PCG 401 Plant Collection & Drying Methods PDF

# PCG 401 - GENERAL PHYTOCHEMICAL METHODS IN DRUG ANALYSIS ## PLANT COLLECTION AND DRYING ### COLLECTION - Drugs can be collected from wild or cultivated plants. - Collection can be done by unskilled or skilled workers. - The season each drug is collected is important. - **The quantities and nature...

# PCG 401 - GENERAL PHYTOCHEMICAL METHODS IN DRUG ANALYSIS ## PLANT COLLECTION AND DRYING ### COLLECTION - Drugs can be collected from wild or cultivated plants. - Collection can be done by unskilled or skilled workers. - The season each drug is collected is important. - **The quantities and nature of the active constituents may vary throughout the year.** - For example: *Ephedra, Podophyllum, wild cherry, Rhubarb, and Aconite* - The age of the plant influences the total quantity of active constituents and the relative proportions of the components of the active mixture. - **The composition of secondary plant metabolites varies throughout the day and night.** - Examples: *Digitalis and Tropane alkaloid-containing plants* - This variability is attributed to the methods of analysis used. - Interconversion of alkaloids and glycosides can occur. - Examples of daily variations: - **Alkaloids** of *poppy, hemlock, lupin, broom (Solanaceous plants), and ergot* - **Steroidal alkaloids** of *industrial shoots of Solanum laciniatum* - **Cardiac glycosides** of *Digitalis purpurea and D. lanata*, - **Simple phenolic glycosides** of *Salix* - **Volatile oil content** of *Pinus and Salvis* - **General Collection guidelines:** - **Leaves:** collected when flowers are starting to open. - **Flowers:** collected just before they are fully expanded. - **Underground Organs:** collected when aerial parts are dying. - **Leaves, flowers, and fruits:** should not be collected when covered with dew or rain. - **Discoloured or insect/slugs-attacked:** should be rejected. - **Hand-picking:** can be difficult and expensive to ensure that they are entirely free from other parts of the plant. - **Official Monographs:** allow a certain percentage of stalks and a limited amount of foreign organic matter. - **Roots and Rhizomes:** a certain amount of aerial stem is usually collected. - **Harvesting:** - **Unbelliferous Fruits:** resemble that of corn. - *Reaping machines* - *Threshed to separate the fruits* - **Ergot and Lavender Flowers:** harvested using *special machines* - **Barks:** collected after a period of damp weather. - **Readily separate from the wood** - **Gums and Gum Resins:** dry weather is indicated. - **Care should be taken to exclude vegetable debris.** - **Underground Organs:** freed from soil. - **Shaking:** before, during and after drying or brushing may be sufficient to separate sandy soil. - **Washing:** necessary for clay or heavy soil. - **Wormy or Diseased Rhizomes or Roots:** should be rejected before drying. - **Small Sizes:** are usually replanted. - **Rootlets:** are cut off e.g. *rhubarb, ginger and marshmallow* - **Large Organs:** are sliced to facilitate drying e.g. *Calumba root and Inula rhizome* - **Gentian Root:** made into heaps and allowed to ferment before drying. - **Seeds:** *Nux vomica and cocoa extracted from mucilaginous fruits* are washed free from pulp before drying. ### DRYING - Drying at moderate temperature is necessary for enzymatic action to occur. - **Examples:** *Orris Rhizome, Vanilla Pods, Cocoa Seeds and Gentian Root* - Should be carried out as soon as possible after collection if enzymatic action is not desired. - Drugs containing volatile oils should be dried quickly, otherwise they will lose their aroma. - Moist drugs are liable to develop mould. - **Drying Apparatus and Stills:** should be located near growing plants for reduced freightage. - Drying Process duration: a few hours to weeks, depending on the weather in case of open-air drying. - **Suitable Climates:** open-air drying is used for *clove, colocynth, cinnamon, and cardamom.