of drugs, reducing

the toxicity, extraction using suitable solvents, conc. & drying of extracts. 

These are further standardized by different methods.

Cutting, Sectioning and Communition :

After thoroughly drying, the herbal materials are processed by cutting and

sectioning into smaller sizes which are convenient for storage as well as

extraction. 

Various sizes can be obtained depending on the part of herb and extraction

methods used. It may be small particles, coarse powder or fine powder.

Aging /Sweating :

Aging refers to storing the raw material for a specified time after harvesting.

It is generally done under sun or in shade for up to a year.

During the process of aging excessive water is evaporated & enzymatic reactions

may occur to alter the chemical composition of herbal material.