Herbs as raw materials. Herbal drug Technology

Pharmacognosy

1. Herbal Drug Technology Unit – I Herbs as raw materials Definition of herb, herbal medicine, herbal medicinal product, herbal drug preparation, Selection, identification and authentication of herbal materials Processing of herbal raw material

2. Definition of herb: Herbs are any plant with leaves, seeds, or flowers used for flavouring, food, medicine, or perfume. They are any seed-bearing plant which does not have a woody stem and dies down to the ground after flowering. Definition of Herbal medicine: It is the art or practice of using herbs and herbal preparations to maintain health and to prevent, alleviate, or cure disease. It may be a plant or plant part or an extract or mixture of these used in herbal medicine Herbal medicine is the study of botany and the use of medicinal plants. It is also called as Phytomedicine / Phytotherapy.

3. Definition of Herbal medicinal products: Herbal medicinal products are defined as any medicinal product, exclusively containing as active ingredients one or more herbal substances, one or more herbal preparations, or a combination of the two. Definition of Herbal Preparations Herbal preparations are obtained by subjecting herbal substances to treatments such as extraction, distillation, expression, fractionation, purification, concentration or fermentation. These include comminuted or powdered herbal substances, tinctures, extracts, essential oils, expressed juices and processed exudates.

4. Herbal Drug Preparation / Formulations Selection of Medicinal Plants Identification and authentication of herbal materials Processing of herbal raw materials Selection of Medicinal Plants for Herbal drug preparation: Randomized approach Ecological approach Chemosystematic approach Ethnoguided approach

5.   Randomized approach: This type of selection provides an endless source of new structures, since nature is a vast chemical laboratory. However, there are many mistaken views and criticisms about this approach due to its randomness. 2. Ecological approach The ecological approach, also known as field observations, consists in observations of interactions between organisms in their ecological environment, inducing to potential biological activity (antibacterial, antifungal, agrotoxic , pesticide)  

6.   Briskin (2000) states that secondary metabolites present in plant species have ecological functions which can justify their use for application in the development of therapeutic resources for humans. For example, metabolites involved in plant defense against microbial pathogens may be useful as antimicrobial drugs in humans. Therefore, the observation of these ecological relationships is a useful tool in the selection of plant species.

7. 3 . The chemo-systematic approach Chemotaxonomy, also called chemosystematics, is  the attempt to classify and identify plants based on the differences and similarities in their biochemical compositions . C hemotaxonomy-based plant selection is a prerequisite for the successful natural product research. E xamples of chemotaxonomy are:  Volatile oils are found in the family Umbelliferae and family Rutaceae . Tropane alkaloids are found in the family Solanaceae. Steroidal alkaloids occur in the family Buxaceae . Diterpenoids are found in the family Euphorbiaceae .

8.   4. Ethno-guided approach: Ethnobotany  is the study of a region's plants and their practical uses through the traditional knowledge of a local culture and people. Ethnopharmacology  is a related study of ethnic groups and their use of plant compounds. It is linked to medicinal plant use and ethnobotany, as this is a source of lead compounds for drug discovery. Ethnomedicine  is a study or comparison of the traditional medicine based on bioactive compounds in plants and animals and practiced by various ethnic groups, especially those with little access to western medicines, e.g., indigenous peoples. 

9. Identification of herbal materials: Manufactures should refer the herbal material monographs in the current national pharmacopoeias like Herbal Pharmacopoeia, Ayurvedic pharmacopoeia, BP or recommended by other authoritative national documents of the end-user’s country. All identification tests in the monograph must be complied with. In this case an authenicated voucher specimen is not essential. If there is no BP or any other official pharmacopoeias, the manufacture should use the scientific literature to choose an authoritative source. I f there is no literature, then comparison should be done against an authenticated reference specimen. A suitably qualified person must perform a comparative analysis between the consignment and the literature reference.