* - **Warm and Dry Weather:** drugs are kept under cover of sheds or tarpaulins at night or during wet season. - **Sheds:** drugs are suspended in bundles from the roof, threaded on strings (e.g. *Chinese rhubarb*), or placed on trays made of sacking or tinned wire-netting. - **Fruits (seeds):** placed on papers spread on a wooden framework. - **Artificial Heat:** more rapid than open-air drying, commonly used in tropical countries (e.g. *West Africa*) due to high humidity. - **Continuous Belt Driers:** used for large crops (e.g. *Digitalis*) - **Open Fires:** used for *nutmegs* - **Drying Sheds:** must have a space of at least 15 cm between superimposed trays for air to circulate freely. - **Drying Temperatures:** - **Flowers and Leaves:** 20 - 40°C - **Barks and Roots:** 30 - 65°C - **Colchicum, Corm and Digitalis Leaf:** refer to *British Pharmacopoiea Codex (BPC) and BP* - **Solar Dryers:** distinct advantages over conventional artificial heat dryers for rural tropical areas. - **Over-Dried Delicate Structures:** become very brittle and tend to break. - **Examples:** *Aloes and opium may require further drying after importation.* ### STORAGE - **Large Scale Storage:** considerable undertaking. - **Avoid Long Storage:** except for *cascara bark* - **Deterioration:** occurs even when carefully stored, *e.g. Indian hemp and sarsaparilla.* - **Containers:** - **Sacks, wooden cases, bales, cardboard boxes, and paper bags:** absorb moisture, termed "air-dry". - **Plastic Sacks:** better in effectively sealing the contents. - **Permissible Moisture Content:** found in the European Pharmacopoeia. - **Starch, acacia gum, etc.** - **Moisture and Temperature:** effects on humidity and subsequent water-condensation should be considered. - **Air-Dry Drugs:** - *e.g. Digitalis and Indian hemp* - **NEVER be allowed to become air-dry** or they'll lose their activity. - **Sealed Containers:** with a dehydrating agent. - *Large Quantities:* bottom of a case can be filled with quicklime separated by a perforated grid or sacking. - Quicklime should be changed or renewed if it becomes moist. - **Volatile Oils:** sealed, well-filled containers, in a cool, dark place, applicable to fixed oils especially cod-liver oil. - **Air in Containers:** replaced with an inert gas. - **Air Dry Drugs:** susceptible to attack of insects and other pests. - **Inspection:** should be carried out frequently. - **Mould or Worminess:** either be rejected or treated. - **Sterilization:** reduce microbial contamination and prevent the development of living organisms. - **Ethylene Oxide or Methyl Chloride:** can be used. - **Toxic Residues:** e.g. *Senna pods, 50 ppm of Ethylene oxide.* ### WHO Guidelines: 1. **Medicinal Plants/Herbal Drugs:** harvested when they are at the best possible quality for the proposed use. 2. **Damaged Plants or Parts:** should be excluded. 3. **Harvesting Conditions:** best possible conditions, avoiding wet soil, dew, rain, or exceptionally high air humidity. - **Wet Conditions:** possible adverse effects on the medicinal plant/herbal drug due to increased moisture levels should be counteracted. 4. **Cutting Devices or Harvesters:** must be adjusted to minimize contamination from soil particles. 5. **Harvested Material:** should not come into direct contact with the soil. - **Prompt Collection:** transported in dry, clean conditions. 6. **Toxic Weeds:** should not mix with harvested medicinal plants/herbal drugs. 7. **Containers:** clean, free of contamination from previous harvests, kept in dry conditions free of pests, and inaccessible to mice/rodents, livestock, and domestic animals. 8. **Mechanical Damage and Compacting:** avoided, attention should be paid to overfilling and stacking of sacks. 9. **Freshly Harvested Material:** delivered as quickly as possible to processing facility to prevent thermal degradation. 