Drying of Crude Drug Techniques

4- Drying of Crude Drug

• Removal of water or most of it from fresh living tissues (up to 80%).
• Careful drying is essential to retain physical and chemical characteristics of the drug and to meet pharmacopoeia requirements for maximum moisture content.
• Drying time varies from a few hours to many weeks.

Why Drying is Necessary

• Stops enzymatic action that may change active constituents.
• Prevents deterioration during storage by preventing the growth of microorganisms (bacteria and fungi).
• Facilitates grinding into a powdered form.
• Reduces weight and bulk, facilitating packing and storage.

The Most Important Factors in Drying Process

• Temperature: Use the lowest temperature possible.
• Time: Carry out the operation as quickly as possible.

Methods of Drying

• Natural Drying:
  • Sun drying
  • Shade drying
• Artificial Drying:
  • Direct fire
  • Heated stove
  • Drying shed chambers
  • Vacuum drying
  • Freeze drying (Lyophilization)

Disadvantages of Artificial Drying

• Requires careful handling to avoid damage or burning.
• Excessive heat can cause gelatinization of starch and a smoky odor.

Drying Chambers

• Closed spaces with movable trays.
• Arrange to allow circulation of heated air.
• Controlled process, with adjustable temperature and ventilation to suit different plant organs.

Freeze Drying (Lyophilization)

• Removes water content from the drug when frozen under vacuum.
• Water sublimes directly into vapor without passing through the liquid state.
• Used for thermo-labile drugs (hormones, vitamins).

Effect of Drying

• Size and weight: Markedly decreases due to loss of 80-90% of water.
• Shape and appearance: Some drugs shrivel, others become wrinkled or reticulated; the drying method affects appearance. Unorganized drugs like aloes can form homogenous glassy masses when heated and cooled quickly, but heterogeneous opaque masses when heated and cooled slowly.
• Texture: Roots become harder, leaves become brittle, while those containing starch become horny.
• Color: Drugs may darken or undergo a total color change (e.g., poppy, tea leaves).
• Odor: Some drugs (e.g., Hyoscyamus, Digitalis) lose their bad odor during drying.
• Taste: Some drugs (e.g., Gentian) become more pleasant in taste after drying.
• Constituents: In some drugs (e.g., Vanilla pods), oxidation and hydrolysis of glycosides result in the liberation of free vanillin during drying.

Precautions for Drying Different Plant Organs

• Leaves: Dry quickly to maintain fresh green color, prevent decomposition of active constituents (e.g., Digitalis leaves). Rapid drying using a vacuum oven at 60°C is often ideal.
• Flowers: Dry rapidly at low temperatures in a shaded area to maintain color.
• Fruits and seeds: Dry on trays in sun or shade.
• Barks, large roots, and rhizomes: Dry in the sun, and slicing can help with the drying process.

Packing Crude Drugs

• Protection: Packing protects the drug from physical damage.
• Less space: Packing reduces space needed for storage and shipment.
• Methods:
  • Leaves and herbs: Baled into compact masses.
  • Volatile oils: Enameled cans.
  • Gum resins and extracts: Barrels.
  • Cape aloe: Wooden boxes.
  • Turkish opium: Sub-cylindrical cakes.

Storage of Crude Drugs

• The last and most important stage of handling crude drugs.
• Storage under uncontrolled conditions can lead to drug deterioration.
• Some drugs may improve in quality with storage (e.g., Frangula and Cascara barks).

What Changes May Occur on Storage?

• Aromatic drugs (containing volatile oils) usually lose their aroma.
• Drugs containing fixed oils may become rancid.
• Digitalis leaves may lose their activity.

Pharmacopeia Instructions for Storage

• Store in well-closed containers.
• Protect drugs from light, moisture, and dust.
• Store at low temperatures.
• Protect drugs from insect infestation.