10. The comparison must include three or more of the following Macroscopical characters Microscopical characters Chromatographic Procedures Chemical reactions

11. Authentication of herbal materials: Authenicated raw material is the basic starting point in developing a herbal medicinal product. Correct identification and quality assurance of the starting material is therefore an essential prerequisite to ensure reproducible quality of herbal medicines which contributes to its safety and efficacy. Authenication is especially useful in cases of drugs that are frequently substituted or adulterated with other varieties which are morphologically and chemically similar.

12. Taxonomical method: Plant taxonomy is the science that finds, identifies, describes, classifies, and names plants. In this method the identification of the plant is done by comparison with previously collected specimens or with the aid of books or identification manuals on the basis of its botanical characters. DNA method: DNA fingerprints led to the identification of closely related plant species. DNA Fingerprinting Methods The basic methods of DNA fingerprinting in plants involve the isolation of DNA from plant cell, quantification and quality assessment of isolation. Further the fingerprinting can be done by PCR method like Random amplification polymorphic DNA (RAPD), Inter simple sequence repeat (ISSR), Amplified fragment length polymorphism (AFLP), DNA amplification fingerprinting (DAF) and non-PCR method like restriction fragment length polymorphism

13. Processing of herbal raw materials / Crude drugs After collection of the herbal material, they should be processed prior to marketing. The reason for processing is to stabilize them in transport and storage and to ensure the absence of foreign organic matter and substituents. It also take care of pharmaceutical elegance. It includes Harvesting / Collecting Garbling (Dressing) Washing Parboiling / Blanching Leaching Drying Packing Storage and preservation of crude drugs.

14. Harvesting / Collection: Harvested/collected medicinal plants and/or their parts undergo a series of good practice post harvest (and post-collection) processing procedures , which in the broadest sense include all steps from the immediate on-site primary clean-up of the desired medicinal plant part to its being processed into a form (herbal materials) ready for therapeutic use or as a starting source material for the production of a finished herbal products.

15. Garbling (Sorting) The garbling process serves as the first step to ensure the purity and cleanness of the medicinal plant materials. After the bulk amount of the desired plant part is harvested or collected, all extraneous and unwanted matters including dirt (e.g. soil, dust, mud, rubbles), impurities (e.g. insects, rotten tissues), and residual non-medicinal parts must be separated from the medicinal part(s). Although sorting may be done by mechanical means in some cases, it is usually performed by hand operation.

16. Washing After sorting, the medicinal plant materials should be cleaned well to remove remaining soil, dirt, dust, and other unwanted matters from the surface. They, especially roots, rhizomes and tubers, are commonly washed with clean water, dried soon after harvest/collection. During the washing process, scraping and brushing may be necessary.

17. Parboiling (Blanching) After washing, certain raw medicinal plant materials may undergo a parboiling or blanching process in which they are put into boiling water for a brief period of time without being fully cooked. Such a heating procedure may serve several purposes, such as improving storage life of the processed materials by gelatinizing the starch and preventing mould /insect contamination, and facilitating further processing such as removal of the seed coat of almonds.

18. Leaching Some impurities can be removed by the action of running water over the raw medicinal plant. The length of leaching has to be controlled in order to prevent excessive loss of other ingredients.

19. Drying: Unless used in the fresh state, the raw medicinal plant materials are to be dried after being sorted and washed. In general, they must be dried as soon as possible to remove as much moisture as possible in order to ensure good keeping qualities and to reduce damage from mould and other microbial infestation. Drying will also avoid tissue deterioration and phytochemical alteration caused by the actions of enzymes and microbial organisms; and will also facilitate grinding and milling, and convert the herbal materials into a convenient form for further processing.