10. **Protection:** harvested crop should be protected from pests, mice/rodents, livestock, and domestic animals. - **Pest Control Measures:** should be documented. ### Drying: - **Moisture Content:** kept as low as possible to reduce damage from mould and other microbial infestations. - **Methods of Drying:** 1. **Open Air (Shaded):** from direct sunlight. 2. **Thin Layers:** on drying frames, wire-screened rooms or buildings. 3. **Direct Sunlight:** if appropriate. 4. **Drying Ovens/Rooms and Solar Dryers:** 5. **Indirect Fire; Baking; Lyophilization (freeze drying); Microwave, or Infrared Devices:** 6. **Vacuum Drying:** 7. **Spray Dryer:** e.g. *Papaya latex and pectin's, etc.* - **Temperature and Humidity:** should be controlled to avoid damage to active chemical constituents. - **Drying Method and Temperature:** impact on the quality of the resulting medicinal plant materials. - **Shade Drying:** preferred to maintain or minimize loss of colour of leaves and flowers. - **Lower Temperatures:** for medicinal plant materials containing volatile substances. - **Open Air Drying:** medicinal plant materials should be spread out in thin layers on drying frames and stirred or turned frequently. - **Drying Frames:** located at a sufficient height above the ground for air circulation. - **Uniform Drying:** efforts should be made to avoid mould formation. - **Bare Ground Drying:** should be avoided. - **Concrete or Cement Surface:** medicinal plant materials should be laid on a tarpaulin or other appropriate cloth or sheeting. - **Pests:** insects, rodents, birds and other pests, and livestock and domestic animals should be kept away from drying sites. - **Indoor Drying:** - **Duration, Temperature, Humidity and Other Conditions:** determined based on the plant part concerned (root, leaf, stem, bark, flower, etc.) and volatile natural constituents e.g. *essential oils*. - **Heat Source (Fire):** limited to *butane, propane, or natural gas*, temperatures below 60°C. - **Other Sources of Fire:** contact between these materials, smoke, and medicinal plant material should be avoided. - **Vacuum Drying:** conducted in steam- heated ovens with perfect closure, a pump is used to exhaust the air. - **Rapid and Complete Drying:** low pressure maintained within the oven ensures rapid and complete drying. - **Digitalis:** example. ### Advantages Of Vacuum Drying: - **Rapid Drying** - **Relatively Low Temperature** - **Cleanliness and Freedom From Odour and Dust** - **Independence of Climate Conditions** - **Control of Temperature** - **Elimination of Risk of Fire** - **Compactness** ### Storage: 1. **Storage Facilities:** well aerated, dry, protected from light, air-conditioning and humidity control equipment, protection from rodents, insects, livestock. 2. **Floor:** tidy, without cracks, easy to clean, sufficient distance from walls, measures should be taken to prevent pest infestation, mould formation, rotting, or loss of oil. - **Inspections:** carried out at regular intervals. 3. **Continuous In-Process Quality Control:** implemented to eliminate substandard materials, contaminants and foreign matter. - **Packaging:** in clean, dry boxes, sacks, bags, or other containers in accordance with standard operating procedures and national and/or regional regulations of the producer and the end-user counties. 4. **Packaging Materials:** non-polluting, clean, dry and in undamaged condition, should conform to the quality requirements for the material. - **Fragile Material:** packaged in rigid containers. 5. **Dried Medicinal Plants/Herbal Drugs:** stored in a dry, well-aerated building, in which daily temperature fluctuations are limited. - **Essential Oils:** included. 6. **Fresh Medicinal Plant Materials:** stored at appropriate low temperatures (ideally at 2-8°C). - **Frozen Products:** less than -20°C. 7. **Small Quantity of Crude Drugs:** readily stored in air tight, moisture proof and light proof containers (such as tin, cans, covered metal tins or amber glass containers). 8. **Wooden Boxes and Paper Bags:** should not be used for storage of crude drugs.