Factors Affecting Deterioration of Crude Drugs

• Physicochemical factors: Moisture, light, temperature, air.
• Biological factors: Bacteria, fungi, insects, rodents.

Moisture

• Bad effects: Hydrolysis of active constituents by enzymes, growth of bacteria and fungi, increase in drug weight and decrease in active constituent percentage.
• Overcoming moisture issues: Temporary stabilization using dehydrating agents (quick lime or calcium chloride), complete stabilization through exposure to alcohol vapor or immersion in boiling alcohol.

Light

• Bad effects: Affects delicate drugs with color (e.g., rose petals), can cause loss of activity (e.g., Digitalis leaves).
• Overcoming light issues: Store drugs in the dark or use opaque/amber-colored glass containers.

Temperature

• High temp. negative effects: High temperatures (up to 45°C) can activate enzymes and cause decomposition of active constituents; volatile oils are especially sensitive.
• Overcoming temp. effects: Lower temps generally help, especially for protecting volatile oil containing products.

Air

• Negative effects of oxygen: Oxygen can lower the quality and cause oxidation, especially for powdered or finely divided drugs.
• Solutions to air issues: Proper packaging techniques are crucial for preserving drugs exposed to air.

Fungi and Bacteria

• Fungal and bacterial attack can degrade the drug.
• The attack often affects nutritive substances and physical properties (color and texture).

Insects

• Insects (and insect eggs) may render drugs unsuitable for preparation of standard extracts.

Rodents

• Rodents can spoil stored crude drugs when kept in unsuitable containers (e.g., paper, cloth, wood).
• Rodents can be prevented from attacking drugs stored in glass, plastic, or metal containers.
• Rodenticides may be used to eliminate rats and mice.

How to Destroy Insects

• Heat treatment: Drugs can be exposed to a temperature of 60–65°C to kill insects and eggs; be aware that this method can sometimes affect the active constituents of the drug.
• Fumigation: Use of insecticides like carbon disulfide or ethylene oxide-carbon dioxide mixtures in sealed areas.

Liming

• Drugs can be dipped in or sprinkled with freshly slacked lime or quick lime to kill insects and their larvae.

Freezing

• Drugs may be stored in refrigerators to kill adult insects, larvae, and eggs at very low temperatures.

Adulteration

• Occurs when a drug is scarce or expensive.
• Forms of Adulteration:
  • Sophistication: Addition of an inferior material.
  • Substitution: Replacing the drug with a different substance.
  • Admixture: Accidentally adding one substance to another.
  • Inferiority: A drug that doesn't meet quality standards.
  • Deterioration/spoilage: Impairment of drug quality due to factors like extraction, moisture, heat, fungi, insects.
• Other forms of adulteration: Adding worthless heavy materials (like stones) and adulteration by presence of adventitious matter (like excessive stem).

Evaluation of Drugs

• Means identifying and determining the quality and purity of a drug.
• Each official drug has quality and purity limits in its monograph of the pharmacopeia.
• Methods for determining identity and quality:
  • Organoleptic methods: Sensory evaluation (taste, smell, look).
  • Microscopic methods: Using a microscope to examine drug samples.
  • Chemical methods: Chemical tests and assays.
  • Biological methods: Tests that rely on biological systems.

Quality of Drugs

• Relates to content of active constituents (carbohydrates, glycosides, alkaloids).
• Factors for high-quality drugs in collecting and preparing:
  • Proper source.
  • Proper time for collection.
  • Proper stage of growth.
  • Proper manner of collection.
  • Proper cleaning and drying processes.
  • Proper protection from insects, fungi, dirt, and moisture.

MCQs (with comments)

• Specific questions and comments on how to select correct collection times and methods for certain plants for medicine.

This quiz explores the crucial methods used in the drying of crude drugs. It covers the importance of drying, key factors affecting the process, and various drying techniques such as natural and artificial methods. Understand the significance of temperature and time in preserving the quality of herbal materials.