20. Proper drying involves three major aspects: control of temperature, humidity and air flow. The drying conditions are determined by the nature of the raw medicinal plant material to be dried (tissue structure and chemical composition) and by the desired appearance of the final form. The drying method used may have considerable impact on the quality of the resulting herbal materials Sun drying Shade drying Drying by artificial heat

21. Packaging and labelling Processed herbal materials or herbal preparations should be packaged as quickly as possible to preserve their quality by preventing deterioration of the herbal medicines and to protect against unnecessary exposure to pest infestations and other sources of contamination. Processed medicinal plant materials should be packaged in clean, dry boxes, breathable bags or other containers in accordance with standard operating procedures. Materials used for packaging should be non-polluting, clean, dry and in undamaged condition and should conform to the quality requirements for the processed herbal materials or herbal preparations concerned.

22. Storage and transportation All processed herbal materials or herbal preparations should be properly stored and preserved before use. They must be protected from microbial and insect contaminations, and rodents and other pests. Every effort should be tried to use the type of packaging that provides ample protection against physical damages to the materials and to keep away, as much as possible, from exposure to moisture, light, heat, and insect attack. Conveyances used for transporting processed herbal materials and herbal preparations from the place of processing to storage should be clean and, where appropriate, well ventilated to keep an appropriate level of and to prevent condensation.

23. 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, concentration and drying of extracts. The following processes are carried out in the secondary processing of herbal raw materials.

24. 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.

25. 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 and enzymatic reactions may occur to alter the chemical composition of herbal material. Example: Cascara bark should be aged for at least one year prior to use in medicinal preparations to reduce its irritant effects.   Sweating is done by subjecting the herbal materials at a temperature between 45 to 65°C with high humidity for a period ranging from one week to few months. The herbal materials are stacked between woollen blankets or other kind of cloth. The sweating process is considered a hydrolytic and oxidative process in which some of the chemical ingredients of the herbs are hydrolysed or oxidised.  Example: Vanilla beans are subjected to sweating between woollen blankets for about 2 months during which they lose up to 80% of weight and develop a characteristic desirable colour and odour.

26. Baking/Roasting   It is a process of drug heating where the herbal material is heated in ovens. The temperature of heating and duration of baking/ roasting vary from one herbal material to another until the drug develops a specific colour.   Example: Nutmeg is roasted till they turn to yellowish brown colour.  

27. Boiling/Steaming   In the boiling process the drug is cooked in water or any other liquid solvent such as vinegar, wine, milk or animal urine.  Example: Acorus calamus rhizome is boiled in cow,s urine to enhance its anticonvulsant effects.   In the steaming process the herbal material is kept in contact with steam using a steamer resulting in development of moist texture.  Example: Roots of Polyganum multiforum are steamed in the presence of black bean decoction to enhance its tonic effects.

28. Stir frying   It is a process in which the herbal materials are put in a pot of frying pan and continuously stirred or tossed for a specific period under heat until the external colour changes, charred or even carbonized. To facilitate uniform heating, the drug material can be admixed with sand, talc or clay. Example: Liquorice roots and rhizomes are stir fried with honey.

29. Fumigation   Sometimes the harvested raw materials are subjected to fumes. Fumigation with sulphur dioxide is commonly employed for some medicinal herbs for the purpose of preserving, colour, improved appearance, bleaching and preventing the growth of insects and moulds.

30. Extraction of herbal materials Extraction is a process of separation in which the chemical constituents present in plant and tissues are removed by using selective solvents which is called as menstruum. Herbal extracts include infusions, decoctions, fluid extracts, tinctures and powdered extracts. The herbal preparation so obtained may be ready for use as medicinal agent or it may be further processed to finished products such as tablets, capsules and pills.

31. i . Infusion  It is a liquid preparation obtained by extracting herbal materials with either cold or hot water without boiling. Other solvents may also be used.   ii. Decoction  It is a liquid preparation obtained by boiling the herbal materials with water.   iii. Fluid extract  It is a liquid preparation obtained by maceration or percolation of herbal materials in alcohol. The ratio will be one part of liquid contain one part of herbs (1:1).   iv. Tinctures  It is a dilute alcoholic extract of herbal materials typically made up of 1 part of herbal material with 5 to 10 parts of the solvent.   v. Powdered extract  It is a form of herbal preparation which is processed into dried, granulated or powdered materials.